Six Random Things

To be honest, I decided a little while ago that I wasn't going to do memes any more, but when not just one but two people ask you to do something it becomes harder to say no. So I'll do it, but I won't tag anyone else to. Here are are six random things concerning yours truly:

(1) I am really, really bad with cars. I haven't driven for ages, and I get nervous even sitting in one. One of my friends once barred me from sitting in the front passenger seat of her car because the sight of my knuckles turning white as I gripped grimly onto the door handle would make her nervous. There is no problem with my driving ability - get me out on the open road and I'm fine - it's the other traffic on the road that makes me nervous.

(2) One of the names I considered calling this site when I first started it was "The Other 99%". When I had been a student, a fellow student and I had joked that medicine must be incredibly dull compared to biology, because how on earth could anyone stand to restrict themselves to a single species when there were over three million to play around with? It wasn't until after I'd started this site that I discovered that it was fortunate that I hadn't gone with that choice. Other taxonomy-related names I considered (but which were both taken) were "The Name of the Rose" and "Rosa canina" (because that is the name of the rose).

(3) I have got to be the world's most spectacularly shitty drawer. I have no skill in visual arts whatsoever - why do you think that, even though I've been running this site for over a year and a half, I still haven't developed any sort of banner for it? This lack of drawing skill is a serious impediment for working in taxonomy, where one does have to prepare illustrations as part of taxon descriptions, after all. Roll on the day when I have enough funds available to pay an illustrator to do my drawings for me.

(4) I left New Zealand after my last relationship there ended spectacularly badly. The break-up was not actually the reason for leaving New Zealand (though it was probably an indirect factor in my losing my last job there), but it certainly didn't make the decision to do so any more difficult.

(5) Some time ago, upon taking note of the ever increasing stack of near-untouched articles I was accumulating, I decided to put a hiatus on getting more articles unless necessary until I had made a significant dent in processing the ones that I already had. Instead, I began noting down articles to obtain later in a notebook, planning on getting them when I had gotten through enough of the ones that I already had. It's now six years later, and I've got a pile of six notebooks sitting in my office filled cover to cover with titles of articles to get "at a later date".

(6) The last random thing is a trivia question for you lot - it's not really about me, but it may give some insight into the way I think. Here's the question:

It was recently mentioned on the radio that a new movie featuring the character of Sherlock Holmes is currently in production, and the role of Sherlock Holmes is to be played by Robert Downey Junior. Why did I think this was funny?

Textbook Death Match: Insect Palaeontology

Rasnitsyn, A. P., & D. L. J. Quicke (eds.) 2002. History of Insects. Kluwer Academic Publishers. 517 pp.



Grimaldi, D., & M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press. 755 pp.

Within the last seven years, we have been blessed by the appearance of two significant textbooks on insect palaeontology that anyone with an interest in the subject would be well advised to read (and if you're not interested in the subject, you damn well should be - see here and here for examples of the sheer awesomeness of fossil insects). Rasnitsyn & Quicke (2002) is a multi-author volume produced by the Russian school of palaeoentomology, while Grimaldi & Engel (2005) is an impressive two-author production. Both of them are more than weighty enough to double as security devices. I've been considering putting some thoughts to paper about RQ since first I read it, and which the subsequent appearance of GE, it only seems logical to compare the two.

To be honest, it's a bit of an unfair comparison, because the two books have different target audiences. Rasnitsyn & Quicke (2002) is a reference for the working student or researcher. As such, it tends to be heavy on detail but also heavy on style, with detailed descriptions of technical characters and long lists of references. Each section follows a fairly rigid format, so that readers can find what they're looking for easily. Grimaldi & Engel (2005) is an entirely different matter - while still presenting the technicalities, it is written to be much more appealing to the interested layperson. The composition is lighter, the format less rigid, and while Rasnitsyn and co-authors remain focused on the matter on hand and deal solely with fossil insects, Grimaldi & Engel are concerned as much with living as with fossil taxa.

Rasnitsyn & Quicke (2002) is divided into three major sections (a table of contents and a few text excerpts from the book can be found online here), the introductory section, the taxon descriptions, and an overview of insect history. That seems a reasonable basis for dividing this review.


Dunbaria fasciipennis, a representative of the Palaeodictyoptera, a Palaeozoic group of plant-sucking insects. Some palaeodictyopterans were exceedingly large, with wingspans of over 50 cm. Photo from Winds of Kansas.

The introductory section of Rasnitsyn & Quicke (2002) presents the rationale for the book's organisation, a brief history of palaeoentomology, and a section on taphonomy of insect fossils. The first of these presents us with what is undoubtedly the main failing of the 2002 volume - the classification scheme used in the book. The cladistic revolution and other scientific events that have revolutionised taxonomy in the western countries have not become as widely accepted among Russian researchers. Rasnitsyn opens with a spirited defense of the virtues of paraphyletic taxa, essentially retaining the "evolutionary taxonomy" approach of authors such as Ernst Mayr whereby monophyly (in the broad sense) is just one of the details considered in constructing a classification, and a derived subgroup may be regarded as worthy of taxonomic separation from its ancestors (e.g. separating birds from reptiles). Rasnitsyn explains it thus: "Both similarity and relatedness are involved in a taxonomic system's organising principles, but their application is not arbitrary... Raw similarity is used there as a heuristic method to construct (delimit) taxa while relatedness (monophyly) works as a method to test the resulting taxon." Despite Rasnitsyn's claim that such a system is not arbitrary, it is impossible to scan the resulting classification without being struck by cases of apparent arbitrariness. Why should the combined stem group of Lepidoptera and Trichoptera be particularly associated with the latter rather than the former? Why should the "order Grylloblattida" include a whole host of mostly winged fossil families dating back to the Carboniferous in addition to the single living wingless family Grylloblattidae, when that same assemblage is explicitly stated to also be ancestral to the living stoneflies, earwigs and webspinners in additional orders? Grimaldi & Engel (2005), in contrast, use a more phylogeny-based system. The Russian authors also differ in using a sytem of typified rank-modified names that is not widely recognised elsewhere, so instead of Strepsiptera, Plecoptera and Thysanoptera we are presented with Stylopida, Perlida and Thripida. The confusion becomes potentially worse within the orders, because many of the authors for various sections do not give alternatives to the unfamiliar subordinal names used. Rasnitsyn et al. have actually relented somewhat compared to earlier publications, so they allow some major non-typified order names such as Coleoptera and Lepidoptera, but again there seems to be a certain degree of arbitrariness involved. Why is Trichoptera an acceptable alternative to Phryganeida, but the Odonata remain labelled by the equally unfamiliar (and nearly unpronounceable) Libellulida? The potential perils of rank-modified names are also demonstrated, I feel, when one considers the bewildering series of Gryllones, Gryllidea, Gryllina, Grylloidea, Gryllidae - so many names just one typo away from complete confusion.

Grimaldi & Engel (2005) also win out over Rasnitsyn & Quicke (2002) in their introduction to insect anatomy and terminology. The former present us with a detailed introduction to the jargon, as well as a strong overview on how taxonomy and phylogeny work. The latter give a few not particularly helpful diagrams hidden in the opening for the section on Pterygota - sorry, I mean Scarabaeona - but for the most part, you're on your own, and what do you mean you don't know what a paraproct is?

Both books include a good introduction to taphonomy, the process of how organisms become fossils, but I actually think the Russian volume wins out in this regard. The late Vladimir Zherikhin, who sadly passed away before Rasnitsyn & Quicke (2002) reached publication and is one of the researchers to whom the book is dedicated, presents a guide to taphonomy and its interpretation that may not have the whizz-bang factor of Grimaldi & Engel (2005), but has enormous practical value as a student reference.


Saurodectes vrsanskyi, a mysterious wingless insect from the Lower Cretaceous. Though suggested to be related to lice (and possibly parasitic on pterosaurs), the supportive evidence is pretty tenuous. Photo from Dracovenator.

The second major section, the taxonomic overview, is of course the greater part of both books, and is also where the differences in approach between the two become most apparent. In Rasnitsyn & Quicke (2002), each order and supra-ordinal taxon is given a section divided into subsections: introductory remarks, definition, synapomorphies, range (both time and species), system and phylogeny, and (usually) history. The writing is dense and rapid-fire, and often focused on the appearance and extinction times for various families. Grimaldi & Engel (2005) present a much more varied range of factoids about each of the various groups, in some places moving into tangential explorations of related issues, so that the chapter on Hymenoptera includes a section on the evolution of sociality, that on Orthoptera reviews the topic of camouflage, while that on Mecopterida (fleas and scorpion flies) discusses the evolution of ectoparasitism. Rasnitsyn and associates leap straight into the insects proper, barely glancing at even the non-insect hexapods such as collembolans and diplurans, while Grimaldi & Engel present us with a background exploration of the other arthropod groups, both living and fossil, discussing their diversity and relationships with insects (though, funnily enough, euthycarcinoids don't even warrant a mention). Both books are widely illustrated, though Grimaldi & Engel (2005) glows with living colour while Rasnitsyn & Quicke (2002) stick to black and white. Grimaldi & Engel are certainly a lot more interesting to read, but if you are trying to look up a specific detail then Rasnitsyn and associates are probably more helpful. Nevertheless, Rasnitsyn & Quicke (2002) does suffer from a severe issue with layout. Illustrations tend to lag behind the sections that they're supposed to illustrate, and to find a figure referred to in the text you may have to look five or six pages into the next chapter.

The Russians also win out over the Americans in the last part of this review. Rasnitsyn & Quicke (2002) ends with a section giving a broad overview of insect history. Zherikhin (for terrestrial insects) and Nina Sinitshenkova and Zherikhin (for aquatic insects) present us with explorations of what types of insects where around when, and how they related to their environments at each time. Indeed, I've found Zherikhin's chapter on terrestrial insect history useful not only for looking up what kind of insects were around at a given time, but also handy for finding out what kind of plants. Grimaldi & Engel (2005), in contrast, give us nothing to compare. A final chapter describes the rise of the modern insect fauna from the Cretaceous onwards, but they dropped the ball somewhat on this one.

There is one final great difference between the two books whose significance cannot be underestimated - the price. For such a large book, with high quality colour images on more than half the pages, Grimaldi & Engel (2005) is an absolute steal. Amazon (link at the top of the page) is offering copies for only $65 (I assume US dollars), which may not sound cheap, but trust me, it'd be worth it. On the other hand, I recall Toby White (though unfortunately I can no longer find just where) referring to Rasnitsyn & Quicke (2002) as "too expensive for all but the most bloated of pocketbooks", and that at a time when it was available for less than the $988 dollars Amazon is asking for it now. I don't know about you, but I'm not about to sink three week's wages (after correcting for the exchange rate) into a single book. Try and talk your local library into getting a copy instead.

Deciding which is the better book overall really does come down to which book you fit the target audience for. If you've only got a non-professional interest in palaeoentomology, and wish simply to feed your curiosity, then there is no doubt that Grimaldi & Engel (2005) is the book for you. The pictures alone are worth the price of admission (check out the invisible grasshoppers on page 206). But try to lay your hands on a (photo)copy of the taphonomy and ecological history chapters from Rasnitsyn & Quicke (2002) - I'm giving the detailed references below. If, on the other hand, you're lucky enough to be working with fossil insects on a professional basis, I suspect that you'll probably find yourself reaching for Rasnitsyn & Quicke (2002) more often due to its superior look-up-ability (and you'll probably be erudite enough to navigate the screwy taxonomy).

Overall Champion: Grimaldi & Engel (2005). $988 is just way too much to pay for any book, ever. For that price, I expect pages made from hammered gold leaf.

REFERENCES

Sinitshenkova, N. D. 2002. Ecological history of the aquatic insects. In History of Insects (A. P. Rasnitsyn & D. L. J. Quicke, eds.) pp. 388-426. Kluwer Academic Publishers: Dordrecht. (section on the Caenozoic written together with V. V. Zherikhin)

Zherikhin, V. V. 2002a. Pattern of insect burial and conservation. In History of Insects (A. P. Rasnitsyn & D. L. J. Quicke, eds.) pp. 17-63. Kluwer Academic Publishers: Dordrecht.

Zherikhin, V. V. 2002b. Ecological history of the terrestrial insects. In History of Insects (A. P. Rasnitsyn & D. L. J. Quicke, eds.) pp. 331-388. Kluwer Academic Publishers: Dordrecht.

The Diversity of Ground Beetles

Mating pair of the ground beetle Leptoferonia hatchi (Harpalinae, Pterostichini). Photo by Kipling Will.

It is well-known that beetles are one of the most diverse groups of animals in existence, and include more described species than any other "order" of organisms (though as we make further inroads into the remaining reservoir of undescribed species, I fully expect mites and Hymenoptera to give beetles a good run for their money). Within the beetles, one of the largest and best-known families, with over 30,000 described species*, are the ground beetles of the Carabidae. By way of comparison, this is a similar number of species to the entire collection of terrestrial vertebrates.

*Tree of Life says 30,000; Wikipedia says 40,000. In the absence of any other authority, I'll go with Tree of Life.

Carabids have been one of the best-studied group of beetles because they are relatively large, often very colourful, and some species (notably the tiger beetles of the Cicindelinae) are often highly visible. Carabids are mostly active predators, generally feeding on any small invertebrate unfortunate enough to cross their path. The phylogeny of carabids is poorly resolved (Beutel et al., 2008), but one large clade that is generally recognised on morphological grounds (if not necessarily on molecular grounds - Maddison et al., 1999) is the Carabidae Conjunctae which, because I've got a thing against taxon names with more than one word in them, I'm just going to call Conjunctae from here on in*. The Conjunctae include three subfamilies (in the broad sense) of carabids, the Broscinae, Harpalinae and Psydrinae (Roig-Juñent & Cicchino, 2001), though Roig-Juñent & Cicchino (2001) indicated that "Psydrinae" was para/polyphyletic with regard to the other two subfamilies, and other sources such as the Carabidae of the World database divide each group among a number of smaller subfamilies. Conjunctae are united by (and get their name from) their conjunct mesocoxae - the plates of the sternum (the underside of the thorax) are expanded to enclose the mesocoxae (the basalmost segments of the second pair of legs). Roig-Juñent & Cicchino (2001) identified a few other features that might unite the Conjunctae, such as the presence of an elytral plica (a distinct indentation at the back end of the elytra), but as those authors didn't include a great many non-Conjunctae carabids in their analysis I'm not sure how certain those features are to be apomorphic.

*I think I can argue that this is fairly standard taxonomic practice. Quite a lot of taxon names are technically plural adjectives used as singular nouns. Plant family names, for instance, are explicitly required to be.


Mormolyce phyllodes, a somewhat different-looking ground beetle (Harpalinae, Lebiini) from South Asia. Photo by Sarefo.

The Conjunctae are one of the largest clades of carabids, but that is primarily due to the inclusion of the Harpalinae, which alone account for more than half of carabid species. Many Conjunctae (particularly many Harpalinae sensu lato) produce noxious defensive secretions when threatened, and members of the harpaline or near-harpaline tribe Brachinini are the infamous bombadier beetles, which are able to mix their defensive secretions to form an explosive mixture. The Harpalinae also include the Harpalini, which are unusual in having abandoned the carnivorous habits of their ancestors and turned to a life of seed-eating.

And just as an example of some of the unexpected things that sometimes turn up when I search online for stuff to use in these posts - it appears that Rita Skeeter might have belonged to the Conjunctae.

REFERENCES

Beutel, R. G., I. Ribera & O. R. P. Bininda-Emonds. 2008. A genus-level supertree of Adephaga (Coleoptera). Organisms Diversity & Evolution 7 (4): 255-269.

Maddison, D. R., M. D. Baker & K. A. Ober. 1999. Phylogeny of carabid beetles as inferred from 18S ribosomal DNA (Coleoptera: Carabidae). Systematic Entomology 24: 103-138.

Roig-Juñent, S., & A. C. Cicchino. 2001. Chaltenia patagonica, new genus and species belonging to Chalteniina, a new subtribe of Zolini (Coleoptera: Carabidae). Canadian Entomologist 133: 651-670.

Butterflies Before there were Butterflies

The giant Jurassic lacewing Kalligramma haeckeli being pursued by the small pterosaur Anurognathus ammoni. Reconstruction by Dmitry Bogdanov.

Lacewings are a remarkable group of insects. Though not an overly large order, they cover a wide diversity of forms, including large narrow-winged forms superficially not dissimilar to dragonflies (previously covered here), minute psocid-like taxa, species with large mantis-like raptorial forelimbs, and large broad-winged forms that might almost be mistaken for moths were it not for the lack of scales on the wings. One living family, the Nemopteridae, includes species in which the hindwings have developed into long ornamental streamers. But it is to the fossil-record that we must turn to see what were perhaps the most spectacular lacewings of all - the giant butterfly-mimics of the Kalligrammatidae.

Though perhaps it is more accurate to say that butterflies are kalligrammatid-mimics, because the kalligrammatids flew through Europe and central Asia in the late Jurassic, at least sixty million years butterflies were even thought of (Grimaldi & Engel, 2005). But while at no time did the two ever share a time-frame, if they could have been brought together the resemblance would have been striking. Kalligrammatids resembled lepidopterans even more than did other broad-winged lacewings because their wings were darkly coloured and densely setose, and their fossils even preserve evidence of bold patterns such as eye-spots. Like butterflies, kalligrammatids would have been slow but aerobatic fliers, and must have been a spectacular sight in the Jurassic forests.


Fossil of Kalligramma haeckeli, showing how the colour-pattern (if not the colour) of the wings remains discernable. Photo from here.

Most lacewings are known for being voracious predators, both as larvae and adults, but kalligrammatids had slender mouthparts that seem to have been developed for sipping nectar, yet another parallel to butterflies. No kalligrammatid larvae have yet been identified (and the extreme morphological differences between larvae and adults of holometabolous insects would make doing so all but impossible), so we have no idea if they shared their parents' genteel habits or whether they remained predatory (either is possible - some modern butterflies have predatory larvae). Specialised nectar-feeders are first recorded from the early Jurassic, though potential nectar production has been inferred from plants as old as the Permian, and many pre-Jurassic insects without obvious specialisations for nectarivory would have still been perfectly capable of feeding on nectar opportunistically if such a resource had been available (Zherikhin, 2002). Nectar is a feature today associated with flowers, and the existence of Jurassic nectarivores has been cited as evidence that angiosperms must have appeared much earlier than the Cretaceous age indicated by fossils (Ren, 1998), but such claims overlook the fact that, even among the modern flora, nectar or nectar-like fluids are also produced by cycads and gnetaleans, both of which (or their stem groups) were present in the Jurassic*. It seems more likely that nectar-feeding insects first evolved in concert with gymnospermous taxa, only to switch to angiosperms as they became the dominant flora.

*Besides, the specific fossils described by Ren (1998) come from the decidedly contentiously-dated Yixian Formation of China, and are quite likely early Cretaceous rather than Jurassic.


A modern thread-winged lacewing of the family Nemopteridae. Thread-wings are among the closest living relatives of the kalligrammatids, but other than that there's not much connection between this photo and the post. I just included it because nemopterids are pretty. Photo by Joaquim Maceira.

REFERENCES

Grimaldi, D., & M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press: New York.

Ren, D. 1998. Flower-associated Brachycera flies as fossil evidence for Jurassic angiosperm origins. Science 280: 85-88.

Zherikhin, V. V. 2002. Ecological history of the terrestrial insects. In History of Insects (A. P. Rasnitsyn & D. L. J. Quicke, eds.) pp. 331-388. Kluwer Academic Publishers.

Gathering Nuts and May

Tomorrow week I'll be hosting this month's edition of Berry Go Round, the monthly plant blog carnival, so get your posts in!

Eating Mum from the Inside Out

Micromalthus debilis feeding on rotting wood. The large specimen on the left may or may not be a mature female. Photo courtesy of Alex Wild.

Life doesn't always go with the easiest way to do things. Sometimes things get complicated. But sometimes things get so complicated, so seemingly unnecessarily confusing and baroque, that one can't help wondering that someone, somewhere, is taking the piss.

Micromalthus debilis is a tiny, wood-boring beetle that has the dubious claim of going through what is perhaps the most complicated life-cycle in the animal kingdom. You have to look at obscure parasites such as Buddenbrockia and Mesozoa before you find possible competitors. Only one species of Micromalthus is currently recognised. This species is found more or less pan-tropically and pan-subtropically in rotten wood, but its range may have been increased by human transport (Pollock & Normark, 2002). Within the beetles, Micromalthus debilis holds a decidedly isolated phylogenetic position - it belongs to the small relictual group known as Archostemata which comprises the sister group to all other beetles, and while fossils of the Micromalthus lineage are only known from amber (dating back to the Cretaceous), the possible sister-group of Micromalthus, the Cupedidae, has a fossil record dating back to the Triassic (Beutel & Hörnschemeyer, 2002; Grimaldi & Engel, 2005).

Most Micromalthus don't even look like beetles. Micromalthus are usually female and become mature while still effectively larvae (Pollock & Normark, 2002). Such females produce eggs asexually by parthenogenesis. Such egg production is usually thelytokous - asexual eggs produced by diploid females hatch into diploid females. Like some other insect lineages (including, most famously, Hymenoptera), Micromalthus has haplodiploid sex determination - females are diploid while males are haploid. Production of males in Micromalthus is rare (more on that in a moment). Like Strepsiptera, Micromalthus is hypermetamorphic (it goes through multiple larval stages). When thelytokous Micromalthus eggs first hatch, out come highly mobile, legged larvae called triungulins. The triungulins feed for a few weeks, then moult to become legless cerambycoid larvae which live a few months more. Remarkably, the ovaries begin to develop in the cerambycoid larva, which then moults directly into the mature paedogenetic adult without going through a pupal stage, making the adult a true reproductive larva. In most holometabolous insects such as beetles, flies and wasps, the reproductive organs don't begin to develop until the pupal stage.

As if the production of parthenogenetic, reproductive larvae was not remarkable itself, that's not actually where the process becomes complicated. Some females at the end of the cerambycoid stage, instead of moulting straight through to adults, actually do go into a pupal stage. When those pupae reach maturity, instead of becoming larviform like their sisters, they produce a fully-developed, winged adult beetle. These winged females are presumably able to disperse to new feeding grounds, though what determines whether a larva becomes a paedogenetic or winged adult seems to be unknown.


One of the rare fully developed adults of Micromalthus debilis. Photo again courtesy of Alex Wild.

An few female larvae differ further from their sisters in that they don't start developing ovaries while still larva, but not until they reach the final instar. These females, instead of producing numerous thelytokous eggs, produce just one arrhenotokous egg - a parthenogenetically produced egg that will develop into a haploid male. When she lays this single egg, it remains attached to her until it hatches into yet another larval type, a legless curculionoid larva. The instant the male larva is hatched, it plunges its head back into its mother, and proceeds to devour the contents of her body. Once it has finished consuming its hapless mother, the cannibalistic offspring will go through a series of moults culminating in a winged adult male. Some arrhenotokous females, if the male egg fails to develop properly or is lost before it hatches, may switch to producing thelytokous eggs that hatch into other females.

Ironically, in light of the terminal cost to the female of producing a male offspring, no matings between males and females and sexually-produced eggs have been observed in Micromalthus, and some authors have suggested that the males produced in this way are all sterile. Reproduction in Micromalthus would then be entirely parthenogenetic. This seems very unlikely - as females that produce males only ever produce a single offspring, surely there would be a strong selective pressure for eliminating production of males entirely if they were completely non-functional. Arrhenotokous females make no attempt to elude the attentions of their hungry sons, but submit readily to their fates. Male production is also more likely when resources become stretched. It seems much more likely that sexual reproduction does occur, probably between the males and the rare winged females, though the two are generally not produced by a colony at the same time and inbreeding between males and females of the same colony would be unlikely.


The full life cycle of Micromalthus debilis, taken from Pollock & Normark (2002).

Why does Micromalthus have such an obscenely complicated and sordid life cycle? Like other wood-living insects, Micromalthus rely on endosymbiotic bacteria to digest the wood they feed, and these endosymbionts may be transmitted to offspring through the ovarian tissue. For bacteria transmitted in such a way, males represent a reproductive dead end, and many such bacteria in insects have been shown to negatively affect male production in order to increase the ratio of female offspring and improve their own chances of transmission (Hurst & Jiggins, 2000; the most famous examples are species of Wolbachia). Pollock & Normark (2002) suggest that endosymbiotic bacteria may be transmitted to female offspring but not to males, and that male cannibalism may be a means of circumventing this handicap. The high cost of producing males would have resulted in selective pressure to keep the number produced to a bare minimum, explaining their rarity. Unfortunately, while this is an intriguing idea, it currently suffers from a dire shortage of evidence. The Micromalthus will not give up their secrets easily.

REFERENCES

Beutel, R. G., & T. Hörnschemeyer. 2002. Larval morphology and phylogenetic position of Micromalthus debilis LeConte (Coleoptera: Micromalthidae). Systematic Entomology 27 (2): 169-190.

Grimaldi, D., & M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press: New York.

Hurst, G. D. D., & F. M. Jiggins. 2000. Male-killing bacteria in insects: mechanisms, incidence, and implications. Emerging Infectious Diseases 6 (4): 329-336.

Pollock, D. A., & B. B. Normark. 2002. The life cycle of Micromalthus debilis LeConte (1878) (Coleoptera: Archostemata: Micromalthidae): historical review and evolutionary perspective. Journal of Zoological Systematics and Evolutionary Research 40 (2): 105-112.

Coral Love

The solitary coral Javania erhardti, a member of the 'caryophylliine' family Flabellidae, from here.

Cnidarian classification can be a terrible thing. Like many other groups of soft-bodied animals, useful characters for distinguishing taxa can be few and far between, and those few characters that are available may be difficult to identify and readily subject to evolutionary change. Corals are no exception. The current generally-used classification of living corals divides them between seven suborders, distinguished from each other primarily by the structure of their septa, the ribs of skeletal material within each polyp. The Caryophylliina, for instance, have simple septa, with little in the way of internal ornamentation. Members of this suborder have been found from as long ago as the early Jurassic, not too long after the modern Scleractinia corals originated in the mid-Triassic. Caryophylliines remain a successful group - nearly five hundred species have been described, and they include both shallow-water and deep-sea forms. The majority of caryophylliines do not contain zooxanthellae (symbiotic dinoflagellates) and while there are some colonial forms, the majority are solitary.

Which sounds all very fine and dandy, but is not anywhere near as informative as one might think. It doesn't take much reading between the lines to note that the 'Caryophylliina' with their 'simple septa' are essentially united by the absence of the features characterising other suborders. As such, it is hardly surprising that they should be nearly as old as the Scleractinia as a whole, because they are quite possibly phylogenetically equivalent to the Scleractinia as a whole. A caryophylliine is simply a coral that doesn't put on airs. This possibility is bourne out by molecular analysis (Le Goff-Vitry et al., 2004), which divides scleractinians between two major clades that have been dubbed the 'robust' and 'complex' clades (or 'Robusta' and 'Complexa' by Kerr, 2005)*. Though not corresponding to earlier morphological divisions, the two clades are not without morphological support. 'Robust' corals have solid, heavily calcified skeletons, while 'complex' corals have lighter, more porous skeletons. Caryophylliines, it turns out, are distributed between both clades, and multiple subclades within those clades. Even the type family of the 'suborder', the Caryophylliidae, is not monophyletic, with a suggested division between no less than five clades scattered among the Robusta and Complexa (Kerr, 2005).


Skeleton of the 'caryophylliine' coral Deltocyathus rotulus, showing the fairly plain septa. Photo by Stephen Cairns.

The necessary changes to scleractinian classification could yet be even more radical. Medina et al. (2006) found that the Complexa were more closely related to the soft-bodied, skeletonless Corallimorpharia than they were to the Robusta. It remains an open question whether the calcified skeleton evolved independently in the two clades, or whether the corallimorpharians represent a secondary loss of the skeleton, but my one suspicions lean towards the latter, especially since it has been demonstrated that the loss of the ability to secrete a skeleton does not constitute a death sentence for a coral (Fine & Chernov, 2007)*. Skeletal construction may yet play a role in coral taxonomy, as researchers identify more reliable ultrastructural characters (Stolarski & Roniewicz, 2001), but I think we can safely say that the 'Caryophylliina' as we have hitherto known it is, well, dead in the water.

REFERENCES

Fine, M., & D. Tchernov. 2007. Scleractinian coral species survive and recover from decalcification. Science 315 (5820): 1811.

Kerr, A. M. 2005. Molecular and morphological supertree of stony corals (Anthozoa: Scleractinia) using matrix representation parsimony. Biological Reviews 80: 543-558.

Le Goff-Vitry, M. L., A. D. Rogers & D. Baglow. 2004. A deep-sea slant on the molecular phylogeny of the Scleractinia. Molecular Phylogenetics and Evolution 30: 167-177.

Medina, M., A. G. Collins, T. L. Takaoka, J. V. Kuehl & J. L. Boone. 2006. Naked corals: skeleton loss in Scleractinia. Proceedings of the National Academy of Sciences of the USA 103 (24): 9096-9100.

Stolarski, J., & E. Roniewicz. 2001. Towards a new synthesis of evolutionary relationships and classification of Scleractinia. Journal of Paleontology 75 (6): 1090-1108.

Christmas Is Coming

Western Australian Christmas tree, Nuytsia floribunda, in flower. Photo from Esperance Blog.

In the last few weeks, the Christmas trees near our house have begun flowering. Nuytsia floribunda, the Western Australian Christmas tree, is without doubt one of the most remarkable plants found in the Perth region. Even coming into my fourth summer here, the sight of a Christmas tree still never fails to catch my attention. Why are they so remarkable?

First, there's the appearance of the tree itself. For most of the year, a Christmas tree is a fairly insignificant, often decidedly scraggly, dark green tree. It can reach a height of about ten metres, but I don't think most of the ones I've seen (and they're not uncommon in remnant bush patches) have been anywhere near so tall. You could be quite readily forgiven for overlooking them. But all that changes about the beginning of November, when they begin to flower - heavily. What was a point of scraggly green becomes a blazing firebrand of burnished gold, as the entire tree becomes covered in individually tiny, but collectively magnificent, yellow flowers. The flowers remain during the next few months, past the end of December (hence, of course, the name), blazing like a beacon all the while.

As noteworthy as this blazing cheer alone would be, Nuytsia has even more points worthy of fascination to draw the attention. Despite its attraction, Nuytsia is rarely grown as a garden plant, and most attempts to do so meet with little success. Why is Nuytsia so recalcitrant? Because this showy shrub is something of a floral femme fatale, with dark secrets hidden beneath the soil. Nuytsia is a parasite, with a double Christmas connection - it is the world's largest mistletoe.


Plant roots with attached white Nuytsia haustoria. Photo from here (which also has a photo of Nuytsia haustoria attached to roots of broomrape, Orobanche minor, itself a holoparasite).

Mistletoes of the family Loranthaceae belong to a clade called Santalales that also includes such plants as sandalwoods. Most Santalales, including mistletoes, are hemiparasites - that is, they derive at least some of their nutrient requirements from other plants, but still retain chlorophyll and produce some of their nutrients themselves. The Santalales also include some non-parasitic species that form the paraphyletic outgroup to the parasitic clade (Nickrent & Malécot, 2001), and recent studies suggest that the holoparasitic (entirely parasitic) Balanophoraceae may also belong to the Santalales (Nickrent et al., 2005). As it is, the parasitic Santalales are, by any measure, the most successful clade of plant-parasitic angiosperms in existence.

The majority of mistletoes are aerial parasites, growing directly on the trunk or branches of the host tree. Nuytsia, however, is a root parasite. It grows in the ground like a normal tree, but its roots hunt through the soil in search of the roots of other plants to latch onto and parasitise. Once the roots come into contact with a potential host, they start growing a pair of lateral projections that wrap around the host root, forming a doughnut-shaped haustorium (nutrient-absorptive tissue). On the inside of the haustorium, a sharp, hard structure develops shaped like a pair of horns, or the blades of a pair of scissors (Calladine & Pate, 2000). The sharp inside edges of this structure quickly cut through the host root (exactly like a pair of scissors), severing it into two parts, and the haustorium then grows over the exposed ends of the roots, diverting the flow of nutrients and water away from the host and into the waiting Christmas tree. Nuytsia does not seem to be choosy when it comes to hosts - it may parasitise any trees within a radius of up to 150 m, but it may also parasitise smaller plants, even grass (allowing it to survive in locations without other trees). Nuytsia have also been recorded attempting to grow haustoria around buried twigs, small stones, and even electrical cables!


Cross-section of a Nuytsia haustorium, showing the hardened structure used to cut through the host root. Photo by Stephan Imhof.

Phylogenetic analysis shows that root parasitism represents the basal condition for parasitic Santalales, with multiple origins of aerial parasitism within the clade (Vidal-Russell & Nickrent, 2008). In fact, the root-parasitic Nuytsia, as well as being the largest member of the family, is also the sister taxon to all other Loranthaceae, making it a fascinating taxon phylogenetically as well as ornamentally and ecologically. So the next time any of you see a Christmas tree in flower, stop for a moment and consider how there's a lot more to it than you can see, hidden below the surface.

REFERENCES

Calladine, A., & J. S. Pate. 2000. Haustorial structure and functioning of the root hemiparastic tree Nuytsia floribunda (Labill.) R.Br. and water relationships with its hosts. Annals of Botany 85: 723-731.

Nickrent, D. L., J. P. Der & F. E. Anderson. 2005. Discovery of the photosynthetic relatives of the "Maltese mushroom" Cynomorium. BMC Evolutionary Biology 5: 38 (http://www.biomedcentral.com/1471-2148/5/38).

Nickrent, D. L., & V. Malécot. 2001. A molecular phylogeny of Santalales. In Proceedings of the 7th International Parasitic Weed Symposium (A. Fer, P. Thalouarn, D. M. Joel, L. J. Musselman, C. Parker, and J. A. C. Verkleij, eds.) pp. 69-74. Faculté des Sciences, Université de Nantes, Nantes, France.

Vidal-Russell, R., & D. L. Nickrent. 2008. The first mistletoes: origins of aerial parasitism in Santalales. Molecular Phylogenetics and Evolution 47 (2): 523-537.

Salticid Spider Bollocks

The "information sheet" below was forwarded to my e-mail this afternoon. The person who forwarded it to me did so as a joke, but apparently it has taken some people in:

Really terrifying

Three women turned up at hospitals over a 5-day period, all with the same symptoms.
Fever, chills, and vomiting, followed by muscular collapse, paralysis and finally, death..

There were no outward signs of trauma.

Autopsy results showed toxicity in the blood. These women did not know each other and seemed to have nothing in common. It was discovered, however, that they had all visited the same Restaurant (Olive Garden , Western Cape ) within days of their deaths. The Health Department descended on the restaurant , shutting it down. The food, water, and air conditioning were all inspected and tested, to no avail.
The big break came when a waitress at the restaurant was rushed to the hospital with similar symptoms. She told doctors that she had been on vacation, and had only went to the restaurant to pick up her check.

She did not eat or drink while she was there, but had used the restroom
That is when one toxicologist, remembering an article he had read, drove out to the restaurant, went into the restroom and lifted the toilet seat

Under the seat, out of normal view, was a small spider. The spider was captured and brought back to the lab, where it was determined to be the Two-Striped Telamonia (Telamonia dimidiata), so named because of its reddened flesh color. This spider's venom is extremely toxic, but can take several days to take effect. They live in cold, dark, damp climates, and toilet rims provide just the right atmosphere..

Several days later a lawyer from Jacksonville showed up at a hospital emergency room. Before his death, he told the doctor, that he had been away on business, had taken a flight from Indonesia , changing planes in Singapore , before returning home He did NOT visit (Olive Garden), while there. He did (as did all of the other victims) have what was determined to be a puncture wound, on his right buttock. Investigators discovered that the flight he was on had originated in India .
The Civilian Aeronautics Board (CAB) ordered an immediate inspection of the toilets of all flights from India and discovered the Two-Striped Telamonia (Telamonia dimidiata) spider's nests on 4 different planes!
It is now believed that these spiders can be anywhere in the country.
So please, before you use a public toilet, lift the seat to check for spiders. It can save your life!




And please pass this on to everyone you care about.

Aww, look! It's a salticid! Innit cute?

I find it fitting that I am writing this post in Australia - which, as we all know, is the spiritual home of all toilet-seat lurking spiders. Not surprisingly, this particular story is total bollocks. And according to Snopes, it's ancient bollocks - this story has been floating about the interweb since 1992, albeit with the occasional variation to where exactly it's supposed to have taken place. Snopes also notes that the "Civil Aviation Board" referred to garbledly in the e-mail hasn't been in existence since 1984. I noticed the problem with "They live in cold, dark, damp climates, and toilet rims provide just the right atmosphere.." Ummm, a toilet-seat isn't a damp climate at all - quite the opposite - and any spider wanting to occupy the damp space under the rim is going to want to have invested in some scuba gear any time anyone flushes.

I'll put this simply ('scuse caps) - THERE ARE VERY FEW SPIDERS THAT CAN HARM YOU. Of those spiders that can harm you (and Telamonia dimidiata - scroll down a bit if you click the link - ain't one of them), even fewer of them are likely to come into contact with you. "Toxic" is not necessarily the same as "dangerous" - most toxic animals such as venomous snakes and spiders are far more likely to discretely get out of your way rather than attack. You probably won't even know they were there.

Why Use Phylogeny?

The Chatham Island snipe, Coenocorypha pusilla. This is not the species referred to later, but it is very similar. Photo by Robin Bush.

Something of a bunfight has broken out in the comments of a post at Darren Naish's Tetrapod Zoology about the merits (or lack thereof) of differing methods of classification. My opinions on the main argument have been expressed before, and I'm still happy with what I said there. However, one of Darren's regular commentors, Jerzy, asked a question that I believe is worth discussing.

Why do we use evolutionary relationships as the basis of classification in the first place?

To those of us working in systematics on a daily basis, instilled with the concept that "nothing makes sense except in the light of evolution", this seems like a natural assumption. To a layperson (or even a non-taxonomic scientist), it may appear unnecessary and pointless. Evolutionary relationships are not the only basis on which we could build a classification - we could use overall similarity, for instance. Why is it wrong to classify falcons and hawks, or herons and storks, together if they are not related evolutionarily? After all, they still look a damn lot like each other, and they are still very similar ecologically. Doesn't it make sense to continue combining them?

The unfortunate truth is that any system of classification is going to be deficient in some way, simply because we are taking the whole gargantuan multi-dimensional field of biodiversity and attempting to distill it down to a two-dimensional hierarchy of taxa*. Combining falcons and hawks despite their convergent origins conceals their evolutionary relationships. Separating them obscures their ecological similarities. Which is the set of features that we most wish to express?

*Assuming, of course, that this is what you are going for. Another alternative would be to abandon purely hierarchical relationships and accept a system in which different taxa may overlap but neither one is a subset of the other, such as "photosynthetic organisms" and "unicellular eukaryotes". While we do this all the time in informal category labels, such systems have rarely been proposed as formal systems, probably because (A) there is then theoretically a nearly infinite number of categories that can be used simultaneously, and (B) people just don't like to think like that.

The important question here is what the purpose of the classification is. On the one hand, a classification is kind of a summary of everything we know to date about an assortment of taxa. If this was our sole purpose, we might argue that a classification by overall similarity (a phenetic classification) was the better option. However, a good classification is more than just a retrospective summary, it is also our source for future predictions. We don't just want the known features of a taxon, we also want some indication of what that taxon's unknown features are likely to be.

To use a basic example, the extinct Little Barrier Island snipe (Coenocorypha barrierensis, Scolopacidae) is known from only a single specimen caught on that island in New Zealand in the late 1800s (Miskelly, 1988). Apart from the features directly observable on that specimen, nothing is directly known about C. barrierensis, but we can infer a number of things from comparison with the taxa with which it is classified. For instance, we know that it probably laid eggs, because all other birds whose reproductive habits are known laid eggs. It was probably a ground nester, because other members of Scolopacidae (including other Coenocorypha) are ground nesters. It is arguably possible that Coenocorypha barrierensis was an arboreal species that reproduced like a coral by growing offspring as buds, because we can't directly prove otherwise, but we can say by inference that such a situation is highly unlikely.

It is in this predictive capacity that the evolutionary basis for classification comes into play. Phylogenetic relationships offer the sturdiest basis we have for inferring likely characters of incompletely known taxa - and needless to say, our knowledge of any taxon (including our own species) is always incomplete. In fact, the amount we don't know about a given taxon at any one time is always far in excess of what we do know. Classifications by overall similarity, on the other hand, only speak about what is known to date - they don't make any predictions about the future. True, phylogeny is far from perfect, and it is not invariably reliable - convergence and divergence do still happen, after all - but it is the most trustworthy in the long run. This is also why, if our understanding or opinions of phylogenetic relationships change, it is preferable for the classification to change with them, because that way we are always making our predictions on the best basis we can.

Hebe or Veronica?

Veronica pimeleoides flowers. Photo from the Hebe Society.

Hebes* are some of the iconic plants of New Zealand. New Zealand doesn't have a huge diversity of flora compared to some other parts of the world, but there are some groups of plants that have just gone ballistic, achieving incredible diversity, and New Zealand is home to more than a hundred hebe species. The botanist Armstrong commented in the late 1800s that the group was so diverse that New Zealand's flora would still be of interest even if the country's vegetation was solely composed of hebes (Metcalf, 2006). Their delicate inflorescences are a common sight in the field and in the garden. This Monday's taxon of the week is a hebe - Veronica pimeleoides subspecies pimeleoides.

*If there's anyone who hasn't encountered the word before, "hebe" is pronounced with two long 'e's - hee-bee.

Those of my readers who are familiar with hebes may have blinked a little there. Our conception of the place of hebes in the botanical world has changed a little in recent years. Not only has there been the transfer of hebes from the Scrophulariaceae to the Plantaginaceae* (Olmstead et al., 2001), there is the small matter of their generic allocation. During the 1800s and early 1900s, most of those New Zealand (and a few South American) species that would later become recognised as hebes were included in the genus Veronica, a genus originally established for an assortment of temperate Northern Hemisphere taxa. The genus name Hebe (after the Greek goddess of youth, the daughter of Zeus and Hera, wife of Heracles after his apotheosis, and the server of ambrosia at the gods' table) was originally established in 1789, but didn't really enter use until the 1920s (Albach et al., 2004). Even after the botanical community recognised the distinctiveness of Hebe, horticulturists still tended for some time to regard the hebes as Veronica (Metcalf, 2006). Over time, everyone seems to have adjusted to the new view, and some groups of 'Hebe' species were even committed to further segregate genera - Parahebe, Chionohebe and (ha ha) Hebejeebie.

*Olmstead et al. (2001) suggested that the family including Hebe be called Veronicaceae, but the Botanical Code requires the correct name to be Plantaginaceae.

Then along came Albach & Chase (2001), ready to shake things up again. As it turns out, Veronica minus Hebe is a paraphyletic assemblage. While zoologists tend to divide genera in such a situation, botanists are more likely to combine, and Hebe has reverted back to part of Veronica - specifically, Veronica subgenus Pseudoveronica section Hebe (Albach et al., 2004; Garnock-Jones et al., 2007). So far, the re-reallocation of hebe species does not seem to have gained a huge acceptance among the general public, so this is currently a work in progress.


Another view of Veronica pimeleoides (this silver-leaved variety seems to be the most popular in cultivation). Photo from here.

The species Veronica pimeleoides is native to the South Island of New Zealand, being found pretty much along the exact midline of the island from the Inland Kaikouras south to central Otago. There are two recognised subspecies, V. pimeleoides ssp. pimeleoides and 'Hebe' pimeleoides ssp. faucicola (Kellow et al., 2003). A form that has been known as Hebe pimeleoides var. glauca-caerulea is only known from cultivation and has never been confirmed in the wild state since its original collection, so is currently regarded as of uncertain status. The two recognised subspecies are mainly distinguished by their growth form and habitat. V. p. ssp. pimeleoides, which is found over most of the species' range, is a low, creeping shrub found near lakes and rivers (Kellow et al, 2003, describe it as growing to 30 cm in height, but Metcalf, 2006, describes it as rarely more than 5 cm tall). V. p. ssp. faucicola is found on rock faces in the southernmost part of the range in central Otago, and is a much taller plant growing up to 70 cm in height. Subspecies faucicola also tends to have lighter flowers than subspecies pimeleoides - the former has flowers that are mauve to pink, while the latter is blue to mauve. The chemical signature of the two subspecies is, as far as is known, indistinguishable, sucggesting that the two have only recently differentiated from each other (Kellow et al., 2003).

REFERENCES

Albach, D. C., & M. W. Chase. 2001. Paraphyly of Veronica (Veroniceae; Scrophulariaceae): evidence from the internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA. Journal of Plant Research 114 (1): 9-18.

Albach, D. C., M. M. Martínez-Ortega, M. A. Fischer & M. W. Chase. 2004. A new classification of the tribe Veroniceae - problems and a possible solution. Taxon 53 (2): 429-452.

Garnock-Jones, P., D. Albach & B. G. Briggs. 2007. Botanical names in Southern Hemisphere Veronica (Plantaginaceae): sect. Detzneria, sect. Hebe, and sect. Labiatoides. Taxon 56 (2): 571-582.

Kellow, A. V., M. J. Bayly, K. A. Mitchell, K. R. Markham & P. J. Garnock-Jones. 2003. Variation in morphology and flavonoid chemistry in Hebe pimeleoides (Scrophulariaceae), including a revised subspecific classification. New Zealand Journal of Botany 41: 233-253.

Metcalf, L. 2006. Hebes: A Guide to Species, Hybrids and Allied Genera. Timber Press.

Olmstead, R. G., C. W. de Pamphilis, A. D. Wolfe, N. D. Young, W. J. Elisons & P. A. Reeves. 2001. Disintegration of the Scrophulariaceae. American Journal of Botany 88(2): 348-361.

Carnivalia

The latest edition of the Boneyard, the monthly palaeontology carnival, is at The Great Dinosaur Mystery and the Big Lie.

The latest edition of Linnaeus' Legacy is up at Life Photo Meme. This month's keywords: fishapod, cockatoo, proposals, crunchy, gulls, challenge, Barsoom, class war.

Next month's Legacy will be at Agricultural Biodiversity Weblog. We still need hosts for the following months!

A Relict Fungus on a Relict Host

Ginkgo leaves infected with the fungus Bartheletia paradoxa (above) and individual Bartheletia telia (below). From Scheuer et al., 2008.

Welcome to Fantastic Fungus Friday! Today brought me word of not just one, but two incredible discoveries involving fungi. For the first one, I'll send you over to Hyphoid Logic to learn about a fungus that not only digests cellulose (that is, wood), but in doing so releases a mix of organic chemicals that might potentially be used as a diesel substitute. Could an unassuming fungus be the saviour of civilisation as we know it?

The second great discovery is perhaps a little more esoteric, but none the less fascinating, and it involves ginkgo trees. Ginkgo biloba is one of the most famous plants to labour under that most unfortunate of labels, the "living fossil". Species assigned to the genus Ginkgo date back to the Lower Jurassic, and Ginkgo biloba is the sole surviving species of the Ginkgoales, which, together with the cycads, Gnetales, conifers and angiosperms, is regarded as one of the five primary divisions of living seed plants (some authors have suggested that Ginkgoales are a derived subgroup of the conifers, but retention by Ginkgo biloba of some plesiomorphic features absent from conifers such as motile sperm make this unlikely). Remarkably, Ginkgo may be unknown in the truly wild state - by the time any Europeans first encountered it, they did so only as plants cultivated in eastern Asia, while the only known small populations of 'wild' Ginkgo have been suggested to be also derived from human cultivation, rather than naturally occurring (Shen et al., 2005).

Despite having only survived to the present by the narrowest of margins, Ginkgo biloba thrives in cultivation, and has been widely planted. Part of the reason that Ginkgo does so well is that almost nothing harms it. Ginkgo leaves are chock-full of toxic compounds, and very little in the way of animals or fungi feeds or grows on them. A paper in the latest edition of Mycological Research (Scheuer et al., 2008) describes an exceptional fungus that does grow on fallen ginkgo leaves - and the fungus is every bit as remarkable as the plant it cleans up after.


SEMs of Bartheletia telia, and of individual basidia (the poppy-head shaped structures) on the telia. From Scheuer et al., 2008.

Bartheletia paradoxa was first recorded in 1954, but Scheuer et al. (2008) represents its first valid publication (botanical nomenclature requires a Latin diagnosis for new taxa, which the 1954 description lacked). It is, to be honest, not a lot to look at macroscopically - just a little black spot of decay on fallen leaves. Microscopically is a different matter. Bartheletia is a basidiomycete - the clade of fungi that includes most familiar mushrooms, as well as plant pathogens such as rusts and smuts. However, Bartheletia bears a number of features unlike any other basidiomycete - most notably, it has a septal structure that is completely unique. In most basidiomycetes, the septa dividing cells within the hyphae are perforated by a large central pore. Bartheletia lacks such a pore, and instead has the septa perforated by a number of narrow perforations that Schuer et al. describe as more like the plasmodesmata connecting plant cells. Phylogenetically, Bartheletia is also remarkable - it belongs to the Hymenomycetes (the clade including mushroom-producing fungi, as well as jelly fungi and wood-ears), but it doesn't seem to belong to any of the hymenomycete clade Schuer et al. compare it with. The suggestion (which requires more detailed analysis to confirm) is that this is a fungus which has been phylogenetically isolated from all other living fungi for nearly as long as its host has been from all other living plants. The fungal fossil record is not too great, but the presence of a fossil mushroom in Cretaceous amber (Poinar & Brown, 2003) indicates that the primary lineages of Hymenomycetes had diverged by at least that date.

Bartheletia seems to be unique to the Ginkgo leaves it holds its monopoly over - attempts by Scheuer et al. to grow it on leaves of other plant species failed miserably. It grew on blueberry leaves, but not on fifty-four other species including five other species in the same family as blueberries (go figure), and infections on blueberry leaves only formed asexual spores. Ginkgo trees lose their leaves rapidly over a couple of days in autumn. How Bartheletia infects fallen leaves is something of a mystery - no sign of it was found on living leaves still attached to the tree, so infection must happen after the leaf is dropped. Scheuer et al. suggest that spores may be transferred from the remains of leaves dropped the previous year. The adhesive spores may also be spread by soil-dwelling invertebrates. The former explanation may also be why Bartheletia seems to be an uncommon fungus, as the clearing of old leaves by cultivators would break the cycle. Once infection does happen, the growth of Bartheletia is extremely rapid. Bartheletia, like many other basal basidiomycetes, has a triphasic lifecycle. When the developing haploid* fungus first erupts through the leaf surface, it produces conidia, asexual spore-producing structures. These are soon replaced by structures called telia, that produce much thicker, larger teliospores. The teliospores remain dormant over the following winter and summer, then germinate to produce diploid basidia. When exactly cross-fertilisation occurs has not been observed - it may be between germinating teliospores. Each basidium then undergo meiosis to form four haploid basidiospores that will germinate into new conidia- and telia-producing hyphae. The entire cycle from teliospore germination to teliospore maturity can be over in as little as two weeks - and then its time to wait out the seasons until the next autumn, and the next leaf fall.

*While animals are diploid for most of their life cycle, fungi are haploid for most of theirs.

REFERENCES

Poinar, G. O., Jr., & A. E. Brown. 2003. A non-gilled hymenomycete in Cretaceous amber. Mycological Research 107 (6): 763-768.

Scheuer, C., R. Bauer, M. Lutz, E. Stabentheiner, V. A. Mel'nik & M. Grube. 2008. Bartheletia paradoxa is a living fossil on Ginkgo leaf litter with a unique septal structure in the Basidiomycota. Mycological Research 112 (11): 1265-1279.

Shen, L., X.-Y. Chen, X. Zhang, Y.-Y. Li, C.-X. Fu & Y.-X. Qiu. 2005. Genetic variation of Ginkgo biloba L. (Ginkgoaceae) based on cpDNA PCR-RFLPs: inference of glacial refugia. Heredity 94: 396–401.

How to be Straight

Before I leave the Palaeozoic cephalopods for a while, I have to sneak in this one last post. As I believe I've well and truly established by now (see earlier posts here, here and here), externally-shelled cephalopods in the Palaeozoic showed a far greater diversity of basic morphologies than their Mesozoic and Caenozoic successors - coiled gyrocones, long straight orthocones, short fat brevicones. By the beginning of the Mesozoic, almost all cephalopod shells were planar coils. A few orthoconic orthocerids lingered into the Triassic (and some ammonoid families did later experiment with different arrangements), but, overall, the coil was king.

I have also referred in association with the posts linked to above to why this was probably so - buoyancy management. The cephalopod shell, with its inbuilt flotation chambers, is a marvellous thing indeed, and was doubtless a crucial factor in allowing some cephalopods to become the biggest animals in the Palaeozoic. An exogastric (i.e. away from the venter) coil brings the centre of buoyancy more or less directly above the animal. Straight-shelled forms, of which there were many during the Palaeozoic, faced more of a challenge in this regard. Simply extending and enlarging the shell would have increased the potential buoyancy, but with the animal's buoyancy shifted towards the back end and its mass centred towards the living chamber at the front, orthoconic cephalopods with simple shells would have ended up floating permanently head-downwards with their arses sticking towards the sky - a rather inconvenient position for doing anything much. Some alternative approach was required to allow the shell to remain horizontal.


Diagram of cameral deposits from Kevin Bylund.

One approach that was used by a number of Palaeozoic cephalopods, such as orthocerids, was the formation of cameral deposits. Cameral deposits were mineralised layers coating the insides of the chambers (Teichert, 1964a). They became progressively thicker as they approached the apex of the shell, thus counter-balancing the weight of the living chamber at the front. They were also generally thicker ventrally than dorsally, to keep the animal upright.

If we were to assume that Palaeozoic cephalopod anatomy was just like that of a modern Nautilus (a completely unwarranted assumption, but one that has been made all too often), explaining cameral deposits poses a major dilemma. In Nautilus, the only part of the soft anatomy extending behind the living chamber is the siphuncle, a backward extension of the mantle. The siphuncle is a narrow cord running (more or less) through the centre of the chambers. Otherwise, the chambers are devoid of tissue, and the internal walls are bare (Stenzel, 1964). If orthocerids and such had the same arrangement, then the cameral deposits would have had to have been laid down in each successive living chamber before that chamber was closed off by the development of a new septa and forward contraction of the mantle. Though such an arrangement has indeed been suggested in the past, Teichert (1964a) pointed out that it was probably impossible. In many orthocones, the cameral deposits are so well-developed that the most apical chambers are entirely or nearly entirely filled by them. If they had been laid down before the formation of the next chamber, there would have been no room left in the shell for the animal itself! Also, when cameral deposits growing from opposing walls of the chamber meet in the middle, they are generally divided by a thin line, a pseudoseptum. It seems more likely that orthocerids and many other Palaeozoic cephalopods differed from modern Nautilus in possessing a "cameral mantle", a further extension of the mantle that lined the inner walls of the chambers*. While a cameral mantle may have been an ancestral feature for cephalopods (in light of the presence of cameral deposits in a number of phylogenetically disparate lineages, though some authors, e.g. Kolebaba, 2002, have recognised an order Pallioceratida defined by the presence of cameral mantle), it has not been preserved in any living cephalopod.

*A third alternative, suggested by some authors such as Mutvei (2002), is that the cameral deposits were not laid down during the lifetime of the animal at all, but instead represent post-mortem deposits formed by minerals precipitating from water penetrating the chambers. If so, they would be completely irrelevant to the animal's lifestyle. I agree with Teichert (1964a) that this seems unlikely considering the even, regular arrangement of the deposits.


Cross-section of the breviconic endocerid Cassinoceras, with the endocones visible in the lower part of the shell. Image from Palaeos.com.

An alternative solution to cameral deposits was employed by groups such as endocerids. Endocerids (which include the largest of all orthocones) had very large siphuncles, sometimes occupying nearly half the diameter of the shell (in another example of how Palaeozoic cephalopods may have differed in anatomy from modern cephalopods, Teichert [1964a] suggested that the siphuncular space in such forms may have been large enough that not only the mantle but also some of the visceral mass probably extended back past the living chamber). Instead of forming cameral deposits, endocerids weighted the apex of the shell by mineralising the siphuncle itself. The siphuncular space became filled with endocones, conical mineral layers stacked one into the next like a series of waffle cones (Teichert, 1964b). A hollow tube running through the centre of the endocones probably contained the living tissue. Because the siphuncle was such a sturdy structure, it is not uncommon for endocerids to be preserved as isolated pieces of siphuncle, with no trace of the more delicate external shell. Some structurally very distinctive groups, such as the Allotrioceratidae with two stacks of endocones pressed into the siphuncle alongside each other, are only known from such fragments of siphuncle (Teichert, 2004b), and what the remainder of the animal looked like is a complete mystery.

I do have to end this post on something of a complaint. The Endocerida, as recognised by Teichert (1964b), contains an assortment of families united primarily (as far as I can tell) by the presence of endocones. However, elsewhere in the same volume, Teichert (1964a) refers to the presence of endocones in some members of at least two other cephalopod orders, the Discosorida and Orthocerida. At least one of the families included by Teichert (1964b) in the Endocerida, the Narthecoceratidae (then known only from isolated siphuncles), has been transferred to the Orthocerida after the discovery of more complete specimens (Frey, 1981). So it would appear that all cephalopods with endocones are endocerids - except for when they are not. The stench of potential polyphyly hangs heavy in the air...

REFERENCES

Frey, R. C. 1981. Narthecoceras (Cephalopoda) from the Upper Ordovician (Richmondian) of southwest Ohio. Journal of Paleontology 55 (6): 1217-1224.

Kolebaba, I. 2002. A contribution to the theory of the cameral mantle in some Silurian Nautiloidea (Mollusca, Cephalopoda). Bulletin of the Czech Geological Survey 77 (3): 183-186.

Mutvei, H. 2002. Connecting ring structure and its significance for classification of the orthoceratid cephalopods. Acta Palaeontologica Polonica 47 (1): 157–168.

Stenzel, H. B. 1964. Living nautilus. In Treatise on Invertebrate Paleontology pt K. Mollusca 3 (R. C. Moore, ed.) pp. K59-K93. The Geological Society of America and The University of Kansas Press.

Teichert, C. 1964a. Morphology of hard parts. In Treatise on Invertebrate Paleontology pt K. Mollusca 3 (R. C. Moore, ed.) pp. K13-K53. The Geological Society of America and The University of Kansas Press.

Teichert, C. 1964b. Endoceratoidea. In Treatise on Invertebrate Paleontology pt K. Mollusca 3 (R. C. Moore, ed.) pp. K160-K189. The Geological Society of America and The University of Kansas Press.

A Different Kind of Shell

Stomatella varia, photographed by Scott Collins.

Both of the readers of this page will doubtless be glad to know that the Taxon of the Week post is bringing a respite from my temporary obsession with Palaeozoic cephalopods. Instead, I'm going to shift my focus wildly through the world's biodiversity and introduce you to... an entirely different type of mollusc. Prepare to meet the marine gastropod genus Stomatella.

Stomatella is a genus of the Trochidae, one of the largest families of marine snails. I'll refrain from giving any actual numbers - there are a number of 'trochid'-type subfamilies, and every single treatment I've seen seems to have a different idea about which subfamilies should be included in the Trochidae proper and which should be placed in separate families (Bouchet et al., 2005; Williams et al., 2008). So I really should say that Stomatella is usually a genus of Trochidae - the two references just cited both include Stomatellinae in Trochidae, but Hedegaard (1997), for instance, indicated that it should be a separate family based on shell microstructure.

Most trochids are conical shells commonly referred to as "top shells". Stomatella, in contrast, is an example of what might be called the "shield-slug" morphology - the shell is flattened and ear-shaped (the technical term is "auriform") and relatively very small compared to the rest of the animal. Not surprisingly in light of this form, Stomatella also differs from other trochids in lacking the otherwise usually well-developed operculum. Being unable to retreat into its shell like other trochids, Stomatella has developed a different defense - it is able to autotomise the back part of the foot, which then wriggles in the manner of a lizard's tail while the animal makes good its escape. Stomatella are broadcast spawners, and are apparently regularly known to spawn and breed in captivity.

Stomatella are well-known animals in the marine aquarium hobby, though a scan of various noticeboards and such suggests that they are not so much something deliberately trafficked in as something that tends to turn up of its own accord, brought in as hitch-hikers on rocks and such, and is then tolerated because of their usefulness in controlling algae. Despite this, there seems to be a spectacularly frustrating lack of research in these animals. A Google Scholar search on "Stomatella" brings up a little over seventy results, including only a single 117-year-old two-page paper specifically focusing on Stomatella (Pilsbry, 1891), and a bit of searching reveals that the species described in that paper isn't even included in Stomatella any more. There isn't even a Wikipedia page for Stomatella. So let this be a lesson to you all - just because something is familiar, doesn't necessarily mean that it's well-known.

REFERENCES

Bouchet, P., J.-P. Rocroi, J. Frýda, B. Hausdorf, W. Ponder, Á. Valdés & A. Warén. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1-2): 1-397.

Hedegaard, C. 1997. Shell structures of the Recent Vetigastropoda. Journal of Molluscan Studies 63 (3): 369-377.

Pilsbry, H. A. 1891. Note on the soft parts and dentition of Stomatella. Proceedings of the Academy of Natural Sciences of Philadelphia 43: 71-72.

Williams, S. T., S. Karube & T. Ozawa. 2008. Molecular systematics of Vetigastropoda: Trochidae, Turbinidae and Trochoidea redefined. Zoologica Scripta 37: 483-506.