A Queenage of Strepsiptera

Those of you wondering about the significance of the title to this post might want to check out the comments for last week's post on Embioptera. I noted there that a collective noun for Strepsiptera would arguably be one of the most useless concepts in the English language. In making that comment, I was referring to the fact that Strepsiptera, to the best of my knowledge, pretty never occur in noticeable groups. In fact, Strepsiptera are one of the rarest of all insect orders - so rare as to be almost mythical*. As such, their existence is not widely known by non-entomologists, and the discovery of a strepsipteran specimen is usually heralded by an unsuspecting research assistant looking down a microscope at a dish of unsorted survey specimens suddenly exclaiming, "What the f*** is that?"

*If you want a more concrete example, an ecological survey being conducted by colleagues of mine has so far collected tens of thousands of specimens - including about three strepsipterans.

Strepsiptera are endoparasites of other insects. The name means 'twisted wing', and you may also find them being called stylops*. Both sexes are parasitic as larvae, and after pupating the winged males leave the host in search of females (the picture above, from Tree of Life, shows a male Pseudoxenos leaving its wasp host. Ick). Mature males never feed, and may only survive for a few hours. The females, except for one primitive family, never leave the host, but remain in a larva-like form.

*By the way, 'stylops' is both the singular and the plural.



In the extremely unlikely event of ever seeing a strepsipteran, you can rest assured that they cannot be easily mistaken for anything else. The picture above comes from here, and shows a generalised strepsipteran male. Strepsiptera have only one pair of functional wings, with the front pair reduced to balancing organs called halteres. The only other insect order to possess halteres are Diptera (flies), but in Diptera it is the hind pair that has been altered (more on that later). The antennae are branched and antler-like. The so-called 'raspberry eye' of Strepsiptera is actually unique in the insect world, with many disjoint ocelli. It can be seen better in the photo below of Caenocholax fenyesi (by Steve Taylor, from here).



The larvae are produced viviparously by the female, and emerge from the host in large numbers (so maybe there is a use for the collective noun, after all). The first instar larvae (known as triungulins) are surprisingly advanced, with well-developed eyes and legs in order to seek out a new host. Once they have found a host and burrowed in, however, all these mod-cons are jettisoned, leaving the larva legless and grub-like. The presence of such distinct larval stages is referred to as hypermetamorphosis. At least one strepsipteran family, the Myrmecolacidae, has particularly unusual host preferences - the males are parasites of ants, while the females favour grasshopppers and crickets (Kathrithamby et al., 2003). I have not been able to find whether the sex of the larva determines the host, or whether the host determines the sex.

Phylogenetically, the Strepsiptera are arguably the second most difficult insect order - probably, only the Zoraptera can claim to have caused more problems. Still, there are two main competitors for the position of nearest strepsipteran relative. For a long time, the Strepsiptera were associated with the beetles, to the extent that some authors even suggested reducing them to a subgroup of the Coleoptera. This was mainly predicated on similarities between the triungulin larvae of Strepsiptera and certain Coleoptera families, some of which shared the Strepsiptera's branched antennae and hypermetamorphosis. However, these features are also found in other unrelated insect groups, and the chance of convergence cannot be dismissed. Molecular analyses, on the other hand, suggested a relationship between Strepsiptera and Diptera, leading to the radical suggestion by Whiting & Wheeler (1994) that the strepsipteran halteres might actually be homologous to those of Diptera, and their difference in position might be due to a homoeotic reversal switching the identities of the wing pairs! At present, it is difficult to imagine how such a thing could have happened without fatally scrambling the rest of the insect's anatomy in that area, and even if they are sister groups, the Strepsiptera and Diptera may have still evolved their respective halteres independently.



Male Stylops pacificus mating with female parasitic on bee. Photo by Edward Ross, from Tree of Life.

And why should a collection of Strepsiptera be called a 'queenage'? It should be noted that parasitism by Strepsiptera (known as stylopisation), despite the inherent ickiness of having a grub-like parasite protruding from your abdomen, is rarely fatal, and males and larvae can emerge without harming the host. Indeed, stylopised hosts may live longer than they would normally. However, stylopisation can have other significant consequences. Gonad development is reduced, and stylopised hosts may often be sterile. Stylopisation may also have a dramatic effect on secondary sexual characteristics of the host - stylopised individuals may lose their expected secondary sexual features and develop features characteristic of the other sex (Salt, 1927). Hughes et al. (2004) discovered that stylopised individuals of one species of wasp did not work in the colony as normal, but abandoned the colony and formed loose aggregations elsewhere.

Parasite-induced castration is not uncommon in invertebrates, and it is believed that it is advantageous for the parasite to sterilise its host because then time and energy that the host would otherwise waste on finding and winning a mate and producing offspring can instead be focused on feeding the host and hence the parasite (think about the behavioural differences between a neutered and entire cat). Colony desertion by stylopised wasps is probably also induced by the parasite (stylopised individuals were not driven away from the colony by uninfected individuals) as the chance of successful male emergence and mating was greater in the aggregations than within the nest, where healthy wasps would destroy any male strepsipterans they spotted.

REFERENCES

Hughes, D. P., J. Kathirithamby, S. Turillazzi & L Beani. 2004. Social wasps desert the colony and aggregate outside if parasitized: parasite manipulation? Behavioral Ecology 15 (6): 1037-1043.

Kathirithamby, J., L. D. Ross & J. C. Johnston. 2003. Masquerading as self? Endoparasitic Strepsiptera (Insecta) enclose themselves in host-derived epidermal bag. Proceedings of the National Academy of Sciences of the USA 100 (13): 7655-7659.

Salt, G. 1927. The effects of stylopization on aculeate Hymenoptera. Journal of Experimental Zoology 48: 223-331.

Whiting, M. F., & W. C. Wheeler. 1994. Insect homeotic transformation. Nature 368: 696.

Linnaeus' Legacy Vivat!

The second edition of Linnaeus' Legacy, the most exciting new carnival in the blog world, is coming next week! Brian Switek at Laelaps has kindly offered to host it, so get your posts in quick. The planned date is the 5th of November, next Wednesday. Get posts into Brian at Laelaps, or me at gerarus at westnet.com.au, or go to Blog Carnival and use the handy submission form. Chop chop!

Reference Review: The Monocot Tree

Dracaena draco, from Flora Canaria

Davis, J. I., D. W. Stevenson, G. Petersen, O. Seberg, L. M. Campbell, J. V. Freudenstein, D. H. Goldman, C. R. Hardy, F. A. Michelangeli, M. P. Simmons, C. D. Specht, F. Vergara-Silva & M. Gandolfo. 2004. A phylogeny of the monocots, as inferred from rbcL and atpA sequence variation, and a comparison of methods for calculating jackknife and bootstrap values. Systematic Botany 29 (3): 467-510.

Abstract: "A phylogenetic analysis of the monocots was conducted on the basis of nucleotide sequence variation in two genes (atpA, encoded in the mitochondrial genome, and rbcL, encoded in the plastid genome). The taxon sample of 218 angiosperm terminals included 177 monocots and 41 dicots. Among the major results of the analysis are the resolution of a clade comprising four magnoliid lineages (Canellales, Piperales, Magnoliales, and Laurales) as sister of the monocots, with the deepest branch within the monocots between a clade consisting of Araceae, Tofieldiaceae, Acorus, and Alismatales, and a clade that includes all other monocots. Nartheciaceae are placed as the sister of Pandanales, and Corsiaceae as the sister of Liliales. The Triuridaceae, represented by three genera, including Lacandonia, are resolved as monophyletic and placed in a range of positions, generally within Pandanales. Dasypogonaceae and Arecaceae diverge sequentially from a clade that includes all other commelinid taxa, and within the latter group Poales s. lat. are sister of a clade in which Zingiberales and Commelinales are sisters. Within Poales s. lat., Trithuria (Hydatellaceae) and Mayaca appear to be closely related to some or all elements of Xyridaceae. A comparison was conducted of jackknife and bootstrap values, as computed using strict-consensus (SC) and frequency-within-replicates (FWR) approaches. Jackknife values tend to be higher than bootstrap values, and for each of these methods support values obtained with the FWR approach tend to exceed those obtained with the SC approach."

A pleasing degree of consensus has developed in recent years in regards to many higher-level relationships among angiosperms (though one can't help wondering how much of this consensus is related to the fact that higher-level plant systematics has become an almost entirely molecular affair, and what would happen were a few sophisticated morphological datasets thrown into the mix. Anywho...) While relationships within the basal "magnoliids" are still a bit iffy, we have become reasonably certain about what are the major clades or grades within the flowering plants.

Many of you will have learnt in school about the differences between dicotyledons and monocotyledons, the supposed two major divisions of flowering plants, and I am sure that most basic biology textbooks still use this division. Technically, this is wrong. The characters that are ascribed to dicotyledons (two seed leaves, netted veins, stem with central xylem and external phloem, etc.) are actually the ancestral characters for flowering plants, and the dicots are paraphyletic with regard to the monocots (though a well-supported clade, the eudicots, does include all the traditional dicots except for the "magnoliids"). At least two "dicot" groups, the Nymphaeales and Aristolochiaceae, have some characters that are more traditionally associated with monocots.

The monocots, on the other hand, are a well-supported clade, both molecularly and morphologically. The Cronquist system of angiosperm classification recognised five subclasses within the monocots, the Alismatidae (aquatic and semi-aquatic forms), Arecidae (palms [Arecales], screw pines [Pandanales] and aroids [Arales]), Liliidae (lily-type plants), Commelinidae (grasses, rushes and allies) and Zingiberidae (gingers and bromeliads). Of these, the Arecidae and Zingiberidae are both currently regarded as polyphyletic, though Cronquist's "zingiberids" are all included in the commelinids*. It is the other three that I'll mainly be referring to here.

*Though the current Angiosperm Phylogeny Group classifications do still recognise higher clades based on the older subclasses, they prefer to use informal names such as "commelinid" or "rosid" rather than recognising them as formal subclasses such as Commelinidae or Rosidae.


Davis et al. (2004) came up with results for their analyses of monocot phylogeny that were fairly similar to what had and has been found elsewhere - basal alismatids (including Arales), then the liliids (including Pandanales) as a grade, then the monophyletic commelinids (including Arecales). Interestingly, Davis et al. in their combined analysis found alismatids as monophyletic - most other analyses have found them to be paraphyletic, with Acorus as the sister group to all other monocots, then a clade of most alismatids. Acorus (shown above in a photo from here) is a Holarctic semi-aquatic plant previously included in the Arales. When Davis et al. ran their analysis using rbcL data only, Acorus returned to its position outside the remaining monocots.



One other result of Davis et al. that definitely caught my eye is that Trithuria (Hydatellaceae) appears snugly nestled within the commelinids (albeit via a long-string of poorly-supported branches). One of the most interesting developments in plant systematics of the past year has been the publication of Saarela et al. (2007), which convincingly showed that the Hydatellaceae, a group of incredibly insignificant aquatic plants previously regarded as monocots (the picture above from Science Daily shows well how minute they are), are in fact part of the ANITA grade at the base of the angiosperms, sister to the Nymphaeales (waterlilies). While Saarela et al. didn't include as many taxa in their analysis as Davis et al., they did use considerably more loci (23 as opposed to only two) and showed that the relationship was also supported (albeit weakly) by morphological data, so I'm inlined to believe Saarela et al. over the earlier analysis. The really big question, then, is how did Davis et al. manage to get Hydatellaceae so deep within the monocots in the first place? What drew the previously used rbcL sequences towards the monocots? Were the sequences even Hydatellaceae at all, or had some sort of mix-up occurred? Regrettably, Saarela et al. gave no suggestions for how the previous analyses could have been so wrong**, and I'm completely stumped.

**Perhaps yet another case of the constrictions of the Nature format dooming us to a far-too-brief article. Humph.

The two papers also differ on the sister group of monocots. Davis et al. joined the monocots to the "core magnoliid" group, while Saarela et al. favoured the eudicots + Ceratophyllum***. While bootstrap support was better for Saarela et al., in neither case was it that great, so the question remains up in the air.

***Ceratophyllum is yet another unassuming aquatic taxon that seemingly exists only to give plant systematists splitting headaches****. For a while it seemed a strong contender for the position of basalmost living flowering plant, but was eventually booted from this position of power by the ANITA group. Since then, it has exacted its revenge for such a rude demotion by refusing to sit in the same place twice between analyses.

****If you're wondering what exactly is so evil about aquatic plants, their shift from a terrestrial to an aquatic habitat is generally associated with an accelerated evolutionary rate, giving them significant long branches. They also tend to develop simplified morphologies relative to their terrestrial relatives.

One thing I find particularly interesting about the state of monocot phylogenetics is the basal position of alismatids, especially if Acorus renders them paraphyletic (if you were wondering, Saarela et al. recovered the Acorus-as-basalmost-monocot topology). This makes me wonder whether monocots as a whole are derived from a semi-aquatic ancestor, which would make the "liliid" + commelinid clade secondarily terrestrial. Could this partially explain how monocots developed their highly derived morphology relative to other angiosperms? Interestingly, the aquatic Nymphaeales + Hydatellaceae clade, though indicated by molecular data to be quite distant from the monocots, shares a number of convergent features with monocots such as loss of the cambium.

One final point of interest about Davis et al. (2004) is their comparison of bootstrap supports calculated using different algorithms. While the differences were not huge, they were certainly there. For me, this definitely came in the "I did not know that" category, and will certainly have to be something I keep in mind in the future.

REFERENCES

Saarela, J. M., H. S. Rai, J. A. Doyle, P. K. Endress, S. Mathews, A. D. Marchant, B. G. Briggs & S. W. Graham. 2007. Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree. Nature 446: 312-315.

There's Treasure Everywhere

I've whinged about it multiple times in the past (see here and here), but the number one misunderstanding that most people seem to have about biodiversity is how much we know about it. Only a relatively small fraction - possibly less than 10% - of the world's species have been described. Corrolary to that is the idea that new species are only discovered in exotic, far-off lands, wonders of darkest Africa and hidden Himalayan Shangri-La. Well yes, doubtless those places do harbour their fair share of undescribed species, but sometimes new species can be discovered right on civilisation's doorstep (by which, being the parochial types we are, we mean Western civilisation, of course).

ArtPlantae Today has a story about a new plant species discovered in California, Brodiaea santarosae (the photo at the top of the post is of a different Brodiaea species, B. californica ssp. leptandra, and comes from Wikipedia). An information page here gives more info on the plant, as well as a link to the actual published paper. It also mentions the tragically interesting fact that B. santarosae is restricted to a basalt soil that has mostly been removed by (natural) erosion, with only some three percent of its area left. With continued erosion, the basalt soil might be expected to disappear within the next 100,000 years or so, carrying the habitat of this new species with it. [Hat-tip to Seeds Aside]

Even more amazing, I hear from Benny Bleiman that not one, not two, not even three, but no less than 57 new species of fish have been identified in a survey of Europe! Benny has the audacity to call this discovery boring, but the idea that there could be so many species yet to be discovered in the very continent that invented the whole concept of scientific taxonomy is just completely mind-blowing!

It's a magical world.

REFERENCES

Chester, T., W. Armstrong & K. Madore. 2007. Brodiaea santarosae (Themidaceae), a new rare species from the Santa Rosa Basalt area of the Santa Ana Mountains of southern California. Madroño 54 (2): 187-198.

Taxon of the Week: Cynortula, Cynortula

Vonones ornatus, one of the few species of Cosmetidae found in the southern United States. Photo by Lynnette Schimming from Bug Guide.

The systematics of South American harvestmen have long been one of the taxonomic world's God-awful messes, with the painstaking work of Pinto-da-Rocha, Kury and associates only recently managing to go some way towards drawing it from the mire. The blame for this morass can be placed almost entirely with a single person - Carl-Friedrich Roewer, who described about a third of the world's total of harvestmen species, some 2,260 taxa. He was able to attain this prodigious output by employing a highly artificial mode of classification. Individual specimens were assigned to species and species assigned to higher taxa on the basis of quite superficial characters such as the number of sub-segments in the legs or the number of spines on the abdomen. Character systems such as genitalia that are now regarded as highly significant were not considered*. Many of the features used by Roewer have since turned out to be variable within individuals of a single species, and sometimes within a single individual - in the case of number of tarsal segments, more than one author (such as Hickman, 1939) has described specimens that have differing numbers of segments on the left side from the right, which would require that each side belong to a different genus, if not subfamily!

*To be fair, Roewer could probably be forgiven for his neglect of genitalic characters. While genitalia had been used by some authors in taxonomy by the early 1900s, the practice was not yet widespread and its importance not widely recognised.

It has to be said that the names he gave his excessive outpourings of taxa were not exactly inspired either. Many of them were derived by sticking some suffix or prefix onto a pre-existing name. For instance, from the original name Cynorta, he gave us Cynortula, Cynortoides, Eucynorta, Cynortella, Cynortellana, Cynortellina, Eucynortula, and I'll stop now before my head explodes. Trust me, there's a lot more. To quote Kury (2003), "The dreadful, uninspired and sometimes cumbersome names created by Roewer and Mello-Leitão and followers, and which are deformations of place names, people's names and (the worst!) pre-existing generic names, are best left alone."

The above-listed genera belong to the family Cosmetidae, one of the largest harvestman families in the Neotropics. While still officially divided into two subfamilies, these are divided solely by whether the claws on legs III and IV are smooth or pectinate and this distinction is not expected to stand up to proper phylogenetic analysis should one ever be conducted (Kury & Pinto-da-Rocha, 2007). While the work of Kury and associates has vastly improved matters with the Gonyleptidae, the other major Neotropical family of short-legged harvestmen*, the Cosmetidae remain almost untouched by modern researchers**.

*Harvestmen fall into three groups, the mite-like, long-legged and short-legged harvestmen. I covered mite-like harvestmen once before. Long-legged harvestmen are the daddy-long-legs type harvestmen. Short-legged harvestmen are generally more heavily armoured, and while they do tend to have shorter legs than long-legged harvestmen, they probably have what would be fairly long legs for any other group of animal. The first episode of Life in the Undergrowth included footage of egg-guarding behaviour in a short-legged harvestman.

**Fortunately, I have reasons, such as the publication of Kury et al. (2007), to hope this may change over the coming years.



The genus Cynortula Roewer, 1912, as it currently stands, contains 32 species from throughout tropical Central and South America, from Mexico and the Bahamas to Bolivia and Brazil (the illustration above, from Goodnight & Goodnight, 1947, shows Cynortula granulata from Trinidad). Lord only knows what will happen to this genus in the future, however. Roewer (1923) seems to have supplied the last description of the genus, and described it as "Schlanke Tiere mit langen, dünnen Beine. 1. und 3. Area mit je 1 mittlerer Tuberkel-Paar; 2., 4. und 5. Area und 1.-3. frei Tergit unbewehrt. 2. Chelicere-Glied auch beim ♂ klein und normal gebaut oder seltener beim ♂ viel dicker als beim ♀ unten oben das 1. Chelicere-Glied weit überragend. Beine: die basal Glied des 3. und 4. Bein auch beim ♂ von gleichem Habitus und gleicher Stärke wie die des 1. und. 2. Bein; Endabschnitt des 2. Tarsus 3-gliedrig; 1. Tarsus 6-gliedrig; 2.-4. Tarsus jeweils mehr als 6-gliedrig, variabel. Sekundäre Geschlechtsmerkmale des ♂ bisweilen am 4. Bein."* This roughly translates (if I translate it correctly through the gibberish of BabelFish) as "Slim animals with long, thin legs. 1st and 3rd areas always with 1 central pair of tubercles; 2nd, 4th and 5th areas and 1st-3rd free tergites unarmed. 2nd cheliceral segment of ♂ small and normally built or more rarely with ♂ much larger than ♀. Legs: basal segments of 3rd and 4th legs the same as 1st and 2nd legs; Final section of 2nd tarsus 3-segemented; 1st tarsus 6-segmented; 2nd-4th tarsus in each case more than 6-segmented, variable. Secondary sexual characteristics sometimes present in 4th leg of ♂." For those not familiar with variation in harvestmen, that's not a very impressive list of distinguishing features. In fact, in Roewer's key to the Cosmetidae, only one character is used to key Cynortula out from similar genera - whether the dorsal ornamentation is a tubercle (Cynortula) or a spine (other genera). Not convincing.

*If there are any German speakers reading this, I apologise profusely for the errors that I have no doubt are all through that. As a result of its publication not too long after the Great War, with materials in short supply in Germany, Roewer (1923) was condensed as much as possible for publication and hence is entirely composed in a series of arcane abbreviations. Any grammatical errors are therefore probably the result of my attempts to restore the description to a readable form.

REFERENCES

Goodnight, C. J., & M. L. Goodnight. 1947. Studies of the phalangid fauna of Trinidad. American Museum Novitates 1351: 1-13.

Hickman, V. V. 1939. Opiliones and Araneae. British, Australian and New Zealand Antarctic Research Expedition Reports Series B 4: 157-188.

Kury, A. B. 2003. Annotated catalogue of the Laniatores of the New World (Arachida, Opiliones). Revista Ibérica de Aracnología, special monographic volume 1: 1-337.

Kury, A. B., & R. Pinto-da-Rocha. 2007. Cosmetidae. In Harvestmen: The Biology of Opiliones (R. Pinto-da-Rocha, G. Machado & G. Giribet, eds.) pp. 182-185. Harvard University Press: Cambridge (Massachusetts).

Kury, A. B., O. Villarreal-Manzanilla & C. Sampaio. 2007. Redescription of the type species of Cynorta (Arachnida, Opiliones, Cosmetidae). Journal of Arachnology 35 (2): 325-333.

Roewer, C. F. 1923. Die Weberknechte der Erde: Systematisches Bearbeitung der bisher bekannten Opiliones. Gustav Fischer: Jena.

Boneyard Redux

Boneyard #10 is up at Self-Designed Student in all its crunchy goodness. I'd particularly like to draw your attention to SV-POW!'s series on Xenoposeidon - start here and keep going! The picture at the top of this post is a rather tongue-in-cheek reconstruction of Xenoposeidon that the authors made based on an illustration of Brachiosaurus by Matt Wedel. Sadly, some of news agencies and such out there apparently failed to notice that it was obviously a joke and used it to illustrate their stories. I rather agree with one of the commentors on Darren Naish's Tetrapod Zoology post on the subject that they should have put big f***-off bat wings on its back.

A Seclusion of Embioptera

A work colleague and I got into a conversation a while ago about collective nouns, and of course that eventually got onto the question of making up appropriate terms for groups of animals that currently lack collective nouns. One suggestion that I came up with that I still rather like the sound of was a "seclusion of embiopterans". From now on, I urge you to use the term when discussing embiopterans.

If through some bizarre oversight you haven't regularly found yourself discussing embiopterans, then you really should be. Also known as webspinners or embiids, embiopterans are one of the definite contenders for the total of world's coolest insects. I have personally come across a specimen in the wild just once that I found clinging to a piece of bark I pulled off its tree - unfortunately, I have to admit, no-one around me quite got what I was getting so excited about.

Webspinners are small insects that live in silken galleries they build in secluded areas such as under bark or rocks (the picture above from the homepage of Janice Edgerly-Rooks shows a female webspinner peeping out of its home). There is something of an esoteric contention about what exactly the correct name for the webspinner order should be - Embioptera, Embiidina or Embiodea all can be found. I'm going to stick with Embioptera for no good reason. The name means "lively wings" and is wildly inappropriate - webspinners are not noticeably lively, and more often than not lack wings (females are invariably wingless, males can sometimes be). It has been suggested that the name refers to the flicking movement of the male wings. The wings of male webspinners have large blood sinuses developed from the veins that are pumped full of haemolymph to make the wings rigid when they fly. When the haemolymph is drained from the sinuses, the wings become limp and floppy, able to move in whatever direction is required to let the male crawl through a female's silk nest, even bending forward over the head if the male goes into reverse.

Webspinners are often referred to as semi-social and females may share inter-connected galleries. Females also show a high level of parental care. However, females will not show any care for the young of others, and social interactions between females should probably be regarded as opportunistic rather than required (Grimaldi & Engel, 2005). The female and juvenile webspinners emerge from their silken palaces at night to feed on vegetation and detritus. Adult males, on the other hand, do not feed.



The webspinner's silk glands are located along the edge of the third segment of the forelimb tarsus, which is noticeable broadened as shown in the diagram above from BugNetMAP. The German name for embiopterans, "tarsenspinner", is therefore entirely apropos. The stunning "Life in the Undergrowth" series that I've had cause to mention before included spectacular footage of a webspinner constructing its silken fortress, waving its forelimbs in front of itself in a motion that can only be described as "wax on, wax off". So impermeable is the resulting wall that the spinner must actually cut through it with its mandibles in order to drink from water drops lying on the surface if it is not to dry up completely.

Reference Review: Parrots in the Early Days of Molecular Analysis

Ovenden, J. R., A. G. Mackinlay & R. H. Crozier. 1987. Systematics and mitochondrial genome evolution of Australian rosellas (Aves: Platycercidae). Molecular Biology and Evolution 4 (5): 526-543.

Rosellas (Platycercus) are a genus of five or more species of smallish parakeet found in more coastal areas of Australia, particularly the eastern states. Significant differences in opinion exist about just how many species there are in the genus - a number of subspecies are recognised that may be raised as separate species depending on author (I'm going to take a neutral position and treat all taxa as if they were species - see Wikipedia for a more detailed taxonomy). At least one taxon in the genus, the variable Platycercus adelaidae (the Adelaide rosella), is claimed by some to be a hybrid swarm derived from cross-breeding between two other subspecies and therefore not a valid taxon at all*. Rosellas are also possibly the most familiar parrot in New Zealand, at least in the north, due to abundant populations of introduced Platycercus eximius (the eastern rosella, shown at the top of the page in a photo from Wikipedia).

*The ICZN (in contrast to the ICBN) does not permit the recognition of taxa based on hybrids. This rule works fine when dealing with singleton hybrid specimens, which were doubtless what the ICZN had in mind when they drafted it, but is somewhat problematic when dealing with populations that have a hybrid origin, some of which may become established as new species.

The species of Platycercus can be readily divided into two groups, referred to as the "P. elegans" and "P. eximius" groups (though the latter should probably be called the P. adscitus group as that species has priority). Platycercus elegans and P. caledonicus are the blue-cheeked rosellas (P. elegans, the crimson rosella, is shown at left from Wikipedia). Platycercus adscitus, P. eximius and P. venustus are the white-cheeked rosellas. The geographically isolated P. icterotis (the western rosella) from the south-west of Western Australia has white or yellow cheeks and was once included in the P. eximius group, but is now generally excluded from either group.

At the time today's paper was published, molecular phylogenetics were still very much in their infancy. PCR, the technique that revolutionised molecular studies, was not to appear until the following year (Saiki et al., 1998). Before the advent of PCR, most molecular techniques were expensive, time-consuming, delicate and often unreliable (after the advent of PCR, they became expensive, delicate, often unreliable, and able to be done much more readily*). As such, most molecular studies in the 1980s used methods that by modern standards appear decidedly rough and ready. In the case of the one I'm looking at today, the method of choice was mitochondrial restriction fragment polymorphisms.

*It's a bit like the joke about the soldiers in the desert camp being to told by their general that there was bad news and good news. The bad news was that supplies had run so low that all they had left to eat was horseshit. The good news was that there was plenty of it.

Restriction endonucleases are enzymes that cut DNA into bits. There are a huge number of endonucleases in use at the present, and each one works by attaching to a specific sequence of bases in a DNA strand and dividing it at that point. Depending on need, there are enzymes that require relatively long sequences of bases and so would cut a given DNA strand rarely if at all, or there are enzymes that only require short sequences and so would be expected to cut strands far more readily. Probably the most familiar use of endonucleases to the general public is in DNA fingerprinting, where the resulting fragments from the endonuclease treatment of DNA samples are compared to see whether or not the samples contain the same fragment. The use of RFLPs (restriction fragment length polymorphisms) in phylogenetics is essentially a distance method - it proceeds by the assumption that samples that are most similar to each other in the resulting restriction fragment pattern are the most closely related phylogenetically. As for the use of mitochondrial DNA, there were a number of reasons why mitochondrial DNA was preferred to nuclear DNA for molecular studies at the time, but not least of them was that there is usually a lot more of it about and it is much easier to extract from a specimen than nuclear DNA. It should not be forgotten that prior to PCR, researchers only had as much sample to work with as they could directly draw out of the specimen.

There are a great many reasons why the use of RFLP for phylogenetics should not work. The assumption that genetic distance is equivalent to phylogenetic distance is simply not reliable, because evolution does not always occur at the same rate in separate lineages. Add to that the fact that in an ideal phylogenetic data set changes in one character state should not affect the state of other characters - a requirement blatantly violated by RFLP data, as the loss of a restriction site causes the resulting data set to "lose" two fragments and gain a whole "new" fragment. Fortunately for this case, the results actually make a certain degree of sense. Ovenden et al. recovered the same two species groups that had already been identified on the basis of morphological data. The only exception was that Platycercus icterotis, rather than clustering with the P. eximius group, came out as the most divergent species of all. However, this, too, had already been suggested on morphological grounds.

Unfortunately, the phylogeny of Platycercus does not appear to have been re-examined since the advent of more reliable analytical methods. There are no obvious reasons not to believe Ovenden et al.'s results, but considering the methodology they can hardly be said to not be worth a further look.

REFERENCES

Saiki, R. K., D. H. Gelfand, S. Stoffel, S. J. Scharf, R. Higuchi, G. T. Horm, K. B. Mullis & H. A. Ehrlich. 1988. Primer-directed enzymatic amplification of DNA with a thermostable DNA polymerase. Science 239: 487-491.

Taxon of the Week: Cotinginae – Neotropical and Fabulous!

Sure you said just fluffy, but did you ever imagine I could do this with your hair?

When I used to look through one of the various bird family books I knew and loved as a young'un, the cotingas were somewhere I was bound to stop. Cotingas are a diverse family of largely frugivorous birds from Central and South America. Don Roberson refers to them as the "birds-of-paradise of the New World", and while perhaps not quite so incredible as the original birds-of-paradise, cotingas are certainly up there (along with hummingbirds and pheasants) in terms of total drag-queen-esque gaudiness.

Preliminary phylogenetic analysis by Prum et al. (2000) divided the Cotingidae into four reasonably well-supported clades, though relationships within the clades were poorly supported. Prum et al. suggested that these clades be recognised as the subfamilies Tityrinae, Phytotominae, Rupicolinae and Cotinginae. A more recent analysis by Ohlson et al. (2007) effectively supported Phytotominae and Cotinginae, though the Rupicolinae of Prum et al. (2000) were polyphyletic. Authors differ on whether the Tityrinae should be included in the Cotingidae or not, and Ohlson et al. (2007) excluded them. It is with the Cotinginae (the "core cotingas" of Ohlson et al.) that I am concerned today.

The name "cotinga" is actually a rather inappropriate one. It comes from a native Amazon name for one of the species meaning "washed white" (Austin, 1961). Despite this, only a few species of cotinga are significantly white, including the bellbirds of the genus Procnias (male three-wattled bellbird, P. tricarunculata, at left from Encyclopaedia Brittanica). Bellbirds get their name from their bell-like call (a single "bock!" according to Don Roberson), which is reputedly one of the loudest sounds made by any bird. Ohlson et al. (2007) placed Procnias in a clade they referred to as the "canopy cotingas", which also includes (among others) Gymnoderus foetidus (the bare-necked fruitcrow) and Carpodectes nitidus (the all-white snowy cotinga). The genus Cotinga has traditionally been regarded as closely related to these genera, but Ohlson et al. were unable to confirm such a relationship.



Going by the results of Prum et al. (2000), the canopy cotingas probably also include Xipholena punicea, the pompadour cotinga (shown above in a picture from the Field Museum). This species received its common name from Jeane-Antoinette Poisson, Marquise de Pompadour, she of the gigantic and ridiculously ornate wigs. Among the exotic paraphernalia Madame de Pompadour incorporated into her stupendous wigs were whole birds, and the first described specimen of the red lavender-coloured pompadour cotinga was described from a shipment of bird skins captured by the British on its way to the Madame.

The two groups of pihas are quite dull-coloured birds, though the screaming piha (Lipaugus vociferans) makes up in volume what it lacks in colour. All pihas were once included in a single genus Lipaugus, but Prum (2001) showed that the two species of Snowornis were not closely related to the other pihas.

Finally, the fruitcrows include the largest of the cotingas. Many of the fruitcrows and the Lipaugus pihas are lek breeders (the fruitcrow genus Querula are monogamous with nest helpers, while the breeding habits of Snowornis pihas are largely unknown but have not been observed to include lekking). The best-known of the fruitcrows are undoubtedly the spectacular umbrellabirds of the genus Cephalopterus with their bouffant hair-dos and long, hanging throat sacs (shown at the top of this post in a photo from BirdQuest). But just as notable is the calfbird (Perissocephalus tricolor), whose cow-like call is accompanied by a strange movement of stretching the neck, puffing the feathers around the head and tottering precariously on the legs. See for yourself!



REFERENCES

Austin, O. L., Jr. 1961. Birds of the World: A survey of the twenty-seven orders and one hundred and fifty-five families. Paul Hamlyn: London.

Ohlson, J. I., R. O. Prum & P. G. P. Ericson. 2007. A molecular phylogeny of the cotingas (Aves: Cotingidae). Molecular Phylogenetics and Evolution 42 (1): 25-37.

Prum, R. O. 2001. A new genus for the Andean green pihas (Cotingidae). Ibis 143: 307-309.

Prum, R. O., N. H. Rice, J. A. Mobley & W. W. Dimmick. 2000. A preliminary phylogenetic hypothesis for the cotingas (Cotingidae) based on mitochondrial DNA. Auk 117 (1): 236-241.

Accretionary Wedge

The third edition of The Accretionary Wedge, a carnival for matters geological, is up at The Other 95%. Kevin has themed the edition around the question of how geology affects biology, and how we all exist at the mercy of a pile of rocks.

Reference Review: Cutting Up the Excess

Nagy, I., T. Tamura, J. Vanderleyden, W. Baumeister & R. DeMot. 1998. The 20S proteasome of Streptomyces coelicolor. Journal of Bacteriology 180: 5448-5453.

Just before I start, I'd like to point out that I have very little understanding of the world of biochemistry. Most of it goes so far above my head that it causes detours on major airline routes. Therefore, I don't expect you to believe a single word of what I'm about to say.



Many of you who have passed through university biology will have seen some variation of the above diagram (this version from Palaeos). It shows the Three Domain Hypothesis of Woese and colleagues, based on 18S rDNA analysis, dividing life into the eukaryotes, eubacteria and archaebacteria. In many cases, you'll have seen it with a root on the branch dividing the eubacteria from the other two domains. A few years back, I wrote an essay for Palaeos on the phylogenetic relationships of bacteria. It wasn't a bad piece of work, and I'm still reasonably happy with it. Toby White wrote a much longer essay last year that largely superseded what I'd written, though I'm not sure I'd agree with everything in it (for instance, we seem to have a tacit agreement to disagree on the usefulness of sequence data). Anyway, the upshot of these two pieces was that, while said division of life has been widely reiterated in textbooks and introductory courses, the actual evidence for it is not as strong as might be hoped. The vast majority of researchers agree that there is some sort of phylogenetic reality to the three domains, but whether a given domain represents a monophyletic clade or paraphyletic grade is a hotly debated topic. There is an even more significant amount of disagreement about what are the correct interrelationships within the eubacteria, and which members of the eubacteria are the most basal or closest to Neomura (archaebacteria + eukaryotes), whether eubacteria are monophyletic or paraphyletic. Both these points are something you may want to keep in mind as you read this post.

Proteasomes are enzymes that function, as Toby has explained elsewhere, to break down polypeptide strands within the cell. The average proteasome is roughly shaped like an open-ended barrel - the image at the top of this post (from Answers.com) shows an example looking down the barrel. Pieces of defective protein are taken in one end and chopped up into small fragments that are ejected at the other - doubtless to be recycled to make newer, better proteins. Proteasomes are a notable shared feature of eukaryotes and archaebacteria, but were believed to be absent from eubacteria until they were identified from the actinobacterium Rhodococcus. Actinobacteria are a collection of Gram-positive bacteria with high G + C content that are generally accepted as forming a distinct clade (I covered one subsection of Actinobacteria earlier). Since then, proteasomes have been identified from a range of other bacteria, including Mycobacterium and, of course, Streptomyces, and are probably found throughout the clade.

Simplified diagram of a 20S proteasome in sideview, showing the terminal α-subunits and the medial β-subunits (from Answers.com).

This is of some significance to the question of bacterial phylogeny, because 18S rDNA trees place Actinobacteria as one of the closer groups of eubacteria to the other two domains. Whether proteasomes are a shared synapomorphy of Actinobacteria, archaea and eukaryotes, or a feature of the common ancestor of all living organisms that was subsequently lost in non-actinobacterial eubacteria, largely depends on where the root of the tree of living organisms turns out to be. Other eubacteria possess a different but closely related enzyme known as HslV, that authors such has Cavalier-Smith (2006) have suggested to be ancestral to proteasomes.

The possibility exists, I suppose, that proteasomes were transferred between Actinobacteria and Neomura by that bugbear of bacterial phylogenetics, horizontal or lateral gene transfer. In this case, I don't think that's likely. In general, the proteasome system replaces the HslV system or vice versa, which is highly suggestive of a single origin of one from the other. Only a single case appears to be known of co-existence of HslV and proteasomes in the one organism, with both being present in the Kinetoplastida, a clade of parasitic protozoans including the causative organisms of such spectacularly unpleasant diseases as sleeping sickness and leishmaniasis (Couvreur et al., 2002). Phylogenetic analysis of the kinetoplastid HslV sequence places it among the eubacterial HslV sequences rather than with the neomuran proteasomes, but is unable to resolve relationship to any particular eubacterial clade (ibid.) The available phylogenetic analyses indicate that kinetoplastids are relatively derived within the Neomura, and it seems more likely that the kinetoplastid HslV is the result of lateral gene transfer. It is worth noting that, confusingly, early diverging Actinobacteria such as Bifidobacterium seem to lack proteasomes (Cavalier-Smith, 2006), but as they also seem to lack HslV they must be regarded as uninformative in this matter.

Structurally, the actinobacterial proteasome is comparable to the archaeal proteasome. In eukaryotes, seven each of different α-type and β-type subunuits go into forming the 20S proteasome, which forms the core, with the addition of several accessory proteins, of the final 26S proteasome. The archaeal and actinobacterial proteasomes, in contrast, are far more minimalist structures, with only a single α- and β-type subunit in archaebacteria, Mycobacterium and Streptomyces. Rhodococcus has a slightly intermediate state, with two different α- and β-type subunits (Nagy et al., 1998).

One particular finding of Nagy et al. deserves highlighting. Activity measures of the Streptomyces proteasome found that it was inhibited by lactacystin, a result found with proteasomes from other organisms. The interesting thing is that at least one Streptomyces strain produces lactacystin itself. Could the production of lactacystin function to regulate the activity of proteasomes in the living organism?

REFERENCES

Cavalier-Smith, T. 2006. Rooting the tree of life by transition analyses. Biology Direct 1: 19.

Couvreur, B., R. Wattiez, A. Bollen, P. Falmagne, D. Le Ray & J.-C. Dujardin. 2002. Eubacterial HslV and HslU subunits homologs in primordial eukaryotes. Molecular Biology and Evolution 19 (12): 2110-2117.

Get Me into Open Lab on Time

Blog Around the Clock is taking the last round of submissions for Open Lab 2007, a collection of the best science blog writing for the past year. So if there's anything from Catalogue of Organisms that's really floated your boat or cooked your kumara, click on the OpenLab logo above or on the right of your screen to access the submission form and say that you love me.

Geology Calling

If something about yesterday's post seemed a little different to you, that was because it was written specially for The Accretionary Wedge, the geological blog carnival that is being hosted this month by Kevin Z at The Other 95%. Kevin would like to hold a carnival installment centred around the theme of how geology affects biology, so get your submissions to him toot-sweet. The Accretionary Wedge will be appearing on the 15th of November, which is today for me but will probably be tomorrow by the time it gets to Kevin.

Of Serpentine Soils

Cape Reinga projects from the north-western end of the Aopouri Peninsula at the very top end of New Zealand. A lone lighthouse stands at the summit of the cape (image at left from Wikimedia), and a venerable pohutukawa tree hanging over the cliffs is pointed out as the very tree from which, in Maori tradition, the spirits of the dead clambered down to the ocean on their way back to Hawaiiki, the mysterious land that was the ancestral point of origin of the Maori to which they returned after their death*. Cape Reinga is a popular tourist spot as the northernmost point in New Zealand. It isn't. If you look carefully at the map at the top of this post (from the Far North District Council), you'll note that at the north-eastern corner of the country, there's a rounded prominence sticking further north. This is the North Cape, and that rounded prominence is the Surville Cliffs.

*There is an unfortunate tendency to refer to 'Maori tradition' as a single unit, when prior to European settlement the different Maori tribes each had their own collection of traditions, agreeing in some points and differing in others. While the concept of a return to Hawaiiki was, I believe, universal among Maori, I haven't been able to find out if this tradition was associated particularly with Cape Reinga for all Maori, or if tribes in other parts of the country identified their own departure points. Apparently more than one Christian missionary, including the memorable William Colenso, tried to have the Cape Reinga pohutukawa chopped down, but these attempts were always rebuffed by local Maori.

So why aren't the tourists all headed for the true northern tip of the country? The Surville Cliffs are part of a conservation reserve (the North Cape Scientific Reserve) that remains closed to the general public. The local Department of Conservation attempts to ruthlessly exclude and/or eradicate introduced taxa from the area, and the primary focus of this protection is a small area of about 120 hectares on the Surville Cliffs and the adjacent plateau that is home to a whole range of plant species found nowhere else on the planet, including Hebe brevifolia (Cheeseman) de Lange 1997, Carex ophiolitica de Lange & Heenan 1997 and Uncinia perplexa Heenan & de Lange, 2001.

Pittosporum serpentinum, an endangered species endemic to the Surville Cliffs area. Seedlings of this species have never yet been observed (photo by Gillian Crowcroft, from New Zealand Plant Conservation Network).

The range of plant species growing in any location is strongly dependent on the soil type. The effect of a change in soil type can be dramatic - sometimes you can practically see a line where one soil abruptly gives way to another. In the case of the Surville Cliffs, the presence of a distinct soil type not found elsewhere in New Zealand is to blame for the unique flora.

The soil at the Surville is serpentine, derived from the exposure of the Tangihua or Northland Ophiolite. Ophiolite forms when part of the sea-floor crust becomes uplifted and integrated into the continental crust. Major ophiolite belts are found in the Alps and the Himalayas where pieces of the oceanic floor between two colliding continental masses have been ripped up and wedged between the fusing continents. In the case of the Tangihua Ophiolite, the rocks that eventually became the ophiolite probably formed in the South Fiji Basin to the north-east of New Zealand (Whattam et al., 2004). They would have then become emplaced onto the New Zealand continental mass with the formation of a subduction zone along the north-east of New Zealand, probably due to the collision of the underwater Hikurangi Plateau with the New Zealand continental shelf further south.



Sketch map showing the disposition of tectonic elements adjacent to Northland. A, Immediately prior to the emplacement of the Northland Ophiolite. B, Immediately after emplacement and as subduction began. SFB, South Fiji Basin; VMFZ, Vening Meinesz Fracture Zone; HP, Hikurangi Plateau. From Whattam et al., 2004.

Ophiolite is very ultramafic rock, meaning it is high in heavy metals such as nickel, iron and magnesium. Soils formed from such rocks are toxic to the majority of plants, which is why they become the preserve of ultramafic specialists. In contrast, most ultramafic specialists do not do well when grown away from their toxic homes (de Lange, 1997; Heenan & de Lange, 2001), which is why the Surville Cliffs flora is so restricted in distribution. The greatest threat to the Surville Cliffs flora is probably invasion by introduced taxa such as Hakea and Cortaderia (pampas grass), though eradication programmes are currently underway to try and reduce the risk from these invaders. Some members of the Surville Cliffs fauna, such as Hebe brevifolia, are present in large numbers and are probably not under immediate threat despite their highly restricted distribution. Others, such as Uncinia perplexa, appear to have always existed in very low numbers, and are seriously endangered.

REFERENCES

de Lange, P. J. 1997. Hebe brevifolia (Scrophulariaceae) - an ultramafic endemic of the Surville Cliffs, North Cape, New Zealand. New Zealand Journal of Botany 35: 1-8.

de Lange, P. J., & P. B. Heenan. 1997. Carex ophiolithica (Cyperaceae): a new ultramafic endemic from the Surville Cliffs, North Cape, New Zealand. New Zealand Journal of Botany 35: 429-436.

Heenan, P. B., & P. J. de Lange. 2001. A new, dodecaploid species of Uncinia (Cyperaceae) from ultramafic rocks, Surville Cliffs, Northland, New Zealand. New Zealand Journal of Botany 39: 373-380.

Whattam, S. A., J. G. Malpas, J. R. Ali, I. E. M. Smith & C.-H. Lo. 2004. Origin of the Northland Ophiolite, northern New Zealand: discussion of new data and reassessment of the model. New Zealand Journal of Geology and Geophysics 47: 383-389.

The Camel that Walked on Two Legs

Hooker, J. J. 2007. Bipedal browsing adaptations of the unusual Late Eocene–earliest Oligocene tylopod Anoplotherium (Artiodactyla, Mammalia). Zoological Journal of the Linnean Society 151 (3): 609-659.

Well, "camel" isn't technically correct. The animal in question, Anoplotherium, is a member of the Tylopoda, a clade of hoofed mammals whose only surviving members are the Camelidae (camels and llamas), but which was once more diverse.

The title of this paper certainly caught my eye when table of contents for the new issue of Zoological Journal of the Linnean Society arrived in my e-mail just now, and the article did not disappoint. Anoplotherium, which I was previously only vaguely aware of as a name to occassionally appear on lists of extinct artiodactyls, turns out to have been a rather interesting creature indeed. For a start, it was apparently one of the earliest fossil mammals to be described, losing out only to Palaeotherium (a distant relative of horses), Mammut (the mastodon), Megalonyx and Megatherium (both giant sloths). Since Cuvier named it in 1804, however, it garnered relatively little attention, largely because of the poor preservation and/or fragmentary nature of the material available. To add insult to injury, the most complete remains were embedded in a gypsum matrix that added to the difficulty of working with them.

The current paper was inspired by the discovery of a far more complete fossil skeleton in the Hamstead Member of the Bouldnor Formation on the Isle of Wight in England (though I wouldn't know how far that is from the old stomping grounds of Darren Naish). The story of the skeleton's discovery is worth the read in itself - pieces of the single individual were recovered by successive amateur palaeontologists over a period of 35 years, as the sea-side cliff it was embedded in eroded away and further pieces of it were exposed or, in some cases, fell out of the cliff.

Anoplotherium differs significantly from living artiodactyls (even-toed hoofed mammals) in a number of ways, some of which you can make out in the reconstruction above, taken from the paper. For a start, it has a longer and thicker tail than any living artiodactyl. Cuvier (mistakenly, as it turned out) compared the tail of Anoplotherium to an otter, leading him to later suggest that Anoplotherium might have been semi-aquatic. This idea was later expanded by Gervais, who suggested that it may have had webbed feet! Later authors, however, agreed that this reconstruction was functionally unlikely. The true significance of the tail, however, will be explained in due course.

The feet are particularly unusual - despite having the typical artiodactyl foot arrangement (with the midline of the foot running between the third and fourth digits, rather than down the third digit as in most mammals including humans), Anoplotherium had only three toes (digit V having been lost). Digit II is the smaller toe you can see above, and stuck out somewhat from the other toes. I should point out here that the new specimen belongs to the species Anoplotherium latipes - another species, A. commune, differed in having a much smaller digit II. However, this appears to be the only significant difference between the two species, and Hooker makes the suggestion that the two 'species' may be different sexes of a single species (the correct name for which would then be A. commune). He suggests that the form with the larger digit II might have been the male, and that the larger digit might have been used in inter-male conflict, allowing the front legs of opposing males to hook together when grappling, much like the tines of deer antlers. Unfortunately, Hooker isn't able to conclusively prove this interesting idea, and I think that a fair degree of skepticism is required for now.



And if all this wasn't enough, there's the matter of the spine and hips. Among other features, Anoplotherium has very widely flared ilia (the plate-like side parts of the pelvis) and a vertebral column seemingly adapted for bearing weight towards the posterior end. It appears that Anoplotherium was quite able to carry itself as a biped! Most likely, it would have only maintained a bipedal stance (as shown in the reconstruction to the left, again from the paper) when feeding or, possibly, fighting. Normal movement would have still been conducted quadrupedally. The unique tail would have provided balancing support, giving Anoplotherium a tripod stance. Admittedly, Anoplotherium differs in this respect from other bipedal browsers, many of which, such as gorillas and chalicotheres, have either a very small tail or none at all. As Hooker explains, this probably represents phylogenetic constraints - most of these other browsers derived from clades in which the tail had already been reduced to the point of insignificance, requiring the development of alternative methods of balance. Other bipedal browsers also developed grasping forelimbs that may have allowed for an extra degree of support - an option that would not really have been available to the hoofed ancestors of Anoplotherium.



If the idea of a bipedal artiodactyl seems unbelievable to you, Anoplotherium is not the only one. The living gerenuk (Litocranius walleri) stands bipedally when feeding (as shown in the photo above from Images of Anthropology), and is even able to take a few tottering steps in this position. The gerenuk has even less features showing its bipedality than Anoplotherium does - Hooker's comment is that "It remains difficult to understand... how Litocranius can function as a bipedal browser with such minimal adaptations... relatively small body size may be a facilitating factor."

Taxon of the Week: Give Us a Kiss!

The fish genus Lethrinus is found in tropical waters of the Indian and western Pacific Oceans, with a single species making an incursion into the eastern Atlantic. The group is commonly known as emperors, though I have heard people here in Australia refer to them as snappers, a confusing piece of terminology for me because they are quite different fish from the one I knew in New Zealand as snapper*. The prominent lips in Lethrinus adults, often a different colour from the surrounding face, have given at least one species the memorable name of "sweetlips" (image above of Lethrinus harak, from Wikimedia). Carpenter & Allen (1989) listed 26 described species and two unnamed species in the genus. One of these undescribed species was named Lethrinus ravus by Carpenter & Randall (2003) (image below of Lethrinus nebulosus from here).



*If you excuse me, I'm just going to have a little rant about the common names of Southern Hemisphere fishes. As with other animals and plants, British settlers in New Zealand and Australia labelled the fish they found in their new country with the names of fish they had been familiar with back in the Old Country. However, when it came to fish the new immigrants seem to have gone to extraordinary lengths to find Northern Hemisphere analogues, with the result that it becomes difficult to see how they ever found a connection. The New Zealand grayling (now unfortunately extinct) was no relation to the Northern Hemisphere grayling. The New Zealand cod is even less like the original. And as I've already indicated, the confusion surrounding the name "snapper" is beyond anyone's ability to sort out. Rant over - please resume normal service.

Emperors are all predators, but are divisible into three ecological groups (Lo Galbo et al., 2002) - low-bodied stalkers with conical teeth that are active hunters of high-speed invertebrates and small fish, high-bodied benthic feeders with molariform teeth that can feed on shellfish and other hard-shelled invertebrates, and high-bodied species with conical teeth that feed on softer-bodied slow-moving invertebrates. The molecular phylogeny of Lo Galdo et al. (2002) recovered a good correlation between trophic type and phylogeny. The high-bodied conical-tooth form appears to be ancestral, with one species (Lethrinus minatus) sister to all the other species, and one species each low down in the two major clades that the other species fell into. Low body-form and molariform teeth both appeared twice, in each case with one clade containing most of the species showing the novel feature, and a single species appearing to have developed it independently.

Of course, what discussion of tropical reef fishes would be complete without a mention of transexuality? Many species of Lethrinus have been shown to be protogynous hermaphrodites - that is, they reach maturity as females before changing sex at a later date to males (Young & Martin, 1982). The mechanism inducing this change in emperors remains unknown. In other protogynous reef fish species, males may maintain harems of females, the largest of which switches sex if the male is removed for whatever reason, but whether emperors have a similar system has not yet been established.

REFERENCES

Carpenter, K. E., & G. R. Allen. 1989. FAO Species Catalogue vol. 9. Emperor Fishes and Large-eye Breams of the World (Family Lethrinidae): An annotated and illustrated catalogue of lethrinid species known to date. Food and Agriculture Organization of the United Nations.

Carpenter, K. E., & J. E. Randall. 2003. Lethrinus ravus, a new species of emperor fish (Perciformes: Lethrinidae) from the western Pacific and eastern Indian oceans. Zootaxa 240: 1-8.

Lo Galbo, A. M., K. E. Carpenter & D. L. Reed. 2002. Evolution of trophic types in emperor fishes (Lethrinus, Lethrinidae, Percoidei) based on cytochrome b gene sequence variation. Journal of Molecular Evolution 54 (6): 754-762.

Young, P. C., & R. B. Martin. 1982. Evidence for protogynous hermaphroditism in some lethrinid fishes. Journal of Fish Biology 21 (4): 475-484.

The Boneyard # 9

For whatever reason, it seems to have been a quiet fortnight in the world of palaeontological blogging, but The Boneyard is sworn not to disappoint. Welcome to the ninth installment of this auspicious carnival!

And what better way to start than with some philosophical musings? Make No Bones has some interesting observations about palaeontology compared to other branches of biology.

I had something this fortnight, but I wasn't even sure if it was a fossil. See if you can work out the mystery object's identity!

Sometimes fossils can tell us more than just their subject's identity. Archaeozoology describes the recognition of bone disease in fossils.

The Hairy Museum of Natural History brings us the spectacular resting traces of a trio of temnospondyls, Palaeozoic amphibian-like animals, and suggests we might be looking at some of the world's oldest pornography. He also treats us to more reconstructions of the crocodile-like phytosaurs.

Microecos brings us a light-hearted look at man as seen by Ichthyosaurus.

Laelaps also gives us behaviour preserved in trace fossils, reporting on the recent discovery of dromaeosaur tracks confirming the two-toed stance most researchers have suspected.



Meanwhile, When Pigs Fly Returns reports on research showing birds may have been a bit slower taking to the trees than previously assumed.

The Dragon's Tales has a double whammy on the subject of mass extinctions - the differences between the end-Permian and end-Cretaceous extinctions, and the various causes of mass extinctions.

Finally, John Hawks tells us that people may have been mining for almost as long as there has been people to mine.

Next fortnight's Boneyard will be hosted by Amanda at Self-designed Student, and you are all ordered to write something for it! Get cracking!

Credits: Image of lunging temnospondyl from Palaeos. Confuciusornis from Answers.com. "The Sorcercer" from Cosmologies