Lace Web Weavers

Male of the Madagascan Ambohima sublima, with enlarged inset of the clasping apparatus of metatarsus I, from Griswold et al. (2012).

The Phyxelididae, the lace web weavers, are one of the families of spiders to have appeared on the scene in recent years as a result of the collapse of the 'amaurobioids'. They are a family of smallish spiders found mostly in eastern Africa (including Madagascar). A single species, Phyxelida anatolica, is found in Cyprus and southeast Turkey, and the genus Vytfutia includes two species found in Sumatra and Borneo. Distinguishing features of the family include a series of thickened setae on the inner side of the pedipalp femur in both sexes. These are expected to function as a stridulatory apparatus; this has not yet been robustly confirmed, though individuals have been observed making jerking movements of the palp prior to copulation that may suggest stridulation (Griswold et al. 2012). Another significant feature is the presence in most species of modified first (and sometimes second) metatarsi in the males, used for grasping the female during mating (Griswold et al. 2012). In Vytfutia and members of the tribe Phyxelidini, a large articulate spur atop an apophysis on the metatarsus sits against a spinose depression. In the tribe Videoleini, there is no spur but there may still be a spinose apophysis (Griswold 1990).

Web of Ambohima sublima photographed by Joel Ledford, from Griswold et al. (2012).

Phyxelididae produce tangled or sheet webs from cribellate silk, which they generally place in secluded locations such as under rocks or logs (a few tropical African species are found in caves). For the most part, the family exhibits what is known as an 'afromontane' distribution: though found in most altitudes in the southernmost part of Africa, tropical African members of the family are restricted to alpine localities or caves. The southeast Asian Vytfutia, placed by Griswold (1990) as the sister taxon to the other phyxelidids, differs in being found in a lower altitude in primary rainforest. A molecular analysis by Griswold et al. (2012) agreed with the morphological analysis of Griswold (1990) in separating Vytfutia from the rest of the Phyxelididae (the molecular analysis also failed to confirm monophyly of Phyxelididae including Vytfutia, but its coverage was perhaps not adequate to make this a reliable result). However, rather than dividing the African phyxelidids between the Vidoleini and Phyxelidini, Griswold et al.'s (2012) analysis placed the Vidoleini as a monophyletic subgroup of a paraphyletic Phyxelidini. Nevertheless, this would strengthen Griswold's (1990) earlier inference that the modified metatarsus I was part of the ancestral morphology of the Phyxelididae, and its absence in certain Vidoleini a secondary loss.

South African phyxelidid photographed by Alan. Though identified as a possible Vidole species, the morphology of metatarsi I indicates a member of the Phyxelidini.

REFERENCES

Griswold, C. E. 1990. A revision and phylogenetic analysis of the spider subfamily Phyxelidinae (Araneae, Amaurobiidae). Bulletin of the American Museum of Natural History 196: 1-206.

Griswold, C. E., H. M. Wood & A. D. Carmichael. 2012. The lace web spiders (Araneae, Phyxelididae) of Madagascar: phylogeny, biogeography and taxonomy. Zoological Journal of the Linnean Society 164: 728-810.

Happy Birthday to Me

On the 27th of May 2007, I made my very first post on Catalogue of Organisms. It wasn't very good. But I persevered, and that mediocrity has become a proud tradition. CoO is five years old today!

I'll admit, it hasn't always been easy. There have been times when I wondered if anyone ever did read this bollocks, or if I was just muttering into the digital void. According to the trackers, this site gets a bit over 200 visitors a day. True, that's a mere droplet compared to what some sites get, but then I think about it: two hundred people a day at least look at what I've written. That's a lot more than I could easily cater for, even if I was just making muffins. Sure, a fair proportion of those people probably came here as a result of a Google search for "amazing pictures of women's organisms", and won't necessarily hang around for long*, but still...

*That said, I recently noticed that I was getting regular visitors from a particular site, and when I clicked on the tracker link I discovered that I had been added to the blogroll of a collection of gay erotica. So perhaps at least someone had decided that what they'd accidentally found was of interest!

So a big thank you has to go out to the commenters on this site: your responses are the best thing about this place. Whether you're a regular like Pat, Mickey Mortimer, Mike Huben, Andreas Johansson, Kai Burington, the Watcher, Neil, Mike Keesey, Laurence Moran, Dartian, Sebastian Marquez, and many others, or whether you're a lurker, thank you for being here! (And if you've never commented before, feel free to say hello!) And a special thank you to someone who's never actually commented, but who I know reads this site sometimes: my partner Christopher, seen below in a rare photograph taken at al-Ajloun in Jordan.

On another leg of that same trip, two of the contacts that had derived from this site offered their gracious hospitality. Thank you to Mo Hassan who played the part of tour guide in the British Museum of Natural History. We talked about elephant tooth replacement, how Richard Owen deserved a bit more respect, and how the BMNH's Raphus are actually fakes made from geese (which is how they're able to have a specimen on display of a non-existent animal). Thank you also to Darren Naish and his wife Toni, who had us around for tea, where we talked about slater spiders, organising references, and a certain prominent palaeo-artist's then-recent comments on the concept of copyright.

And because, as long-term readers of this site may have noticed, I am never able to end a post appropriately, I will simply finish by saying again: thanks for reading, and hope to see you again!

The Mushroom Tree

The familiar field mushroom Agaricus arvensis, photographed by Fred Stevens.

Autumn being the height of mushroom season, it is appropriate that mushrooms should be my subject today. Recent years have seen great advances in our understanding of fungal evoluton: you could almost say our knowledge has mushroomed.

The great majority of the macroscopic fungi that most people would be familiar with belong to the clade of dikaryotic fungi, so called for their production of dikaryotic (double-nucleate) hyphae. When these fungi reproduce, separate hyphae fuse to form a hypha containing nuclei from both parents, like a sperm fusing to an egg in human fertilisation. However, unlike a sperm and an egg, the parent nuclei do not immediately fuse. Instead, the resulting dikaryotic hypha grows and divides, and the nuclei divide within it while remaining separate from each other. It is the dikaryotic hyphae that produce the fruiting bodies of the fungus, so when you look at a mushroom you are not looking at the product of a single individual but of two conjoined individuals working in concert. Fusion of the nuclei for sexual reproduction will only take place when the actual spores are produced.

View of a basidium (left) and ascus (right), from here.

Within the dikaryotic fungi there are two main lineages, the ascomycetes and the basidiomycetes. The two are distinguished by how their spores are produced, as shown in the photos above: in ascomycetes, groups of spores are produced within a sac called an ascus, while in basidiomycetes they are produced on top of a 'pedestal' called a basidium. Ascomycetes are by far the more diverse of the two lineages, but basidiomycetes (such as mushrooms) probably include more familiar members because less ascomycetes produce large visible fruiting bodies (examples of well-known ascomycetes include morels, truffles and most lichens). Within the basidiomycetes, most macroscopic forms belong to a group called the Agaricomycotina or hymenomycetes. The other basidiomycete lineages include parasitic forms such as rusts and smuts, and a wide range of yeasts.

Chantarelles Cantharellus cibarius, photographed by Strobilomyces. Chantarelles differ from mushrooms in lacking true gills; instead, they have 'false gills' formed from folds of the reproductive membranes that are not divided from the main fruiting body.

These distinctions were recognised some time ago, but recent years have seen a shake-up within the Agaricomycotina. Earlier authors divided this group between the heterobasidiomycetes, in which the basidia are divided by internal septa, and the homobasidiomycetes, in which the basidia are not divided. Mushrooms belong to the homobasidiomycetes; heterobasidiomycetes are a bit more obscure, but representatives include 'jelly fungi' with gelatinous fruiting bodies, such as the edible wood-ear fungus Auricularia auricula-judae. Phylogenetic studies have confirmed, however, that the heterobasidiomycetes are paraphyletic with regard to the homobasidiomycetes (Hibbett 2006). What was perhaps more surprising, though, is that the homobasidiomycetes appear to be polyphyletic: one basal clade, the Cantharellales (including the chanterelles and hedgehog fungi), includes both 'heterobasidiomycetes' and 'homobasidiomycetes', and is phylogenetically distinct from the clade including the remaining 'homobasidiomycetes'. As a result, recent authors have mostly not recognised homobasidiomycetes as a formal taxon, but instead referred to the clade of Agaricomycetes including homobasidiomycetes and a few closely related heterobasidiomycetous taxa.

The flower fungus Aseroe rubra, photographed by Hugh Smith.

As well as familiar gilled mushrooms, Agaricomycetes include such diverse forms as puffballs, stinkhorns, bracket fungi, earthstars, boletes,... Some of the more unusual forms even include false truffles, or marine taxa producing underwater fruiting bodies (Hibbett 2007). Molecular phylogenetic studies have recognised a dozen or more major lineages within the Agaricomycetes, some of which were unexpected. Many of the latter include lineages dominated by so-called resupinate forms that do not form well-developed fruiting bodies but instead generally form an undifferentiated crust; molecular studies have revealed a previously unsuspected diversity among such morphologically simple taxa. Phylogenetic studies have also confirmed the polyphyletic origins of the so-called 'gasteromycetes', forms such as puffballs in which spores are produced internally within the fruiting body and only released when the tissues of the fruiting body break down. Other results, however, have corroborated morphological expectations: one prominent example being the Russulales, a lineage whose members produce fruiting bodies varying from mushroom-like to truffle-like, but united by the production of latex within the fruiting bodies giving them a distinct chalky texture.

Giant puffball Calvatia gigantea, from here.

REFERENCES

Hibbett, D. S. 2006. A phylogenetic overview of the Agaricomycotina. Mycologia 98 (6): 917-925.

Hibbett, D. S. 2007. After the gold rush, or before the flood? Evolutionary morphology of mushroom-forming fungi (Agaricomycetes) in the early 21st century. Mycological Research 111: 1001-1018.

Prickly Pears

Indian-fig prickly pear Opuntia ficus-indica in fruit, photographed by Luigi Rignanese.

A couple of months ago, I engaged in something of an experiment. One of the houses alongside the park where we exercise The Great Beast That is Called Dragon has a prickly pear tree overhanging its fence and, having a vague understanding that they are supposed to be edible, I picked a ripe fruit as I walked past. Very carefully, of course, in order to avoid touching the spines (not entirely successfully, unfortunately). When I got home I cut it open and tried it. The verdict: not unpleasant, not dissimilar to pawpaw but without the somewhat vomity overtones that I've found pawpaw tends to have. The fruit wasn't hugely sweet, contrary to what I've heard, but that can probably be explained by the tree I'd picked it off not being a variety directly selected for eating. Christopher also tried some and suggested that they might work well as a base for muffins, so a few days later I went down to the park with a bag and filled it with fruit. The resulting muffins (made using a generic fruit muffin recipe from good old Alison Holst) were, again, not unpleasant but fairly bland: the overall taste in this case resembled cornbread. More problematic were the numerous seeds, which the baking process turned into unbreakable pieces of buckshot with an unfortunate tendency to stick in the crown of one's teeth. So, not an unsuccesful experiment overall, but not something that gave me a surefire winner for the next pot luck.

Arborescent prickly pears Opuntia megasperma from Santa Fe in the Galapagos Islands, photographed by Arthur Morris.

So what are prickly pears, anyway? Prickly pears and their close relatives form a clade within the cacti known as the Opuntioideae, distinguished by the possession of small, fine, easily detached spines known as glochids (Griffith & Porter 2009). It was these that had parts of my hand itching like mad after picking my first fruit despite my best efforts to avoid being spiked (for the second batch, I had the sense to take a pair of garden gloves). Despite this armament, prickly pears are deliberately grown in some areas for their fruit, with the glochids being removed by processes such as washing the fruit in sand. The broad flat pads of the stem may also be peeled and used as a vegetable, and they have been used in the southwest United States as feed for livestock during droughts with the spines being burnt off beforehand by the application of a propane torch, referred to as a 'pear burner' (Russell & Felker 1987). Prickly pears are also the host of the commercially significant cochineal insect Dactylopius coccus, discussed in a previous post.

Prickly pear pads with woven nests hung on them for the collection of cochineal bugs, photographed by Oscar Carrizosa.

Generic divisions within the Opuntioideae have been shuffled around over the years, with some authors placing the majority of species in a broad Opuntia. Alternatively, Opuntia may be restricted to species with broad flattened stem segments (cladodes), with cylindrical-stemmed species separated into genera such as Cylindropuntia (the chollas). A molecular analysis of relationships within the Opuntioideae by Griffith & Porter (2009) supported the monophyly of the flat-stemmed opuntioids, though Opuntia in the strictest sense could not be resolved as monophyletic relative to two segregate genera, Nopalea and Consolea, each distinguished by derived flower morphologies*. Even in the strict sense, Opuntia is a genus of a couple of hundred species, though issues such as morphological plasticity and rampant hybridisation make the exact number of species debatable.

*Leading to the statement, "if strict monophyletic generic classification is desired, Consolea and Nopalea may be sunk into a slightly wider Opuntia" (Griffith & Porter 2009). Once again, as with the Anolis vs Norops situation I referred to last week, we have the recognition of a 'genus' determined not by questions of their own established monophyly, but by their relationship to another less clearly established 'genus'.

The invasive Opuntia stricta growing on cliffs at Watsons Bay in Sydney, Australia, photographed by Tony Rodd.

The prickly pear genus Opuntia is native to drier parts of the Americas, but various species have become naturalised in other parts of the world such as Australia and the Mediterranean (one of the main commercially grown species, Opuntia ficus-indica, received its generic name meaning 'Indian fig' from its Mediterranean connection). Though mostly native to hot dry climates, species of prickly pear are found growing as far north as Alberta, and one species has even become established in the mountains of Switzerland (Russell & Felker 1987). The history of prickly pears as an invasive weed in Australia and their subsequent suppression by the moth Cactoblastis cactorum has been widely cited as one of the world's most successful cases of biological pest control. Two famous photos of Opuntia stricta growing at the Alan Fletcher Research Station in Queensland demonstrate just how successful this was. This was the station before the introduction of Cactoblastis:

This was after:

Of course, when it comes to biological control, context is everything. Though hailed as a saviour in Australia, the spread of Cactoblastis in the southern United States has been the subject of some concern, as it threatens endangered native Opuntia species.

REFERENCES

Griffith, M. P., & J. M. Porter. 2009. Phylogeny of Opuntioideae (Cactaceae). International Journal of Plant Sciences 170 (1): 107-116.

Russell, C. E., & P. Felker. 1987. The prickly-pears (Opuntia spp., Cactaceae): a source of human and animal food in semiarid regions. Economic Botany 41 (3): 433-445.

Anole, Anole, Anole, Anole

Brown anole Anolis sagrei, a species that has become widely distributed in the Caribbean and also in Florida, photographed by Ianaré Sévi.

Today, the watchword is Anolis. Anolis, the anoles, is an enormous assemblage of lizards found in warmer parts of the Americas: with well over 350 species, it is the largest genus generally recognised among the amniotes. Species within the genus have received a lot of attention for their ecological diversity. In some parts of Cuba, there may be fourteen or fifteen Anolis species found in a single locality, each occupying their own distinct niche (Thomas et al. 2009). Examples of anole ecotypes include crown-giants, up to and above half a metre in length, that live in the forest canopy; slender, short-legged twig anoles, that creep along narrow branches; and also slender, but much longer-legged, grass-bush anoles that are found in dense undergrowth (Losos 2009).

The Gorgona Island anole Anolis gorgonae, photographed by Luke Mahler.

Some species of anole have even been the subjects of direct experimental studies on evolutionary processes. Hind limb length in different anole species has been observed to correlate with substrate usage: those species that prefer wider branches have longer hind legs than those utilising smaller branches. In order to test whether natural selection played a direct part in determing leg length, the brown anole Anolis sagrei was introduced in 1977 and 1981 to fourteen small islands, of varying vegetation type, in the Bahamas that had been previously uninhabited by anoles. After ten years had passed, measurements were taken of anoles on each of the islands where they had persisted and compared back to the source population. It was demonstrated that (a) many of the experimental populations were statistically significantly different from the source population after ten years, and (b) the degree of difference between populations was correlated with the degree of difference in the vegetation oof the two localities (Losos et al. 1997). However, later studies of brown anoles in the laboratory reared in cages with different-sized available substrates indicates that leg length in anoles is, to some extent, phenotypically plastic depending on environmental pressures (Losos et al. 2000). Nevertheless, a selective component to variation was supported by experiments involving translocation between montane and lowland habitats of the Dominican anole Anolis oculatus (Thorpe et al. 2005).

The Hispaniolan hopping anole Anolis barbouri, a species long included in a separate genus Chamaelinorops, photographed by Rob Op 't Veld.

Being such a huge genus, it is not surprising that attempts have been made to break Anolis down to more manageable units, with varying success. Hillis (1996, as quoted in Poe 2004) described anoles as "a huge group where all the species look virtually the same": a quite unfair aspersion (see above) but nevertheless expressive of the difficulties in establishing relationships between species (ecological convergence, for instance, is rampant). Anoles have been divided into two major subgroups, the Alpha and Beta anoles, on the basis of the presence (Beta) or (Absence) of transverse processes on the caudal vertebrae, and some authors have proposed recognising the Beta anoles as a separate genus Norops. Recent phylogenetic analyses have agreed that the Beta anoles are monophyletic, but nested deeply in the Alpha anoles (Poe 2004; Nicholson et al. 2005). Because of difficulties in defining usual subgroups among the Alpha anoles, recent authors have therefore continued to maintain a super-sized Anolis*.

*Which just highlights again how the binomial system can force false dichotomies. The nested position of 'Norops' within 'Anolis' means that one must either (a) subdivide Anolis, perhaps impractically, (b) sink Norops and obscure that group's distinctiveness, or (c) recognise a paraphyletic Anolis, obscuring the closer relationships between some Anolis and Norops species. Three suboptimal choices, but you must pick one because you can't have species without genera. Surely it would be better overall if one could just sidestep the question by recognising a clade Norops within a clade Anolis?

The Cuban false chamaeleon Anolis chamaeleonides, another species previously in a separate genus (Chamaeleolis), photographed by Lubomir Hlasek.

Also of interest are the biogeographic patterns within Anolis that phylogenetic analysis has revealed. Both the Alpha and Beta anoles have species on the Caribbean islands as well as continental South America (a little less than half the currently recognised Anolis species are found on Caribbean islands). The South American Alpha anoles form a clade (sometimes recognised as a separate genus Dactyloa) that, together with the Anolis roquet group of species found in the southern Lesser Antilles, forms the sister group of most or all of the remaining Anolis species (Poe 2004; Nicholson et al. 2005). Most lineages within the remaining anoles are Caribbean; the South American Beta anoles also form a single clade whose nested position among Caribbean taxa indicates a relatively rare demonstrable case of dispersal from an island to a continent (as opposed to the other way around, the more usual expectation in biogeography). Most of the Greater Antillean islands are home to multiple lineages of anoles; the exception is Jamaica which, except for the recently arrived Anolis sagrei, is inhabited by a single clade of Beta anoles (the sister group to the South American Beta anoles). The Carolina anole Anolis carolinensis of the southeast United States is also of Caribbean origin, being nested among a clade of Cuban species. It is worth noting that this last continental colonisation is, in a way, currently repeating itself: though probably brought by human agents, a number of Caribbean anole species are now known in the wild from Florida.

REFERENCES

Losos, J. B. 2009. Lizards in an Evolutionary Tree: Ecology and adaptive radiation of anoles. University of California Press.

Losos, J. B., D. A. Creer, D. Glossip, R. Goellner, A. Hampton, G. Roberts, N. Haskell, P. Taylor & J. Ettling. 2000. Evolutionary implications of phenotypic plasticity in the hindlimb of the lizard Anolis sagrei. Evolution 54 (1): 301-305.

Losos, J. B., K. I. Warheit & T. W. Schoener. 1997. Adaptive differentiation following experimental island colonisation in Anolis lizards. Nature 387: 70-73.

Nicholson, K. E., R. E. Glor, J. J. Kolbe, A. Larson, S. B. Hedges & J. B. Losos. 2005. Mainland colonization by island lizards. Journal of Biogeography 32: 929-938.

Poe, S. 2004. Phylogeny of anoles. Herpetological Monographs 18: 37-89.

Thomas, G. H., S. Meiri & A. B. Phillimore. 2009. Body size diversification in Anolis: novel environment and island effects. Evolution 63 (8): 2017-2030.

Thorpe, R. S., J. T. Reardon & A. Malhotra. 2005. Common garden and natural selection experiments support ecotypic differentiation in the Dominican anole (Anolis oculatus). American Naturalist 165 (4): 495-504.