Arrow Poison and Arrow without Poison

Central and South America are home to a remarkable diversity of frogs, coming in nearly all the shapes and sizes a frog can possibly come in. Among this diversity, probably the most famous representatives are the arrow-poison frogs of the Dendrobatidae.

Two dendrobatid frogs of two different subfamilies: dyeing dart frog Dendrobates tinctorius (Dendrobatinae, left) and phantasmal poison frog Epipedobates tricolor (Colostethinae, right), copyright H. Krisp. Offhand, has someone been playing silly buggers with dendrobatid species names? Dendrobates auratus is green and black, not gold, and I'm sure I only see two colours on that E. tricolor.

The Dendrobatidae are themselves a diverse family, with somewhere in the area of two hundred currently recognised species. Many of these have only recently been recognised: nearly half of the currently known species have been named since 1985 (Grant et al. 2006). There are also ninety or so species in the closely related family Aromobatidae that were historically treated as dendrobatids and still may be in some sources. The Dendrobatidae are currently divided between three subfamilies: about half the species belong to the subfamily Dendrobatinae, a bit less than a quarter to the Colostethinae, and close to sixty species are placed in the genus Hyloxalus that forms its own subfamily (Grant et al. 2006).

Panama rocket frog Colostethus panamensis, copyright Brian Gratwicke.

Members of the Dendrobatidae are best known, of course, for their remarkable toxicity, associated with bright, striking warning colours. The name 'arrow-poison frog' reflects this trait as an arrow scraped across a frog's skin would pick up some of the frog's own lethality. The toxin, comprising various alkaloids, is not produced directly by the frog itself but is instead acquired through its arthropod diet. Most of the alkaloids sequestered by arrow-poison frogs come from ants (Darst et al. 2005) but other potential sources include beetles, millipedes and oribatid mites. However, not all dendrobatids are toxic and colourful. In fact, these features are largely characteristic of the Dendrobatinae only. Members of the Colostethinae and Hyloxalus are mostly cryptic in coloration and largely do not sequester alkaloids. The distinction is not an unshakeable rule: some non-dendrobatine dendrobatids are quite colourful in their own right and a handful of colostethines (members of the genus Epipedobates) are toxic, having seemingly evolved the ability to secrete alkaloids independently of the dendrobatines. Laboratory studies indicate that at least some non-toxic colostethines are able to consume alkaloid-bearing prey without ill effects, suggesting that alkaloid resistance is ancestral for the family as a whole.

Male Hyloxalus nexipus carrying tadpoles, copyright Santiago Ron.

More characteristic of dendrobatids as a whole is their breeding behaviour. As a rule, dendrobatids are more or less terrestrial, not habitually living in water, though many species are found alongside the margins of water bodies and may dive into the water to escape danger. Others will be found among leaf litter or be completely arboreal. Eggs are laid in damp terrestrial locations such as under leaves; males may deposit their sperm before or after the female deposits her eggs. Hatching tadpoles are then carried on the back of one of the parents to a suitable body of water such as a pool or stream. In members of the Dendrobatinae, tadpoles are deposited in phytotelmata, water-filled hollows in vegetation (such as in the cenre of bromeliads or holes in trees). Adelphobates castaneoticus, found in Pará in Brazil, has a habit of using the fallen husks of Brazil nuts. In some species, tadpoles are transferred one at a time; in others, groups of tadpoles will be carried en masse. In most genera, the male parent is the primary or sole transporter of tadpoles. Females of some species may also carry tadpoles; in others, a female finding an unattended cache of eggs will simply eat them. In the dendrobatine genus Oophaga, tadpole transport is the sole responsibility of the female. Following deposition, developing tadpoles of many species live on a diet of detritus. Others, particularly among the phytotelm-inhabiting species, are carnivorous, feeding on insects and other aquatic vertebrates, or even on their own siblings. In the aforementioned Oophaga, the transporting female will also lay a deposit of unfertilised eggs at the same time as she drops off the tadpoles. As well as providing food for the developing larvae, these eggs may also carry a shot of alkaloids to provide a head start in developing their defenses.

Strawberry poison-dart frogs Oophaga pumilio, two different colour morphs, copyright Pavel Kirillov.

Despite their often bright colours, many dendrobatids are poorly known due to cryptic habits and many species are only found in restricted ranges. As well as the usual threats to their survival from habitat destruction and the like, many dendrobatid species are threatened by collection for the pet trade. Their bright colours make dendrobatids popular specimens and captive individuals lose their toxicity if not provided with the prey from which alkaloids are derived. Unfortunately, about a quarter of dendrobatid species are currently recognised as endangered, many severely so. The highest diversity of endangered species is in the northern Andean region, in Venezuela, Colombia and Peru, which is also the centre of diversity for the family as a whole (Guillory et al. 2019). Urgent action may be required if we are to preserve these tiny, shiny, toxic beauties.

REFERENCES

Darst, C. R., P. A. Menéndez-Guerrero, L. A. Coloma & D. C. Cannatella. 2005. Evolution of dietary specialization and chemical defense in poison frogs (Dendrobatidae): a comparative analysis. American Naturalist 165 (1): 56–69.

Grant, T., D. R. Frost, J. P. Caldwell, R. Gagliardo, C. F. B. Haddad, P. J. R. Kok, D. B. Means, B. P. Noonan, W. E. Schargel & W. C. Wheeler. 2006. Phylogenetic systematics of dart-poison frogs and their relatives (Amphibia: Athesphatanura: Dendrobatidae). Bulletin of the American Museum of Natural History 299: 1-262.

Guillory, W. X., M. R. Muell, K. Summers & J. L. Brown. 2019. Phylogenomic reconstruction of the Neotropical poison frogs (Dendrobatidae) and their conservation. Diversity 11: 126.

Monkey Frogs

Following my last post, it looks like we're staying in the Neotropics for a while longer. The leaf frogs or monkey frogs of the Phyllomedusinae (a subfamily of the tree frog family Hylidae) are perhaps the most famous group of frogs to be found in South America. One particular species, the red-eyed tree frog Agalychnis callidryas, would for many people be the first image that comes to mind when they picture a frog, owing to its regular appearance in popular media.

The aforementioned red-eyed tree frog Agalychnis callidryas, copyright Carey James Balboa.

The phyllomedusines are a group of about sixty species of slender, arboreal frogs that live as ambush predators of invertebrates. The inner digits of the hands and feet are opposable and can be used to grasp slender twigs while adhesive pads at the ends of the digits allow the frog to grip onto flat surfaces such as leaves. Darren Naish at Tetrapod Zoology (Wayback Machine version; the current iteration of Tetrapod Zoology is at tetzoo.com) has described leaf frogs as superficially resembling "slow-climbing primates like lorises". Phyllomedusines will perch with all four hands and feet firmly grasping the substrate, waiting for suitable prey to inadvertently stray too close. Prey is captured by means of a highly protrusible tongue, not found in other hylids. In at least some species, light markings are present on the outer toes which may be drummed while in ambush to attract prey. Bertoluci (2002) suggested that the movement of these light patches in Phyllomedusa burmeisteri may resemble those of a worm or caterpillar but I would suggest that merely the appearance of the small moving points alone may pique a wandering arthropod's interest while the camouflaged remainder of the frog blends into the background.

Orange-legged tree frog Phyllomedusa oreades, copyright Danielvelhobio.

Though phyllomedusines begin their lives as aquatic tadpoles, their eggs are laid in clutches outside the water, in locations such as on leaves, tree trunks, rock crevices, etc. In some species, one or more leaves are folded together to construct a nest in which the eggs are laid. Some phyllomedusines in the genera Agalychnis and Cruziohyla are capable of gliding by means of extensive webbing on enlarged hands and feet and/or skin flaps on arms and legs. Interestingly, possession of gliding ability in phyllomedusines is correlated with explosive breeding patterns, suggesting that its main function is to facilitate synchronised movement of members of a population between their usual upper canopy habitat and suitable breeding locations near ground-level water bodies (Faivovich et al. 2009). Females of the two gliding genera (or sometimes a mating pair) may also spend time sitting in water prior to egg-laying; during this time, the female draws water into her bladder that she will then release over the eggs while laying them. In the majority of phyllomedusines (except Agalychnis) egg masses contain a mixture of eggs and empty, eggless capsules. In those species that construct nests from folded leaves, these extra capsules act as the glue holding the leaf surfaces together. Their function in other species is less obvious; they may help to protect the egg mass from drying out.

Upon hatching, the tadpoles will wriggle out of the egg mass to drop into a nearby body of water, whether a pond, a stream, or a pool of water collected in the hollow of a tree. After a childhood spent scraping algae for food, they will eventually transform into a new generation of frogs, ready to ascend once again into the trees above.

REFERENCES

Bertoluci, J. 2002. Pedal luring in the leaf-frog Phyllomedusa burmeisteri (Anura, Hylidae, Phyllomedusinae). Phyllomedusa 1 (2): 93–95.

Faivovich, J., C. F. B. Haddad, D. Baêta, K.-H. Jungfer, G. F. R. Álvares, R. A. Brandão, C. Sheil, L. S. Barrientos, C. L. Barrio-Amorós, C. A. G. Cruz & W. C. Wheeler. 2010. The phylogenetic relationships of the charismatic poster frogs, Phyllomedusinae (Anura, Hylidae). Cladistics 26: 227–261.

Hydromantes: Salamanders in Different Places

There are times when biogeography is able to throw us some real puzzlers: organisms whose distribution seems to defy expectations. Among these mysteries, special mention must be made of the salamanders of the genus Hydromantes.

Gene's cave salamanders Hydromantes genei courting, copyright Salvatore Spano.

Hydromantes is a genus containing a dozen species from among the lungless salamanders of the family Plethodontidae. Plethodontids are the most diverse of the generally recognised families of salamanders, with over 450 known species found mostly in Central and South America. Hydromantes, however, is a geographically isolated genus in this family with its species found in two widely separated regions: California in western North America, and mainland Italy and Sardinia in Europe. Though some authors have advocated treating the species found on each continent as separate genera, both morphological and molecular studies have left little doubt that the group represents a discrete clade.

Distinctive features of Hydromantes compared to other plethodontids include feet with five, partially webbed toes and a weakly ossified, flattened skull (Wake 2013). Members of this genus capture prey with a projectile tongue which is the most extensive of any amphibian, extending up to 80% of the animal's total body length (Deban & Dicke 2004). There are some differences between North American and European species notable enough for the recognition of separate subgenera (there is something of a gigantic clusterfuck surrounding the names of said subgenera but the details are far too tedious to relate here). The three North American species of the subgenus Hydromantes have bluntly tipped tails that they use as a 'fifth leg' when navigating smooth and/or slippery surfaces, whereas the European species have unremarkable pointed tails. Historically, the North American Hydromantes species have been poorly known, being isolated to restricted ranges. Hydromantes shastae is found in limestone around Lake Shasta whereas H. brunus is found in a small area of mossy talus habitat along the Merced River in the foothills of the Sierra Nevada (Rovito 2010). The third species, H. platycephalus, is found at higher altitudes in the Sierra Nevada, well over 1000 m above sea level. Individuals found living on steep slopes are known to escape predators by tightly coiling their bodies and simply rolling down the slope (García-París & Deban 1995). A molecular analysis of H. platycephalus and H. brunus by Rovito (2010) identified the former species as derived from within the latter, and Rovito suggested that H. brunus may have originated in a remnant population from when H. platycephalus moved into lower altitudes during the Ice Age.

Mt Lyell salamander Hydromantes platycephalus, copyright Gary Nafis.

The seven or eight European species are mostly placed in the subgenus Speleomantes; a single species, Hydromantes genei, is divergent enough to be placed in its own subgenus Atylodes (though most recent studies have indicated that the European Hydromantes overall form a discrete clade). Hydromantes genei and three species of Speleomantes are found in caves on the island of Sardinia; the remaining Speleomantes species on mountains of mainland Italy. Molecular analysis suggests that H. genei became isolated on Sardinia about nine million years ago, with the ancestors of the Sardinian Speleomantes arriving later about 5.6 million years ago when the Mediterranean dried out during what is known as the Messinian Salinity Crisis (Carranza et al. 2008). The absence of any Hydromantes on neighbouring Corsica is something of a mystery, and it has been suggested that they may have been present there in the past before going extinct.

Extinction also seems the most likely explanation for Hydromantes' unusual distribution. The fossil record for the genus is minimal, and provides little information not already available from living species, but molecular dating attempts agree that the division between European and North American Hydromantes happened too recently to be related to the tectonic separation of the two continents. Such a scenario would also leave open the Hydromantes' absence in eastern North America. The description in 2005 of the Korean lungless salamander Karsenia koreana demonstrated the presence of plethodontids in eastern as well as far western Eurasia, and it seems possible that Hydromantes dispersed into Eurasia via the Bering Strait landbridge, becoming widespread across the continent before extinction reduced it to the isolated relicts it is today.

REFERENCES

Carranza, S., A. Romano, E. N. Arnold & G. Sotgiu. 2008. Biogeography and evolution of European cave salamanders, Hydromantes (Urodela: Plethodontidae), inferred from mtDNA sequences. Journal of Biogeography 35: 724–738.

Deban, S. M., & U. Dicke. 2004. Activation patterns of the tongue-projector muscle during feeding in the imperial cave salamander Hydromantes imperialis. Journal of Experimental Biology 207: 2071–2081.

García-París, M., & S. M. Deban. 1995. A novel antipredator mechanism in salamanders: rolling escape in Hydromantes platycephalus. Journal of Herpetology 29 (1): 149–151.

Rovito, S. M. 2010. Lineage divergence and speciation in the web-toed salamanders (Plethodontidae: Hydromantes) of the Sierra Nevada, California. Molecular Ecology 19: 4554–4571.

Wake, D. B. 2013. The enigmatic history of the European, Asian and American plethodontid salamanders. Amphibia-Reptilia 34: 323–336.

Riding a Frog's Pouch

Most people are familiar with the concept of marsupials, the group of mammals whose young spend the earliest part of their life nurtured within a pouchon their mother's underside. Kangaroos, koalas, wombats—all have their established place in popular culture (even if a person can't really ride inside a kangaroo's pounch, and anyone trying to is likely to find themselves picking their intestines off the floor). But perhaps less people are aware that a nurturing pouch is not unique to marsupial mammals: among others, there are some frogs that do it too.

Horned marsupial frog Gastrotheca cornuta female carrying eggs, copyright Danté B. Fenolio.

The marsupial frogs are found over a great part of South America, being particularly diverse in upland regions. Many (particularly members of the genus Hemiphractus) are somewhat gargoyle-ish beasts with flattened heads and/or prominent 'horns' above the eyes. Until recently, marsupial frogs were usually classified as a subfamily of the treefrog family Hylidae but more recent phylogenetic studies have agreed on the polyphyly of the latter family in its broad sense. As a result, the marsupial frogs are now placed in their own distinct family, the Hemiphractidae, as part of a broader association of a number of South American frog families. The influential phylogenetic study of amphibians by Frost et al. (2006) suggested that the marsupial frogs themselves were polyphyletic and divided them between no less than three families (Hemiphractidae, Cryptobatrachidae and Amphignathodontidae) but more recent studies have agreed on their monophyly. Frost et al.'s results are generally thought to have resulted from their poor coverage of members of this clade.

So what makes them marsupials? In all hemiphractids, the female carries her eggs after fertilisation until they hatch. In three of the five recognised genera (Hemiphractus, Cryptobatrachus and Stefania), the eggs are carried exposed on the surface and the young hatch directly as fully-formed froglets without a free-living tadpole stage. In the other two genera, Flectonotus and Gastrotheca (the latter genus being the most diverse in the family), the eggs are contained in a pair of pouches on the female's back. In some Gastrotheca species the eggs hatch into froglets as in the other genera, but in other Gastrotheca and in Flectonotus they hatch into tadpoles that the female then releases into a suitable pool of water.

Female Spix's horned treefrog Hemiphractus scutatus carrying a load of young froglets, copyright Santiago Ron.

Considering that a tadpole stage in development is evidently the original condition for frogs as a whole, it might be assumed the tadpole-bearing hemiphractids represent the basal taxa in the group with loss of the tadpole being derived. But intriguingly, recent phylogenetic analyses have indicated that the tadpole-bearing Gastrotheca occupy quite deeply nested positions in the hemiphractid family tree (Wiens et al. 2007; Flectonotus is placed as the sister taxon of all other hemiphractids, more as one might expect). This has led to the suggestion that the presence of tadpoles in Gastrotheca may represent a reversal to the original condition from direct-developing forebears. Now, I'm going to admit up front that I tend to be skeptical about claims for the reappearance of complex characters (and only partially because such studies never fail to cite that "stick insects re-evolved wings" thing of which I've already said I'm not a fan). In their analysis of breeding trajectories in hemiphractids, Wiens et al. (2007) found that, if one assumed that loss of the tadpole stage was equally likely to its gain, then the hemiphractid phylogeny supported a re-gain of tadpoles. However, if one presumed that loss was more likely than gain, then their analysis supported multiple losses with the tadpole-bearing Gastrotheca retaining the ancestral state. Nevertheless, they argued that a re-gain was more likely. Tadpole-bearing hemiphractids are all inhabitants of high altitudes where their young are often the only tadpoles about, suggesting that competition with other frogs excludes them from lower altitudes. Assuming multiple origins of direct development would require that the low-altitude hemiphractids evolved from low-altitude tadpole-bearers of which there is no current sign. But could it be that more recent changes in the South American environment changed the competitive regime for hemiphractids? Have the frog lineages that supposedly exclude them for lower altitudes been in the area for as long as the hemiphractids have? On the other hand, hemiphractids are unusual among direct-developing frog in that their embryos still develop some tadpole-like features (such as an incipient beak) only to lose them before emerging from the egg. Could this retention of ancestral features in an incipient form made it easier for them to re-establish at a later date?

The only living frog with mandibular teeth, Gastrotheca guentheri, copyright Biodiversity Institute, University of Kansas.

There is an evolutionary reversal among hemiphractids that seems more unequivocal, however: one species, Gastrotheca guentheri, is the only known frog in the modern fauna to have teeth in the lower jaw (Wiens 2011). There are a number of other frogs (including some other hemiphractids) in which the lower jaw has tooth-like serrations but G. guentheri is the only species with honest-to-goodness teeth. There seems little doubt that this is a true reversal; for G. guentheri to be the only living frog species to retain the ancestral state would require close to two dozen independent losses with no sign of the feature's retention elsewhere. In this case, while other frogs do not have teeth in the lower jaw, many of them do have teeth in the upper jaw (in some, such as Hemiphractus species, these upper teeth may be modified into prominent fangs for prey capture). So the genes for tooth development are still in place; presumably, G. guentheri has been able to re-develop its lower teeth through the genes for upper teeth being effectively re-deployed to take action elsewhere.

REFERENCES

Frost, D. R., T. Grant. J. N. Faivovich, R. H. Bain, A. Haas, C. F. B. Haddad, R. O. de Sá, A. Channing, M. Wilkinson, S. C. Donnellan, C. J. Raxworthy, J. A. Campbell, B. L. Blott., P. Moler, R. C. Drewes, R. A. Nussbaum, J. D. Lynch, D. M. Green & W. C. Wheeler. 2005. The amphibian tree of life. Bulletin of the American Museum of Natural History 297: 1–370.

Wiens, J. J. 2011. Re-evolution of lost mandibular teeth in frogs after more than 200 million yeatrs, and re-evaluating Dollo's Law. Evolution 65 (5): 1283–1296.

Wiens, J. J., C. A. Kuczynski, W. E. Duellman & T. W. Reeder. 2007. Loss and re-evolution of complex life cycles in marsupial frogs: does ancestral trait reconstruction mislead? Evolution 61 (8): 1886–1899.

East Asian Forest Frogs

Black-striped frog Sylvirana nigrovittata, from here.

One group of animals that has somewhtat flown (or at least hopped) under the radar here at Catalogue of Organisms is the frogs. Frogs are perhaps one of the most instantly recognisable of all terrestrial animal groups, with a combination of features that is truly unique (see this post at an older iteration of Tetrapod Zoology for a list of some of their eccentricities—I mean, the things don't have a rib-cage. Maybe fish can get away with those sorts of shenannigans, but I expect any vertebrate crawling around on land to be fully skeletoned up, thank you.) Frogs come in a wide range of shapes and sizes, but perhaps the group most often thought of as the classic 'frogs' are the members of the family Ranidae. A large proportion of these mostly smooth-skinned, long-legged frogs were classified until recently in a single genus Rana. This was always seen as something of a generalised group, characterised as much by the absence of the derived features of other ranid genera such as the torrent-dwelling Amolops as by anything else. As such, it was long expected that more detailed studies of ranid relationships would lead to the Rana monolith being broken down somehow. In 1992, Alain Dubois presented a classification of the Ranidae in which he divided Rana between a number of subgenera, some of which were further divided into sections and species groups. This classification was presented by Dubois as explicitly provisional: the arrangement of taxa was based on overall similarities rather than any explicit analysis, and was largely intended to provide some sort of starting point for future analyses.

One of the new taxa recognised by Dubois (1992) was Sylvirana, which he erected as a new subgenus of Rana containing an assortment of species found in southern and eastern Asia. Members of this group had a foot with an external metatarsal tubercle, suction pads on digit III of the fore foot and digit IV of the hind foot but often not on fore digit I, and males with a humeral gland and internal or external subgular vocal sacs. Their tadpoles had long papillae along the edge of the lower lip, and often had dermal glands. As indicated by the name, species of Sylvirana were mostly found in forests.

Günther's frog Sylvirana guentheri, copyright Thomas Brown.

When the broad genus Rana was later carved up by Frost et al. (2006), they recognised Sylvirana as a separate genus (albeit without quite the same composition as Dubois' version). Since then, the status of Sylvirana has shifted around a bit; some authors have sunk it into a broader Old World tropical genus Hylarana on the grounds of non-monophyly. Oliver et al. (2015) conducted a molecular phylogenetic analysis of the Hylarana group that lead them to propose Sylvirana as the name for a clade of southeast Asian frogs that they recovered. A number of Indian species previously assigned to Sylvirana formed a separate clade that they recognised as a distinct genus Indosylvirana. Morphological differences between Sylvirana and Indosylvirana are slight, but males of the former have a larger humeral gland: three-quarters the length of the humerus vs two-thirds the length in Sylvirana. It's worth noting that, although Dubois (1992) recognised a number of ranid taxa as lacking a humeral gland, most if not all of them do indeed possess this gland, just not raised and readily visible externally as in Sylvirana.

The species of Sylvirana sensu Oliver et al. (2015) are generally medium-sized, robust frogs with a shagreenate back and smooth or slightly warty sides. They generally have a dark stripe along the side of the body, becoming broken into dark spots lower down. Widespread species include Sylvirana nigrovittata, commonly known as the black-striped frog (a completely non-distinct name, I have to say, considering that it could apply to any one of dozens of ranid species; Wikipedia calls it the sapgreen stream frog, which on the one hand is a much more distinctive name, but on the other hand suffers from the point that all the individuals I've seen photographed of this species look more brown than green). This species is found over pretty much the entire continental range of the genus, from eastern India and Nepal to Vietnam and Malaysia. Also widespread is Günther's frog S. guentheri, which is found in southern China, Taiwan and Indochina. This species is also found in Guam where it was first recorded in 2001 and has since become well-established (Christy et al. 2007). It is believed to have made its way there as a stowaway in shipments of aquaculture stock though, as it is itself captured for food in its native range, it is not impossible that it may have been introduced deliberately.

REFERENCES

Christy, M. T., J. A. Savidge & G. H. Rodda. 2007. Multiple pathways for invasion of anurans on a Pacific island. Diversity and Distributions 13: 598–607.

Dubois, A. 1992 Notes sur la classification des Ranidae (Amphibiens Anoures). Bulletin Mensuel de la Société Linnéenne de Lyon 61 (10): 305–352.

Frost, D. R., T. Grant, J. Faivovich, R. H. Bain, A. Haas, C. F. B. Haddad, R. O. de Sá, A. Channing, M. Wilkinson, S. C. Donnellan, C. J. Raxworthy, J. A. Campbell, B. L. Blotto, P. Moler, R. C. Drewes, R. A. Nussbaum, J. D. Lynch, D. M. Green & W. C. Wheeler. 2006. The amphibian tree of life. Bulletin of the American Museum of Natural History 297: 1–370.

Oliver, L. A., E. Prendini, F. Kraus & C. J. Raxworthy. 2015. Systematics and biogeography of the Hylarana frog (Anura: Ranidae) radiation across tropical Australasia, Southeast Asia, and Africa. Molecular Phylogenetics and Evolution 90: 176–192.

Most Unbelievable Organisms Evah!

Last week I asked for nominations for the title of Most Incredible Organism Ever. Thank you very much to those of you who responded with your selections. Some of them were organisms I'd already selected myself, some of you reminded me of amazing organisms that were even better than the ones that I'd considered*. Certainly, getting the list down to ten top nominations was not easy, and I'm sure anyone else would have chosen differently from myself. Allen Hazen pointed out that, strictly speaking, "incredible" means "inspires disbelief", and certainly some of the things I have lined up do exactly that.

*As an aside, something that never fails to amuse is looking up what Google search terms have brought people to Catalogue of Organisms. Trust me, "amazing organism" is bound to bring in the punters.

Honorable mentions should be given to those organisms that people nominated that I didn't end up using, because they're certainly all incredible. Allen Hazen suggested the platypus, while Alan nominated the aye-aye. Dave Coulter was all for the Osage orange, while Amie Roman asked me to "pick an onychophoran, any onychophoran".

But I'm afraid I ended up passing over these wonders. In no particular order, here are my nominations for "Most Incredible Organism" (click on the pictures to be taken to their source):



Homo sapiens Linnaeus, 1758: Both myself and Mike Keesey agreed on this one. As much as I hate to stoke this species' notoriously smug satisfaction, it has to be admitted that humans are pretty amazing. Douglas Adams once explained that "The History of every major Galactic Civilization tends to pass through three distinct and recognizable phases, those of Survival, Inquiry and Sophistication, otherwise known as the How, Why and Where phases. For instance, the first phase is characterized by the question How can we eat? the second by the question Why do we eat? and the third by the question Where shall we have lunch?" As far as we know, Homo sapiens is the only species on this planet to have reached Adam's second stage, let alone the third.



Polyascus polygenea (Lützen and Takahashi, 1997): Polyascus polygenea is a member of the Rhizocephala, notorious crustacean parasites of crabs. The larval rhizocephalan looks very similar to the larva of a barnacle (to which it is closely related), but when it finds a decapod host it burrows in and transforms into an almost fungus-like mass spreading through the hosts body. The only externally visible part of the parasite is its large egg-sac (the orange tube in the picture above, which does not show a Polyascus but another rhizocephalan species, Peltogaster paguri). The rhizocephalan egg-sac grows at the base of the crab's tail, where it would normally hold its own eggs. In order to make sure this spot is free, the rhizocephalan chemically castrates its host, preventing it from ever reproducing. It also affects its host's behaviour so that the crab lovingly tends the parasite's egg-sac as if it were its own. So powerful is the parasite's mental ju-ju that even male hosts that would not naturally produce eggs will tend the parasite just as a female would.

Vasha nominated the best-known rhizocephalan, Sacculina carcini, but I've decided to go with Polyascus polygenea because this species adds a further twist to the tale. A single Sacculina larva will give rise to a single egg-sac. But Polyascus reproduces within the host asexually by budding, so that one larva will give rise to multiple egg-sacs (Glenner et al., 2003).

Polyascus is also acting as the stand-in for all mind-controlling parasites. As we learn more about the natural history of parasitic organisms, it turns out that behavioral control of parasites over their hosts is not uncommon. Parasitic wasps make caterpillars guard the wasp's cocoons. Horsehair worms make crickets drown themselves so the aquatic adult worm can emerge. Tanya reminded me about Cordyceps unilateralis, a fungal parasite of ants that, when it's ready to produce spores, makes its host climb to the highest available point so that the spores will spread as far as possible. The ways of parasites are disturbing. And speaking of disturbing...



Acarophenax tribolii Newstead & Duvall, 1918: It is not uncommon for pregnant women to express delight at feeling their baby kick inside them. But what if it was doing more than just kicking? Mites of the genus Acarophenax are parasites of beetles that can claim to have perhaps the just-plain-ickiest life history of any animal. The sex ratio of this genus is highly skewed - depending on the species, a brood may contain up to thirty females, but usually only a single male. These offspring reach sexual maturity before they are even born, and the male proceeds to fertilise all of his sisters while still within their mother. In fact, the male doesn't even survive to become free-living - by the time the already-fertilised females emerge from their parent, the male has reached the end of his short (but extremely busy) lifespan. The advantage to the mite in this twisted incestuous life cycle? An exceedingly short generation time, of course - Acarophenax mahunkai, for instance, has a generation time of only three to five days (Steinkraus & Cross, 1993).



Mites of the closely related family Pyemotidae have a similar life cycle - the offspring reach full sexual maturity while in their mother, and begin copulating the instant that they emerge from their proud parent. Females of Pyemotes herfsi (shown in the picture above), known as "itch mites" and facultative biters of humans, can produce more than 250 fully mature offspring.



Welwitschia mirabilis Hook.f.: I also have to thank Tanya for reminding me of the wonder that is Welwitschia. Welwitschia mirabilis is unique to the Namib Desert in Angola and Namibia, and is a member of the gymnosperm order Gnetales along with the genera Ephedra and Gnetum. The Gnetales have received a lot of attention due to their much-debated phylogeny (morphological characters suggest they are the living sister group to angiosperms, while molecular analyses place them closer to conifers), but that's not what's so amazing about Welwitschia. It's not even the bright pink, insect-pollinated cones. What makes this plant so incredible is the way it grows. Welwitschia mirabilis only ever produces two adult leaves, followed by the death of the plant's apical meristem (growing tip). The two strap-like leaves, however, continue to grow indefinitely, and can reach lengths of over eight metres (most individuals look like they have more than two leaves, but this is only because of the leaves splitting as the ends get frayed). Welwitschia is very slow-growing, and individual specimens can live to be hundreds, if not thousands of years old.



Argentinosaurus huinculensis Bonaparte & Coria, 1993: There's no other way to say it - sauropods were just stupidly huge. And Argentinosaurus was one of the most ridiculous of all, being the largest well-characterised sauropod (potentially outdone only by such almost-apocryphal taxa as Amphicoelias fragillimus and Bruhathkayosaurus matleyi). With an estimated total length of nearly thirty metres, and potential weight of up to 80 tonnes... well, there's nothing much that can be said in response except "Whoa".

Sauropods are so huge that when a popular blog was set up dedicated to them, the site authors couldn't fit in the entire animal and were forced to dedicate themselves to a single section. I refer, of course, to the famed Sauropod Vertebra Picture Of the Week - SV-POW!. Rumour has it, however, that a second site is in the works devoted to sauropod crania, to be called "Sauropod Heads - Anatomy, Zoology And Morphology".



Rhizanthella slateri (Rupp) M. A. Clem. & P. J. Cribb, 1984: Rhizanthella is a small genus of three orchid species unique to Australia. What makes Rhizanthella so amazing is that its entire life cycle is spent underground. The plant is saprophytic, dependent on an associated fungus for nutrition, and its stems are entirely subterrean. Even the flowers do not have to break the surface - they are pollinated by minute gnats that can reach them through tiny cracks in the covering litter. The first known Rhizanthella specimens were discovered in 1928 when they were brought up by a farmer's plough, and only intermittent finds were made for a long time afterwards. Even today, their obscure habits mean that Rhizanthella species are poorly known. Sad to say, they are also all regarded as endangered. They are only known from restricted, scattered ranges, limited by the presence of their associated fungus and the tree of which it is in turn connected to mycorrhizally (in Rhizanthella gardneri, the tree is Melaleuca uncinata, but the associations of Rhizanthella slateri are still unknown).

Vasha reminded me of Rhizanthella by telling me of the American saprophytic plant Thismia americana, which also spends most of its life underground with only the minute flowers emerging above the surface. Thismia americana has not been recorded since 1916, and is feared to be extinct, though it is hard to know for certain. As described at the link, an intensive search in the early 1990s failed to find any specimens, but a concurrent dummy run using scattered white beads about the same size as T. americana flowers was also a failure.



Puccinia monoica Arthur, 1912: The object of the photo above is not a flower. It grew from a flowering plant, but it's not a flower. Puccinia monoica is a fungus parasitic on Brassicaceae (mustard) species. Like rhizocephalans on their crabs, Puccinia monoica changes the reproductive biology of its host, preventing it from growing its own flowers. Instead, it makes the host plant grow a tight whorl of leaves, which are covered by the bright yellow sporangia of the fungus. Not only does the fungus-induced 'false flower' look like a real flower, it even produces nectar and scent like a real flower, attracting insect pollinators just like a real flower would (Raguso & Roy, 1998). And just like pollen from a real flower, these pollinators carry spores from fungus to fungus, cross-fertilising the fungi as they do so.



Deinococcus radiodurans (ex Raj et al. 1960) Brooks and Murray 1981: A dose of radiation of 10 joules per kilogram will kill a human being. Sixty joules per kilogram will kill Escherichia coli. Deinococcus radiodurans may look like a fairly unremarkable bacterium at first glance, but it can withstand a radiactive dose of 5000 joules per kilogram and not even blink (that is, if it had eyes they wouldn't blink). It can withstand radiation so strong that its genome is simply blasted to pieces, stoically knitting the fragments back together again afterwards. Deinococcus can withstand extreme heat, extreme cold, and strong acidity. In a pun so bad that it demands to be repeated, this organism has been dubbed Conan the Bacterium. Pavlov et al. (2006) went so far as to suggest that Deinococcus' incredible resilience to radiation indicated an extraterrestrial origin, carried from Mars on an asteroid, but it seems more likely to be a by-product of resilience to other stressors such as desiccation (Cox & Battista, 2005). Still, one can't help wondering if, even if it didn't come from Mars in the first place, it has managed to make it over there on one of Earth's probes.

So resistant is Deinococcus to everything possibly imaginable, in fact, that we still have no idea where it lives naturally. It was first isolated from cans of irradiated beef, and has not yet been found to be abundant in any particular environment. Phylogenetically, Deinococcus forms a clade with the thermophilic bacterium Thermus (one species of which, Thermus aquaticus, is of enormous significance to molecular biology as the source of the Taq enzyme used in PCR). This clade is most commonly referred to (rather unimaginatively) as the Deinococcus-Thermus group, but I personally prefer the name given to them by Cavalier-Smith (2002) - Hadobacteria, the bacteria of Hades.



Proteus anguinus anguinus Laurenti, 1768: The white olm, the only truly cave-dwelling tetrapod (the closely related black olm, Proteus anguinus parkelj, is a surface-dweller). [Update: Much to my chagrinn, Nick Sly has reminded me that there are other cave-dwelling salamanders out there.] I've included the olm not only for its own sake, but as a representative of the entire world of troglobitic and stygobitic fauna (troglobitic animals are those that live in actual caves while stygobitic taxa live buried in the ground, usually in aquifers). In this strange, silent world, animals are almost entirely dependent on food particles washing down from the surface, so life underground is slow, and patient. Troglobites can go for incredible amounts of time without eating - Darren Naish informs us of an olm that was supposedly kept at the Faculty of Biotechnology in Ljubljana without food for twelve years! If that is what a large, complex vertebrate is capable of, imagine what is possible for the smaller invertebrates with their lower metabolic requirements.

And last, but certainly not least:



Wasmannia auropunctata (Roger, 1863): Commonly known as the little fire ant or electric ant (the latter name has been promoted in recent years to dissuade confusion with the larger, not closely related fire ants of the genus Solenopsis), Wasmannia auropunctata is regarded as one of the world's worst invasive organisms. It has been linked with decreases in biodiversity in locations to which it has been introduced, and has a painful sting to boot. It also has one of the world's most remarkable reproductive systems (Fournier et al., 2005). Like other ants, Wasmannia has both haploid males and diploid females, with the females divided between reproductive queens and non-reproductive workers. Genetically, though, Wasmannia is a little different from other ants. While males appear to mate with queens the normal way, only workers are produced by male fertilisation. Any new queens that are produced are genetically identical to their mothers. Still, the male lineage doesn't disappear - somehow, the male genes are able to eliminate the female genes from some of the eggs, and the resulting male Wasmannia are genetically identical to their fathers.

Wasmannia is one of very few organisms that exhibit androgenesis - clonally reproducing males. The only other known natural habitual cases are a cypress species, Cupressus dupreziana, and freshwater bivalves in the genus Corbicula, though odd cases of androgenesis have been recorded in laboratory and cultivated organisms (Hedtke et al., 2008). Effectively, the male and female Wasmannia are reproductively isolated from each other - they are separate species.

REFERENCES

Cox, M. M., & J. R. Battista. 2005. Deinococcus radiodurans — the consummate survivor. Nature Reviews: Microbiology 3 (11): 882–892.

Fournier, D., A. Estoup, J. Orivel, J. Foucaud, H. Jourdan, J. Le Breton & L. Keller. 2005. Clonal reproduction by males and females in the little fire ant. Nature 435: 1230-1234.

Glenner, H., J. Lützen & T. Takahashi. 2003. Molecular and morphological evidence for a monophyletic clade of asexually reproducing Rhizocephala: Polyascus, new genus (Cirripedia). Journal of Crustacean Biology 23: 548-557.

Hedtke, S. M., K. Stanger-Hall, R. J. Baker & D. M. Hillis. 2008. All-male asexuality: origin and maintenance of androgenesis in the Asian clam Corbicula. Evolution 62 (5): 1119-1136.

Pavlov, A. K., V. L. Kalinin, A. N. Konstantinov, V. N. Shelegedin & A. A. Pavlov. 2006. Was Earth ever infected by martian biota? Clues from radioresistant bacteria. Astrobiology 6 (6): 911-918.

Raguso, R. A., & B. A. Roy. 1998. 'Floral' scent production by Puccinia rust fungi that mimic flowers. Molecular Ecology 7 (9): 1127-1136.

Steinkraus, D. C, & E. A. Cross. 1993. Description and life history of Acarophenax mahunkai, n. sp. (Acari, Tarsonemina: Acarophenacidae), an egg parasite of the lesser mealworm (Coleoptera: Tenebrionidae). Annals of the Entomological Society of America 86 (3): 239-249.

Relict Frog Sex

At least one piece of genetics that almost everyone is familiar with is how our sex is determined - that women possess two X chromosomes while men produce an X and a Y chromosome. What may not be so familiar to most people is that this system is far from universal. Different animals exhibit a wide range of methods of sex determination, both genetic (like our own system) and environmental (such as temperature in crocodiles). In Hymenoptera (ants, bees and wasps) unfertilised eggs produce haploid males, while fertilised eggs produce diploid females. In birds, it is the females that possess two different forms of sex chromosomes (referred to as W and Z), while the male possesses two Z chromosomes. But perhaps the oddest little tale of sex determination (and one I only discovered recently) involves the strange relictual frog genus Leiopelma (the species Leiopelma archeyi is shown in a photo from the page of Dr. Bruce Waldman).

Leiopelma is a small genus of four living species of frog restricted to New Zealand (a further three species are known from sub-fossil remains - Bell et al., 1998). They represent a basal grade of frogs of which the only other member is the "tailed frog" Ascaphus truei from western North America (different studies disagree as to whether Leiopelma and Ascaphus form the sister clade to or are paraphyletic to all other living frogs - Green & Cannatella, 1993; Hay et al., 1995). Leiopelma and Ascaphus retain a number of primitive features that have been lost in other frogs, such nine vertebrae in front of the sacrum and tail-wagging muscles (though the 'tail' of male Ascaphus is actually the copulatory organ). Leiopelma also lack a tadpole stage in their life-cycle, hatching straight out into froglets.

The really remarkable thing about Leiopelma, though, is that of the four species living today, at least three have different methods of sex determination from each other. And within two of those species, there are even different populations that differ in their mode of sex determination!

The most primitive state is perhaps that shown by Leiopelma archeyi, in which most populations don't have distinguishable sex chromosomes. This is the condition in most amphibians, though it has been shown that even in taxa that don't have heteromorphic chromosomes, sex is still determined genetically (Hayes, 1998). However, a heteromorphic W sex chromosome has been recorded in one population of L. archeyi from Whareorino in the King Country (Green, 2002). In other features (including genetic features) the Whareorino L. archeyi are almost indistinguishable from Coromandel populations that lack the W chromosome.

The Whareorino Leiopelma archeyi are therefore more like L. pakeka in sex differentiation. Leiopelma pakeka also has a female-ZW/male-ZZ set-up (Green, 1988)*. There is only a single population of L. pakeka, restricted to Maud Island, which diesn't give much scope for variation.

*The species Leiopelma pakeka was recognised only recently (Bell et al., 1998). Previously it had been regarded as a population of the genetically distinct but morphologically almost identical L. hamiltoni, and its genetic structure was described under the latter name. Leiopelma hamiltoni proper is uber-rare, with a population of less than 300 individuals restricted to less than one hectare of habitat on Stephens Island, and does not seem to have yet been investigated for sex chromosomes.

The ultimate wierdness, however, comes when we look at Leiopelma hochstetteri. Most populations of L. hochstetteri have a single sex chromosome in females, while males lack a sex chromosome. This female-0W/male-00 system is unique - no other animal has it. Not one. In fact, it's so bizarre that not even all L. hochstetteri have it - females of the population on Great Barrier Island lack the lonely W chromosome, and like Coromandel L. archeyi this population does not have morphologically distinct sex chromosomes (Green, 1994). The Great Barrier population also lacks the non-sex-related supernumerary chromosomes (or "B" chromosomes) found in other populations (Green et al., 1993). B chromosomes are small, seemingly dispensable chromosomes that are found in a broad scattering of taxa. In species where they are found, numbers of B chromosomes can vary significantly within and between populations, probably because their lack of significant function means a lack of selective control on their propagation. This variation is also seen in L. hochstetteri, where up to 15 B chromosomes were found in individuals of five different populations. The variation in chromosomes between populations is shown below in a figure from Green (1994).



So how did all this come about? I am not aware of any other group of closely-related organisms showing this much variation in so few species. However, it is possible to imagine ZW chromosomes evolving through differentiation of morphologically indistinct sex-determining chromosomes, and this is what appears to have occurred in Leiopelma pakeka and Whareorino L. archeyi. Leiopelma hamiltoni appears to be more closely related to L. archeyi than L. pakeka (Bell et al., 1998), so it would be very interesting to know whether or not it has distinct sex chromosomes.

As for Leiopelma hochstetteri, the sister taxon to all other Leiopelma, phylogenetic analysis of chromosome characters shows that the Great Barrier population, without the extra W chromosome, is probably sister to all other populations. Green et al. (1993) suggest that the 0W/00 system could evolved from a ZW/ZZ system. Either the Z chromosome may have been lost, or (as the authors of the latter study think more likely) it could have been duplicated, giving a ZZW/ZZ pattern that would be karyotypically indistinguishable from 0W/00.

REFERENCES

Bell, B. D., C. H. Daugherty & J. M. Hay. 1998. Leiopelma pakeka, n. sp. (Anura: Leiopelmatidae), a cryptic species of frog from Maud Island, New Zealand, and a reassessment of the conservation status of L. hamiltoni from Stephens Island. Journal of the Royal Society of New Zealand 28 (1): 39-54.

Green, D. M. 1988. Heteromorphic sex chromosomes in the rare and primitive frog Leiopelma hamiltoni from New Zealand. Journal of Heredity 79 (3): 165-169.

Green, D. M. 1994. Genetic and cytogenetic diversity in Hochstetter's frog, Leiopelma hochstetteri, and its importance for conservation management. New Zealand Journal of Zoology 21: 417-424.

Green, D. M. 2002. Chromosome polymorphism in Archey's frog (Leiopelma archeyi) from New Zealand. Copeia 2002 (1): 204-207.

Green, D. M., & D. C. Cannatella. 1993. Phylogenetic significance of the amphicoelous frogs, Ascaphidae and Leiopelmatidae. Ecol. Ethol. Evol. 5: 233-245.

Green, D. M., C. W. Zeyl & T. F. Sharbel. 1993. The evolution of hypervariable sex and supernumerary (B) chromosomes in the relict New Zealand frog, Leiopelma hochstetteri. Journal of Evolutionary Biology 6 (3): 417-441.

Hay, J. M., I. Ruvinsky, S. B. Hedges & L. R. Maxson. 1995. Phylogenetic relationships of amphibian families inferred from DNA sequences of mitochondrial 12S and 16S ribosomal RNA genes. Molecular Biology and Evolution 12 (5): 928-937.

Hayes, T. B. 1998. Sex determination and primary sex differentiation in amphibians: Genetic and developmental mechanisms. Journal of Experimental Zoology 281 (5): 373-399.

Sooglossidae: Deja vu all over again

Every couple of weeks or so I go into the Western Australian Museum library to look over the new journals and see if anything interesting has come out that I've missed. I did so this morning, and among the papers I noticed was van der Meijden et al. (2007) in the Biological Journal of the Linnean Society which established a new genus Leptosooglossus for the frog species previously known as Sooglossus gardineri from the Seychelles (shown above in an adorable image from the Nature Protection Trust of the Seychelles). A second species, Sooglossus pipilodryas, was also transferred into the new genus.

This was all well and good, until a few journals later I came across Nussbaum & Wu (2007) in Zoological Studies which established a new genus Sechellophryne for the frog species previously known as - yep, you know what's coming - Sooglossus gardineri (again, So. pipilodryas was also transferred). Oh dear. Two papers, published very close together in time, coining different names for the same thing.

Before anyone madly leaps to any suspicions, I can't find any obvious signs of plagiarism or claim-jumping in either paper. Both recognised the new genus on the basis of paraphyly of the genus Sooglossus, but van der Meijden et al. only used molecular data, while Nussbaum & Wu only used morphological data. It does seem somewhat incredible that there could be two separate groups of people both working on as small a group as Sooglossidae (only four species restricted to the Seychelles, a small group of islands in the Indian Ocean roughly the size of a postage stamp) and unaware of each other, but I can't find any obvious indications otherwise (if there is any sort of scandal, I'm chucking in a vote that it be referred to as 'Bubblegate'). It is good that the two papers using completely different methods agree so much in their results.

So the next question becomes - which is the correct name to use? The van der Meijden et al. paper was in the July issue of the journal it appeared in, while Nussbaum & Wu appeared in a May issue. So the first round would appear to favour Sechellophryne over Leptosooglossus. However, the cover date of a journal issue is not necessarily identical to the actual print release date, which is what is supposed to determine priority. The online release date for van der Meijden et al. (which may not be identical to the print release date, but is usually at least an indication) is given as 5th July at the journal website. Unfortunately, the website for Zoological Studies doesn't appear to list specific release dates, and there doesn't appear to be one on the paper. If anyone out there in the know is able to confirm the release date for me, I would be quite grateful (it suddenly occurs to me that I should have looked inside the cover or on the table of contents or such of the journal itself, but I'm no longer at the museum and can't do that now - d'oh!). Again, at the moment Sechellophryne appears to be the senior name unless proven otherwise.

Oh, and if you're wondering why Bubblegate, it's a reference to one of my partner's current favourite jokes (warning - PG rating):

Three frogs are brought before the court. As the first frog is taken to the stand, the judge asks the bailiff for his name and crime, to which the bailiff replies, "This is Frog, and his crime is blowing bubbles in the pond". The second frog is taken in, and again the judge asks for his name and crime. The bailiff replies, "This is Frog-Frog, and his crime is blowing bubbles in the pond". The third frog is then brought in, and the judge asks, "I suppose this is Frog-Frog-Frog?" "No," replies the bailiff, "this is Bubbles".

REFERENCES

Meijden, A. van der, R. Boistel, J. Gerlach, A. Ohler, M. Vences & A. Meyer. 2007. Molecular phylogenetic evidence for paraphyly of the genus Sooglossus, with the description of a new genus of Seychellean frogs. Biological Journal of the Linnean Society 91: 347-359.

Nussbaum, R. A., & S.-H. Wu. 2007. Morphological assessments and phylogenetic relationships of the Seychellean frogs of the family Sooglossidae (Amphibia: Anura). Zoological Studies 46 (3): 322-335.

Taxon of the Week #3: Rana

The taxon that has been chosen to receive the coveted Taxon of the Week spot today is the frog genus Rana. Rana is a large primarily Holarctic genus of frogs, and probably the inspiration for most depictions of frogs in the world (see the page on Wikipedia and linked pages for images). Well-known species are the edible frog (Rana × esculenta - actually not a true species but a hybrid) and the European common frog (Rana temporaria).

I thought I'd look up the info on Rana over lunchtime. Pretty soon, my head was swimming. The genus Rana has been hit with two major investigations in recent years, both of which have received some frosty responses. Frost et al. (2006) in their investigation of the 'Amphibian Tree of Life' divided Rana between more than fifteen smaller genera to remove its previous paraphyly (for instance, the above-mentioned Rana esculenta would become Pelophylax esculentus). As happens with any wholesale name change, there has been quite a bit of outcry at the idea of having to update the filing systems. Also, a number of authors have felt that the number of taxa sampled by Frost et al. was not enough to inspire confidence in their results. The review by Wiens (2007) was particularly vitriolic - the scientific equivalent of attempting to hold the subject down and kick them repeatedly in the teeth. Smith and Chiszar (2006) have suggested the more mollifying approach of treating Frost et al.'s various genera as subgenera, though unless one was willing to accept a paraphyletic genus this would also require sinking some well-established genera such as Staurois within Rana. Division of the genus Rana was also supported by Che et al. (2007).

The other cause of debate was perpetrated by Hillis & Wilcox (2005), who investigated the phylogeny of New World species of 'Rana' (most of which would belong to Lithobates in the Frost et al. system). The problem came when Hillis & Wilcox suggested a whole series of subgeneric taxa for nested groups of species that they defined according to the rules of the PhyloCode, but also allowed for use under the ICZN as subgenera. Debate promptly exploded about whether Hillis & Wilcox's names were validly published and usable (Dubois, 2006, 2007; Hillis, 2007). Compared to this argument, Frost et al.'s division appears quite simple. I may return to this in a later post, if my brain doesn't implode first. Check out the Dubois (2006) paper in particular - Dubois thinks that the answer to our problems is to make the ICZN more complicated. No. Thank. You.

REFERENCES

Che, J., J. Pang, H. Zhao, G.-F. Wu, E.-M. Zhao & Y.-P. Zhang. 2007. Phylogeny of Raninae (Anura: Ranidae) inferred from mitochondrial and nuclear sequences. Molecular Phylogenetics and Evolution 43 (1): 1-13.

Dubois, A. 2006. New proposals for naming lower-ranked taxa within the frame of the International Code of Zoological Nomenclature. Comptes Rendus Biologies 329 (10): 823-840.

Dubois, A. 2007. Naming taxa from cladograms: A cautionary tale. Molecular Phylogenetics and Evolution 42 (2): 317-330.

Frost, D. R., T. Grant, J. Faivovich, R. H. Bain, A. Haas, C. F. B. Haddad, R. O. de Sá, A. Channing, M. Wilkinson, S. C. Donnellan, C. J. Raxworthy, J. A. Campbell, B. L. Blotto, P. Moler, R. C. Drewes, R. A. Nussbaum, J. D. Lynch, D. M. Green & W. C. Wheeler. 2007. The amphibian tree of life. Bulletin of the American Museum of Natural History 297: 1-370.

Hillis, D. M. 2007. Constraints in naming parts of the Tree of Life. Molecular Phylogenetics and Evolution 42 (2): 331-338.

Hillis, D. M., & T. P. Wilcox. 2005. Phylogeny of the New World true frogs (Rana). Molecular Phylogenetics and Evolution 34 (2): 299-314.

Smith, H. M., & D. Chiszar. 2006. Dilemma of name-recognition: why and when to use new combinations of scientific names. Herpetological Conservation and Biology 1 (1): 6-8.

Wiens, J. J. 2007. Review: The Amphibian Tree of Life. Quarterly Review of Biology 82: 55-56.