It’s been a good couple of years for studying lizard smarts. Last year, Manuel Leal demonstrated keen cognitive abilities in Anolis evermanni. More recently a couple of studies Down Under have shown that slippery Aussie skinks have a lot going on upstairs as well. Over at The Lizard Lab, Martin Whiting has just posted a nice review of these studies.
Year: 2012 Page 10 of 47
httpv://www.youtube.com/watch?v=LVdLNIXujL8
My vain attempt at alliteration with the title, here’s a news story on those pesky lizards mucking about with electrical power (sorry I don’t know how to avoid you watching the ad at the beginning).
From Dustracks on the Web.
Janson Jones has a binder full of anoles.
In the latest issue of Copeia, Eric Pianka provides the latest positive review of Lizards in an Evolutionary Tree. Its easy to understand why this review appears more than three years after the book’s publication when you remember that Pianka has been a busy dude who most recently gained attention for recovering from the dead. Anole Annals also has archived links to other reviews of the book for those interested.
Photographs from Jaime Palacio Sierra. We are currently reviewing reptiles from our home department and have doubts on two specimens captured by Jaime. can anyone help us confirm their taxonomic identities?
Colombian caribbean Anolis
For those who work primarily in the West Indies, it can be difficult to imagine a lizard fauna dominated by anything other than anoles. However, if you’re interested in learning more about lizard communities that don’t include anoles, no book fits the bill better than L. Lee Grismer’s recent monograph on the Lizards of Peninsular Malaysia, Singapore and their Adjacent Archipelagos. Grismer takes readers on a tour of Peninsular Malaysia’s impressive lizard diversity, with species-by-species accounts that include morphological diagnoses, notes on coloration in life and among sexes, dot maps, and detailed notes on each species’ natural history. Grismer is the first to comprehensively review Peninsular Malaysia’s 128 lizard species, and his book represents the “first time the entire distribution of this fauna has been precisely mapped.” Of course, Grismer’s book is also chalk full of spectacular photographs, including many of Grismer’s trademark photos of animals in their natural habitat.
Map from Malaysian Bat Education Adventure: http://www.ttu-mbea.org/krau-wildlife-reserve/
Sandwiched between Thailand and Myanmar to the north and Indonesia to the south, Peninsular Malaysia is a geographically, historically, and ecological diverse region that includes numerous mountain ranges, offshore archipelagos, and isolated karstic rock outcrops. The habitats of Peninsular Malaysia range from mangrove forest to lush multi-layered Dipterocarp forest to “post-apocalyptic” oil palm plantation dominated landscapes. Grismer does a great job familiarizing readers with the region by beginning his monograph with detailed information of the region’s biogeography and environmental diversity.
Most importantly, of course, Peninsula Malaysia is home to 128 lizard species, mostly geckos, skinks, or agamids, but also the occasional dipamid, lacertid, varanid, and leiolepid. Some 45% of these species are endemics, the vast majority of which are skinks and geckos that are narrowly distributed in montane habitats, isolated karstic rock outcrops, or off-shore archipelagos. The agamids, however, are likely to attract the immediate attention of anole lovers because this group includes most of the region’s arboreal, diurnal, and often conspicuous, lizards.
Image from http://animals.nationalgeographic.com/animals/reptiles/draco-lizard/
The most diverse agamid radiation in Peninsula Malaysia is Draco, the remarkable genus of gliding lizards that is found throughout much of southeast Asia.
Variation in the back patterns of Anolis sagrei in the Bahamas. From Calsbeek and Cox (2010).
Last year, we had a series of posts discussing the evolution of dorsal patterns of female anoles, as well as several studies that reported intrapopulation variation in female patterning. Why such variation should exist is a mystery, and studies on both A. humilis in Costa Rica and A. sagrei in the Bahamas failed to find evidence that natural selection was acting on this variation.
Now, Calsbeek and Cox report an experimental study of natural selection on dorsal pattern on small islands in the Bahamas. They introduced anoles with the three patterns shown on the left onto four small islands. Two of the islands had birds and snakes, the other two had neither. One predator-exclusion island was studied in 2008, the other three in 2009. In addition, the authors measured selection in a natural population over the course of four years.
The major result of the study is that not only was survival reduced on islands with predators, but also in the presence–but not absence–of predators, the intermediate diamond-bar pattern had higher survival than the other two patterns. How this intermediate pattern leads to heightened survival is not clear, and the authors propose a few hypotheses for future testing.
R. CALSBEEK & R.M. COX (2012). An experimental test of the role of predators in the maintenance of a genetically based polymorphism Journal of Evolutionary Biology DOI: 10.1111/j.1420-9101.2012.02589.x
Three weeks ago, I initiated discussion of Nicholson et al.’s recent monograph by noting that it is the most important paper on anoles published in recent years. We’ve had a lot of interesting discussion of many aspects of the paper since then, but we should keep in mind, even in the light of this discussion, that regardless of what one thinks about the various issues debated on our pages, this paper certainly represents a comprehensive compendium of knowledge about anole taxonomy, systematics, biogeography and ecology, and as such will remain an important resource for years to come.
Having said that, I wanted to use this last post of mine to synthesize what I see as the conclusions of the past three weeks’ discussion concerning the “bold hypothesis” of anole biogeography and evolution presented by Nicholson et al. Their hypothesis can be boiled down to three main points: Anolis is much older than previously recognized; divergence into eight major clades of anoles (which this paper raises to generic status) occurred when the geological blocks that now form the Caribbean islands separated from their previous, connected position where they had served as a landbridge connecting North and South America (and, hence, anole biogeography is primarily the result of vicariance, rather than dispersal); and the history of anole habitat use is primarily one of change from a large, crown-inhabiting species to smaller species found on or near the ground. How does this scenario stand up in light of discussion on AA?
Anolis Is Much Older Than Previously Recognized
Nicholson et al. conclude that the ancestor of anoles diverged from their nearest relative 95 million years ago (mya) and that diversification to produce the eight major clades occurred 72-87 mya. These dates are far older than other estimates; three recent studies have pegged the split between Anolis and its sister taxa as occurring 25-80 mya.
Nicholson et al. molecular phylogeny with their dates of divergence and with dates corrected assuming a younger date for the Mexican amber anole, A. electrum in parentheses. The arrow points to the phylogenetic position where A. electrum was placed by Nicholson et al.
This proposed antiquity of anoles is surprising, but is almost surely mistaken.
I have followed the controversy over anole classification with interest. Amphibian taxonomists faced a similar issue with the reclassification of Bufo and Rana, among many lesser-known genera. I discovered that most herpetologists quickly accept new taxonomies (with the exception of extreme and ill-founded taxonomies, like those proposed by Hoser). So attempts to resist will likely fail. However, there is an intermediate option that is being used successfully for some taxa and I think it could be profitably pursued for anoles. That is, use subgenera. In short, keep using Anolis as you have historically, but if you think the phylogenetic analysis of Nicholson et al. meets your standards of quality, treat their genera as subgenera. Anolis is the oldest valid taxon and so it has priority. I argue that the name Anolis (Dactyloa) latifrons is more informative taxonomically, phylogenetically and biogeographically than is the name Dactyloa latifrons. What are the arguments against using subgenera? I can think of none. I advocate doing this for Bufo and Rana (making certain that each is monophyletic, of course). The argument against this move is that some relatively well-known names of genera would be lost, but I do not think that is the case. For anoles nothing is lost if one uses subgenera. Subgenera are being used successfully for salamanders. Hydromantes is a well-known group of salamanders, admittedly small in relation to Anolis. It is clearly a clade based of substantial DNA sequence data and osteological-myological data. Yet some wanted to break it up because it occurred in Europe and North America. To me this is one of the best reasons for keeping it a single genus. So I have advocated a three-subgenera classification: Hydromantes (Hydromantes) for the American species and Hydromantes (Speleomantes) and Hydromantes (Atylodes) for the European species. This highlights the fact that Hydromantes is monophyletic (no-one questions this) and also reminds us of the extraordinary distribution. With colleagues I have proposed seven subgenera for the 121 species of Bolitoglossa, three subgenera for the 36 species of Oedipina, and two subgenera each for the 22 species of Batrachoseps and the 55 species of Plethodon.
Why not use subgenera for anoles?
In my three previous posts [1,2,3], I have discussed Nicholson et al.’s ecomode concept and their conclusion from it that the ecomorph concept should be rejected. Here I conclude my discussion by addressing two other related points raised in Nicholson et al., whether differences in forest structure are responsible for different evolutionary patterns in the islands and on the mainland, and their critique of my 1992 paper on the sequence of ecomorph evolution.
Are Differences in Forest Structure Responsible for Different Evolutionary Patterns in Mainland and Island Anoles?
Nicholson et al. state (pp. 54-55): “In discussing differences between island and mainland anoles, Losos (2009) considered, but dismissed, forest structure as a driving factor in shaping anole assemblages, suggesting that, to anoles, a tree is a tree…[W]e are impressed with the complex nature of the moist, wet, and rain forests of Central and South America (Solé et al. 2005) that are home to the majority of anole species. The heavily fluted bark of Neotropical rainforest canopy trees such as Lecythis must require substantially different limb and toe pad shapes in anoles that use these trees than those that use the smooth bark of canopy trees such as Pterocarpus. The facts that bark texture is likely to be much more diverse in mainland than island forests, and that trees with appropriate bark texture are likely to be so much more widely dispersed in mainland than island forests, must play an important role in making morphology of mainland anoles so much less predictable than it is for island anoles. The fact that island forests are dominated by a relatively few short, smooth-barked tree species must limit the number of morphs that anoles can attain, must increase the density that anole populations can maintain, and must increase the interactions among sympatric species above that experienced by mainland anoles. Additionally, the differences in the structure of understory shrubs associated with mainland areas possessing an ancestral fauna that includes grazing mammals, compared to island areas that lacked such grazers (Dirzo and Miranda, 1990), must affect habitat available for adaptive radiation in anoles. In short, we see little evidence that the assembly rules proposed for anole communities on Caribbean islands will ever be discovered as applicable to mainland anoles, because the factors shaping vegetation structure are so different between island and mainland forests.”
And by the end of the paper (p.68), the idea has been transformed into a firm conclusion: “We note that evolution of ecomodes appears to be widely constrained within anoles and does not necessarily lead to constrained morphology within an ecomode because variation in forest structure across the geographic range of anoles is so great.”
It is certainly plausible that differences in vegetation structure between mainland and island forests are responsible for different patterns of ecomorphological evolution in the two regions. But what is the evidence for this? I have actually looked for comparisons of structure between mainland and island forests and have not found any relevant literature. The authors only cite two papers and neither documents differences between mainland and island forests: Solé et al. (2005) is about differences between canopy and understory at Barro Colorado Island, and Dirzo et al. (1990) is a comparison of mainland sites with and without large mammal herbivores (note: these references were presented by Nicholson et al. to document appropriate points about mainland forests; I am not claiming they were inappropriate citations, only that application to Caribbean forests is entirely an extrapolation of the authors). The authors may well be correct that mainland and island forests differ, but they do not provide any evidence to support this claim. Moreover, even to the extent that mainland and island forests do differ in structure, the effect such differences have had on anole evolution is entirely conjectural (e.g., perhaps different bark texture would select for differences in toepad structure, but to date, there are no data relevant to such a claim).
Indeed, one may question how likely it is that differences in tree structure actually affect anole morphological adaptation.