Ian Wang stumbled across a recently-published species description of an unbelievable new Anolis species that may be a new ecomorph – the ground-ground anole!! You have to read it for youself!
Author: Yoel Stuart Page 3 of 6
I am interested in whether, how, and why ecology shapes evolution (and evolution shapes ecology) through time, with an emphasis on microevolutionary pattern and process, adaptation, and field experiments. I completed my Ph.D. on Anolis lizards in the Department of Organismic and Evolutionary Biology at Harvard University. I am currently a post-doctoral researcher at the University of Texas, Austin studying threespine stickleback. They're not anoles, but they're cool too.
During our Anolis distichus work in the DR last summer, we found one male who had a portion of his dewlap that was completely transparent!
Holey dewlapped Anolis distichus from near Higuey
Of course, there was a hole in his dewlap. (Sorry Manuel).
It’s fairly common to find male anoles with damaged dewlaps. Sometimes there’s a hole punched through like the individual pictured here. (Did he snag it on a thorn? Was he pecked at by a bird?) Other times, the hyoid process is broken such that the dewlap doesn’t fully extend, if it extends at all. Yet these males often successfully hold territories that include females.
A previous post on AA asked, “What’s all the fuss about dewlaps?” Link to that post to read about research that experimentally reduced or disabled the dewlap to study the consequences. These studies did not find an appreciable effect of a disabled dewlap on the outcome of male-male battles (staged in the lab) or on copulation success (measured in the field after dewlap manipulation). These results suggest, counterintuitively, that dewlaps may not play a large role in reproductive success.
"Fig. 33. Sitana minor. Male, with the gular pouch expanded (from Gunther's 'Reptiles of India')."
In The Descent of Man and Selection in Relation to Sex (1871), Darwin laid out his ideas about sexual selection. Darwin believed that sexual selection was distinct from natural selection; while natural selection operates through survival and fecundity, sexual selection operates through differences in mating success among individuals.
The puzzle that Darwin set out to solve was the existence of traits like the peacock’s tale or the elk’s antlers. These traits differ between sexes but aren’t related directly to mating. And, these traits appear to be quite costly. Darwin reasoned that these costly traits must benefit the bearer in some way related to mating success. Most likely, these benefits accrued during battle with other members of same sex for mates or during the courtship of the opposite sex. In both cases, having the costly trait benefitted an individual’s mating success beyond the incurred survival or fecundity cost.
Now, how does this discussion relate to anoles?
Cover of Science, 2 March 2012
Anoles have gotten the cover again! This time it’s on tomorrow’s issue of Science for this work by Jason Kolbe and colleagues, covered here on Anole Annals. The photograph of A. sagrei is by Neil Losin, whose photo- and videographic works have been profiled on Anole Annals several times before.
Clockwise from bottom left: Keats, Dickenson, Frost, You
Dear readers,
Here are the poems submitted to the Anole Annals Poetry Competition. We’ve decided to forgo public voting and merely list them for your enjoyment. For (to paraphrase), “poems are like gossamer, and one does not dissect gossamer.” Read on…
This is the last post (for a while, anyways) about species richness patterns in anoles. Unlike the previous papers and discussions (found here, here, and here), Algar and Losos (2010) zoom out from the Caribbean and take aim at the entire Anolis radiation.
Islands are often species depauperate relative to mainland settings, likely because their small size makes them difficult to colonize and those species that do make it are more susceptible to extinction. Yet, islands also house many iconic evolutionary examples of adaptive radiation. Algar and Losos (2010) point out that this discrepancy stems mainly from the role that in situ evolutionary diversification plays in these two scenarios. In their paper, Algar and Losos, using anoles of course, explore how in situ diversification on islands affects the relationship between island and mainland species richness.
Lineage accumulation curves (Fig. 2, Rabosky and Glor 2010) showing that Hispaniola (blue), Jamaica (purple), and Puerto Rico (orange) have reached speciation-extinction equilibrium. Cuba (red) is still gaining species.
Losos, J.B., and D. Schluter. 2000. Analysis of an evolutionary species-area relationship. Nature 408: 847-850.
Losos and Schluter (2000) return to Caribbean anoles to test three hypotheses about the species-area relationship: (1) that there is an area threshold above which speciation surpasses immigration as a source of new species; (2) above the threshold size, speciation events per unit time should increase with island area; and (3) the slope of the species-area relationship should become steeper above the area threshold. Qualitatively similar to Losos (1996), this paper was novel in that a newly available, nearly complete, mt-DNA phylogeny allowed Losos and Schluter to reconstruct immigration and speciation events and to model whether species number has reached speciation-extinction equilibrium.
As alluded to previously, MacArthur and Wilson (1967) did consider evolutionary processes when they developed their Theory of Island Biogeography. Specifically, in situ evolutionary diversification (i.e. speciation) may contribute substantially to the species diversity of an island and should be considered in any general attempt to model species-area relationships on islands. Building on Rand’s 1969 paper studying the ecological determinants of species richness in Caribbean anoles, Losos (1996) incorporates an evolutionary perspective into the Caribbean Anolis species-area story.
This is the first of a series of posts that will review a number of papers that examined species richness patterns in anoles, starting with Rand’s 1969 paper described below and moving towards the present day understanding. Read on!
Species richness predictions from the Theory of Island Biogeography
The empirically observed species-area relationship (SAR) is one of the closest things to a law that we have in evolutionary ecology. All else equal, the larger the area, the more species will be in it. In a paper in 1963, and a book in 1967, MacArthur and Wilson (M&W) put forward the Theory of Island Biogeography (TIB) to explain the species-area relationship on islands. They observed that the number of species that inhabit an island scales positively with island area and negatively with distance of an island from the mainland species source. M&W argued that the SAR is governed by two ecological processes: colonization and extinction. Colonization probability increases with the size of an island and decreases with island distance from the mainland. Extinction probability increases as island size decreases because small islands support smaller population sizes and leave species are more vulnerable to fluctuations in abiotic and biotic environmental factors. Thus, the TIB predicts that large islands close to the mainland will be species rich, while small islands far from the mainland will be species poor. The TIB inspired thousands of papers: according to Google Scholar, the 1967 book has been cited 11,148 times and the 1963 paper has been cited 1,416 times.
By Allison Hsiang, Fall 2007. A flatbed digital scanner is a great tool in the lab and the field for getting area, width, and scale counts from toepads.