Category: New Research Page 50 of 67

Brad Lister and Andres Garcia report from Guanica, Puerto Rico:

Most likely, every researcher working in the field with anoles has had the same questions that we’ve wondered about for many years.  How much time do resident species spend in the canopy where they are hidden from our view? What is the home range of males and females? On average, how far do individuals move per day? On days when most of the lizards in a given habitat seem to disappear, where do they go? We tried to answer these and related questions by conducting hundreds of hours of observation on Anolis nebulosus in the Chamela dry forest in Jalisco, Mexico. Anolis nebulosus is very rare in this area and we spent more time finding lizards (2-3 hrs/individual) than actually making observations. Often, after hours of searching, the focal individual would disappear from view within minutes.

Obviously the ability to easily find and track small anoles using radio telemetry would be a major asset in our efforts to understand their behavior and ecology.  Previously, transmitter size limited radio tracking to relatively larger lizards such as Sceloporus, Phrynosoma, and Ameiva. Recently, however, Advanced Telemetry Systems has developed 0.2 and 0.5 gram transmitters that make tracking even 3-4 gram female anoles feasible. We are currently in Puerto Rico continuing with our research on climate change and Anolis ecology, and decided to use the ATS transmitters to track A. gundlachi, A. cooki, and A. cristatellus.

The photo to the left illustrates the ATS equipment we are using in the Luquiilo rainforest and the Guanica tropical dry forest.

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What can a kitty cam tell us about the secret lives of anoles? Photo from http://blogs.inlandsocal.com/pets/4501cat.jpg

The 97^th annual meeting of the Ecological Society of America begins Sunday in Portland. These meetings are truly enormous, and given the great amount of ecological research, past and present, on anoles, it’s surprising that there are not more anole talks scheduled. Nonetheless, there are three, and they look to be good ones. On Tuesday, Sean Giery will talk about studies on the ecosystem role of anoles in Miami. Basically, by examining stomach contents and measuring stable isotopes, he determined the extent to which terrestrial resources enter arboreal ecosystems. For A. equestris and A. distichus, the route is terrestrial insects walking up trees and being eaten, whereas for A. sagrei, it results from foraging on the ground. Also on Tuesday, Jason Kolbe talks on an experimental study of founder events in the Bahamas. We’ve already reported on this study, but Jason will be providing at least a few snippets of new data from this year’s field season. Finally, on Thursday, Kerrie Anne Lloyd will talk about a study looking at predation rates by domestic cats in Georgia, as determined by placing Kitty Cams on housecats. Turns out that a favorite prey item is, alas, green anoles.

Check out the abstracts for these talks below the fold, and if any AA readers attend the talks, please file a report.

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Photos from Cádiz and Birds report in IRCF Reptiles & Amphibians.

Trunk anoles are the least diverse and most enigmatic of the six replicated anole ecomorph categories (the others are grass-bush, trunk-ground, trunk-crown, twig, and crown giant). Numerous species of trunk anoles belonging to the distichus species group are a dominant component of Hispaniola’s anole fauna, but Cuba has only one very rare trunk anole species and Jamaica and Puerto Rico have no trunk anoles whatsoever.  In the latest IRCF Reptiles & Amphibians: Conservation and Natural History, Cádiz and Bird report the first occurrence of the Cuban trunk anole – A. loysianus – on Isla de Juventud.  This is the first time that this spectacular little anole species has been reported from Cuba’s largest satellite island.

As impressive as their current diversity may be, anoles have a rather pathetic fossil record.  Aside from a smattering of subfossils that are less than a million years old, all we have to work from are a few amber specimens from the Dominican Republic preserved over a narrow temporal window (15-20 mybp).  This lack of fossils is problematic because molecular genetic data suggest that that Anolis may be more than 50 million years old.  The fossil record for anole relatives isn’t much better, with only a handful of well-characterized fossils that are greater than 10 or 20 million years old existing across Iguania.  Although they are relatively uncommon, previous reports of iguanian fossils have occasionally been sloppy about assignment to extant clades.  Daza et al. (2012) have done a remarkable job of clarifying our understanding of fossil iguanians by providing not only a remarkably detailed and nuanced description of a new fossil iguanian from the Late Pliocene, but also by conducting quantitative phylogenetic analyses that place this fossil in a large tree that includes a diverse range of other fossil and extant iguanians.

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Anolis carolinensis is increasingly used as a genetic model organism, but we know suprisingly little about the distribution of geographic genetic variation in this species across its native range.  At this year’s evolution meetings, Marc Tollis presented his recently published work on phylogeography of Anolis carolinensis.  His work provides basic information on geographic genetic diversity within A. carolinensis, and permits tests of hypotheses about the contribution of riverine barriers, sea-level changes, and southern refugia to this diversity.  Tollis sampled 190 anoles from 9 states and obtained sequence data from mtDNA and 10 novel nuclear loci (4 introns and 6 anonymous loci).  Using phylogenetic analyses and the Bayesian clustering algorithms in Structurama, Tollis identifies four major clades that appear to have diverged from one another around 2 million years ago: North Carolina, Gulf-Atlantic, Suwannee, and Everglades.  Although these populations appear to have experienced range expansions, Tollis rejects the southern refugium hypothesis because expansion events predate the inter-glacial, genetic diversity is no greater in the south, and there is no consistent pattern of northern genotypes nested within southern genotypes.  Instead, Tollis’s data points to a rapid and recent westward expansion.    Tollis’s work also rejects the hypothesis that rivers are important barriers to Anolis carolinensis dispersal, a result that he suggests is not surprising given the group’s well-established overwater dispersal capabilities.  Because this phylogeographic work on Anolis carolinensis rejects both the riverine barrier and refugium hypotheses, it appears that the distribution of genetic diversity is somewhat unique and not widely shared with other taxa distributed across the same region.  Phylogeographic analyses of A. carolinensis are long overdue and Tollis’s presentation and associated publication are a most welcome contribution to the field.

Tollis M, Ausubel G, Ghimire D, & Boissinot S (2012). Multi-Locus Phylogeographic and Population Genetic Analysis of Anolis carolinensis: Historical Demography of a Genomic Model Species. PloS one, 7 (6) PMID: 22685573

As regular readers of this site will know, anoles are remarkable for the repeated, independent evolution of ecomorphs on the four islands of the Greater Antilles. Each ecomorph is defined by a suite of ecological and morphological traits that appear to be shaped by natural selection.

In a recent paper, Kolbe et al. ask whether those suites of morphological traits are actually suites. In other words: is convergence in form across islands reached by evolving the same sets of characters in a similar manner? Do all trunk-ground ecomorphs, for example, achieve relatively long limbs by growing both the femur and the humerus (i.e. those traits covary together)? Or do some trunk-ground anoles achieve long limbs by only growing the tibia and the radius while others grow the femur and radius etc.?

Covariance ellipses for 8 species for five trait sets. Find the ellipse for Anolis distichus in the first column. It suggests that A. distichus will have a short humerus when it has a short femur and a long humerus when it has a long femur and this covariance is fairly tight (an oblong ellipse). For lamella# and femur length, however, there isn’t a tight relationship (a circular ellipse) and it’s hard to predict lamella# from femur length. Note the similar shape of the covariance ellipses for the three trunk-ground anoles, A. gundlachi, A. sagrei, and A. cybotes. These suggest convergent evolution of trait sets in that ecomorph.

Understanding whether and how different sets of traits vary together can give a good understanding of how natural selection and evolutionary history combine to explain the convergent evolution of Anolis ecomorphs.

The authors ask several questions in this paper.

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The first poster session at Evolution 2012 got off to a great start last weekend with Rosario Castañeda’s poster on ecomorphological evolution in mainland Anolis.  Currently a post-doc in the Losos Lab at Harvard, where she’s working to bring Anolis to the Encylopedia of Life, Rosario’s Ph.D. thesis with Kevin de Queiroz and associated publication investigated phylogenetics and ecomorphological diversification of the Dactyloa clade of Anolis.  For those who aren’t already familiar with the Dactyloa clade, this group of impressive anoles can be found in the Lesser Antilles and South America.  In her poster, Rosario presents results obtained by combining her multi-locus phylogeny with morphometric data.

Using UPGMA analyses of principal component axes extracted from morphological measurements of 50 species of Dactyloa and 28 species from the Greater Antilles, Rosario initially reported recovering nine distinct morphological clusters (four of which include only one species).  Rosario further reported that these phenotypic clusters do not correspond with monophyletic groups on her phylogenetic tree, suggesting that each cluster did not simply evolve a single time.  Finally, Rosario used distances among species in morphometric space to show that fifteen species in the Dactyloa clade are similar to one of the replicated Greater Antillean anole ecomorphs.  She specifically reported that species from the Dactyloa clade can be assigned to trunk-crown, trunk-ground, and twig ecomorphs.

The Evolution meetings are now ended, but the fond memories linger on. Such as Yoel Stuart reporting the results of his study of character displacement in Mosquito Lagoon, Florida. Dredge spoil islands were created about 50 years ago when the area was dredged, producing big piles of sand which were subsequently colonized by plants and, eventually, green anoles. Within the last 10 years, many islands were invaded by brown anoles, but some remained sagrei free. Yoel set out to compare the green anoles on islands with and without brown anoles.

First, though, he demonstrated the islands with and without brown anoles didn’t differ consistently in any environmental parameter. Thus, nature has set up a very good experiment.

Yoel found that green anoles perch higher in the presence of brown anoles, presumably a result of interspecific interactions. Moreover, on brown anole islands, green anoles have better developed toepads. A common garden experiment reveals that these differences are  not the result of plasticity. Hence, morphological differences have evolved in a very short time as a result of a habitat shift caused by the presence of another species–an excellent example or rapid evolutionary change and character displacement in action.

Many studies find that two populations are extremely genetically differentiated and assume that they are reproductively isolated. Last night, Anthony Geneva reported results of a study that goes the next step, actually testing for the form of reproductive isolation. His focus was on two parapatric members of the Anolis distichus group in Hispaniola that differ in dewlap color and genetically differentiated (see previous talk in this meeting  by Julienne Ng). By bringing individuals into the laboratory and conducting a massive breeding experiment, he tested whether they would mate and produce offspring and, if so, whether the offspring were viable. This is an enormous undertaking–something like this has never been done on anoles.

After one generation of the two generation experiment, some results are already clear. Members of the  interspecific crosses (based on genetic differentiation, they have been named as different species) will mate–no pre-mating isolation, apparently, despite the different dewlap colors; or at least, not complete isolation. However, the number of inviable eggs is greater in the hybrid crosses. No signs yet of Haldane’s rule of any asymmetric degree of postmating isolation, but more work is yet to come.