We’ve previously reported on Anolis equestris introduced to the Bahamas and elsewhere, and brown anoles (A. sagrei) introduced to Turks and Caicos. Now the knight anole is in T&C and people are worried about the impact they may have.
Author: Jonathan Losos Page 21 of 130
Professor of Biology and Director of the Living Earth Collaborative at Washington University in Saint Louis. I've spent my entire professional career studying anoles and have discovered that the more I learn about anoles, the more I realize I don't know.
Read all about it in the (almost) latest from the October 2016 issue of Herpetological Review.
Two years ago, McCranie and Kohler published The Anoles of Honduras: Systematics, Distribution, and Conservation(available on Amazon for under twenty bucks and downloadable for free on the Museum of Comparative Zoology website).
In turn, two mostly favorable reviews were published. However, one of the reviews, by Levi Gray, did question whether a number of anole species recognized from small distributions in Honduras should be recognized as valid species, rather than just as populations of species that are widespread throughout Central America.
Writing in Zootaxa, Randy McCranie has now responded to this point, forcefully arguing that the species should be recognized and challenging his critics to present their own data if they feel otherwise. You’ll have to read Gray’s review and McCranie’s rebuttal yourself to decide what you think. Gray made his skepticism clear, he also did clearly call for more research to address the question.
These pages have previously told the tale of Anolis lineatus, the species whose dewlap is different on one side compared to the other. Now the work has been published in Breviora. Like all publications of the Museum of Comparative Zoology, the paper can be downloaded from the museum’s publications webpage.
The research project was actually explained in a delightful video put together by the three joint first authors, all of whom are headed to college this fall.
Photo by Carissa Wickens
Eileen Wickens, who just finished the fourth grade in north central Florida, is a lizard-catching machine and particularly adept at nabbing blue-colored green anoles (Anolis carolinensis). Here’s the story, relayed by her mom, Carissa:
The teal lizards do seem rare as we have only seen a few. We had one at our house last spring and the photo I sent you was taken at our horse teaching unit in Gainesville. We were running an equine behavior trial that day (we’re actually investigating startle phenotypes and genetics in our Quarter Horse herd), and I saw the lizard as we were packing up our gear. My daughter is very good at spotting and catching them, so we will definitely keep our eyes out and would be happy to provide a specimen for your genetic research if we can. I’ve attached the photo of the lizard we had at the house last spring. The green anoles are scare in our neighborhood and on campus compared to the brown anoles (short snouts with distinct, dorsal diamond or striped markings). They seem to far outnumber the greens.
From our brief observations of those two blue lizards this past year it does not appear they turn the bright green you see on the other Carolina Anoles, but it would be good to observe them for a longer period of time to be certain.
The Sensory Drive hypothesis predicts that species will evolve communication signals that are effective in the particular light environment in which they occur. Anolis lizards are an excellent example: in dark habitats, they tend to have light-colored, highly reflective (and transmissive) dewlaps that are usually yellow or white in color, whereas in bright, open environs, dewlaps tend toward blue, black, orange or red. However, demonstrating that these dewlaps are actually effective at being visible in their particular habitats has proven surprisingly challenging.
Leo Fleishman has been a leader in this area and in a talk at the sensory ecology symposium at the evolution meetings, he presented new and exciting developments. First, in line with previous work, he showed that the spectral reflectance/transmittance of dewlaps is not particularly well-matched to that of the background. Rather, the same colored dewlaps appear to be maximally contrasting with the radiance of the background across all habitats: basically all habitats have mostly green backgrounds, and red or orange stands out the best against the green background, no matter what the habitat. So much for sensory drive, it would seem!
But more recent work saves the day: it turns out that habitats differ in the total intensity of light (number of photons coming down) they receive and that, furthermore, across species, dewlap intensity (total photons reflected and/or transmitted) is negatively related to habitat intensity (with one notable outlier, the enigmatic A. gundlachi). Under the relatively low light conditions of forest shade or partial shade, color discrimination becomes more difficult, and colors such as red and orange and other dark colors do not stand out well against the background, because they simply do not emit enough photons to efficiently drive color vision. Yellow or white works better. Conversely, in intense light environments, there is enough light to easily see the darker colors, and these stand out well against the green background. Moreover, behavioral experiments confirm that in bright light conditions red stimuli are most visible against a green background, whereas in low light yellow stimuli are more visible. Thus, even though most Anolis habitats have similar spectral properties, differences in total light intensity strongly influence what colors are most effective, and thus appear to have played a major role in the shaping the evolution of dewlap colors.
Leo Fleishman discusses color space in four dimensions, corresponding to the four cones in the anole eye. For each species, red dots are color of the dewlap and green dots are the color of the background, indicating that dewlaps stand out against their background.
The Day’s Edge team combined with lizard behavior guru Manuel Leal–what could be better? Turns out that anoles have amazing navigation abilities, able to make incredible journeys over vast distances. Check it out, in either English (above) or en español (below).
The latest work on genetic differentiation and species status within the Anolis distichus group has just been published by MacGuigan, Geneva and Glor in Ecology and Evolution. In line with previous work from the Glor lab, the study finds evidence for seven distinct evolutionary lineages worthy of recognition as species, and further finds that variation in dewlap color in some cases does not correlate with geographic isolation. Finally, geographic isolation seems to play a key role in genetic divergence.
Here’s the abstract, followed by a few comments:
Abstract
Delimiting young species is one of the great challenges of systematic biology, particularly when the species in question exhibit little morphological divergence. Anolis distichus, a trunk anole with more than a dozen subspecies that are defined primarily by dewlap color, may actually represent several independent evolutionary lineages. To test this, we utilized amplified fragment length polymorphisms (AFLP) genome scans and genetic clustering analyses in conjunction with a coalescent-based species delimitation method. We examined a geographically widespread set of samples and two heavily sampled hybrid zones. We find that genetic divergence is associated with a major biogeographic barrier, the Hispaniolan paleo-island boundary, but not with dewlap color. Additionally, we find support for hypotheses regarding colonization of two Hispaniolan satellite islands and the Bahamas from mainland Hispaniola. Our results show that A. distichus is composed of seven distinct evolutionary lineages still experiencing a limited degree of gene flow. We suggest that A. distichus merits taxonomic revision, but that dewlap color cannot be relied upon as the primary diagnostic character.
The authors suggest that there are at least seven species within the distichus complex, but they suggest that it is premature to recognize them officially at this time. Nonetheless, Poe et al. in their recent Systematic Biology paper (hey! who’s going to write a post on this one?) recognize at least some of these taxa as distinct species.
Finally, I do have one tiny bone to pick. The authors state:
“Together these results suggest that dewlap color is not by itself a reliable diagnostic trait in the A. distichus complex, and perhaps in anoles more broadly.”
I take umbrage with the final statement, “and perhaps in anoles more broadly.” The distichus complex has always been recognized as the major exception to the idea that dewlap color variation relates to reproductive isolation. Consequently, demonstrating what has been suggested—with some evidence—for 40 years doesn’t necessarily argue against the role of the dewlap in reproductive isolation more generally. Now, you may quibble with the data underlying this general proposition, and it certainly is worthy of further study, but the results of this study confirm what was already recognized as an exception to this general rule..
Bill Rainey observed this lizard on a restored portion of one temple at Altun Ha, an ancient Mayan city in modern-day Belize, in an area shaded by trees. Anyone know what it is?
The following is taken from the Society for the Study of Amphibian and Reptile’s website:
Catalogue of American Amphibians and Reptiles
The Catalogue consists of accounts of taxa prepared by specialists, including synonymy, description, diagnosis, phylogenetic relationships, published descriptions, illustrations, distribution map, and comprehensive list of literature for each taxon. Over 900 accounts have been published since the initiation of the series in 1963. The series covers amphibians and reptiles of the entire Western Hemisphere. Previously, accounts were published as loose-leaf separates; beginning in 2013 accounts are published as on-line PDFs. All accounts are open access and are available for free download at the University of Texas Library Repository.
Just this week, one of the latest catalogue entries is for the little known Anolis ruibali of Cuba, written by Robert Powell, Javier Torres, and Nils Navarro Pacheco.
