Anole Annals

Bob Trivers is renowned as one of the most important theorists in the history of evolutionary biology. Less well known, however, is undoubtedly his most important work, on the mating behavior of Anolis lizards. Seriously, his 1976 Evolution paper showing size-assortative mating in the beautiful A. garmani of Jamaica was an important demonstration of sexual selection back in the days before its prevalence was widely appreciated, and his book chapter in the Ernest Williams festschrift on A. valencienni is also a classic*. (note: most of Trivers’ papers can be found on his website)

Bob is currently back in Jamaica and is keeping an eye on the green guanas, as they’re called. He reports:

“Here is the largest male on my property copulating for 34 minutes—impervious to my camera—with a long, slender—dare I say?—attractive female but here is the kicker, two hours earlier he had copulated with another female and so far as I can tell, he used his left hemipenis on the first and the right one on the second.”

Several days later, the same fellow was up to it again: “didn’t think i could get any closer to the monster male, did you? Watched the whole courtship from a distance of several trees and 20 yards; she stayed posing the whole time—beautiful sight—with her whole body off the substrate except the tip of her tail raised in a captivating arc; she never moved once as he traversed the distance dewlap-ing and head-bobbing—she head bobbing sometimes as well.”

Note that the big fella’ has switched sides again, using his left hemipenis this time.

And on the subject of hempenial switching, here’s a summary of what we know about that, from Lizards in an Evolutionary Tree (footnote 174, p.137):

Anoles (at least A. carolinensis and A. sagrei, the only species so studied) alternate the use of hemipenes. Each hemipenis is connected to its own testis. If prevented from using one hemipenis (by placing tape over one side of the cloaca), the male transfers significantly fewer sperm when it continually reuses the same hemipenis (Tokarz, 1988; Tokarz and Slowinski, 1990).”

* Hicks, R.A., and R.L. Trivers. 1983. The social behavior of Anolis valencienni. Pp. 570–595 in A.G.J. Rhodin and K. Miyata, Eds., Advances in Herpetology and Evolutionary Biology: Essays in Honor of Ernest E. Williams. Museum of Comparative Zoology, Harvard University: Cambridge, MA.

Baby Anolis proboscis. Photo by Santiago Ron

After prolonged efforts, Ecuadorian anole maestro Fernando Ayala-Varela succeeded in hatching out a baby horned anole. And break out the blue wrapping paper–it’s a boy! And lo and behold, answering a question we all had, the little fellows have little nubbly horns! Well done, Fernando!

The Museum of Comparative Zoology will soon publish a major monograph on the anoles of Honduras in the Bulletin of the MCZ and we are looking for a photo of a Honduran anole to put on the cover. We’re looking for an eye-catching shot, suitable for presentation in a vertical format. If you have one that we could use, please let me know.

A while back we had a post featuring a photo of Anolis limifrons in full battle mode, tongues sticking out. Check out the comments on that post for discussion of the prevalence of this behavior. One commenter said that he’d seen it in A. cupreus, and now here’s visual proof.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

New readers to Anole Annals may be unaware of the AA Ecomorph Line of Wristwear. These snazzy chronometers will be the hit of any party, and would make an excellent gift for the punctuality-impaired. Our initial  release featured four of everyone’s favorite habitat specialists, but grass-bush anoles were subsequently added. Who knows what’s next? Suggestions? These retail at at zazzle.com for the low, low price of $47.95, but if you act quickly, there’s a 50% off sale through midnight tonight–use the code “SUNDAYDEAL47” at checkout. Don’t be the last one on your block to not have a lizard on your watch!

Trunk-Crown: Anolis allisoni

Crown-giant: Anolis equestris

Twig: Anolis occultus

Trunk-ground: Anolis marcanoi

Grass-bush: Anolis pulchellus

 

Photographer and videographer extraordinaire Rick Stanley, whose work has appeared on AA previously, has just put together a short video of a number of Draco  species signaling and gliding. Some of the shots are extraordinary—it’s particularly cool to see them use their throat lappets and wings for communication. Check it out on Vimeo!

Adam Freedman is spearheading an effort to identify the genes responsible for anole dewlap color. He’s looking for information on the ontogeny of color in male green anoles, i.e., when the red first appears in a juvenile male. Here’s what he has to say: “In our ongoing work on the genetic basis of dewlap pigmentation, we are looking to investigate changes of gene expression as pigmentation emerges in juvenile male A. carolinensis. However, we do not have any information as to approximately how long after hatching red/pink pigment starts to be visible on the throat, even if perhaps the dewlap has yet to fully form. Does anyone have any information from following hatchlings that could inform our efforts?”

Can anyone help?

 

Martha Muñoz presented data on how shifts in behavior constrain evolution of thermophysiology and drive morphological differentiation in the Anolis cybotes complex. The A. cybotes complex occurs across a large altitudinal range on the Caribbean island of Hispaniola and Martha was interested in whether and how lizards are adapted to thermal differences at different elevations. Martha tested whether body temperatures differ between lizards found in the different thermal habitats. Sampling more than 400 individuals, Martha did not find differences in body temperature between the populations. This is surprising because ambient temperature differed by more than 10 degrees Celsius between the low and high elevation localities.

So, if temperatures differ so dramatically among the different altitudinal habitats, how do lizards maintain similar body temperatures? Habitat use data from the two populations show that the high elevation lizards use rocky substrates more often than low elevation lizards, which are mostly found on tree trunks and other types of vegetation. Data obtained by using copper models that measure temperature as a lizard would experience it in a given habitat show that rock habitats are too hot at lower altitudes, but ideal at higher ones. This suggests that lizards keep their body temperatures stable by shifting from arboreal habitat type to rocks in higher elevations.

Martha then asked whether similarity in body temperature was matched with similarity in underlying thermal physiology. In ectotherms such as lizards, the ability to perform a task is dependent on temperature such that is optimized over a narrow range and then drops at lower and higher temperatures until the animal is immobilized. She found that lizards from all populations have similar preferred temperatures, and so their underlying physiologies do not appear to be evolving.

While thermoregulation keeps thermal physiology stable, the shift in structural habitat affects morphology. Martha measured morphological characters such as head shape, limb proportions, and lamella number to test whether habitat use has driven morphological change. Martha found that lizards in high elevations have wider and flatter heads and shorter limbs than populations in lower habitats. Thus, she found that a thermoregulatory behavior impedes physiological evolution while simultaneously driving morphological evolution.