Tulane University. Photo by Sally Asher.
Hello, Anolis community! I wanted to give a brief heads up that I will be starting a faculty position in the Department of Ecology and Evolutionary Biology at Tulane University this fall. If you or someone you know is interested in a graduate or postdoc position studying physiological ecology and evolution in anoles or other reptiles while living in the great city of New Orleans, let me know. You can find out more information about my work here. Thanks!
We as a species are rapidly changing the global environment. The changes that get the most press are those related to climate, but we are also changing the structure of environments through land development. This leads to many important questions, one of which is whether or not the novel environments that we construct can drive evolutionary change. Kristin Winchell, a graduate student in Liam Revell’s lab at UMass Boston, has been addressing this question in the Puerto Rican lizard Anolis cristatellus, which is common in urban settings. Kristin hypothesized that urban environments should select for longer legs and greater surface area of lamellae (the morphological structures on anole toes that let them grip flat surfaces). Her reasoning was that long legs should allow animals to run faster, which should be beneficial in cities where perches and refuges are further apart than in dense natural forests. Greater surface area of lamellae should be beneficial for better grip of smooth man-made surfaces. Kristin compared morphological traits of multiple pairs of urban/natural environment populations and her hypotheses were supported. Not only that, but differences between populations were maintained in individuals developed under common garden conditions, consistent with a genetic basis of the differences. You can see these results in Kristin’s excellent recent paper in Evolution. Kristin also presented some new preliminary results that directly link the morphological changes she has observed to performance on man-made surfaces. Overall, Kristin’s work indicates that urban environments can be a potent force of rapid microevolutionary change and highlights that we are not only changing the abiotic landscape of the globe, but the evolutionary landscape as well.
Anolis sagrei. Photo by Alex Gunderson
The concept of trade-offs, that if you want to increase your performance in one function you have to decrease performance in another, is fundamental to ecology and evolution. However, detecting trade-offs and the underlying mechanisms that give rise to them is extremely difficult. In his talk, Bob Cox summarized years of research that he and his collaborators have done to understand life-history trade-offs in realistic ecological contexts using the brown anole (Anolis sagrei). Bob’s general approach is to experimentally manipulate the reproductive effort of individuals by removing ovaries and testes before releasing them onto cays in the Bahamas. He then estimates important ecological and physiological parameters such as survival, fat reserves, and immune function to see if he can detect trade-offs between reproductive effort and these other traits. In general, he has found that reproductive investment significantly decreases survival and physiological performance and that effects are often contingent upon factors such as the presence or absence of predators. Check out Bob’s website for a more information about his integration of experimental, ecological, and evolutionary studies to understand how trade-offs shape animal life-histories.
Anolis sagrei. Photo from Wild about Spain
An important problem in climate change biology is understanding how evolutionary dynamics will influence the ability of populations or species to persist as environmental conditions change. In general, there are three ways that such evolutionary change can occur: (1) novel beneficial mutations can arise de novo; (2) rare alleles within a population can become beneficial and sweep to fixation; or (3) gene flow between locally adapted populations can introduce beneficial alleles to populations that did not previously have them. The potential for this latter scenario was investigated by Mike Logan using A. sagrei on a system of cays off of the Bahamian island Exuma. Mike measured operative thermal environments on the cays and Exuma, as well as temperature-dependent physiology of the animals in each population. He found that the islands differed in mean temperature and variability, and that optimal temperatures for physiological performance correlated with mean island temperature. Next, Mike used genetic markers to estimate population structure and rates of migration between the keys and the mainland. He found evidence for extensive gene flow between the populations, but with an interesting twist: gene flow was highest between populations that had the most similar thermal environments. Within the context of climate change, the observation of gene flow among islands based on thermal conditions suggest that as conditions change across a species’ range, beneficial alleles may be able to move into the populations where they are needed most. Mike’s work adds an important piece to an emerging picture about the interplay between standing genetic variation, local adaptation, and responses to global change.
Jamal Murray. Photo from Johnson Lab website.
Activity is where the rubber meets the road in the interaction between organisms and their physical and social environments: in order to acquire energy, attract mates, and produce offspring you have to get up and move around. But what dictates how much activity an individual will engage in? We know a fair amount about what causes organisms to be more or less active, with temperature a particularly important one for ectotherms like anoles. Nonetheless, the physiological mechanisms that underlie activity variation are less well understood. Jamal Murray, an undergraduate in Michele Johnson’s lab, presented a poster at SICB that begins to address this question with the Puerto Rican Anolis stratulus. He put lizards into an enclosure with grids marked on all sides, and measured activity rates as the number of times individuals moved from one grid to another. Afterward, he measured blood glucose levels and found that individuals with higher glucose levels were more active. This suggests a proximate physiological mechanism driving differences in activity rates among individuals and, potentially, populations and species.
I think it’s time we had a talk. How do I put this? There’s going to come a time in your life where you start to notice, you know, things around you that maybe you didn’t notice before. You might not fully understand it, it can be confusing, and, well, I just want to make sure you’re prepared. What am I trying to say? Well, er, I’ll just say it. Anole sex. That’s right. That magical event when a male anole and his old lady get together to make sweet love. There have been a some posts recently on the morphology of the male’s one-twig-per-berry genitalia, anole copulation, and Isabella Rossellini. I thought I’d throw my hat into the ring focusing on the behaviors anoles exhibit while copulating, accompanied by a video of mating A. stratulus, a species of Puerto Rican trunk-crown anole.
The video starts out with the male displaying with bobs and dewlap, and moving a lot, appearing agitated. From what I’ve seen in Puerto Rico and the Bahamas, this is classic male anole hallelujah-I-think-I-might-get-lucky behavior. When the camera moves to the female and the male approaches her, you see her adopt a receptive posture. The male does a couple of push-ups, then bites her neck and the act begins.
During copulation both the male and the female bob, and the male displays his dewlap. Displaying during mating is common in anoles, and from the video you can see that these displays, and especially the dewlap, are pretty conspicuous. Which leads me to wonder why in the world they do it? This is brazen behavior. I saw lizard cuckoos and crown giant anoles (A. cuvieri) at this site on a daily basis, and I doubt either of these predators would pass up on a two-for-one meal if they saw it. Displaying seems to greatly increase the risk of an already compromising and thus dangerous pastime. Is it just a correlated response to the excited physiological state that likely accompanies copulation? Are the males and females communicating with each other? Good old-fashioned exhibitionism? David Crews has published some interesting work on anole display and female receptivity, but I’ve never seen anything that explicitly addresses the topic of display during the act of mating.
A male Anolis cristatellus from Puerto Rico. Photo by Dave Steinberg.
It is somewhat intuitive to assume that the body temperatures of “cold-blooded” animals like anoles must closely match ambient temperatures. For example, lizards from cold climates should be active at colder body temperatures than those from warm climates, and body temperature should change throughout the day in concert with air temperature. As Martha Muñoz has discussed, Cowles and Bogert laid this expectation to rest in 1944. They demonstrated that lizards can behaviorally thermoregulate, altering the effective thermal environment that they experience to remain within a “preferred” temperature range while active.
The potential benefits of behavioral thermoregulation are pretty obvious. Seek out a little sunlight on a cold day and you can go from freezing your hemi-penes off to enjoying a fulfilling day of doing whatever a lizard might find fulfilling. So for many years after Cowles and Bogert, observing patterns consistent with behavioral thermoregulation became the expectation.
Hello anolers. A friend of mine named Ryan Killackey is making a documentary film about the Yasuni region of Ecuador, home to indigenous tribes and incredible biodiversity (including anoles!). The region is also, not surprisingly, under pressure for development and the film is documenting that struggle.
Many anologists spend a lot of time travelling far and wide to work with our little lizard friends. I think this is one of the great perks of studying anoles, but it presents a host of logistical problems, one of which is finding convenient, affordable lodging in the myriad places you might go. Unfortunately, there are no centralized places to find information on where to stay, but I thought this blog would be a good place to start.
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