Author: Martha Muñoz Page 3 of 8

When I was a kid, the first week of January used to be such a bummer for me because it meant that the holidays were over. But now the first week of each year means that the annual meeting of the Society for Integrative and Comparative Biology (SICB) is underway! The meetings run from January 3rd until January 7th, and there are 30 talks/posters this year about anoles! I won’t be attending this year, as I’m currently based out of Australia (AKA land of no anoles), so I’ll be looking forward to the posts on this blog to hear what’s new and exciting in Anolis research. Stay tuned!

Winter is coming to the Northern Hemisphere, which can only mean one thing: SICB is upon us. Every January, the Society for Integrative and Comparative Biology (SICB) hosts its annual meeting. SICB 2015 will take place in West Palm Beach, Florida. Perhaps it’s due to the fact that southern Florida is the global epicenter for Anolis invasions, but talks and posters about anoles will be particularly numerous at this meeting. By searching for presentations containing the keyword “Anolis,”,  got 30 hits! That’s a much better turnout than the last few years, and hopefully a sign that Anolis presence at large annual meetings is on the rise. What’s more, there are two Anolis talks scheduled for the Huey symposium. This symposium is a competition for the best student talk hosted by the Division of Ecology and Evolution, and is named after anolologist and distinguished evolutionary biologist Ray Huey. I won’t be there this year, but I look forward to reading about all the new and interesting research involving anoles on this blog. Best of luck to all the presenters!

 Robert Cox, from the University of Virginia, presented his work examining the relationship between fitness and body condition in Anolis sagrei from the Bahamas. Many evolutionary biologists want to understand selection in wild populations. But in order to do that we need to measure fitness. Finding out who survives to maturity, who finds more mates, and who produces the most viable offspring, however, is quite difficult. For this reason, many researchers use body condition, or the ratio of body mass to body size, as a proxy for fitness.

One of the issues with using body condition as a proxy, however, is that it varies a lot, even within the same individual! When resources are plentiful, even less fit individuals can fatten up. And, when the going gets tough, even vigorous individuals fare poorly. For his study, Bob wanted to know whether body condition was actually a good proxy for fitness. He did this by actually measuring fitness in the wild by tracking survivorship in A. sagrei from the Bahamas. Most studies examining survivorship are performed over a single season or a few seasons, but Bob managed to gather data for 41 estimates of selection over 10 years of work. The numbers are impressive: He tracked survivorship over the summer, which is the height of the reproductive season, for 4,608 adults from 7 populations.

What he found was surprising – it turns out that, in these populations of A. sagrei, fatter is not fitter. He found no evidence for selection favoring better body condition in males or in females. He did find, however, strong selection for body size, rather than body condition. He also found correlational selection on body condition and body size – Specifically, he found that body condition did matter, but only in really large males. But this effect only explained a small proportion of the residual variance. The selection on body size, he found, was much stronger.

Bob’s work emphasizes that we, as a community, need to be wary of the traits that we use as proxies for fitness. In the case of A. sagrei, it didn’t matter what condition the lizards were in, except in the case of larger lizards. However, survival is only one piece of the fitness puzzle. To know how body condition influences fitness, we would ideally also want to know whether fatter individuals gain more access to mates and produce more viable offspring (i.e., more fecund). Together, Bob’s work highlights the importance of body size in survivorship and provides new evidence that fitness proxies need to be experimentally verified before being widely applied.

Mean CTmin for invasive (gray) and native range (green) populations of Anolis sagrei.

Most anole enthusiasts are familiar with the brown anole, Anolis sagrei, because it is a highly successful invader. Although it can be found as far away from its native Cuba (and nearby islands) as Hawaii and Taiwan, most of what we know about invasive populations of this species come from work conducted in Florida. A recent study by Jason Kolbe and colleagues demonstrated that physiological traits vary with latitude in A. sagrei from Florida. Specifically, cold tolerance (CTmin) and desiccation resistance were lowest at higher latitudes in Florida. Tamara Fetters, a graduate student in Joel McGlothlin’s lab at Virginia Tech, supplemented this work by adding data from a native population of A. sagrei found on the island of San Salvador in the Bahamas.

Box plots showing rates of evaporative water loss in invasive (gray) and native range (green) populations of Anolis sagrei.

Tamara found that mean CTmin for A. sagrei from the Bahamas was close to 12°C, which was significantly higher than in Tifton, the most northerly population from Jason Kolbe’s study, but not significantly different from the lower latitude populations in Orlando and Miami. Similarly, she found that desiccation tolerance in native range A. sagrei was significantly higher than in lizards from Tifton, a result that she attributes to the lower relative humidity found at higher latitudes in Florida. Tamara’s future goals include measuring more physiological traits, such as oxygen consumption and heat tolerance (CTmax), along with morphological traits associated with desiccation resistance (scale number and scale area), for various invasive and native populations of Anolis sagrei.

I may have given the Evolution 2014 logo an Anolis upgrade.

It’s that time of year again! The annual Evolution meeting is upon us. In just under a month, scientists from around the world will converge on Raleigh, North Carolina to learn about new and emerging trends in evolutionary biology. As with the Society for Integrative and Comparative Biology meetings, anoles have had a strong presence at Evolution. It appears that this year will be no different. A quick search for talks including the terms “anole” or “Anolis” yielded seven presentations, and so this meeting should be quite fruitful for those of us interested in what’s new and exciting in Anolis. You can view the list of scheduled presentations here – simply put Anolis into the keyword search at the bottom and all seven presentations will be displayed. Or just look below. As in previous years, we’ll be blogging live from the conference, so stay tuned.

Tropical ectotherms such as anoles are considered to be especially vulnerable to climate change. Given that tropical lizards already function near their upper tolerances, even a modest increase in ambient temperature can have disproportionately large negative fitness consequences. Most models that predict how climate warming will impact tropical ectotherms rely on ambient temperature. Michael Logan, a graduate student at Dartmouth College, presented a study suggesting that temperature alone is insufficient to predict the impacts of environmental warming on organismal fitness. He points out that other abiotic factors, such as humidity and wind speed, may be equally important in determining whether and how organisms will be impacted by climate warming.

For this study, Michael explored how daily variation in temperature, humidity, and wind speed interact to determine the abundance of two species of anole, Anolis allisoni and A. lemurinus, from the Bay Islands of Honduras (see map above). He deployed sensors that recorded temperature, humidity, and wind speed in a forest site, where A. lemurinus is found, and an open-habitat site, where A. allisoni is found.

Contrary to expectations, he found that environmental temperature alone is a poor predictor of lizard abundance in the open habitat. Rather, wind speed constrained lizard activity in the open habitat more than any other environmental factor. Further, environmental temperature predicted lizard abundance only when wind speed was low. Michael posits that there might be a trade-off between thermoregulation and evaporative water loss on windy days, such that the ability to achieve high body temperatures through basking may be counterbalanced by the ability to maintain water balance. Michael found that in the closed forest habitat, the variance in environmental temperature and the degree to which the temperature varied from the lizard’s optimal range were important predictors of A. lemurinus abundance. These results suggest that this species might thermoregulate more than was previously thought, as forest anoles are generally considered to be thermoconformers.

Together, Michael’s results suggest that factors besides temperature are important determinants of lizard abundance, and that they should be more explicitly considered in predictive models for the biological impacts of climate warming.