Hot off the press — the latest anole journal cover! In this issue of Nature Ecology & Evolution, Shane Campbell-Staton and I led a team of researchers to explore the effects of urban heat islands on anoles. We found that not only can urban Anolis cristatellus tolerate higher temperatures than their forest counterparts, but also identified genomic regions associated with divergent thermal tolerance. Check out a summary of this work at the urban evolution blog I co-edit, Life in the City: Anoles Adapt to Beat the Urban Heat.
Tag: thermal
Abigail Dennis at SICB 2020
Embryonic environment is arguably one of the most influential factors on offspring development and later-life phenotypes. For oviparous species, this critical stage can experience potential fluctuations in moisture, temperature, and oxygen-availability. However, maternal choice in nest-site has the opportunity to buffer embryos from environments that might negatively affect survival or disadvantageous phenotypes. Undergraduate student Abigail Dennis of Trinity University in San Antonio, TX in Dr. Michelle Johnson’s lab, sought to investigate maternal nest-site choice when mothers are given nesting conditions that have been shown to be unfavorable to offspring development.
To address this, Abigail housed female brown anoles (Anolis sagrei) in groups of 2-3 with 1 males per cage. Within each cage, females were given an option to nest in a heated box or an unheated box (ambient box). The heated nesting box was placed over a thermostat-controlled mat and both boxes were checked for eggs every 2-3 days. When an egg was found, depth and water proportion in surrounding soil were recorded. She predicted that females would avoid the deeper, warmer nesting conditions in the heated box and that nesting depths would be more variable in the ambient box. Thermal readings from the surface and base of the soil were recorded for each box. These temperatures were averaged in the ambient boxes and coupled with depth and temperature models for the heated boxes. Thermal conditions varied from 25.5 to 38 °C, although most nesting sites were found between 26.5 and 31 °C.
At SICB’s poster session on Monday, Abigail reported that there was no difference between the number of nest sites (N=36) found in heated or ambient boxes. However, females tended to avoid nesting in sites greater than 33 °C and there was a trend suggesting nests in the ambient box were deeper than those in the heated box. Soil moisture readings also did not differ between nest boxes. Abigail speculated that if global change increases surface soil temperatures, females may avoid higher temperatures that would negatively influence offspring development by altering their nest depth. Abigail is writing this work as part of her Senior Thesis and is interested in pursuing graduate work in the evolution of development.
Evolution 2015 is officially over and we have all sadly left beautiful Guarujá, Brazil. There were a lot of great talks and posters and a great representation of South American students and researchers. For coverage on the conference as a whole, check out #evol2015 on twitter! The herps were few and far between (I only saw 2 in my 16 days in Brazil!) but the posters and talks on herps were numerous. Unfortunately, anoles were poorly represented at Evolution this year with only three anole talks and a couple of others that briefly highlighted anoles. If you weren’t able to make it to Brazil, I’ve got the recap for you here.
A glimpse at the variation in gecko toepads
Starting off in one of the first sessions was a talk by Travis Hagey titled “Independent Origins, Tempo, and Mode of Adhesive Performance Evolution Across Padded Lizards.” Although his talk was mostly about geckos, he did shine the spotlight on anoles for a few minutes. He focused on the phylogenetic pattern of toepad adhesion in pad-bearing lizards: geckos, skinks, and anoles. Specifically he looked at how clinging ability (measured as angular detachment – check out one of his videos showing this) varied within and among clades. Unsurprisingly, he found that anoles don’t cling nearly as well as geckos. He also demonstrated that gecko toepad diversification best followed a Brownian motion model with weak OU and anole toepad diversification was best fit by a strong Ornstein–Uhlenbeck process. In other words, gecko toepads diversified slowly over a very long period while anoles were quickly drawn towards an optimum over a short time-period. Travis concluded that these patterns explain why there is a large amount of diversity in gecko toepads but not in anole toepads.
Next up was Joel McGlothlin, who also gave a non-anole talk titled “Multiple origins of tetrodotoxin‐resistant sodium channels in squamates.”
Lizard in an Evolutionary Tree's reworking of Williams' classic figure. Note that A. gundlachi is a trunk-ground anole, not, as indicated, a trunk-crown anole.
In this famous figure, Ernest Williams sketched out his view of how anole diversification occurred on the Greater Antilles, using Puerto Rico as an example. First, species diverge to use different structural habitat, producing the different ecomorphs. Subsequently, within-ecomorph divergence produces species that use the same structural habitat, but which occupy different climatic micro-climates, ranging from cool and moist rainforest to blazing hot and dry semi-desert. This two-stage pattern of evolution is displayed not only on Puerto Rico, but also on Cuba and Hispaniola (Jamaica, the most species deprived island, has little within ecomorph diversity).
In contrast to the plenitude of research in recent years on the adaptive basis of morphological differences among the ecomorphs, relatively little work has focused on the extent to which closely related species—members of the same ecomorph class—have adapted to occupying different microclimates.