Anole Embryos Don’t Mind the Heat

Adult male A. cristatellus in survey position on a tree next to an urban street. Photo credit: Renata Brandt

Walking down “Red Road” in Pinecrest neighborhood of Miami, FL, it is hard to miss a myriad of lizards on trees and street lamps. Among the many city-dwelling residents, the Cuban brown anole (A. sagrei) and the Puerto Rican crested anole (A. cristatellus) are seen virtually everywhere. While there is evidence that anoles are adapting to urban landscapes, most past studies have focused on adult stages (Kolbe et al., 2012; Winchell et al., 2016; Lapiedra et al., 2017) and early life stages have been largely ignored. Our recently published study in the Journal of Thermal Biology (Tiatragul et al., 2017) was the first to address how anole embryos could facilitate establishment of populations in cities.

The transformation of natural habitats into urban landscapes dramatically alters thermal environments, which in turn, can impact local biota. For ectothermic organisms that are oviparous (like anoles), developing embryos are particularly sensitive to these altered environments because they cannot behaviorally thermoregulate and are largely left to the mercy of their surrounding environment. Yet, we know little about how thermal environments in urban and forested areas affect embryo development and hatchling phenotypes.

Figure 2. Mean incubation duration is shorter when eggs are incubated at urban temperatures (hotter). See publication for full results.

Mean incubation duration is shorter when eggs are incubated at urban temperatures (hotter). See publication for full results.

To determine if embryos from urban and forested sites are adapted to their respective thermal environments, we incubated eggs with temperature regimes that mimic likely nest conditions in both urban and forested environments. Our results show that for two species (A. sagrei and A cristatellus), urban thermal environments accelerated development, but had no impact on egg survival or any hatchling phenotypic traits measured (including body size, running performance, and locomotor behavior). Furthermore, there is no evidence that embryos from either habitat are adapted to their respective thermal environments. Rather, this lack of major effects suggests that both anole species are physiologically robust to novel environments. This may explain their success in establishing populations in human-modified landscapes.

Physiological adaptation by embryos are not required for a population to establish successfully. Maternal behaviors, like maternal nest site selection could shield embryos from lethal conditions. Hence, our next study is going to involve quantifying maternally selected nest sites in the urban and forested landscapes.

About Putter Tiatragul

I'm a graduate student in the Warner Lab broadly interested in how animals adapt to urban environments and other human disturbances. Learn more about my research at stiatragul.weebly.com

5 thoughts on “Anole Embryos Don’t Mind the Heat

  1. Excellent topic and research! I would be interested to see if Anolis equestris embryos are as robust and if the temperatures in Anolis incubation environments impacts sex determination. Good stuff, thanks.

    1. Thank you for your comments Chuck, I did see several A. equestris in Miami while catching some A. sagrei for Josh Hall’s project to study how urban heat spikes may influence embryos.

      This post: http://www.anoleannals.org/2013/04/21/nesting-knight-anoles/
      by Sean Giery talked about equestris nesting in the ground so I think it will be interesting to see how they do as well. If I find equestris eggs over the summer I’ll make sure to report it here as well!

    1. Thanks Ambika!

      In early March, Josh Hall (Warner lab mate) and I spent about 10 minutes running our fingers through the leaf litter under ficus trees along Red Road (Miami) where A. cristatellus was abundant and found 8 hatched eggs. Most of them were in the moister areas closest to the roots. Perhaps you could try that your study site at University Gardens? I’ll be curious to see what you find!

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