Anyone who has set up an anole breeding colony in the lab knows how critical it is to provide the lizards with an appropriate substrate, with the right moisture content, for egg laying and incubation. Yet, in the field, lizards utilize a wide range of available egg-laying substrates. Graduate student Corey Cates in Dan Warner’s lab at the University of Alabama, Birmingham, considered the fitness implications of different egg substrates in a talk in the DEE (Division of Ecology and Evolution) Huey Award Competition for Best Student Presentation at SICB this week.
Corey studied populations of brown anoles (Anolis sagrei) on spoil islands in Tomoka State Park in Florida. Some of these islands contain organic soil and others are covered in broken shell pieces – substrates that differ in both physical structure and moisture content. Corey collected eggs from a laboratory population and incubated them in the lab under “wet” and “dry” conditions in both substrates. He then measured hatching rate, hatchling size, and desiccation tolerance, and his experimental results were striking: hatchlings from the dry soil treatment lost less water than the other treatments in the desiccation tolerance test! When Corey released the hatchlings in the field onto the different types of islands, he found that dry soil hatchlings had higher success than hatchlings from the other treatments on the dry (shell) islands, whereas wet and dry treatment hatchlings survived equally well on wet (soil) islands. Corey also found that the moisture level of the incubation substrate was more critical to hatchling success than the substrate type.
Overall, the adaptive significance of the plastic responses demonstrated in this study is intriguing. Corey’s next steps will include a study of one of the possible mechanisms underlying these results – whether scale number differs between hatchlings in the different moisture treatments.