Maternal nesting behavior in lizards enhances colonization of urban environments

Abstract

Lizards occupy diverse habitats around the world from dense forests to arid deserts. The environments in which lizards exist pose different challenges for nesting females because embryo development is directly affected by nest microenvironments. For lizards that occupy urban environments, the nesting situation for females is exacerbated as ground temperature can extend beyond tolerable limits for developing embryos. Despite this, many species have established populations in urban areas outside their native ranges and habitats. Without physiological adaptations by embryos to markedly hotter conditions, maternally-selected nest sites may facilitate embryonic survival. Mothers may choose nests in microenvironments that are, on average, cooler than microenvironments that are not used for nesting. In turn, maternal choice of nest microenvironment should facilitate egg survival. To test the hypothesis, I studied the Puerto Rican crested anole (Anolis cristatellus) from urban area in Miami, FL. I searched random plots for nests and recorded microenvironment variables in the field. In the lab, I incubated eggs from a captive colony of wild-caught A. cristatellus from Miami under thermal conditions that mimic 1) maternally-selected nests in urban areas, 2) sites not used for nesting in urban areas, and 3) nests sites in a nearby forest. My results indicate that thermal regimes of maternally-selected urban nests yield higher egg survival than those of sites that were not used by nesting females. Survival did not differ between urban and forest nest treatments. However, eggs incubated under urban treatments developed faster and hatched earlier than those incubated under forest thermal regimes. My study revealed that maternal nest sites in urban areas shield embryos from potentially lethal conditions, which enhances colonization of anoles in Miami.