Author: Lauren Neel

Recent increases in non-native species introductions by humans have spurred a flurry of research examining the subsequent impacts of species invasions. However, often times non-native species introductions go unnoticed until the species is already established. When predicting the effects of a species invasion, it is important to understand how population demographics change during the colonization and establishment stages. Amélie Fargevieille addressed this issue in her talk entitled “Population demographics of an invasive lizard following experimental introduction on small islands.”

Fargevieille and colleagues released adult Anolis sagrei onto islands off the northeast coast of Florida prior to the reproductive season and monitored survival and reproduction over the first reproductive season. The total density of lizards introduced to islands were the same, but four of their islands were introduced with male-biased populations and four with female-biased populations. They then examined the survival and reproduction of the descendants of the founding populations over the next two years. They found that male-biased and female-biased founding populations did not differ in survival rates. In addition, across all islands, juveniles had the highest mortality, which suggests that the ecological factors facilitating or deterring colonization in the earliest stages following an introduction play an important role in invasion biology. Looking forward to future work from Fargevieille and colleagues in the Warner lab!

Many biologists are interested in understanding how temperature affects animals throughout ontogeny. Egg incubation experiments are often done to examine how nest temperatures influence embryo development. However, the information gleaned from these experiments are only useful when comparing ecologically relevant thermal regimes.

Mallory Turner, an undergraduate researcher in the Warner lab at Auburn University, examined how embryo development differs between incubator thermal regimes in Anolis cristatellus and A. sagrei. Nest temperatures peak at different times of the day due to differences in the local environment (e.g., habitat structure, shade, etc.). Turner examined how incubator thermal regimes that were uncentered and peak-centered influenced development. Nest temperature data were used to create two 24-hour diel cycles. Anole eggs were incubated in incubators programmed to mimic hourly nest temperature data with temperatures either uncentered (uncentered regime), or with hourly nest temperature data aligned temporally at thermal peaks (peak-centered regime). She examined how thermal regimes impacted incubation duration and offspring phenotype. Incubator thermal regime did not impact incubator duration, mass, or SVL in either anole species. Uncentered thermal regimes have lower maximum incubation temperatures compared to peak-centered regimes, although interestingly enough these differences do not appear to influence development.

Different environments promote different life history strategies. The way an organism allocates resources in an environment can have large consequences on growth, reproduction, and immune function. Furthermore, energy allocation tradeoffs may differ between sexes. The energetic costs of immunity can differ between sexes due to differences in energetic demands and ecology. However, the reason some organisms exhibit sex-based energy allocation, and the causes of this phenomenon, remain enigmatic.

Zachariah Degon, an undergraduate student at Georgia Southern University, and colleagues examined the relationships between ectoparasite load, organ mass, fat body mass, and total body size in the Panamanian anole, Anolis apletophallus. Mainland populations of adult male (n=72) and female (n=34) A. apletophallus were sampled in Gamboa, Panama during the reproductive season. Each lizard was visually inspected for mites. The density of mites, and the location of each mite on the lizard body, were recorded. Lizards were dissected and all fat-storing organs were removed. Fat-storing organs included the fat bodies, livers, and gonads. Organs were dried and weighed before measuring organ mass. They found that overall males had more mites than females, and that this difference was driven by the high density of mites located on male dewlaps. Larger lizards, regardless of sex, had higher mite loads. Higher fat body mass was linked to decreased mite loads, although this was only true for male lizards. Liver mass had no effect on mite load in either species. However, mite load increased with ovary mass in females, but there was no relationship between testes mass and mite load in males.

Overall, sex-based differences in energy allocation may have important implications for maintaining immune function in variable environments. Male A. apletophallus had higher mite loads due to their heavily parasitized dewlaps. And interestingly, males with increased fat body masses had lower mite loads. This suggests that males may be allocating energy away from storage and towards increasing immune function.