Author: Sozos Michaelides

Whereas in the Greater Antilles islands anoles evolved ecomorphs and live in communities with up to 11 species in sympatry, islands in the Lesser Antilles support only one or two species each. However, islands such as Dominica have populations of anoles that experience selective pressures resulting in different ecotypes.

Figure from Thorpe et al. 2004

While Dominica is relatively small, the mountainous topology results in highly variable environmental conditions across the island with cool mountainous regions and warm coastal regions and thermal vents. The single endemic anole species present on the island, Anolis oculatus, exhibits four morphologically distinct ecotypes (Montane, Atlantic, North Caribbean and South Caribbean) and despite levels of gene flow between these ecotypes are high, adaptive differentiation in this system is maintained.

Photo by Aurélien Miralles

Tricia Neptune, a graduate student in the Watson lab, at Midwestern State University, explored whether these ecotypes also show any differences in metabolic rate (by measuring oxygen consumption) and its sensitivity to temperature (Q10) at ecologically-relevant temperatures.

Results show that size differences between ecotypes are reflected in their physiology with the south Caribbean ecotype exhibiting higher oxygen consumption and Q10 compared to the other three ecotypes. Tricia hypothesize that these differences in metabolism and temperature sensitivity are in part responsible for maintaining relaxed geographic segregation among ecotypes.

Tricia plans to incorporate data on sprint speed, bite force as well as investigate thermoregulation strategies in this species. It will also be interesting to see a comparative study between the A. oculatus ecotypes and the introduced Puerto Rican crested anole, A. cristatellus.

Figure from Thorpe et al. 2004

Sperm storage is widespread in all major reptilian taxa and in combination with multiple mating it could have indirect benefits in polyandrous systems for example by increasing genetic diversity among offspring. Hannah Marshall, a junior majoring in Biomedical Sciences at Auburn University in Tonia Schwartz’s lab, set out to test the utility of microsatellite markers in paternity analysis in a population of brown anoles, Anolis sagrei, in Florida and to assess the extent and pattern of sperm storage from field matings.

Brown anoles from the field were housed in pairs (control) and in groups of four (2M:2F) and six (3M:3F) in 23 experimental laboratory enclosures. Eggs were collected over one breading season and hatchlings and their candidate parents were genotyped at seven microsatellite loci. The software CERVUS was used to determine the most probable parental pair for each hatchling and to disentangle paternity from experimental males to sperm storage.

Results show that these markers are sufficiently polymorphic to allow paternity assignments with high confidence. With regards to the use of stored sperm, 58% of the eggs produced in the lab were from field matings, which is consistent with previous findings in Anolis sagrei. However, Hannah’s data suggest that these lizards continue to use their stored sperm up to 4 months, longer than previously documented.

These findings are preliminary and Hannah is currently collecting and analyzing more data from these experimental enclosures. Understanding the dynamics of reproductive output in this focal population is valuable for planning further experiments to measure fitness.