Morphological divergence and reduced ectoparasite prevalence in an introduced population of a Caribbean anole

Abstract

As biological invasions become increasingly common understanding what factors drive a species’ ability to rapidly colonize new habitats will be important for future conservation management. Theoretical models predict that spatial sorting of an invasive population will select for enhanced dispersal‐related traits and lower prevalence of parasitic infections. Supporting these, there is a growing body of evidence that demonstrates both features are common in invasive populations, although, these observations stem from mainland systems, over larger spatial scales. Here, we investigated the morphology and ectoparasite prevalence of Maynard's anole (Anolis maynardi) in its native range Little Cayman, and across its introduced range Cayman Brac where it invaded 31 years ago. We tested for morphological divergence, ectoparasite prevalence between the native population and the core, intermediate and range edge populations within the introduced range. In addition, we compared the overall body condition of lizards from each sex between islands using the scaled‐mass index. Our results suggest that spatial sorting could have selected for less parasitized individuals on the range edge of the introduced population, across an area of just 39 km2. However, there was no difference in hind‐limb length, the character that is expected to enhance dispersal ability, across the range of the introduced population. Instead, the greatest variation in morphology across the introduced range was found in fore‐limb length. Finally, both males and females from the introduced population were of significantly higher body condition than the native population, yet ectoparasite intensity had no effect on the body condition of infested hosts. These results highlight the rapid change in forelimb length and overall morphology has occurred rapidly since the species’ first introduction and a clear reduction in parasite prevalence on the range edge of the introduced population. Together these attributes have likely contributed to the successful colonization of Cayman Brac by A. maynardi.

Sex differences in morphology across an expanding range edge in the flightless ground beetle, Carabus hortensis

“…We believe that our study is the first to report the increase in size of morphological traits associated with movement toward a species' range edge in just one sex, in an insect. Some vertebrate studies of morphological changes across species' range expansions are in line with our own, reporting that only male morphological traits increase with proximity to the range edge of an expanding or shifting range (Bodden & Puschendorf, 2019;Campbell & Echternacht, 2003;Gunnarsson et al, 2012). Conversely, for other vertebrates, traits that increased with proximity to the range edge did so in both sexes, but the effect was stronger in males than females (Padilla et al, 2019;Simberloff et al, 2000).…”

“…Strong sexual disparities in trait distribution across species' ranges may be especially prominent in scramble-competition type mating systems, in which males evolve adaptations that improve locomotion to increase mate searching efficiency (Husak & Fox, 2008). Although sex differences in morphological traits at range edges have been observed in a few studies, results differ and studies are largely restricted to vertebrates (e.g., Bodden & Puschendorf, 2019;Campbell & Echternacht, 2003;Gunnarsson et al, 2012;Miller et al, 2017;Simberloff et al, 2000, but see Laparie et al, 2013 for a study on an insect species). This may be explained by differences in reproductive and mating systems across the different taxa.…”