Contemporary Survival Selection Fails to Explain Observed Patterns of Phenotypic Divergence Between Suburban and Forest Populations of the Cuban Endemic Lizard, Anolis homolechis.

Abstract

Although urbanization is a major threat to biodiversity, some native species have managed to persist in urban areas. Populations of such species often show phenotypic differences with their rural counterparts. A crucial question is whether such differences result from different selection regimes between habitats. As previous studies showed that suburban and forest populations of Anolis homolechis differ in both body size and sex ratio, we tested the effect of urbanization on adult survival in those populations based on a long-term capture-marking-recapture survey and replicated design. We assessed the evidence for directional and stabilizing selection on size in two suburban and two forest populations by modeling apparent adult survival and recapture probability separately. Adult survival did not differ between habitat types. In addition, there was no evidence for size-related differential selection on adult survival between habitats. However, irrespective of habitat, we found significant stabilizing selection on female size, whereas male survival was independent of size. Overall, sex had a significant effect on survival independent of habitat type (monthly survival probability: 0.80 for males vs. up to 0.89 for females of optimal size). We discuss our results in relation to the potential mechanisms involved in the observed phenotypic differentiation of A. homolechis and other lizard species in areas transformed by urbanization.