COS 278-4 - Recolonization of secondary forests by locally extinct fauna follows predictions from range expansion theory: Anoles in a chronosequence in Puerto Rico

Abstract: Even though deforestation is ongoing, particularly in the tropics, recovering forests are becoming a central trait of the Anthropocene landscape. Many of these recovering forests are the result of the abandonment of agricultural areas due to socioeconomic changes. With time these abandoned areas will undergo succession eventually providing the minimum requirements for the recolonization of locally extinct fauna. Previous studies and meta-analyses show that animal species richness recovers quickly after abandonment, but species composition takes longer. Still, we know less about the ecological processes that drive these patterns. Range expansion theory is commonly invoked to describe the eco-evolutionary mechanisms that drive multiple types of expansions. This theoretical framework predicts that animals in the expansion front would be characterized for having (1) phenotypic traits related to dispersal ability such as longer limbs, larger body sizes, or better body conditions, (2) experience density independence, and (3) lower rates of parasitism because they recolonize in smaller numbers. The goal of this study is to test these predictions during the recolonization of secondary forest by Anolis gundlachi---a shade specialist lizard---in Puerto Rico. We compared phenotypic traits, abundance, growth rates, and rates of malaria parasitism in a chronosequence of forests of < 30 years (young), 50-70 years (mid), and > 70 years (old). Our results show that individuals in the young forests are characterized for having larger bodies ( β = 0.05 ± 0.02 SE) with smaller radius ulna (β = -0.05 ± 0.02 SE) when compared to old forests. Moreover, these young forests had lower abundances when compared to old forests (e.g. Ny ₌ 135.52 ± 11.86 SE; No = 196.51 ± 15.86 SE) and higher population growth rates ( λy = 3.06 ± 0.001 SE ), followed by the mid ( λm = 1.81 ± 0.0001 SE ), and old forests ( λo = 1.31 ± 0.0001 SE ). Young forests also had lower rates of malaria parasitism when compared to old forests ( β = -2.49 ± 1.09 SE). Overall, our results show that secondary forest recolonization follows predictions from range expansion theory regarding the traits of expanding animal populations.