The role of parasites mediating coexistence of hosts is a key ecological process at the interface of community and disease ecology. Parasites can drive apparent competition among hosts species by shifting the outcome of competitive interactions. For instance, coexistence between Anolis lizard species in St. Martin has been observed only in the presence of the malaria parasite Plasmodium azurophilum. However, there has been disagreement if this is a generalizable pattern or an isolated event. To address this issue, we ask: (Pattern) do Plasmodium prevalence drive the long-term composition of the Anolis lizard community in a Caribbean rain forest? If so, (Mechanism) is this pattern partly driven by infection-induced changes in key behavior characteristics such as decrease in territory size? We address the pattern through an observational long-term study on Plasmodium infection and the long-term drivers of Anolis community composition. We address the potential mechanism of behavioral change in territory use through mark-resight study to quantify the territory area used by anoles. We expect that if malaria parasites reduce A. gundlachi territory size, this will lead to a reduction in fitness and use of resources which would lead to an observed pattern in change of Anolis community composition.
Results/Conclusions
(Pattern) Yearly variation in Anolis community composition was best predicted by temporal variation in Plasmodium infection prevalence in the dominant species, A. gundlachi. (Mechanism) This pattern is partly due to infected individuals holding on average smaller territories than non-infected ones. Results from a log-normal model (R2=0.1773) show that on average infected individuals hold smaller territories (β1 =-0.798 ± 0.378 SE, t=-2.11, p=0.04), while controlling for sex (β2 =0.224 ± 0.438 SE, t=0.512, p=0.6115), and body size (β3 =0.0346 ± 0.180 SE, t=1.92, p=0.624). All in all, our results suggest that Plasmodium infection is an important driver of Anolis community composition. This pattern is partly explained by an infection-induced reduction in the competitive ability of otherwise dominant individuals. A reduction in competitive ability can lead to the observed reduction in territory size, which leads to a decrease in anole fitness. This reduction in territory and competitive ability can lead to open resources that other species in the anole lizard community can exploit.