Analyzing the impact of a dual lizard introduction on orbweaving spider communities in the Bahamas: an experimental approach

Abstract

With the global increase in introduced species, it is important to understand the contexts in which these species negatively impact ecosystems. Species introductions are particularly important in structuring island ecosystems, which have high rates of disturbance and colonization (Tilman, 1997). Through a manipulative field experiment, I examined how two introduced lizards (the predatory Leiocephalus carinatus [curly-tailed lizard] and Anolis smaragdinus [green anole]) affected the native lizard (Anolis sagrei [brown anole]) and orbweaving spiders on small islands offshore from Staniel Cay, Bahamas. I showed that while the introduced species strongly affected brown anole height and weakly affected web spider height, they did not affect either brown anole density or web spider density. This suggests that behaviorally mediated interactions like predator avoidance are more important than consumptive interactions in structuring our island communities after the introductions. While many other studies have demonstrated the negative impacts of introduced species, in our system, the introduced species co-existed with native species without affecting population abundances (Towns, 2006; Gillespie et al, 2008).