Equivalent per-capita food web effects of native and invading Anolis lizards despite perching and foraging behavioral differences

Background/Question/Methods

Invasive species often displace ecologically similar native species, but the equivalence of such species pairs in food webs is not well-studied, especially for terrestrial vertebrates. In Florida, the invasive brown anole (Anolis sagrei) displaces the native and ecologically similar green anole (Anolis carolinensis). Although the two lizard species likely interact with nearly identical sets of predator and prey species, they differ in their perching and foraging tendencies and thus may differ in the relative strengths of their trophic interactions. I tested the hypothesis that perching and foraging behavioral differences cause green and brown anoles to differ in their per-capita effects on various arthropod prey taxa. I constructed enclosures around 18 small cabbage palms (Sabal palmetto) growing in an open field and stocked them with several individuals of a single prey taxa and a single adult male green or brown anole. Anoles and prey remained in the enclosures for several days, after which I assessed the number of prey remaining and then repeated the experiment with a different prey type and new anoles. In each experiment I also collected observational data on anole perch use and movement patterns.

Results/Conclusions

As expected, I found that green anoles perched higher, used different perch types, moved more frequently, and moved smaller distances on average than did brown anoles. Despite these differences, the two species had equivalent effects on flatid planthoppers, grasshoppers, mogoplistid crickets, cursorial anyphaenid spiders, and web spiders. They differed only in their effects on a large jumping spider, Phidippus regius, which almost certainly was unrelated to anole perching or foraging differences. These unexpected results indicate that the perching and foraging tendencies of green and brown anoles do not necessarily lead to differences in their per-capita effects on prey. Differential impacts of green and brown anole populations on arthropod communities may thus be driven primarily by differences in anole densities.