ESA 2016: Top-Down Effects of Brown Anoles on Islands Following Hurricanes

Following up with summaries of anole talks at ESA 2016, Dave Spiller presented a broad summary of his and his colleague’s (Tom Schoener and Jonah Piovia-Scott) research investigating the effects of hurricanes on long term food web dynamics of small Bahamian islands, which has just recently been published in Ecology (see Spiller et al. 2016).

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Spiller opened by explaining some of the patterns of food web dynamics that have been learned from this research. Most notably, that the elimination of brown anoles – which act as top predators in these simple ecosystems – leads to increased levels of herbivory as arthropods experience a relaxation of predation pressure (Spiller and Schoener 1990).Specifically, the presence of a common moth (Achyra rantalis) on islands without brown anoles can lead to extreme levels of herbivory upon a common island plant, Sesuvium portulacastrum (below).

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Spiller and his colleagues began to notice that following hurricanes, one of the most extreme natural disturbance events in this region, islands with lizards experienced a much more rapid recovery of Sesuvium .

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In an attempt to understand how ecosystems may be stable despite experiencing extreme disturbance regimes, Spiller and colleagues measured the percent ground cover of Sesuvium and abundance of Achyra moths on 11 islands with lizards present and 21 islands without lizards annually for 10 years.

Overall abundance of Achyra was 4.6 times higher on no-lizard islands than on lizard islands. The percent cover of Sesuvium exhibited lower temporal variability on lizard islands when the study site was undisturbed by hurricanes, and higher recovery rate on lizard islands following hurricanes.

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Spiller concluded by suggesting that these stabilizing phenomena are linked to a trophic cascade in which predators (brown anoles) control herbivores (Achyra moths), and therefore enhance plant recovery following hurricanes.

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