Host-tree selection by Florida tree snails, Liguus fasciatus (Muller, 1774), 1n Big Cypress National Preserve, Florida, USA

Bennetts, Robert; Sparks, Steven; Jansen, Deborah

A study that assesses the relative use of host trees in eight hammocks in the Big Cypress National Preserve for which the relative availability of each tree species was known. It has frequently been suggested that the Florida tree snail, Liguus fasciatus, exhibit preferences for specific host trees, although most accounts of host-tree selection are based on anecdotal observations. We assessed the relative use of host trees in eight hammocks in the Big Cypress National Preserve for which the relative availability of each potential host-tree species was known. Based on a total of 1,464 tree snail observations on 21 species of host tree within our study plots, host trees were not used in proportion to their availability when the expected values are derived either from the number of trees or from basal area. Of the most common tree species on our study area, wild tamarind (Lysilorna latisiliqum) was consistently used in excess of its availability. Wild lime (Zanthoxylum fagara), was not a common tree species, but was also used far in excess of its availability. Pigeon plum (Coccoloba diversifolia) and gumbo-limbo (Bursera sirnaruba) were consistently used less than expected from their respective availabilities. Based on Akaike's Information Criterion (AIC), the most parsimonious loglinear model, after accounting for availability, was one that included only tree species effects. In contrast to the model selected using AIC, likelihood ratio tests indicated that there may also be differences among hammocks, but not in relation to a linear gradient of hurricane damage. We obseiVed differences in length among 3-year-old snails on different host trees, and these differences were consistent with the hypothesis that host-tree selection reflects food availability. Snails found on host-tree species that were used in greater than expected frequency had the greatest length, those found on trees used less than expected frequency were the smallest, and those found in proportion to their availability were intermediate in length.

Host-tree selection by Florida tree snails, Liguus fasciatus (Muller, 1774), 1n Big Cypress National Preserve, Florida, USA

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