The Science Seminar Series: Janurary 24, 2008 4pm

STOCK ISLAND TREE SNAILS IN PERIL IN THE FLORIDA KEYS

Dr. E. L. Mihalck

Dept. of Biology, Florida A&M University

Tallahassee, FL

Powell Hall

Time: 4:00 - 5:00pm

Abstract

In the summer and winter of 2007, we surveyed the main islands of the Florida Keys which included Key Largo to Key West for the target species the endangered Stock Island Tree Snail, Orthalicus reses reses. This study is being supported by the .U.S. Fish and Wildlife Department, Department of Interior which wanted a current distribution of this species. This snail was named where this species was originally collected on Stock Island a neighboring island to Key West. The field work was conducted in the hardwood hammocks of the Florida Keys. We used vegetation maps to find these hammocks and made visual observations on the trunks of trees, branches and underneath leaves for these tree snails. Over 50 locations were surveyed. We compared our data to past surveys of the endemic range of the Stock Island Tree Snail. The few remaining hardwood hammocks are restricted and isolated due to the changes in vegetation by residential and business districts. The number of tree snails were limited to only several individuals at each location. However, we still found a few living Stock Island Tree Snails on Pigeon Plum trees in several different areas of the Florida Keys which include 4 different locations (Key Largo, Big Pine Key, No Name Key). Stock Island only yielded a dead shell. The number of sightings of the Stock Island Tree Snail has been significantly reduced from the 1995 USFWS survey. This may be due to drought conditions in south Florida which would leave the tree snails still estivating underground beneath the trees. Also we believed that the scientists in South Florida had been misidentifying these snails because to the untrained eye they resemble each other closely. Because of this, the mollusk research collection at the Florida Museum of Natural History was visited before the survey work began to differentiate between the target species and its similar taxonomic relatives Orthalicus reses nesodryas, Orthalicus floridensis, Liguus fasciatus, and Drymaeus multilineatus. The Stock Island Tree Snails seem to have a very restricted range due to the destruction of the native vegetation such as the Pigeon Plum trees.