ON SOUTHERN WINDS: MODERN FRESHWATER OSTRACODE DISTRIBUTIONS IN THE FLORIDA KEYS AND THEIR SIGNIFICANCE TO OSTRACODE BIOGEOGRAPHY IN THE SOUTHEASTERN UNITED STATES

Little is known about the modern distributions of freshwater ostracodes in the Florida Keys, and yet this region is an important corridor linking the fauna and flora of the Caribbean with North America. Here we present results of a survey of 46 small rainwater collectors, natural and manmade, located throughout twelve of the upper Florida Keys, sampled from January 2007 through December 2009. The manmade rainwater collectors were sampled as part of routine mosquito surveys, and ranged from birdbaths and garden fountains to plastic buckets, flower pots, and rainwater pooled in small open boats. Natural collectors included bromeliads, solution holes, and puddles.

Thirteen species are present in these 46 samples. The cosmopolitan Cypridopsis vidua is the most common species, followed by Elpidium maracaoensis, a species known from bromeliads on the Florida mainland as well as from the Caribbean islands. Among other species are Cypricercus centrura, Stenocypris major, Eucypris cf. cisternina, Physocypria globula, and Cypretta cf. intonsa. All but two of these species (C. vidua and P. globula) are restricted to the tropics. Several species here have no reported occurrences on mainland Florida or in the southern states of the U.S. (C. centrura, S. major, E. cisternina). Vaca Key was sampled monthly throughout a year, and eight species were observed to appear and disappear as the months went by. Common features shared by all species in this study include: 1) all are swimmers; 2) all are known to occur in fresh water habitats in the Caribbean islands or South America, and 3) no more than two species co-occur in any sample. Passive transport is the likely mechanism bringing these species northward across the Keys, either alive or as desiccated eggs. Because the majority of these specimens were collected from small rainwater collectors, it is unlikely that waterfowl were the transporters (except in the case of solution holes), but rather, that migrating song birds travelling northward in the Atlantic Flyway were the carriers. Most of these species have not been reported from the few Quaternary paleolimnologic records of non-marine ostracodes in Florida, with the exceptions of Cypriodpsis vidua and Physocypria globula. Further study should show the significance of this hitherto unrecognized fauna to the ecology of mainland Florida.