Diapause in copepods (Crustacea) from ephemeral habitats with different hydroperiods in Everglades National Park (Florida, USA)

Water management practices in the Everglades have severely stressed the nat ural system, particularly by reducing the hydroperiods of much of the regio n. During the dry season of 1999, we investigated the influence of hydroper iod on the species composition and dormancy patterns of freshwater copepod communities in seasonal wetlands of Everglades National Park, Florida, U.S. A. The habitats were characterized by an annual dry season, from December t hrough June. We sampled at two locations: the Long Pine Key area of the Roc ky Glades region (short hydroperiod, ca. 4-5 months), and western Taylor Sl ough (intermediate hydroperiod, ca. 8-10 months). Both areas have experienc ed a reduction in natural hydroperiods and an increase in the frequency of dry-down. We collected weekly plankton samples from Rocky Glades solution h oles to assess the potential species pool of copepods. To document the taxa capable of surviving dry-down by resting, we performed three immersion tri als in which we rehydrated, in laboratory aquaria, sediment patches from so lution holes and surface soils from all stations. Only a subset of the plan ktonic species collected emerged from the dried sediments. The cyclopoids M icrocyclops rubellus and Paracyclops poppei were dominant. This is the firs t record of diapause for P. poppei. Species distributions from the differen t hydroperiod soil patches indicated that more diapausing species occurred at the sites that dried for shorter periods. Emerging individuals of M. rub ellus and P. poppei were mainly ovigerous females, demonstrating a resting strategy seldom before recorded. The cyclopoid Diacyclops nearcticus had no t been previously reported to diapause, but they emerged from the dried sed iments in our trials. Our collections included six new records for Florida: Diacyclops nearcticus, Megacyclops latipes, Orthocyclops modestus, Elaphoi della marjoryae, Bryocamptus sp. and Bryocamptus cf. newyorkensis. Paracycl ops poppei, Macrocyclops fuscus and Arctodiaptomus floridanus are new recor ds for Everglades National Park. Clearly, diapause is an important strategy for the persistence of copepods in short-hydroperiod wetlands. The duratio n of the dry period appears to be inversely related to the number of specie s that emerge from diapause.