GENETIC-STRUCTURE IN A COASTAL DUNE SPIDER (GEOLYCOSA-PIKEI) ON LONG-ISLAND, NEW-YORK BARRIER ISLANDS

In this study, we analyse genetic structure among ten isolated populat ions of a sedentary burrowing M;olf spider, Geolycosa pikei, collected from Long island, New York barrier islands. Using allozyme electropho resis to estimate ge:le frequencies at 12 loci, only four loci were po lymorphic (i.e. Ant, Apk;, Gpi, Idh-1), and populations showed little differentiation (mean F-ST=0.020). Contrary to stepping-stone model pr edictions, the matrix of genetic distances among sites was not signifi cantly associated with the physical distance matrix, which suggests th ar G. pikei on Long Island barriers does nor adhere to a stepping-ston e model. Geolycosa pikei may be better dispersers than previously esti mated and/or the ephemeral quality of the inlets may not allow for the development of significant inter-populational genetic differences. In addition, geologic evidence suggests that these barriers became relat ively stable only 8000 BP. Therefore, these habitats have been only re cently colonized, which may result in low genetic variability and inte r-populational differentiation possibly due to genetic drift from repe ated and prolonged bottlenecks during recolonization (i.c. founder eve nts). (C) 1998 The Linnean Society of London.