Correlations of allozymic variation with habitat parameters using the grass shrimp Palaemonetes pugio.

Collections of the grass shrimp Palaemonetes pugio, were made on and around Galveston Island, Texas. Four were from small ponds, 3 from lagoons, and 2 from the bay system. The individuals were analyzed for 16 allozyme loci, and genic variaton was estimated using the average heterozygosity within populations (.hivin.H) and the number of alleles at polymorphic loci (n). Based upon simple stochastic evolution, the isolated populations in small and/or young ponds ought to exhibit lower levels of genic variation than the large populations which were in older bodies of water open to migration. The pond populations exhibited lower values of both measures of genic variation. .hivin.H and Ne (estimated from n) were positively correlated with habitat area, habitat age and the locality's potential for immigration.