GENETIC-STRUCTURE OF POPULATIONS OF THE THREATENED EASTERN MASSASAUGARATTLESNAKE, SISTRURUS-C-CATENATUS - EVIDENCE FROM MICROSATELLITE DNAMARKERS

Throughout its distribution in North America, the threatened eastern m assasauga rattlesnake (Sistrurus c. catenatus) persists in a series of habitat-isolated disjunct populations of varying size. Here, we use s ix microsatellite DNA loci to generate information on the degree of ge netic differentiation between, and the levels of inbreeding within pop ulations to understand how evolutionary processes operate in these pop ulations and aid the development of conservation plans for this specie s. Samples were collected from 199 individuals from five populations i n Ontario, New York and Ohio. Our results show that all sampled popula tions: (i) differ significantly in allele frequencies even though some populations are < 50 km apart, and may contain genetically distinct s ubpopulations < 2 km apart; (ii) have an average of 23% of alleles tha t are population specific; and (iii) have significant F-IS values (mea n overall F-IS = 0.194) probably due to a combination of Wahlund effec ts resulting from fine-scale genetic differentiation within population s and the presence of null alleles. Our results imply that massasauga populations may be genetically structured on an extremely fine scale e ven within continuous populations, possibly due to limited dispersal. Additional information is needed to determine if dispersal and mating behaviour within populations can account for this structure and whethe r the observed differentiation is due to random processes such as drif t or to local adaptation From a conservation perspective, our results imply that these massasauga populations should be managed as demograph ically independent units and that each has high conservation value in terms of containing unique genetic variation.