Geographic allozyme variation in Atlantic white-cedar, Chamaecyparis thyoides (Cupressaceae)

Chamaecyparis thyoides (L.) B.S.P. is an important wetland tree species occurring along the Atlantic and Gulf Coasts of the United States. Substantial decline over the past two centuries has led to interest in the geographic pattern of genetic variation of the species, as it affects both restoration and ongoing management. We examined the extent and distribution of allozyme variation among 31 populations throughout the species' range. Averaged across populations, the mean number of alleles per locus (A) was 1.94, the effective number of alleles per locus (A(e)) was 1.31, expected heterozygosity (H-e) was 0.16, and the proportion of polymorphic loci (P) was 63.6%. Significant population differentiation was apparent, with F-ST = 0.085. Using analysis of molecular variance (AMOVA), we were able to ascribe 6% of the total variation to differences between varieties. We identified three main geographical regions: (1) Atlantic Coastal, (2) peninsular Florida, and (3) Gulf Coast. Within the Gulf Coast region, three subregions are apparent: central Florida panhandle, western Florida panhandle, and Mississippi. This geographic pattern may have resulted from three or more separate Pleistocene glacial refugia and suggests that propagules for regeneration and restoration activities should not be moved out of their region of origin.