Isozyme variation in eastern hemlock

Abstract

Tsugacanadensis (L.) Carr., commonly known as eastern hemlock, is a coniferous tree native to eastern North America. The western and southern edges of its geographic distribution are characterized by disjunct populations 50–100 km or more from the continuous distribution. Genetic variation was measured using starch gel electrophoresis of needle tissue enzymes from 17 populations throughout the species' distribution. Six enzyme systems including 10 putative loci were assayed, with only 1 of the 10 loci being polymorphic. The polymorphic locus, cytochrome oxidase, consisted of two alleles present in all but two populations. Allele frequencies averaged 0.69 and 0.31. The low level of genetic variation in eastern hemlock was an unexpected result, given that most coniferous species are highly variable.