Population genetic structure in green dragon (Arisaema dracontium, Araceae)

Abstract

The clonal perennial herb, Arisaema dracontium (L.) Schott., is considered "vulnerable" in Canada but is more abundant in the adjacent northeastern United States. In Canada, sexual reproduction may be limited since the species is self-incompatible, and populations at the edge of a species' range may contain limited genetic diversity. We compared genetic variation in nine enzymes systems, sampled at 19 populations across eastern North America. Based on chromosome counts and interpretable banding patterns, A. dracontium is tetraploid over most of its range (2n = 56). However, plants in Florida were diploid, lacked 10 out of a total of 19 interpretable alleles, had distinct allelic frequencies, and clustered a large distance from the other populations. Some plants from Baton Rouge, Louisiana, were also diploid, but all allozyme samples were tetraploid. Most genetic variation occurred within populations; only 29% of variation was between populations. Individuals in two adjacent, otherwise isolated Ontario populations were fixed for most loci and were balanced heterozygotes for the got-2 locus. All samples but one were also identical for an additional six non-interpretable enzyme banding patterns, suggesting these two populations comprise multiple ramets of a single multilocus genotype, propagated clonally via corms. Ecologically marginal populations were typically more distant from the nearest neighboring population and were more genetically distinct from one another; however, with the exception of the two monoclonal populations, marginal populations were not genetically depauperate.