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

The clonal perennial herb, Arisaema dracontium (L.) Schott., is considered "vulnerable" in Canada but is more abundant in the adjacent northeastern Un ited States. In Canada, sexual reproduction may be limited since the specie s is self-incompatible, and populations at the edge of a species' range may contain limited genetic diversity. We compared genetic variation in nine e nzymes systems, sampled at 19 populations across eastern North America. Bas ed on chromosome counts and interpretable banding patterns, A. dracontium i s tetraploid over most of its range (2n = 56). However, plants in Florida w ere diploid, lacked 10 out of a total of 19 interpretable alleles, had dist inct allelic frequencies, and clustered a large distance from the other pop ulations. Some plants from Baton Rouge, Louisiana, were also diploid, but a ll 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 l oci and were balanced heterozygotes for the got-2 locus. All samples but on e were also identical for an additional six non-interpretable enzyme bandin g patterns, suggesting these two populations comprise multiple ramets of a single multilocus genotype, propagated clonally via corms. Ecologically mar ginal populations were typically more distant from the nearest neighboring population and were more genetically distinct from one another; however, wi th the exception of the two monoclonal populations, marginal populations we re not genetically depauperate.