Geographical Variation and Biosystematics of Sand Myrtle, Leiophyllum buxifolium (Ericaceae)

Abstract

Leiophyllum buxifolium occurs in a series of disjunct population systems in three areas: the New Jersey Pine Barrens, the Coastal Plain of North and South Carolina, and the southeastern Blue Ridge Province. Twelve populations from six regions within this range were examined for divergence in morphology and allozyme frequencies. There is significant variation at the level of region for seven of the 15 morphological characters examined and significant variation at the level of population within region for 12 characters. Allozyme variation in L. buxifolium is lower than in other long-lived, woody species, with HT = 0.118 ? 0.022 (mean ? standard deviation) and Hs = 0.108 ? 0.062. On the other hand, the percentage of loci polymorphic is high (64.6 ? 21.8). More of the total variation in gene frequencies occurs among regions (GRT = 0.075 ? 0.059) than among populations within regions (GPR = 0.036 ? 0.035). Multivariate analyses indicate that the Hanging Rock region in the Piedmont of North Carolina is distinct based on morphology, but not based on isozyme markers. No other region appeared to be distinct from the others either morphologically or genetically. Leiophyllum should, therefore, be treated as a monotypic genus that, despite its high degree of morphological variability within and among disjunct areas, cannot be easily split into well-defined infraspecific taxa.