A Systematic Review of the Viola palmata Species Complex in the Gulf Coastal Plain and Southern Appalachians

The Viola palmata species complex (Violaceae) consists of one to several species of acaulescent, heterophyllous, blue violets that are native to most of eastern North America. This study was conducted in order to evaluate the variation within the V. palmata species complex in the southeastern United States and to determine whether consistent morphological, genetic, and/or ecological patterns exist across identified morphotypes. Both quantitative morphological measurements and qualitative observations were made using both herbarium specimens and live specimens kept in a common garden in a greenhouse. These measurements included characters from the lobed leaves, chasmogamous flowers, and cleistogamous seeds. Multiple nDNA and cpDNA regions were amplified, sequenced, and analyzed for phylogenetic analysis; four microsatellite loci were amplified, run on a gel for detection and sizing of alleles, and analyzed for population and/or geographic patterns. At each population, soil characteristics including soil texture, pH, percent organic matter, and environmental parameters including slope degree, slope aspect, and geographic coordinates were recorded for analysis. Statistical analyses of morphological characters all revealed at least some degree of quantitative separation among all identified morphotypes and the broader V. palmata. DNA data were phylogenetically uninformative, likely due to the effects of hybridization, concerted evolution, and/or minimal variation among sequences. Analysis of microsatellite loci did show separation among individuals classified as Viola palmata and of other morphotypes. Measured soil and ecological characteristics showed no statistically significant variation among sampled populations. Overall, all identified morphotypes warrant further systematic investigation and formal description.