TAXONOMIC STUDY OF THE CLEMATIS RETICULATA SPECIES COMPLEX (RANUNCULACEAE: SUBGENUS VIORNA)
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Abstract
Chapter 1 is a literature review of the taxonomic history of Clematis subg. Viorna. Chapter 2 is a morphometric study and taxonomic treatment of the Clematis reticulata species complex. Clematis subgenus Viorna of North America currently consists of 21 species, most of which are distributed in the southeastern United States. Past taxonomic treatments of subg. Viorna have varied greatly, which has led to unclear species limits. Often recognized as a single, polymorphic species with a high degree of ecological amplitude, variation in C. reticulata s.l. species complex is typically attributed to phenotypic plasticity. A combination of herbarium specimen examination and extensive fieldwork led to formation of seven a priori morphological groups, or hypothesized taxa, in the C. reticulata species complex based on previously used and novel morphological characters. A total of 16 morphological characters, quantitative and qualitative, were measured to generate two datasets from herbarium specimens and a common garden experiment which were subjected to the same statistical analyses. To visualize morphological separation in multivariate space, data were subjected to factor analysis of mixed data. To infer if hypothesized taxa were diagnosable, partial least squares discriminant analysis models were used to assess classification accuracy based on a priori groups. Morphological characters were subjected to non-parametric univariate analyses. Of the seven hypothesized taxa, six were supported by evidence from morphology, biogeography, and ecology. Four new species are recognized: C. arenicola sp. nov., C. cumberlandensis sp. nov., C. ouachitensis sp. nov., and C. terminalis sp. nov. Viorna subreticulata is given a new combination in Clematis and the newly defined C. reticulata s.s. is re-circumscribed. An updated dichotomous key, species descriptions, ecological notes, and distribution maps are provided.