Morphometric and Molecular Evidence Delimit Six Species in Clematis reticulata s.l. (Ranunculaceae: Clematis subg. Viorna)

Abstract

Abstract— Clematis subgenus Viorna of North America currently consists of 21 species with most of the diversity found in the southeastern United States. Past taxonomic treatments of Clematis subg. Viorna have varied greatly, which has led to unclear species limits across multiple species complexes. Often recognized as a single, polymorphic species with a high degree of ecological amplitude, variation in the Clematis reticulata species complex has previously been attributed to phenotypic plasticity. A combination of herbarium specimen examination and extensive fieldwork led to the formation of seven a priori morphological groups, or hypothesized taxa, in the C. reticulata species complex based on previously used and novel morphological characters. We employ an integrative approach to species delimitation with data from morphometric studies of herbarium and common garden datasets, as well as a phylogeny inferred from ddRADseq. Of the seven hypothesized taxa, six were supported by evidence from morphology and phylogeny with corroborating biogeography and ecology. Recognition of Clematis terminalis sp. nov. renders C. subreticulata comb. nov. paraphyletic. Because of its morphological, ecological, and phenological distinctiveness, it may represent a case of peripheral speciation by isolation. 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.

A New Endemic Smilax (Smilacaceae) from Tafelberg, Suriname, Supported by Morphometric and Phylogenetic Evidence

“…Rather, we acknowledge the possibility of peripheral isolate speciation, in which a species may form a clade nested within another, rendering the latter species paraphyletic (cladospecies vs. paraspecies; e.g. Sharples and Tripp 2019, Majure et al 2022, Murphy et al 2022). We also consider evidence from supporting criteria based in ecology and biogeography.…”

Riverscour Ecosystems of Eastern Unglaciated North America: A Review

“…oklahomensis (Schrader and Graves 2003), Baptisia australis sensu stricto, Conradina verticillata, Eurybia saxicastellii (Campbell and Medley 1989), Marshallia pulchra (Knapp et al 2020), Pityopsis ruthii, Solidago arenicola (Keener and Kral 2003), Solidago plumosa (Small 1898), Sporobolus arcuatus (Rogers 1970), and Vernonia lettermannii (Gray 1880). Near-endemic taxa of riverscour, those with 90% of their known occurrences in riverscour habitats, include Amsonia hubrichtii (Woodson 1943), Clematis cumberlandensis and C. ouachitensis (Murphy et al 2022), Harperella nodosa, Spiraea virginiana, and Vitis rupestris. Currently, multiple apparently undescribed endemic species known from riverscour communities of EUNA are under study and awaiting description.…”