Clematis or Leatherflowers

Untangling the Viny Viornas: A Taxonomic and Biogeographic Study of Eastern North American Clematis (Leatherflowers)

Project Overview

This project, led by BRIT Biodiversity Explorer Dr. Dwayne Estes in collaboration with Aaron Floden (University of Tennessee), Theo Witsell (Arkansas Natural Heritage Program), and Dr. Joey Shaw (University of Tennessee, Chattanooga), aims to revolutionize the way botanist/horticulturalists view the North American leatherflowers, a group of beautiful herbaceous vines known for their small urn-shaped, leathery flowers. Most recent botanists have recognized up to 16 species, but this work indicates that there may be as many 25 species in the Southeast, with at least 9 that are undescribed and new-to-science. Their work will present detailed morphological descriptions, updated habitat and distribution maps, full illustrations with photos and line-drawings, and a molecular phylogeny that shows relationships based on DNA.

Dr. Estes’ studies in Clematis first began in 2003 as a graduate student at the University of Tennessee. While studying herbarium specimens, Dr. Estes discovered that outlying populations of Clematis versicolor from the sandhills of east Texas were morphologically distinct and represented a new species, Clematis carrizoensis D.Estes, which he described in 2006 in the BRIT's journal Sida (now Journal of the Botanical Research Institute of Texas).

In 2004, Dr. Estes and Chris Fleming, both then-graduate students at the Univ. of Tennessee, discovered the federally endangered Morefield’s leatherflower new to Tennessee. It had previously been known from 10 populations in just two counties in northeastern Alabama. The species is distinctive in its clusters of short-stalked, pinkish-green flowers hanging from the leaf axils. BRIT Research Associate, Dr. Robert Kral, described this species in 1987.   

Will the real Clematis viorna please stand up? 

During the past five years, Dr. Estes and colleagues have been puzzling over the morphological variation of some “species” of Clematis. In particular, two species, C. viorna and C. reticulata, have proven to be considerably variable. For example, Estes and colleagues noted that populations of C. viorna in the Appalachian Mountains are very different from those in central Tennessee and northern Arkansas. Past researchers had claimed that this variation was due to different ecological factors acting on different populations across the wide range of the species. Estes and colleagues have arrived at a different conclusion: that the observed morphological differences are instead due to the presence of numerous distinct species, each with its own ecological preferences, range of morphological variation, and distinct geographic distribution. Many of the new species are narrow endemics and should be considered as rare species.

Where do we go from here?

Over the next year we will continue to study herbarium specimens, examine living plants in the wild and in our home gardens, examine specimens microscopically, map records, and evaluate molecular data to generate a comprehensive reclassification of Clematis subgenus Viorna. We also hope to address what kinds of evolutionary forces have been responsible for the evolution of this group.