Abstract Detail

Systematics Section/ASPT

Wallace, Lisa [1], Dorman, Hanna Elizabeth [1], Hosseinalizadehnobarinezhad, Mahboubeh [2].

Intraspecific variation and its importance to taxonomy of Chamaecrista in the Southeast.

Species with broad distributions may be among the best study systems for understanding population level changes that ultimately lead to the origin of new species because they often exhibit intraspecific adaptive variation. Chamaecrista (Fabaceae) is a genus of tremendous diversity in South America and includes C. fasciculata and C. nictitans, two species that exhibit broad geographic distributions and intraspecific morphological variation in eastern North America. Chamaecrista fasciculata occurs as far north as New England and the Great Lakes region, south to the Gulf Coast, and westward from the Atlantic coast to the Midwest. Chamaecrista nictitans has a similar distribution but does reach the northern Midwest. Regional morphological and ecological variants are commonly recognized in both species and have been treated at different ranks by taxonomists. Populations in the Southeast are particularly diverse, possibly reflecting a long history of evolutionary divergence. To gain a better understanding of the nature of this variation across geographic space and to test the hypothesis that there are consistently identifiable morphological forms that would correspond to named taxa, we quantified morphological variation and developed distribution maps using herbarium specimens, focusing on collections from Mississippi herbaria. Both species are common throughout Mississippi and grow in many different habitats, from grasslands to open woodlands. Collections of C. nictitans are relatively uniform in morphology in Mississippi and are consistent with the var. nictitans. By contrast, specimens of C. fasciculata exhibited considerable variation in size, woodiness, and leaf pubescence. Based on leaf pubescence, the specimens were readily distinguishable as two groups, which correspond to var. fasciculata with glabrous leaves and an unnamed variety with pubescent leaves. Samples in this latter group are restricted to southern Mississippi. Leaflet pubescence may reflect environmental adaptations given that their occurrence is associated with a latitudinal gradient in temperature in Mississippi. That intraspecific variation in C. fasciculata was identified in collections from just a small portion of the species’ range suggests that other cryptic forms may also exist. Further study of genetic divergence and plasticity of leaf pubescence will aid in understanding the phylogeographic history of this species throughout eastern North America and in recognizing distinct evolutionary lineages as taxa.

1 - Mississippi State University, PO Box GY, Mississippi State, MS, 39762, USA
2 - Mississippi State University, P.O. Box GY, Mississippi State, MS, 39762, USA

Keywords:
Chamaecrista
morphological features
distribution.

Presentation Type: Oral Paper:Papers for Sections
Session: 5
Location: Salon 9/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 10:15 AM
Number: 5009
Abstract ID:572
Candidate for Awards:None