SYSTEMATICS AND BIOGEOGRAPHY OF ORCONECTES, SUBGENUS TRISELLESCENS, IN THE SOUTHEASTERN UNITED STATES, A TEST OF MORPHOLOGY-BASED CLASSIFICATION

Diagnosable taxonomic units are fundamental to conservation biology and management of resources and the need for sound science in both fields is more pressing for aquatic ecosystems. Within freshwater crayfishes, the North American genus Orconectes is one of the most diverse in the World. Accurate assessments of species level relationships and species boundaries within the genus have historically been hampered by a low number of variable morphological characters and inadequate sampling from across the ranges of many taxa. We examine a diverse group of southeastern United States stream dwelling Orconectes in the subgenus Trisellescens using 16S, COI mtDNA, and morphology to resolve uncertainties in species boundaries. Our results suggest that strong divergences exist between taxa found above and below the Fall Line in parts of the southeastern United States and the taxonomy for taxa found in that region should remain unchanged. However, using both molecular and morphological datasets we are unable to determine species limits for some taxa found on and below the Fall Line. Analysis of DNA data suggests that historical and ongoing genetic events such as gene introgression may contribute to these uncertainties. For taxa found on and below the Fall Line, we suggest tentative, taxonomic assignments. Finally, we argue for increased sampling of independent molecular datasets and increased sample sizes for all cambarid crayfish biogeographic studies.