Floden, Aaron , Mayfield, Mark H. .
Leatherwood in Kansas: a morphological assessment of an anomalous population of Dirca palustris (Thymelaeaceae).
THE genus Dirca is comprised of three species: D. palustris L., D. occidentalis A. Gray, and D. mexicana G. L. Nesom & M. H. Mayfield. Dirca palustris occurs infrequently within a broad area of eastern North America (Florida and Louisiana to southern Ontario), whereas D. occidentalis (California, USA) and D. mexicana (Tamaulipas, MEXICO) are both narrowly endemic and disjunct by more than 1000 kilometers from the nearest populations of D. palustris. Dirca was first documented from Kansas in 1998 and regarded without comment as D. palustris. Observations of the Kansas plants in the field have prompted the present study which compares them to several populations of D. palustris, D. occidentalis, and D. mexicana using herbarium specimens and live plants. Among distinguishing characteristics, only a more distal filament insertion is shared between the Kansas plants and D. palustris, but this feature is also shared with D. mexicana. Moreover, the Kansas plants are more similar to D. occidentalis and D. mexicana in their larger, lobed calyces; sessile flowers/fruits; dense hoary pubescence on the bud scales; and persistently pubescent leaves and stems. These similarities are intriguing in light of the much closer proximity of Kansas plants to the nearest populations of D. palustris. Our results suggest that the single Dirca population occurring in Johnson County, Kansas is taxonomically distinct from D. palustris. However, it is not clear from our preliminary analysis whether this population deserves separate taxonomic recognition, or if it is better considered an outlying population of either D. occidentalis or D. mexicana. Further studies including genetic and morphological data with a broader sampling of D. palustris are being undertaken in order to better understand the status of the Kansas Leatherwoods.
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1 - Kansas State University, Herbarium, Division of Biology, Ackert Hall, Manhattan, Kansas, 66506, USA
2 - Kansas State University, Herbarium and Division of Biology, Ackert Hall, Manhattan, Kansas, 66506-4901, USA
Presentation Type: Array
Location: Auditorium/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 12:30 PM