Shelton, Glenn W.K. .
Sympatry without intergradation: an evaluation of the Trifolium longipes complex in northern California.
The Trifolium longipes complex comprises about 12 infraspecific taxa endemic to vernally wet meadows on serpentine substrates in the western United States, from Montana to New Mexico and west to the Pacific States. Some of these taxa clearly intergrade, but others differ strongly by a combination of traits including plant height, peduncle length, leaflet and calyx shape, corolla color, and the extent to which the pedicels reflex with age. Some of the more distinct taxa have been regarded as separate species in the past, but the prevailing view is that they are linked by intergradation and are best considered one species. Current study focuses on two pairs of significantly distinct subspecies occurring sympatrically in northern California: subspecies hansenii (Greene) J.M. Gillett with ssp. oreganum (Howell) J.M. Gillett in Humboldt and Trinity Counties, and ssp. elmeri (Greene) J.M. Gillett with ssp. shastense (House) J.M. Gillett in Shasta County. In both cases, the subspecies occur in the same meadows, bloom concurrently, and maintain their morphological distinction without intergradation, although the differences between ssp. hansenii and ssp. oreganum are less striking than those separating spp. elmeri and ssp. shastense. Herbarium data are being used to locate additional instances of sympatry. Field observations are particularly critical in this group because traits such as corolla color and the degree to which the pedicels reflex can be difficult to interpret on herbarium specimens. If additional field reconnaissance reveals clear distinction across a broad geographic range, the recognition of separate species will be strongly encouraged. Conversely, an unanticipated significant intergradation will warrant a study of reinforcement of reproductive isolation in areas of sympatry without intergradation. The ultimate goal of this evaluation is a comprehensive revision of T. longipes in northern California and adjacent Oregon including updated ranges and descriptions of some of the taxa.
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1 - Humboldt State University, Department of Biological Sciences, 1 Harpst Street, Arcata, CA, 95521, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lindell A/Chase Park Plaza
Date: Wednesday, July 13th, 2011
Time: 3:15 PM