Systematics Section / ASPT
Lambert, Sarina , Vanden Heuvel, Brian , Potter, Daniel .
Microsatellite Variation Within the Cercocarpus ledifolius Species Complex.
The genus Cercocarpus HBK (Rosaceae) has long resisted systematic classification, and to date the genus lacks a consensus classification and phylogeny. Past taxonomic treatments have focused on leaf morphology, yet leaf characters intergrade within and among taxa. The absence of distinct morphological discontinuities has left rank, number, and circumscription of species within the genus uncertain. Taxa within the C. ledifolius Nutt. complex (C. intricatus Wats., C. ledifolius var. ledifolius N. Holmgren, and C. ledifolius var. intermontanus N. Holmgren) are equally perplexing. Previous authors have proposed three main hypotheses to explain intermediate forms: 1) intermediates are a distinct taxon, 2) intermediates are due to hybridization, or 3) intermediate forms result from selection during seedling establishment due to yearly climate variation. We undertook a study using microsatellite markers to explore whether molecular variation corroborated any of the three earlier hypotheses. We collected leaf tissue from throughout the geographic distribution of the species complex, including type localities and four putative hybrid zones. We found that microsatellite variation does not conform with currently defined taxonomic boundaries based on leaf morphology, suggesting that such boundaries may be artificial.
1 - University of California, Davis, Pomology, One Shields Ave., Davis, California, 95616, USA
Cercocarpus ledifolius complex.
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Tuesday, August 3rd, 2004
Time: 2:15 PM