Molecular Ecology and Evolution
Hipp, Andrew L. , Rothrock, Paul E. , Weber, Jaime A. .
Interaction between chromosome divergence and isolation by distance in gene flow and speciation: evidence from Carex scoparia (Cyperaceae).
Chromosome evolution is an important driver of plant speciation. As a consequence, extensive chromosome diversity within plant species begs the question of what role chromosome evolution may play in the partitioning of genetic variance within species. Sedges (Carex: Cyperaceae) are an ideal system in which to study this question, as they display the most remarkable chromosomal diversification known among angiosperms. The current study focuses on Carex scoparia, a morphologically diverse eastern North American species that demonstrates a particularly broad range of chromosome numbers (2n = 58 to 2n = 70). Our findings to date demonstrate that (1) Carex scoparia var. scoparia is a genetically coherent species despite its extensive chromosomal diversity; (2) there is a weak relationship between latitude and chromosome number, and overall chromosome number differences are little if at all correlated with geographic distance; and (3) both chromosome number differences and geographic distance correlate significantly with genetic diversity. Chromosome number changes alone are thus insufficient to drive speciation in Carex, but they play an important role in genetic structure within species. As a consequence, chromosome number changes likely contribute to sedge speciation by interacting with geographic and ecological determinants of genetic diversification between populations. Our work in this species also demonstrates that the Maine endemic Carex scoparia var. tessellata (2n = 68) is genetically distinct from the typical variety. The difference in chromosome diversity and genetic diversity between the varieties is compatible with the hypothesis that C. scoparia var. tessellata is either a relative young species or has gone through a relatively recent genetic bottleneck.
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1 - The Morton Arboretum, 4100 Illinois Route 53, Lisle, IL, 60532-1293, USA
2 - Taylor University, Randall Environmental Studies Center, W 236 Reade Avenue, Upland, Indiana, 46989-1001, USA
3 - The Morton Arboretum, Herbarium, 4100 Illinois Route 53, Lisle, IL, 60532-1293, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Boulevard B/Hilton
Date: Wednesday, July 11th, 2007
Time: 9:15 AM