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An Electrophoretic Study of Evolution in Capsicum (Solanaceae)

Michael J. McLeod, Sheldon I. Guttman, W. Hardy Eshbaugh and Richard E. Rayle
Evolution
Vol. 37, No. 3 (May, 1983), pp. 562-574
DOI: 10.2307/2408269
Stable URL: http://www.jstor.org/stable/2408269
Page Count: 13
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An Electrophoretic Study of Evolution in Capsicum (Solanaceae)
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Abstract

The evolutionary relationships of 12 taxa of Capsicum peppers in three species groups were investigated by starch gel electrophoresis. These included all of the domesticated taxa of chili peppers as well as all of the wild peppers that have been suggested as possible progenitors. The peppers examined are all New World in origin and, with the exception of C. cardenasii, are primarily inbreeding. Genetic variability was surveyed for 26 loci in 1,010 individuals representing approximately 275 collections. We found that each population consists of one or more homogeneous subpopulations. The relatively high percentage of polymorphic loci in some taxa, and the low amount of heterozygosity, suggests that the populations maintain a large amount of variation while still being predominantly inbreeding. There was a relatively uniform distribution of genotypes throughout the range of most taxa. The biochemical data presented here support the recognition of three distinct clusters of wild and domesticated taxa. These data also support the hypothesis of several wild progenitors for the domesticates and at least three centers of domestication. We suggest that three taxa (purple-flowered C. cardenasii, C. tovarii, and white-flowered C. praetermissum) arose from small isolated populations of wild taxa. The electrophoretic evidence strongly supports a close relationship between the wild and domesticated taxa in both white-flowered groups. Capsicum baccatum var pendulum appears to have been domesticated directly from C. baccatum var. baccatum. The four named taxa of the C. annuum subgroup are also biochemically highly similar. We suggest that these taxa represent a single polytypic species with a large geographic range and that multiple, independent, domestications occurred from this wild gene pool. Evidence for relationships in the purple-flowered group is less clear. Capsicum eximium is the wild taxon which is biochemically most closely related to the cultivated C pubescens. However, the genetic distance is much greater than that between wild and cultivated white-flowered pairs. Therefore, it is not possible at present to suggest a progenitor for C. pubescens. Finally, C. chacoense does not belong to either white-flowered subgroup, but is the white-flowered taxon most closely related to the purple-flowered group. Capsicum chacoense may be the ancestor, or an unmodified descendent of the ancestor, of the two major groups of Capsicum.

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