Asymmetry of gene flow and differential geographical structure of molecular diversity in wild and domesticated common bean (Phaseolus vulgaris L.) from Mesoamerica

Abstract

Using amplified fragment length polymorphisms (AFLPs), we analyzed the genetic structure of wild and domesticated common bean (Phaseolus vulgaris L.) from Mesoamerica at different geographical levels to test the hypothesis of asymmetric gene flow and investigate the origin of weedy populations. We showed both by phenetic and admixture population analyses that gene flow is about three- to four-fold higher from domesticated to wild populations than in the reverse direction. This result, combined with other work, points to a displacement of genetic diversity in wild populations due to gene flow from the domesticated populations. The weedy populations appear to be genetically intermediate between domesticated and wild populations, suggesting that they originated by hybridization between wild and domesticated types rather than by escape from cultivation. In addition, the domesticated bean races were genetically similar confirming a single domestication event for the Mesoamerican gene pool. Finally, the genetic diversity of the domesticated bean population showed a lower level of geographic structure in comparison to that of the wild populations.

Investigation of the domestication of common bean (Phaseolus vulgaris) using multilocus sequence data

“…This single domestication model showed similar posterior probabilities for the two gene pools. These results support hypotheses proposed in common bean by previous researchers Papa and Gepts 2003;Rossi et al 2009). The parameters estimated here suggest a short duration with a large founding population.…”

“…Statistically significant differences are indicated: *, P < 0.05; **, P < 0. and 0 in Andean). This a strong indicator of gene flow and is consistent with the earlier results by Papa and Gepts (2003) and Papa et al (2005) for common bean, as well the bidirectional gene flow observed in 12 of the 13 most important food crops (Ellstrand et al 1999;Stewart et al 2003). Moreover, for 7 of these 13 crops, introgression of domesticated traits increased the competitiveness of the related weed species (Ellstrand et al 1999;Ellstrand and Schierenbeck 2000).…”

“…This data clearly suggests that landraces within a gene pool arose by a domestication event specific to that gene pool. The hypothesis of independent domestication events in each gene pool was suggested previously Papa and Gepts 2003;Rossi et al 2009).…”

“…A single MA domestication event Papa and Gepts 2003;, Rossi et al 2009) would imply that divergence into races followed the domestication process instead of resulting from separate domestications. Beebe et al (2000) used random amplified polymorphic DNA (RAPD) data to suggest that the MA gene pool was the result of two distinct domestication events.…”

Population genetic structure of two primary parasitoids of Spodoptera frugiperda (Lepidoptera), Chelonus insularis and Campoletis sonorensis (Hymenoptera): to what extent is the host plant important?

“…The fact that isolation by distance was detectable only when considering a large spatial scale may indicate that gene flow is more important than drift in these two parasitoid species and that the chance of local adaptation will be limited. Interestingly, absence of isolation by distance in cultivated beans and associated bruchid beetles has previously been explained by frequent long-distance transportation by humans of beans for consumption (Gepts 1998;Papa & Gepts 2003;Alvarez et al 2007). However, this explanation can be ruled out in our system, as the two parasitoids attack either eggs or second instar larvae (Cave 1995), which are only found on immature plants.…”