The impact of local extinction on genetic structure of wild populations of lima beans (Phaseolus lunatus) in the Central Valley of Costa Rica: consequences for the conservation of plant genetic resources

Abstract

Plant populations may experience local extinction and at the same time new populations may appear in nearby suitable locations. Species may also colonize the same site on multiple occasions. Here, we examined the impact of local extinction and recolonization on the genetic structure of wild populations of lima beans (Phaseolus lunatus) in the Central valley of Costa Rica. We compared genetic diversity from the samples taken from the populations before and after extinction at 13 locations using microsatellite markers. Locations were classified according to the occurrence of extinction episodes during the previous five years into three groups: 1) populations that experienced extinction for more than one year, and were later recolonized (recolonized), 2) populations that did not experience local extinction (control), and 3) populations that did not experience local extinction during the study, but were cut to experimentally simulate extinction (experimental). Our data did not show a clear tendency in variation in allele frequencies, expected heterozygosity, and effective number of alleles within and between groups of populations. However, we found that the level of genetic differentiation between samples collected at different times at the same location was different in the three groups of populations. Recolonized locations showed the highest level of genetic differentiation (mean Fst = 0.2769), followed by control locations (mean F st = 0.0576) and experimental locations (mean F st = 0.0189). Similar findings were observed for Nei ' s genetic distance between samples (d i,j = 0.1786, 0.0400, and 0.0037, respectively). Our results indicate that genetic change in lima beans depends on the duration and frequency of local extinction episodes. These findings also showed that control populations are not in equilibrium. Implications of these results for the establishment of conservation strategies of genetic resources of lima beans are discussed.

Differentiation and genetic diversity of Phaseolus lunatus wild populations from Chiapas, Mexico, and their genetic relationships with MI and MII groups

“…Also, wild populations of Phaseolus lunatus have a metapopulation behavior (Barrantes et al 2008), implying the existence of extinction and recolonization processes that may affect their genetic structure. It has been noted that the founder effect associated with recolonization increases the differentiation between subpopulations (Wright 1977).…”

Genetic structure within the Mesoamerican gene pool of wild Phaseolus lunatus (Fabaceae) from Mexico as revealed by microsatellite markers: Implications for conservation and the domestication of the species

“…Another aspect that could affect the distribution and genetic differentiation of the wild populations of P. lunatus is their metapopulational behavior (Barrantes et al, 2008). Wright (1977) noted that the founder effect associated with recolonization increases differentiation among subpopulations.…”

“…Selfing is favored by the synchronized maturation of pollen grains and stigma and by their proximity within the flower bud (Webster et al, 1979), but outcrossing rates up to 48% have been reported (Baudoin et al, 1998). Wild populations have metapopulation dynamics (Barrantes et al, 2008) and generate important seed banks in the soil that can remain viable for up to 3 yr after dispersal (Degreef et al, 2002).…”