Fine-scale spatial genetic structure analysis in two Argentine populations of Prosopis alba (Mimosoideae) with different levels of ecological disturbance

Spatial genetic structure (SGS) in plants is primarily determined by the interaction between pollen and seed dispersal, but it is strongly affected by both evolutionary and ecological processes. SGS studies in forest species also allow evaluating the consequences of human-mediated disturbance on pollen and seed movement and designing strategies of sustainable use of native forest resources. The present paper compares fine-scale SGS between two populations of Prosopis alba: Fernandez-Forres (FF) and Campo Duran (CD), based on the variation of 12 SSR markers. Populations show different history, management, and levels of disturbance. FF is highly disturbed and fragmented by agricultural activity and stockbreeding. Although no significant differences were observed in genetic variability parameters, highly significant genetic differentiation was detected with virtually no admixture between populations. SGS was positive and significant at short distances only in the non-disturbed population of CD. Accordingly, estimated neighborhood size and effective gene dispersal are higher in FF than in CD. This result might be explained by the higher incidence of livestock in seed dispersal and the patchy structure favoring longer pollen movement and artificial thinning and selection in FF. The results are relevant to conservation and breeding programs, suggesting that the distance between seed trees to be sampled should be larger than 22 m, the estimated distance of significant SGS in P. alba.