Abstract
The fast expansion of human population around La Paz, Bolivia (3,200–4,100 m.a.s.l.) triggered new suburban settlements in nearby areas in valleys and mountain feet. The white mesquite, Prosopis alba Griseb. (Leguminosae), is a resource (originally used by native communities) that is strongly affected by changes in land use. A gradient in the level of disturbance is found moving away from the La Paz city toward less altitude areas. The main objective of this study was to characterize genetically three P. alba populations with different levels of human disturbance located at different altitudes in Bolivia, in order to provide some guidelines for management and conservation of these species. Based on 10 SSR loci, the populations showed high level of genetic diversity in comparison with other forest species. The population less disturbed and situated at the lowest altitude was the most variable (H e = 0.51–0.42), whereas the less variable was the most disturbed and situated at the highest altitude. Heterozygote excess was observed in all populations. Most of genetic diversity (99%) is contained within populations. Genetic differentiation among populations is low (1%), suggesting low gene flow among populations. No evidence of recent bottlenecks events was detected. The estimates of the effective population size were low in all populations. The results are in agreement with the hypothesis that genetic diversity is reduced by the impact of anthropic disturbance in the population located at higher altitude in comparison with the lightly disturbed situated at lower altitude and farther from urban settlements.
Highlights
Highland landscapes are constituted by heterogeneous topogra‐ phy and environmental gradients that characterize the habitats (Körner, 2003)
The main objective of this study was to examine the level of genetic diversity of populations of P. alba with different levels of human disturbance located in valleys at different altitudes in Bolivia
We addressed the following questions: (a) Is there dif‐ ference in the genetic diversity level found in the populations at dif‐ ferent altitude? (b) Are genetic diversity parameters affected by the level of disturbance? (c) Are populations located in different valleys significantly differentiated from each other? (d) Have the popula‐ tion undergone recent bottleneck processes? v) What are the pop‐ ulation effective sizes? We compared the results obtained in these populations with previous reports on two P. alba Argentinean pop‐ ulations (Campo Duran and Fernandez‐Forres) (Bessega, Pometti, Ewens, Saidman, & Vilardi, 2016) situated at much lower altitudes (150–450 m.a.s.l) with different levels of disturbance produced by agricultural activities
Summary
Highland landscapes are constituted by heterogeneous topogra‐ phy and environmental gradients that characterize the habitats (Körner, 2003). Steep valleys and mountain ridges demarcate the plant population habitats where gene flow is reduced favoring an important differentiation among populations (Hafdıs Hanna, Kuss, & Stöcklin, 2009). Bolivian communities sited in valleys and mountain foots in Tarija, Chuquisaca and La Paz, use wood from native forest species such as the “aliso” (alder tree, Alnus acuminata), “algarrobo blanco” (white mesquite, Prosopis alba) and “tipa colorada” (Pterogyne nitens) to make punts, ax handles, and utensils like dishes and spoons (Beck, Paniagua, & Yevara, 2001; McKean & Robinson, 1996; Nagashiro, 1992; Villanueva, 1997)
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