Abstract
In the Atacama Desert from northern Chile (19–24°S), Prosopis (Leguminosae) individuals are restricted to oases that are unevenly distributed and isolated from each other by large stretches of barren landscape constituting an interesting study model as the degree of connectivity between natural populations depends on their dispersal capacity and the barriers imposed by the landscape. Our goal was to assess the genetic diversity and the degree of differentiation among groups of Prosopis individuals of different species from Section Algarobia and putative hybrids (hereafter populations) co‐occurring in these isolated oases from the Atacama Desert and determine whether genetic patterns are associated with dispersal barriers. Thirteen populations were sampled from oases located on three hydrographic basins (Pampa del Tamarugal, Rio Loa, and Salar de Atacama; northern, central, and southern basins, respectively). Individuals genotyped by eight SSRs show high levels of genetic diversity (H O = 0.61, A r = 3.5) and low but significant genetic differentiation among populations (F ST = 0.128, F ST‐ENA = 0.129, D JOST = 0.238). The AMOVA indicates that most of the variation occurs within individuals (79%) and from the variance among individuals (21%); almost, the same variation can be found between basins and between populations within basins. Differentiation and structure results were not associated with the basins, retrieving up to four genetic clusters and certain admixture in the central populations. Pairwise differentiation comparisons among populations showed inconsistencies considering their distribution throughout the basins. Genetic and geographic distances were significantly correlated at global and within the basins considered (p < .02), but low correlation indices were obtained (r < .37). These results are discussed in relation to the fragmented landscape, considering both natural and non‐natural (humans) dispersal agents that may be moving Prosopis in the Atacama Desert.
Highlights
The Atacama Desert in northern Chile extends for more than 1,000 km along the western coast of South America and is one of the most arid deserts on Earth
Genetic diversity can be spatially structured at different levels, such as landscape, population, or between nearby individuals, due to different ecological process of habitat characteristics such as population density and community structure operating in natural populations (Zeng et al, 2012)
Prosopis populations in the Chilean Desert show low but significant genetic differentiation (FST = 0.128, FST-ENA = 0.129, and DJOST = 0.238) and is consistent with the differentiation evaluated by the discriminant analysis of the principal components (DAPC), where differentiation is not observed at the uppermost hierarchical level as populations from northern, central, and southern basins were not grouped forming clusters
Summary
The Atacama Desert in northern Chile extends for more than 1,000 km along the western coast of South America and is one of the most arid deserts on Earth. In Pampa del Tamarugal or northern basin, the vegetation corresponds to the “Desierto del Tamarugal” (Gajardo, 1994) and is distributed in areas where the water table is relatively shallow or receives riparian flows originated in the Andes by summer precipitations (Barros, 2010) This basin has evidence of several human settlements since the Late Pleistocene, and it is connected by a small ravine with the lower course of the Loa River, nearby its mouth in the Pacific Coast (Nester et al, 2007; Pfeiffer et al, 2018). The main objective of this study was to assess the genetic diversity and the degree of differentiation among groups of Prosopis individuals of different species from Section Algarobia and putative hybrids (hereafter populations) co-occurring in the isolated oases from the Atacama Desert and determine whether genetic patterns are related to dispersal barriers. The dispersal limitation described for Prosopis species (Bessega, Ferreyra, Julio, et al, 2000; Bessega et al, 2011, 2017) and the barriers imposed by the landscape should be reflected in population genetic structure
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