Genetic studies of various Prosopis species (Leguminosae, Section Algarobia) co‐occurring in oases of the Atacama Desert (northern Chile)

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 (HO = 0.61, Ar = 3.5) and low but significant genetic differentiation among populations (FST = 0.128, FST‐ENA = 0.129, DJOST = 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.

Silvopastoralism and the shaping of forest patches in the Atacama Desert during the Formative Period (ca. 3000–1500 years BP)

“…As preliminary analyses become more solid, we will be able to establish the role of camelids as vectors of these trees, while understanding human agency and anthropogenization of these oases, especially if desert distances between them are too large great for herbivores to act as dispersers, or for water to connect trees populations by floods (Bessega et al, 2021; McRostie, 2014; McRostie et al, 2017). Indeed, when Gajardo (1994) defines the vegetation of these oases,’ he states that the current level of human intervention makes it hard to define what was the “original vegetation composition.” It is likely that the cultural modification of these landscapes began several millennia ago during the Formative period, with agroforestry and silvopastoralism being a primary activity in the reproduction and inhabitation of these landscapes.…”

“…The high concentration of sugary pods is a good spot for bruchids to lay their eggs and reproduce, minimizing the spread and regeneration of these forests. Delatorre (2005) interprets ancient P. alba populations in the Pampa del Tamarugal basin as relicts, considering that most of these northern Algarobia populations are confined to isolated patches (Bessega et al, 2021;Carevic et al, 2012;Delatorre, 2005). This scenario resembles what Janzen and Martin (1982: 21) described as neotropical anachronisms, regarding the extinction of Gomphotheres and the Scheelea palm, "within a month as many as 5000 fruits accumulate .…”

“…Legume forests of algarrobo are ubiquitous and abundant in these rising settlements. These have been recovered in the form of stumps, charcoal, wood, thorns, leaves, pods, seeds, and endocarps, and although scant attention has been paid to their historical ecology (Bessega et al, 2021; McRostie, 2014; McRostie et al, 2017; Palacios and Brizuela, 2005), there is a close correlation between human settlements, caravans, and the flourishing of Algarobia patches during this period (Adán and Urbina, 2007; Agüero and Uribe, 2011; Benavente, 1982; García et al, 2014; Llagostera et al, 1984; McRostie et al, 2019; Rivera and Dodd, 2013; Uribe et al, 2020).…”

Desarrollo de nuevos loci de microsatélites para Geoffroea decorticans (Gillies ex Hook. & Arn.) Burkart

“…Los 38 loci SSR polimórficos obtenidos en este trabajo también podrían ser útiles para estudiar poblaciones de chañar en Bolivia, Chile, Perú, Paraguay y Uruguay. Además, estos marcadores codominantes podrían identificar y confirmar especies (Daïnou et al, 2016), subespecies (Besnard et al, 2008) En el norte de Chile, particularmente en el Desierto de Atacama, recientemente se han realizado estudios con marcadores SSR específicos en especies de Fabáceas como Prosopis chilensis, Prosopis alba, Prosopis flexuosa (Moncada et al, 2019;Bessega et al, 2021) y Balsamocarpon brevifolium (Stoll et al, 2020), sin embargo, no se han estudiado marcadores SSR específicos para G. decorticans. En esta última especie, se realizó un estudio con cinco marcadores SSR en ocho poblaciones de chañar (84 individuos en total), de los cuales tres marcadores (Gsp.A149, Gsp.B284 y Gsp.A104) mostraron un elevado polimorfismo (PIC > 0,78) y elevado número de alelos (>9) (Contreras et al, 2019), mientras que en el presente trabajo, para 30 individuos, se observó un elevado polimorfismo (PIC > 0,78) en siete marcadores (SSRGD20374, SSRGD27558, SSRGD10786, SSRGD17837, SSRGD17951, SSRGD11258 y SSRGD12427) y también elevados valores (PIC > 0,5) en 31 marcadores SSR.…”

Pre-Columbian cultivation of vegetatively propagated and fruit tree tropical crops in the Atacama Desert

“…The Atacama Desert of northern Chile is a unique region for the study of agricultural adoption processes. Here between the second and first millenium before the present era, societies primarily focused on the exploitation of marine resources from the highly productive Pacific coast began to adopt the cultivation of different complex of introduced domesticated plants throughout the Desert (García et al, 2020;Bessega et al, 2021;Ugalde et al, 2021). The evidence of these processes is constituted by uniquely preserved archaeobotanical materials including dried tissues of different anatomical parts such as tubers, roots, fruits, and others, thanks to prevailing hyper-arid conditions rarely present in other regions.…”