Managing diversity: Domestication and gene flow in Stenocereus stellatus Riccob. (Cactaceae) in Mexico

Abstract

Microsatellite markers (N = 5) were developed for analysis of genetic variation in 15 populations of the columnar cactus Stenocereus stellatus, managed under traditional agriculture practices in central Mexico. Microsatellite diversity was analyzed within and among populations, between geographic regions, and among population management types to provide detailed insight into historical gene flow rates and population dynamics associated with domestication. Our results corroborate a greater diversity in populations managed by farmers compared with wild ones (HE = 0.64 vs. 0.55), but with regional variation between populations among regions. Although farmers propagated S. stellatus vegetatively in home gardens to diversify their stock, asexual recruitment also occurred naturally in populations where more marginal conditions have limited sexual recruitment, resulting in lower genetic diversity. Therefore, a clear-cut relationship between the occurrence of asexual recruitment and genetic diversity was not evident. Two managed populations adjacent to towns were identified as major sources of gene movement in each sampled region, with significant migration to distant as well as nearby populations. Coupled with the absence of significant bottlenecks, this suggests a mechanism for promoting genetic diversity in managed populations through long distance gene exchange. Cultivation of S. stellatus in close proximity to wild populations has led to complex patterns of genetic variation across the landscape that reflects the interaction of natural and cultural processes. As molecular markers become available for nontraditional crops and novel analysis techniques allow us to detect and evaluate patterns of genetic diversity, genetic studies provide valuable insights into managing crop genetic resources into the future against a backdrop of global change. Traditional agriculture systems play an important role in maintaining genetic diversity for plant species.

Diversity and genetic structure of the husk tomato (Physalis philadelphica Lam.) in Western Mexico

“…Exact differentiation analysis (Raymond and Rousset 1995) showed significant differences in allele frequencies (p \ 0.05) between pairs of P. philadelphica populations, confirming that the processes mentioned above influenced genetic condition. Furthermore, there was a structure of *9 % between population management categories (AMOVA, Table 2) that may have been influenced by anthropogenic management, as has been shown for other species (Oyama et al 2006;Shi et al 2008;Cruse-Sanders et al 2013). Consistent with this result, our cluster analysis and Bayesian assignment analysis show the separation of two large genetic groups (Figs.…”

Consecuencias de la domesticación de Stenocereus stellatus en el tamaño de las semillas y en la germinación en un gradiente de estrés hídrico

“…En las poblaciones cultivadas hay una mayor proporción de individuos que producen frutos de mayor tamaño, con sabor más dulce, menos espinas, pericarpio más delgado y con mayor proporción de variedades con pulpa distinta al color rojo (anaranjado, amarillo, rosado y morado), que prevalece en las poblaciones silvestres (Casas et al, 1999a). Estudios de genética de poblaciones Cruse-Sanders et al, 2013) identifi caron pequeñas, aunque signifi cativas, distancias genéticas entre poblaciones; sin embargo, tales distancias se correlacionan con la distancia geográfi ca más que con el tipo de manejo. Patrones similares de divergencias morfológicas y genéticas se han documentado en otras especies de cactáceas columnares del Valle de Tehuacán-Cuicatlán que reciben manejo tradicional similar a Stenocereus stellatus; tales son los casos de S. pruinosus (Luna-Morales y Aguirre, 2001; Parra et al, 2008Parra et al, , 2010Parra et al, , 2012, P. chichipe (Otero-Arnaiz et al, 2003;2005a, b;Carmona y Casas, 2005), Lemairocereus hollianus (Rodríguez-Arévalo et al, 2006) y Myrtillocactus schenckii (Blancas et al, 2009), y aun en especies que solamente reciben manejo silvícola y no se cultivan en huertas, tales como Polaskia chende (Cruz y Casas, 2002) y Escontria chiotilla (Arellano y Casas, 2003;Tinoco et al, 2005).…”

Effects of natural and artificial selection on survival of columnar cacti seedlings: the role of adaptation to xeric and mesic environments

“…In the present study, S. pruinosus was the species with the highest rate of development. The differences in rates of development found in the three species could explain the differences in management intensity found for these species in previous studies, in addition to artificial selection (Casas et al , 2007Parra et al 2010Parra et al , 2012Cruse-Sanders et al 2013). In all species, roots showed the greatest development in xeric conditions.…”

“…Cultivation is uncommon for plants in which vegetative propagation is difficult but is common in species that combine vegetative propagation and fast growth. Morphometric and population genetics studies that compared wild and managed populations of several species showed divergences among these population types that were proportional to the intensity of the management (Casas et al , 2007Parra et al 2010Parra et al , 2012Cruse-Sanders et al 2013).…”