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Population Biology |
2Programa de Recursos Genéticos, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Apartado Postal 112, Celaya, Guanajuato 38000, México; 3Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, Apartado Postal 70-275, México, D. F., 04510, México
Cultivated squash (Cucurbita argyrosperma ssp. argyrosperma and C. moschata) are important in the Mexican traditional agroecosystem. They are typically cultivated within maize fields where adjacent populations of a wild, close relative, C. argyrosperma ssp. sororia, occur. Consequently, there are ample opportunities for gene flow between domesticated and free-living Cucurbita populations. We used allozymes to examine genetic variation and gene flow among these three Cucurbita taxa in the state of Jalisco in Western Mexico. Twelve polymorphic allozyme loci were used to calculate genetic diversity for 16 populations of Cucurbita. We found high levels of genetic variation: polymorphism of 0.96, mean allelic diversity of 2.08, average expected heterozygosity 0.407, and little differentiation among conspecific populations (D = 0.081; FST = 0.087; Nem = 5.22). These findings indicate that Cucurbita possess a high pollen dispersal potential, a somewhat surprising result considering they have specialist pollinators. Unweighted pair group method with arithmetic means (UPGMA) analysis of allozymes suggests the existence of at least two distinct groups of populations, one consisting of both subspecies of C. argyrosperma and another consisting of C. moschata.
Key Words: Cucurbita Cucurbitaceae cultivated squash gene flow genetic diversity genetic structure wild gourd
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