Genealogy and gene flow among annual domesticated species of Cucurbita

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Abstract
Over the years, workers have gathered data from various sources in the attempt to understand the evolutionary histories and relationships of the domesticated members of Cucurbita. We used allozyme data to address questions of genealogy, interspecific gene flow, and allelic diversity for 23 commercial cultivars and 17 indigenous landraces of C. maxima, C. mixta, C. moschata, and C. pepo. Allelic diversity was greatest in C. pepo (especially ssp. ovifera) and C. moschata, reflecting complex histories for these taxa. Cucurbita maxima and C. mixta were relatively homogeneous despite morphological heterogeneity. Infraspecific classifications based on morphological characters were not supported by the allozyme data for C. maxima, C. mixta, and C. moschata. The allozymes supported morphological evidence of introgression from C. mixta in Oriental cultivars and southwestern United States and northwestern Mexico landraces of C. moschata. Phylogenetic analyses indicated that C. moschata and C. mixta are probably sister species and that C. pepo shares a common ancestor with these species that is not shared with C. maxima.