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Phylogenetic relationships among domesticated and wild species of Cucurbita (Cucurbitaceae) inferred from a mitochondrial gene: Implications for crop plant evolution and areas of origin - PubMed

  • ️Tue Jan 01 2002

Phylogenetic relationships among domesticated and wild species of Cucurbita (Cucurbitaceae) inferred from a mitochondrial gene: Implications for crop plant evolution and areas of origin

Oris I Sanjur et al. Proc Natl Acad Sci U S A. 2002.

Abstract

We have investigated the phylogenetic relationships among six wild and six domesticated taxa of Cucurbita using as a marker an intron region from the mitochondrial nad1 gene. Our study represents one of the first successful uses of a mtDNA gene in resolving inter- and intraspecific taxonomic relationships in Angiosperms and yields several important insights into the origins of domesticated Cucurbita. First, our data suggest at least six independent domestication events from distinct wild ancestors. Second, Cucurbita argyrosperma likely was domesticated from a wild Mexican gourd, Cucurbita sororia, probably in the same region of southwest Mexico that gave rise to maize. Third, the wild ancestor of Cucurbita moschata is still unknown, but mtDNA data combined with other sources of information suggest that it will probably be found in lowland northern South America. Fourth, Cucurbita andreana is supported as the wild progenitor of Cucurbita maxima, but humid lowland regions of Bolivia in addition to warmer temperate zones in South America from where C. andreana was originally described should possibly be considered as an area of origin for C. maxima. Fifth, our data support other molecular results that indicate two separate domestications in the Cucurbita pepo complex. The potential zone of domestication for one of the domesticated subspecies, C. pepo subsp. ovifera, includes eastern North America and should be extended to northeastern Mexico. The wild ancestor of the other domesticated subspecies, C. pepo subsp. pepo, is undiscovered but is closely related to C. pepo subsp. fraterna and possibly will be found in southern Mexico.

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Figures

Figure 1
Figure 1

(A and B) Geographic range of putative wild ancestors of domesticated Cucurbita spp. in the U.S., Central America, and South America. Numbers on the maps are individual numbers for wild taxa listed in Table 1 and in supporting information on the PNAS web site (

www.pnas.org

). Question marks indicate potential areas of domestication for species that presently lack a wild ancestor.

Figure 2
Figure 2

ML tree for 11 species of Cucurbita. Individual numbers in parentheses are those listed in Table 1 and in supporting information on the PNAS web site (

www.pnas.org

). Taxa in bold print are domesticated species. Bootstrap values above the branches: parsimony in bold (100 bootstraps); distance in italics (1,000 bootstraps). Values below the branches represent ML steps (50,000 puzzle steps).

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