II.2. SQUASHES, PUMPKINS, ZUCCHINIS, GOURDS (CURCURBITA SPECIES) – 87
Cucurbita argyrosperma
A number of researchers have investigated Cucurbita argyrosperma, which was
formerly known as C. mixta Pang (e.g. Nabhan, 1984; Merrick and Nabhan, 1985;
Merrick and Bates, 1989; Merrick, 1991, 1990). C. argyrosperma is a collection of
interfertile domesticated, feral and wild plants. Based on morphological variation,
geographical distribution and allozyme variation, Merrick and Bates (1989) and Merrick
(1990) have divided C. argyrosperma into two subspecies: 1) ssp. argyrosperma, with
four varieties, three of which (var. argyrosperma, var. callicarpa, var. stenosperma)
encompass all the cultivated types of the species, and one that encompasses the wild
populations from northern Mexico (var. palmeri); and 2) ssp. sororia, which is considered
the evolutionarily ancestral wild stock (based on its ecogeographical distribution,
morphological similarity and reproductive compatibility) and is comprised of the wild
populations from Mexico through Central America. Hybridisation studies (Merrick, 1990)
and field data (Nabhan, 1984; Merrick and Nabhan, 1985; Decker, 1986; Lira, 1991) have
revealed that all five of these taxa are completely interfertile and thus belong to the same
biological species.
Spontaneous hybrids between the wild and cultivated plants of the group have been
documented for some regions of Mexico in populations quite separated from each other,
as reported by Decker (1986), between plants from various taxa of ssp. argyrosperma
in the state of Jalisco. Moreover, the characteristics of cultivated varieties do not differ
much from those that can be found in the wild plants of the group, nor from those of
spontaneous hybrids between the wild and cultivated plants of the group. It is therefore
not easy to readily distinguish between the various subspecies and varieties. For these
reasons, this chapter follows the general convention and recognises only the
two subspecies, placing all the cultivated types within ssp. argyrosperma, and the wild or
spontaneous plants within ssp. sororia (as in Table 2.1).
Cucurbita pepo
Cucurbita pepo is probably the most well-studied species of the genus. Systematic,
ethnobotanical and morphometric research, together with archaeological information,
constitute the main sources of information concerning its origin and domestication.
Similar to C. argyrosperma, C. pepo is a collection of interfertile domesticated, feral and
wild plants.
Morphometric and molecular research, as well as studies on artificial and spontaneous
hybridisation, indicate that the wild taxa most closely related to C. pepo L. are: 1) C. pepo
ssp. fraterna (also known as C. fraterna), only found currently in a few localities in
northeastern Mexico (in the states of Tamaulipas and Nuevo León; Bailey, 1943; Andres,
1987a; Nee, 1990; Rodríguez and Lira, 1992; Wilson, Lira and Rodríguez, 1994); and
2) two wild Cucurbita originally identified as C. texana (identified now as C. pepo ssp.
ovifera var. texana and C. pepo ssp. ovifera var. ozarkana), which are endemic to parts of
the United States (Gray, 1850; Bailey, 1943; Fursa and Filov, 1982; Decker, 1988, 1986;
Andres, 1987a; Decker and Wilson, 1987; Kirpatrick and Wilson, 1988; Wilson, 1990,
1989; Decker-Walters et al., 1990; Wilson, Doebley and Duvall, 1992; Sanjur et al.,
2002).
There is still some disagreement concerning the appropriate taxonomic relationship of
the members of the Pepo group, with no fewer than three different reclassifications
suggested, including those from Decker (1988, 1986); Andres (1987a);
Decker-Walters et al. (1993, 1990). The first proposal by Decker (1988, 1986) recognised