Evolution of Polaskia chichipe (Cactaceae) under domestication in the Tehuacan Valley, central Mexico:: Reproductive biology

Polaskia chichipe, a columnar cactus, is cultivated for its edible fruits in central Mexico. This study analyzed whether artificial selection has modified its reproduction patterns and caused barriers to pollen exchange between wild, managed in situ, and cultivated populations. Anthesis was diurnal (similar to16 h in winter, similar to10 h in spring) as well as partly nocturnal (similar to12 h in winter, similar to3 h in spring), and flowers were pollinated by bees, hummingbirds, and hawk moths. Manual cross-pollination was similar to37-49% effective in all populations. Self-pollination was similar to12% successful in the wild, but twice as successful (similar to22-27%) in managed and cultivated populations. Diurnal pollination was similar to35-55% effective in winter and 100% in spring. Nocturnal pollination was successful only in winter (15%). Crosses among individuals were more effective within populations than among populations, including populations under a similar management regimen. The least successful crosses were between wild and cultivated populations. Flowers were produced in all populations from January to March, but flowering peaks differed by 1 mo among wild, managed, and cultivated populations and by 2 mo, between wild and cultivated populations. The latter interrupted pollen exchange in May. Seeds from managed and cultivated populations germinated faster than those from wild individuals. Domestication has seemingly favored self-compatible P. chichipe plants with higher fruit yield, a longer period of fruit production, and faster seed germination, attributes that have resulted in partial reproductive barriers between wild and manipulated populations.