Pollination biology of Myrtillocactus schenckii (Cactaceae) in wild and managed populations of the Tehuacán Valley, México

Abstract

Myrtillocactus schenckii occurs in thorn-scrub forests of the Tehuacan Valley where people gather its edible fruits. It is also silviculturally managed and cultivated, people selecting plants with higher fruit production. We compared phenology, pollination biology, and breeding systems of wild and managed populations to determine whether humans have influenced changes in these aspects. Flower production was markedly higher in cultivated populations. Flowering peak of all managed populations occurred in December whereas in the wild it occurred in February. Anthesis was diurnal, with Plebeia mexicana being the most frequent flower visitor in the wild, Apis mellifera and Tabanus sp. in silvicultural populations, and Xylocopa mexicanorum in cultivated populations. Natural pollination was more successful in cultivated than in wild and silvicultural populations (83.3%, 40%, 26.66% fruits, respectively). Out-crossing was the most successful breeding system in all populations. Self-pollination was higher in cultivated (23.3% successful fruits) than in other populations (3.3% successful fruits in wild, and 10.0% in silviculture populations). Differences in flower production influenced by artificial selection and pollinator type explain different fruit production in managed and wild populations, whereas environmental heterogeneity influences differences in reproductive patterns, limiting pollen flow and contributing to maintaining phenotypic divergence among populations of M. schenckii.