Morphological variation and reproductive biology of Polaskia chende (Cactaceae) under domestication in Central Mexico

The columnar cactus Polaskia chende, endemic to Central Mexico, occurs in the wild and in silviculturally managed populations where artificial selection for better edible fruits operates by sparing and favouring desirable phenotypes during vegetation clearance. Wild and managed populations were compared in morphology and reproductive biology to analyse if human selection has influenced phenotypic divergence, if it has modified breeding systems and if reproductive isolation exists between them. Fruits from managed populations were larger (6.36+/-0.17 cm(3)), heavier (19.62 +/- 1.32), sweeter (9.07+/-0.25 degreesBrix), and with thinner peel (2.09+/-1.32mm) than those from wild populations (5.77+/-0.18 cm(3), 15.73+/-0.85g, 8.23+/-0.31 degreesBrix, and 2.58+/-0.14mm, respectively). Both population types bloom synchronically, show diurnal anthesis, with bees as the most likely pollinators, and have breeding system predominantly self-incompatible. Spatial and temporal barriers to pollen exchange between wild and managed populations are unlikely, and morphological differences would be related with an ongoing process of artificial selection. (C) 2002 Elsevier Science Ltd.