Genetic Resources and Crop Evolution (2006) 53: 277–287 DOI 10.1007/s10722-004-6147-4 # Springer 2006 Reproductive biology in wild and silvicultural managed populations of Escontria chiotilla (Cactaceae) in the Tehuaca´n Valley, Central Mexico Brenda Oaxaca-Villa, Alejandro Casas* and Alfonso Valiente-Banuet Centro de Investigaciones en Ecosistemas, UNAM. Apartado Postal 27-3 (Xangari), Morelia, Michoaca ´n 58089 M exico; *Author for correspondence (e-mail: acasas@oikos.unam.mx; phone: (443) 3 22 27 38; fax: (443) 3 22 27 19) Received 28 November 2003; accepted in revised form 27 February 2004 Key words: Columnar cacti, Crop evolution, Domestication, Escontria chiotilla, Genetic resources, Reproductive biology, Tehuaca´n Valley Abstract Reproductive biology of the columnar cactus Escontria chiotilla was analysed in wild and silvicultural managed populations in the Tehuaca´n Valley, Central Mexico, where this cactus is under domestication because of its edible fruits. Anthesis is diurnal, flowers opening between 8:00 and 17:00 h, the period between 12:00 and 13:00 appearing to be crucial in pollination success since at this time the maximum opening of flowers, turgidity of stigma, and activity of flower visitors, as well as the highest nectar production and pollen release occur. The bees Apis mellifera, Bombus pensylvanicus and Xylocopa mexicanorum, and the hummingbirds Amazilia violiceps, Cynanthus sordidus and Cynanthus latirostris were the most frequent flower visitors during the crucial period, and were observed contacting both stamens and stigma of E. chiotilla. No differences were found in anthesis nor in flower visitors among both population types. Distances separating the populations studied and bridges of individuals of E. chiotilla between them are within the radius that bees and hummingbirds may travel, indicating that spatial barrier to pollen flow are unlikely. Breeding system is self-incompatible. Production of flowers occurs during the whole year in both population types, allowing continual pollen flow among them. This observation confirms reports of high gene flow among the populations studied in previous population genetics studies. The high pollen flow among wild and managed population explains that however the occurrence of artificial selection, the process of domestication is in incipient stages presumably because gene flow counteracts effects of artificial selection. Introduction Escontria chiotilla (F. A. C. Weber) Rose, tradi- tionally called ‘‘jiotilla’’, is a common element in tropical deciduous and thorn-scrub forests of arid and semiarid areas in Central Mexico. Forests in which E. chiotilla is the dominant species were described as ‘‘jiotillal’’ by Rzedowski (1978). Jiotilla is also one of the most culturally and eco- nomically important cactus species in the area, since its edible fruits are particularly appreciated by people for direct consumption and commercia- lization in regional markets. Fruits are consumed fresh, and their flavour is preferred over fruit of other cacti species. Jams, ice cream, the wine called ‘‘nochoctli’’, and the spirit called ‘‘vinillo’’ can also be prepared, branches are used as fodder and its wood is used as fuel and for construction of fences (Hammer 2001; Arellano and Casas 2003). Escontria chiotilla may be 7 m height, with numerous branches twisted when old. Flowers, pro- duced at the top of the branches, are infundi- buliform, nearly 3 cm long including the ovary and the floral tube. Tepals are yellow, and the