Differential survival and growth of wild and cultivated seedlings of columnar cacti: Consequences of domestication

American Journal of Botany 100(12): 1–16, 2013 ; http://www.amjbot.org/ © 2013 Botanical Society of America Domestication is an evolutionary process through which plant or animal populations used by humans become adapted to human culture and human-made environments, causing morphological, physiological, and genetic divergences with respect to the original wild populations ( Hawkes, 1983 ). The main evolutionary force of domestication is artifi cial selection, which operates intentionally to favor the fi tness of organisms that humans prefer because of their use attributes and performance in human-made environments. Comparatively, natural selection may occur in both natural and artifi cial environments, but humans do not guide the process intentionally. Natural and artifi cial selection continually contributes to shape the adaptation of organisms in different contexts, and such processes throughout time determine evolutionary divergence. However, natural selection operating in artifi cial contexts may also contribute signifi cantly to adaptation of domesticates to human-made environments and divergences between domesticated and natural populations ( Gepts, 2004 ; McKey et al., 2012 ). Studies of domestication of plants have documented morphophysiological traits commonly changing associated with artifi cial selection ( Hawkes, 1983 ; Harlan, 1992 ; Evans, 1993 ). In those domesticated plants propagated by seeds, the most relevant changes associated with the fi rst steps of the life cycle are the loss of seed dormancy and germination synchronicity and the increased vigor and establishment of seedlings in human-made environments, but patterns may be different in plants clonally propagated or with mixed reproduction systems ( Hawkes, 1983 ; Harlan, 1992 ; Evans, 1993 ). Changes produced by domestication generally determine that domesticated organisms lose capacity of survival and reproduction in wild environments ( Frary and Doganlar, 2003 ). In populations that are fully domesticated, plants are totally dependent on humans to survive and reproduce ( Harlan, 1992 ), but in rural areas of the world it is still common to fi nd plant populations at different degrees of domestication. This variation appears to be related to the intensity of artifi cial selection, the degree of isolation of wild and 1 Manuscript received 9 July 2013; revision accepted 7 October 2013. The authors thank the Posgrado en Ciencias Biologicas, UNAM and the National Council for Science and Technology (CONACYT), Mexico for supporting the postgraduate studies of S.G. They also thank CONACYT (research project CB-2008-01-103551) and PAPIIT, DGAPA, UNAM (research projects IN205111-3 and IN209214) for funding the research and DGAPA-UNAM for a postdoctoral grant to S.G. The authors thank Edgar Perez-Negron and Juana Rodriguez for fi eld and laboratory assistance. 5 Author for correspondence (e-mail: acasas@cieco.unam.mx)