01908nas a2200145   4500008004100000245014600041210006900187260000900256300001400265490000700279520138000286100002301666700001601689856005701705       2009                        eng d00aMolecular, morphological, and ecological niche differentiation of sympatric sister oak species, Quercus virginiana and Q. geminata (Fagaceae)0 aMolecular morphological and ecological niche differentiation of   c2009  a1690-17020 v963 aThe genus Quercus (the oaks) is notorious for interspecific hybrization, generating questions about the mechanisms that permit coexistence of closely related species. Two sister oak species, Quercus virginiana and Q. geminata, occur in sympatry in Florida and throughout the southeastern United States. In 11 sites from northern and southeastern regions of Florida, we used a leaf-based morphological index to identify individuals to species. Eleven nuclear microsatellite markers significantly differentiated between the species with a high correspondence between molecular and morphological typing of specimens. Nevertheless, Bayesian clustering analysis indicates interspecific gene flow, and six of 109 individuals had mixed ancestry. The identity of several individuals also was mismatched using molecular markers and morphological characters. In a common environment, the two species performed differently in terms of photosynthetic performance and growth, corresponding to their divergent ecological niches with respect to soil moisture and other edaphic properties. Our data support earlier hypotheses that divergence in flowering time causes assortative mating, allowing these ecologically distinct sister species to occur in sympatry. Limited gene flow that permits ecological differentiation helps to explain the overdispersion of oak species in local communities.1 aCavender-Bares, J.1 aPahlich, A.  uhttp://www.amjbot.org/cgi/content/abstract/96/9/1690