02506nas a2200217   4500008004100000245006100041210006100102260000900163300001200172490000700184520191500191653001202106653001802118653001802136653002102154653002202175653001302197100001502210700002002225856004302245       2004                        eng d00aSelection and disperal in a multispecies oak hybrid zone0 aSelection and disperal in a multispecies oak hybrid zone  c2004  a261-2690 v583 aThe four western North American red oak species (Quercus wislizeni, Q. parvula, Q. agrifolia, and Q. kelloggii) are known to produce hybrid products in all interspecific combinations. However, it is unknown whether hybrids are transitory resulting from interspecific gene flow or whether they are maintained through extrinsic selection. Here, we examine cryptic hybrid structure in Q. wislizeni through a broad region including contact and isolation from three other western North American red oaks using amplified fragment length polymorphism molecular markers. All four species were simultaneously detected in the genetic background of individuals morphologically assigned to Q. wislizeni, although the contribution of Q. kelloggii was minor. In some cases, introgression was detected well outside the region of sympatry with one of the parental species. Molecular structure at the individual level indicated this was due to long-distance pollen dispersal and not to local extinction of parental species. Species admixture proportions were correlated with climatic variables and greater proportions of Q. agrifolia and Q. parvula were present in the genetic background of Q. wislizeni in sites with cooler and more humid summers, corresponding with habitat preferences of the parental species. Partial Mantel tests indicated that climate was more important than distance from pollen source in this association. Despite high levels of introgression, species integrity was maintained in some populations in close proximity to the other species, providing further support to environmental selection in determining population genetic structure. Thus, the contribution of species mixtures to population genetic structure varies across the landscape according to availability of pollen, but more importantly to varying environmental selection pressures that produce a complex pattern of hybrid and pure gene pools.10aClimate10aHYBRIDIZATION10aintrogression10apollen dispersal10aQuercus wislizeni10ared oaks1 aDodd, R.S.1 aAfzal-Rafii, Z.  uhttps://quercus.myspecies.info/node/39