00570nas a2200181   4500008004100000245010700041210006900148260000900217300001400226490000700240520001600247100001500263700001700278700001700295700001600312700001700328856004300345       1997                        eng d00aHow discrete are oak species? Insights from a hybrid zone between Quercus grisea and Quercus gambelii.0 aHow discrete are oak species Insights from a hybrid zone between  c1997  a747 - 7550 v513 anot aviable1 aHoward, D.1 aPreszler, R.1 aWilliams, J.1 aFenchel, S.1 aBoecklen, W.  uhttps://quercus.myspecies.info/node/7102506nas 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/3901925nas a2200145   4500008004100000245010800041210006900149260000900218300001200227490000700239520143800246100001601684700002401700856005501724       2009                        eng d00aExtreme host plant conservatism during at least 20 million years of host plant pursuit by oak gallwasps0 aExtreme host plant conservatism during at least 20 million years  c2009  a854-8690 v633 aDiversification of insect herbivores is often associated with coevolution between plant toxins and insect countermeasures, resulting in a specificity that restricts host plant shifts. Gall inducers, however, bypass plant toxins and the factors influencing host plant associations in these specialized herbivores remain unclear. We reconstructed the evolution of host plant associations in Western Palaearctic oak gallwasps (Cynipidae: Cynipini), a species-rich lineage of specialist herbivores on oak (Quercus). (1) Bayesian analyses of sequence data for three genes revealed extreme host plant conservatism, with inferred shifts between major oak lineages (sections Cerris and Quercus) closely matching the minimum required to explain observed diversity. It thus appears that the coevolutionary demands of gall induction constrain host plant shifts, both in cases of mutualism (e.g., fig wasps, yucca moths) and parasitism (oak gallwasps). (2) Shifts between oak sections occurred independently in sexual and asexual generations of the gallwasp lifecycle, implying that these can evolve independently. (3) Western Palaearctic gallwasps associated with sections Cerris and Quercus diverged at least 20 million years ago (mya), prior to the arrival of oaks in the Western Palaearctic from Asia 520137 mya. This implies an Asian origin for Western Palaearctic gallwasps, with independent westwards range expansion by multiple lineages.1 aStone, G.N.1 aHernandez-Lopez, A.  uhttp://dx.doi.org/10.1111/j.1558-5646.2008.00604.x