@article {166,
	title = {Influence of climatic niche suitability and geographical overlap on hybridization patterns among southern Californian oaks},
	journal = {Journal of BiogeographyJournal of Biogeography},
	year = {2014},
	pages = {n/a-n/a},
	abstract = {Aim Information on the association between geographical patterns of hybridization and the climatic niche requirements and co-occurrence of the species involved can provide important insights that further our understanding of the factors promoting the formation of hybrid zones. Here, we test whether climatic niche suitability explains patterns of hybridization beyond spatial overlap in distributions of the geographically restricted Engelmann oak (Quercus engelmannii) and the widespread scrub oak species complex (Quercus spp.). Location Southern California, USA. Methods We sampled Engelmann and scrub oaks across 31 localities and genotyped 343 individuals at nine microsatellite loci. We used climatic niche modelling to assess the suitability of habitats for each parental species and hybrids and to analyse whether climatic niche suitability in addition to co-occurrence are associated with observed spatial patterns of hybridization. Results Our data indicated that hybrid zones are located in areas that are geographically constrained by the presence of scattered patches of Engelmann oak within a matrix broadly occupied by scrub oaks. However, the climatic niche of hybrids differed from that occupied by both Engelmann and scrub oaks, suggesting the importance of climate on their establishment and persistence beyond the simple role of geographical overlap of parental species distributions. We also found that even moderate levels of introgression contributed to increased genetic diversity in Engelmann oak but not in scrub oaks. Main conclusions These results show that hybrid zones follow a mosaic pattern constrained by the presence of scattered patches occupied by Engelmann oak and climatically suitable~areas that favour the establishment of hybrids. The low rates of ongoing hybridization and the bimodal distribution of parental genotypes found here suggest that hybridization is not threatening Engelmann oak and this phenomenon could instead be promoting the acquisition of favourable alleles that may increase the adaptive potential of this vulnerable species.},
	keywords = {Ecological niche modelling, extinction through hybridization, genetic diversity, HYBRIDIZATION, introgression, Maxent, microsatellite markers, peripheral populations, Quercus engelmannii, southern California},
	isbn = {1365-2699},
	author = {Ortego, Joaqu{\'\i}n and Gugger, Paul F. and Riordan, Erin C. and Sork, Victoria L.}
}
@article {115,
	title = {Selection and disperal in a multispecies oak hybrid zone},
	journal = {Evolution},
	volume = {58},
	year = {2004},
	month = {2004},
	pages = {261-269},
	abstract = {The 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.},
	keywords = {Climate, HYBRIDIZATION, introgression, pollen dispersal, Quercus wislizeni, red oaks},
	author = {Dodd, R.S. and Afzal-Rafii, Z.}
}
@article {73,
	title = {Taxonomy of Hill{\textquoteright}s Oak (Quercus ellipsoidalis: Fagaceae): Evidence from AFLP Data},
	journal = {Systematic Botany},
	volume = {33},
	year = {2008},
	note = {TY - JOUR},
	month = {2008},
	pages = {148-158},
	abstract = {Abstract:Quercus ellipsoidalis (Hill{\textquoteright}s oak), an endemic of east-central North America, is morphologically similar to Q. coccinea (scarlet oak) and is subsumed into that species in several floristic treatments. This study uses data from more than 250 amplified fragment length polymorphism (AFLP) markers to investigate whether Q. coccinea and Q. ellipsoidalis are genetically distinct from one another. Whereas Q. coccinea and Q. ellipsoidalis separate from one another in all analyses, Q. velutina (black oak) populations collected from the geographic range of both Q. coccinea and Q. ellipsoidalis do not separate out by geographic region. This, combined with the strong differentiation between Q. coccinea and Q. velutina but weak differentiation between Q. ellipsoidalis and Q. velutina, supports the view that Q. coccinea and Q. ellipsoidalis are not simply regional variants of a single taxon. Moreover, while there is no evidence from the molecular data we collected of hybridization between Q. coccinea and Q. ellipsoidalis, the data suggest that there may be gene flow between Q. ellipsoidalis and Q. velutina. A clearer understanding of the relationships among these taxa is essential to understanding the taxonomy of Quercus section Lobate in eastern North America.},
	keywords = {AMPLIFIED FRAGMENT LENGTH POLYMORPHISMS (AFLP), HYBRIDIZATION, OAK TAXONOMY, QUERCUS SECTION LOBATAE},
	url = {http://www.ingentaconnect.com/content/aspt/sb/2008/00000033/00000001/art00017},
	author = {Hipp, A.L. and Weber, J.A.}
}
