02317nas a2200181   4500008004100000245006500041210006500106260003000171300001100201490000600212520176900218100002601987700002002013700001902033700002002052700001902072856004402091       2012                        eng d00aGenetic Diversity Increases Insect Herbivory on Oak Saplings0 aGenetic Diversity Increases Insect Herbivory on Oak Saplings  bPublic Library of Science  ae442470 v73 a<p>A growing body of evidence from community genetics studies suggests that ecosystem functions supported by plant species richness can also be provided by genetic diversity within plant species. This is not yet true for the diversity-resistance relationship as it is still unclear whether damage by insect herbivores responds to genetic diversity in host plant populations. We developed a manipulative field experiment based on a synthetic community approach, with 15 mixtures of one to four oak (<italic>Quercus robur</italic>) half-sib families. We quantified genetic diversity at the plot level by genotyping all oak saplings and assessed overall damage caused by ectophagous and endophagous herbivores along a gradient of increasing genetic diversity. Damage due to ectophagous herbivores increased with the genetic diversity in oak sapling populations as a result of higher levels of damage in mixtures than in monocultures for all families (complementarity effect) rather than because of the presence of more susceptible oak genotypes in mixtures (selection effect). Assemblages of different oak genotypes would benefit polyphagous herbivores via improved host patch location, spill over among neighbouring saplings and diet mixing. By contrast, genetic diversity was a poor predictor of the abundance of endophagous herbivores, which increased with individual sapling apparency. Plant genetic diversity may not provide sufficient functional contrast to prevent tree sapling colonization by specialist herbivores while enhancing the foraging of generalist herbivores. Long term studies are nevertheless required to test whether the effect of genetic diversity on herbivory change with the ontogeny of trees and local adaptation of specialist herbivores.</p>1 aCastagneyrol, Bastien1 aLagache, Lélia1 aGiffard, Brice1 aKremer, Antoine1 aJactel, Hervé  uhttps://quercus.myspecies.info/node/14302151nas a2200241   4500008004100000020001400041245006200055210006100117300001200178520145400190653001601644653001601660653002201676653002301698653002201721653002001743653001801763100002001781700002301801700002001824700002101844856004401865       2012                        eng d  a1365-294X00aFine-scale environmental control of hybridization in oaks0 aFinescale environmental control of hybridization in oaks  an/a-n/a3 aNatural hybridization is attracting much interest in modern speciation and conservation biology studies, but the underlying mechanisms remain poorly understood. In particular, it is unclear why environmental changes often increase hybridization rates. To study this question, we surveyed mating events in a mixed oak stand and developed a spatially explicit individual-based hybridization model. This model, where hybridization is frequency-dependent, pollen is nonlimiting and which allows immigrant pollen to compete with local pollen, takes into account species-specific pollen dispersal and sexual barriers to hybridization. The consequences of pollen limitation on hybridization were studied using another simple model. The results indicate that environmental changes could increase hybridization rates through two distinct mechanisms. First, by disrupting the spatial organization of communities, they should decrease the proportion of conspecific pollen available for mating, thus increasing hybridization rates. Second, by decreasing the density of conspecifics, they should increase pollen limitation and thus hybridization rates, as a consequence of chance pollination predominating over deterministic pollen competition. Altogether, our results point to a need for considering hybridization events at the appropriate level of organization and provide new insights into why hybridization rates generally increase in disturbed environments.10adisturbance10aimmigration10amass action model10apaternity analysis10apollen limitation10aQuercus petraea10aQuercus robur1 aLagache, Lélia1 aKlein, Etienne, K.1 aGuichoux, Erwan1 aPetit, Rémy, J.  uhttps://quercus.myspecies.info/node/147