02151nas 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/14702295nas a2200169 4500008004100000245006500041210006500106260003000171300001100201490000600212520178700218100001802005700001802023700002102041700001902062856004402081 2010 eng d00aExploring Species Limits in Two Closely Related Chinese Oaks0 aExploring Species Limits in Two Closely Related Chinese Oaks bPublic Library of Science ae155290 v53 aBackground

The species status of two closely related Chinese oaks, Quercus liaotungensis and Q. mongolica, has been called into question. The objective of this study was to investigate the species status and to estimate the degree of introgression between the two taxa using different approaches.

Methodology/Principal Findings

Using SSR (simple sequence repeat) and AFLP (amplified fragment length polymorphism) markers, we found that interspecific genetic differentiation is significant and higher than the differentiation among populations within taxa. Bayesian clusters, principal coordinate analysis and population genetic distance trees all classified the oaks into two main groups consistent with the morphological differentiation of the two taxa rather than with geographic locations using both types of markers. Nevertheless, a few individuals in Northeast China and many individuals in North China have hybrid ancestry according to Bayesian assignment. One SSR locus and five AFLPs are significant outliers against neutral expectations in the interspecific FST simulation analysis, suggesting a role for divergent selection in differentiating species.

Main Conclusions/Significance

All results based on SSRs and AFLPs reached the same conclusion: Q. liaotungensis and Q. mongolica maintain distinct gene pools in most areas of sympatry. They should therefore be considered as discrete taxonomic units. Yet, the degree of introgression varies between the two species in different contact zones, which might be caused by different population history or by local environmental factors.

1 aZeng, Yan-Fei1 aLiao, Wan-Jin1 aPetit, Rémy, J.1 aZhang, Da-Yong uhttps://quercus.myspecies.info/node/131