Opportunity for hybridization between two oak species in mixed stands as monitored by the timing and intensity of pollen production

Varela, Maria Carolina; Brás, Rita; Barros, Isabel R.; Oliveira, Paulo; Meierrose, Carola

doi:10.1016/j.foreco.2008.06.049

Cited by 17 publications

(15 citation statements)

References 14 publications

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“…More strikingly, effective pollen flow between the two largest trees was completely uni-directional (from T4 to T1). A phenological difference in the reproduction of trees T1 and T4 is unlikely to have caused this pattern: while holm oak is protandrous, the delay between male and female flowers on the same branch is only 2-3 days, much less than the temporal variation in flower anthesis that exists across the tree crown [31]. The combination of predominant winds and unequal canopy size (and hence uneven pollen production) could possibly result in such an asymmetric gene flow.…”

Section: Discussionmentioning

confidence: 99%

Efficient mitigation of founder effects during the establishment of a leading-edge oak population

2013

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Numerous plant species are shifting their range polewards in response to ongoing climate change. Range shifts typically involve the repeated establishment and growth of leading-edge populations well ahead of the main species range. How these populations recover from founder events and associated diversity loss remains poorly understood. To help fill this gap, we exhaustively investigated a newly established population of holm oak (Quercus ilex) growing more than 30 km ahead of the nearest larger stands. Pedigree reconstructions showed that plants belong to two non-overlapping generations and that the whole population originates from only two founder trees. The four first-generation trees that have reached maturity showed disparate mating patterns despite being full-sibs. Long-distance pollen immigration was notable despite the strong isolation of the stand: 6 per cent gene flow events in acorns collected on the trees (n ¼ 255), and as much as 27 per cent among their established offspring (n ¼ 33). Our results show that isolated leading-edge populations of wind-pollinated forest trees can rapidly restore their genetic diversity through the interacting effects of efficient long-distance pollen flow and purging of inbred individuals during recruitment. They imply that range expansions of these species are primarily constrained by initial propagule arrival rather than by subsequent gene flow.

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Section: Discussionmentioning

confidence: 99%

Efficient mitigation of founder effects during the establishment of a leading-edge oak population

2013

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“…The hybrid mother tree was mainly pollinated by Q. alnifolia, while we could not detect any Q. coccifera paternal contribution among progenies of Q. alnifolia mother trees. An important factor playing a role in pollination patterns is the relative abundance and spatial distribution of the two species (Lepais et al 2009, Varela et al 2008. In our study stand, Q. alnifolia is predominant (Fig.…”

Section: Discussionmentioning

confidence: 91%

Interfertile oaks in an island environment. II. Limited hybridization between Quercus alnifolia Poech and Q. coccifera L. in a mixed stand

et al. 2011

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Hybridization and introgression betweenQuercus alnifolia Poech and Q. coccifera L. is studied by analyzing morphological traits, nuclear and chloroplast DNA markers. The study site is a mixed stand on Troodos Mountains (Cyprus), and the analyzed material includes both adult trees and progenies of specific mother trees. Multivariate analysis of morphological traits shows that the two species can be well distinguished using simple leaf morphometric parameters. A lower genetic diversity in Q. alnifolia than in Q. coccifera and a high interspecific differentiation between the two species are supported by an analysis of nuclear and chloroplast microsatellites. The intermediacy of the four designated hybrids is verified by both leaf morphometric and genetic data. Analysis of progeny arrays provides evidence that interspecific crossings are rare. This finding is further supported by limited introgression of chloroplast genomes. Reproductive barriers (e.g. asynchronous phenology, postzygotic incompatibilities) might account for this result. A directionality of interspecific gene flow is indicated by a genetic assignment analysis of effective pollen clouds with Q. alnifolia acting as pollen donor. Differences in flowering phenology and species distribution in the stand may have influenced the direction of gene flow and the genetic differentiation among effective pollen clouds of different mother trees within species.

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“…Given the strong introgression pressure suggested above, the question remains how then the apparent separation of the gene pool of Q. pubescens in Bielinek can be explained. Three mutually non-exclusive possibilities could occur: (1) reproductive barriers, (2) microsite selection and (3) assortative mating (Bruschi et al 2000;Curtu et al 2007;Gugerli et al 2007;Varela et al 2008;Lepais et al 2009). Controlled pollination experiments revealed that oaks in the studied species complex are potentially interfertile (Steinhoff 1993;Orlik and Kjaer 2007).…”

Section: Discussionmentioning

confidence: 99%

Genetic evidence of reproductive isolation in a remote enclave of Quercus pubescens in the presence of cross-fertile species

et al. 2012

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Peripheral populations may be crucial for understanding processes underlying adaptive genetic variation. Their evolution and ecology are driven by various genetic and demographic processes, such as selection, gene flow and bottleneck. Peripheral populations often experience a reduction in density resulting in the Allee effect. The presence of interfertile species increases the opportunity for hybridisation, which allows for a rescue from the Allee effect, but at the risk of genetic extinction through introgression. In this article we investigated a peripheral population of Quercus pubescens, a European tree species. The study population is located in Poland, several hundred kilometres northwards from the main species range. Due to geographic separation, the study population exists under strong pressure of introgression from potentially inter-fertile Q. petraea and Q. robur, which are the only common oaks in Poland. The intermediate morphology between typical Q. pubescens and a common oak species found in the study population supports the introgression hypothesis, which could be in line with the earlier studies of this species complex conducted in the main range of Q. pubescens. Alternatively, the intermediate morphology could reflect the founder effect or selection at an ecological extreme. We attempted to verify these hypotheses using microsatellites and a reference of common oak species. The results showed that the study population is genetically distinct from both Q. petraea and Q. robur. Additionally, the population is characterised by a low effective population size and limited gene dispersal. This suggests that the study population reveals strong reproductive isolation from common species, implying alternative sources of atypical morphology.

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Opportunity for hybridization between two oak species in mixed stands as monitored by the timing and intensity of pollen production

Cited by 17 publications

References 14 publications

Efficient mitigation of founder effects during the establishment of a leading-edge oak population

Efficient mitigation of founder effects during the establishment of a leading-edge oak population

Interfertile oaks in an island environment. II. Limited hybridization between Quercus alnifolia Poech and Q. coccifera L. in a mixed stand

Genetic evidence of reproductive isolation in a remote enclave of Quercus pubescens in the presence of cross-fertile species

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