Thank you for not flowering: conservation genetics and gene flow analysis of native and
non-native populations of Fraxinus (Oleaceae) in Ireland |
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Authors: | M Thomasset T R Hodkinson G Restoux N Frascaria-Lacoste G C Douglas J F Fernández-Manjarrés |
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Institution: | 1.School of Natural Sciences, Trinity College
Dublin, Dublin, Ireland;2.Teagasc, Kinsealy Research Centre, Dublin, Ireland;3.Trinity Centre for Biodiversity Research,
Trinity College Dublin, Dublin, Ireland;4.Laboratoire d''Ecologie
Systématique et Evolution, UMR 8079, Université Paris-Sud, Orsay, France;5.AgroParisTech, Paris, France;6.CNRS, UMR 8079, Orsay, France |
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Abstract: | The risks of gene flow between interfertile native and introduced plant populations are
greatest when there is no spatial isolation of pollen clouds and phenological patterns
overlap completely. Moreover, invasion probabilities are further increased if introduced
populations are capable of producing seeds by selfing. Here we investigated the mating
system and patterns of pollen-mediated gene flow among populations of native ash
(Fraxinus excelsior) and mixed plantations of non-native ash (F.
angustifolia and F. excelsior) as well as hybrid ash (F.
excelsior × F. angustifolia) in Ireland. We analysed the flowering
phenology of the mother trees and genotyped with six microsatellite loci in progeny arrays
from 132 native and plantation trees (1493 seeds) and 444 potential parents. Paternity
analyses suggested that plantation and native trees were pollinated by both native and
introduced trees. No signs of significant selfing in the introduced trees were observed
and no evidence of higher male reproductive success was found for introduced trees
compared with native ones either. A small but significant genetic structure was found
(φft=0.05) and did not correspond to an isolation-by-distance
pattern. However, we observed a significant temporal genetic structure related to the
different phenological groups, especially with early and late flowering native trees; each
phenological group was pollinated with distinctive pollen sources. Implications of these
results are discussed in relation to the conservation and invasiveness of ash and the
spread of resistance genes against pathogens such as the fungus Chalara fraxinea
that is destroying common ash forests in Europe. |
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Keywords: | Fraxinus hybridization introduction gene flow paternity analysis |
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