| 1. |
- De La Torre, Amanda R., et al.
(författare)
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Adaptation and exogenous selection in a Picea glauca x Picea engelmannii hybrid zone : implications for forest management under climate change
- 2014
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Ingår i: New Phytologist. - Hoboken : Wiley-Blackwell. - 0028-646X .- 1469-8137. ; 201:2, s. 687-699
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Tidskriftsartikel (refereegranskat)abstract
- The nature of selection responsible for the maintenance of the economically and ecologically important Picea glaucaxPicea engelmannii hybrid zone was investigated. Genomic, phenotypic and climatic data were used to test assumptions of hybrid zone maintenance and to model future scenarios under climate change. Genome-wide estimates of admixture based on a panel of 86 candidate gene single nucleotide polymorphisms were combined with long-term quantitative data on growth and survival (over 20yr), as well as one-time assessments of bud burst and bud set phenology, and cold hardiness traits. A total of 15498 individuals were phenotyped for growth and survival. Our results suggest that the P.glaucaxP.engelmannii hybrid zone is maintained by local adaptation to growing season length and snowpack (exogenous selection). Hybrids appeared to be fitter than pure species in intermediate environments, which fits expectations of the bounded hybrid superiority model of hybrid zone maintenance. Adaptive introgression from parental species has probably contributed to increased hybrid fitness in intermediate habitats. While P.engelmannii ancestry is higher than P.glauca ancestry in hybrid populations, on average, selective breeding in managed hybrid populations is shifting genomic composition towards P.glauca, potentially pre-adapting managed populations to warmer climates.
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| 2. |
- De La Torre, Amanda R., et al.
(författare)
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Genome-wide admixture and ecological niche modelling reveal the maintenance of species boundaries despite long history of interspecific gene flow
- 2014
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 23:8, s. 2046-2059
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Tidskriftsartikel (refereegranskat)abstract
- The maintenance of species boundaries despite interspecific gene flow has been a continuous source of interest in evolutionary biology. Many hybridizing species have porous genomes with regions impermeable to introgression, conferring reproductive barriers between species. We used ecological niche modelling to study the glacial and postglacial recolonization patterns between the widely hybridizing spruce species Picea glauca and P.engelmannii in western North America. Genome-wide estimates of admixture based on a panel of 311 candidate gene single nucleotide polymorphisms (SNP) from 290 genes were used to assess levels of admixture and introgression and to identify loci putatively involved in adaptive differences or reproductive barriers between species. Our palaeoclimatic modelling suggests that these two closely related species have a long history of hybridization and introgression, dating to at least 21000years ago, yet species integrity is maintained by a combination of strong environmental selection and reduced current interspecific gene flow. Twenty loci showed evidence of divergent selection, including six loci that were both F-st outliers and associated with climatic gradients, and fourteen loci that were either outliers or showed associations with climate. These included genes responsible for carbohydrate metabolism, signal transduction and transcription factors.
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| 3. |
- Erlichman, Adèle, et al.
(författare)
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Planting long-lived trees in a warming climate : Theory shows the importance of stage-dependent climatic tolerance
- 2024
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Ingår i: Evolutionary Applications. - : John Wiley & Sons. - 1752-4571. ; 17:6
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Tidskriftsartikel (refereegranskat)abstract
- Climate change poses a particular threat to long-lived trees, which may not adapt or migrate fast enough to keep up with rising temperatures. Assisted gene flow could facilitate adaptation of populations to future climates by using managed translocation of seeds from a warmer location (provenance) within the current range of a species. Finding the provenance that will perform best in terms of survival or growth is complicated by a trade-off. Because trees face a rapidly changing climate during their long lives, the alleles that confer optimal performance may vary across their lifespan. For instance, trees from warmer provenances could be well adapted as adults but suffer from colder temperatures while juvenile. Here we use a stage-structured model, using both analytical predictions and numerical simulations, to determine which provenance would maximize the survival of a cohort of long-lived trees in a changing climate. We parameterize our simulations using empirically estimated demographic transition matrices for 20 long-lived tree species. Unable to find reliable quantitative estimates of how climatic tolerance changes across stages in these same species, we varied this parameter to study its effect. Both our mathematical model and simulations predict that the best provenance depends strongly on how fast the climate changes and also how climatic tolerance varies across the lifespan of a tree. We thus call for increased empirical efforts to measure how climate tolerance changes over life in long-lived species, as our model suggests that it should strongly influence the best provenance for assisted gene flow.
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| 4. |
- Hamilton, Jill A., et al.
(författare)
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Fine-scale environmental variation contributes to introgression in a three-species spruce hybrid complex
- 2015
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Ingår i: Tree Genetics & Genomes. - : Springer Science and Business Media LLC. - 1614-2942 .- 1614-2950. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Hybridization is common for many forest trees, where weak barriers to reproduction obscure species boundaries. We characterized the genomic structure of Picea populations comprising three species spanning two well-known contact zones, the Picea sitchensisxPicea glauca and the P. engelmanniixP. glauca hybrid zones, using a set of 71 candidate-gene single nucleotide polymorphisms. The genetic structure of populations suggests a complex genomic architecture shaped by interspecific gene flow and strong environmental selection, with increased genetic diversity in hybrids. The presence of admixture among all three species suggests that three-way hybrids with mixed ancestry occur where species ranges overlap in transitional environments. Significant clinal variation and associations with climatic variables (including continentality, temperature, and precipitation) differ between hybrid zones, indicating that individual species and their hybrids are adapted to distinct environmental niches. Allele-environmental association analysis revealed that most of the candidate genes with evidence of selection were unique to either the Sitkaxwhite or the Engelmannxwhite hybrid zones, with few shared between these zones. Management of these widespread and diverse gene pools will be best served through development of climate-based seed transfer, with recommended seed sources informed by a combination of genetic and climatic information for future climates.
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| 5. |
- Hoban, Sean, et al.
(författare)
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Genetic diversity targets and indicators in the CBD post-2020 Global Biodiversity Framework must be improved
- 2020
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Ingår i: Biological Conservation. - : Elsevier BV. - 0006-3207 .- 1873-2917. ; 248
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Tidskriftsartikel (refereegranskat)abstract
- The 196 parties to the Convention on Biological Diversity (CBD) will soon agree to a post-2020 global framework for conserving the three elements of biodiversity (genetic, species, and ecosystem diversity) while ensuring sustainable development and benefit sharing. As the most significant global conservation policy mechanism, the new CBD framework has far-reaching consequences- it will guide conservation actions and reporting for each member country until 2050. In previous CBD strategies, as well as other major conservation policy mechanisms, targets and indicators for genetic diversity (variation at the DNA level within species, which facilitates species adaptation and ecosystem function) were undeveloped and focused on species of agricultural relevance. We assert that, to meet global conservation goals, genetic diversity within all species, not just domesticated species and their wild relatives, must be conserved and monitored using appropriate metrics. Building on suggestions in a recent Letter in Science (Laikre et al., 2020) we expand argumentation for three new, pragmatic genetic indicators and modifications to two current indicators for maintaining genetic diversity and adaptive capacity of all species, and provide guidance on their practical use. The indicators are: 1) the number of populations with effective population size above versus below 500, 2) the proportion of populations maintained within species, 3) the number of species and populations in which genetic diversity is monitored using DNA-based methods. We also present and discuss Goals and Action Targets for post-2020 biodiversity conservation which are connected to these indicators and underlying data. These pragmatic indicators and goals have utility beyond the CBD; they should benefit conservation and monitoring of genetic diversity via national and global policy for decades to come.
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| 6. |
- Wang, Baosheng, 1983-
(författare)
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Hybridization and Evolution in the Genus Pinus
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gene flow and hybridization are pervasive in nature, and can lead to different evolutionary outcomes. They can either accelerate divergence and promote speciation or reverse differentiation. The process of divergence and speciation are strongly influenced by both neutral and selective forces. Disentangling the interplay between these processes in natural systems is important for understanding the general importance of interspecific gene flow in generating novel biodiversity in plants. This thesis first examines the importance of introgressive hybridization in the evolution of the genus Pinus as a whole, and then focusing on specific pine species, investigates the role of geographical, environmental and demographical factors in driving divergence and adaptation.By examining the distribution of cytoplasmic DNA variation across the wide biogeographic range of the genus Pinus, I revealed historical introgression and mtDNA capture events in several groups of different pine species. This finding suggests that introgressive hybridization was common during past species’ range contractions and expansions and thus has played an important role in the evolution of the genus. To understand the cause and process of hybrid speciation, I focused on the significant case of hybrid speciation in Pinus densata. I established the hybridization, colonization and differentiation processes that defined the origin of this species. I found P. densata originated via multiple hybridization events in the late Miocene. The direction and intensity of introgression with two parental species varied among geographic regions of this species. During the colonization on Tibetan Plateau from the ancestral hybrid zone, consecutive bottlenecks and surfing of rare alleles caused a significant reduction in genetic diversity and strong population differentiation. Divergence within P. densata started from the late Pliocene onwards, induced by regional topographic changes and Pleistocene glaciations. To address the role of neutral and selective forces on genetic divergence, I examined the association of ecological and geographical distance with genetic distance in Pinus yunnanensis populations. I found both neutral and selective forces have contributed to population structure and differentiation in P. yunnanensis, but their relative contributions varied across the complex landscape. Finally, I evaluated genetic diversity in the Vietnamese endemic Pinus krempfii. I found extremely low genetic diversity in this species, which is explained by a small ancestral population, short-term population expansion and recent population decline and habitat fragmentation.These findings highlight the role of hybridization in generating novel genetic diversity and the different mechanisms driving divergence and adaptation in the genus Pinus.
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