Eco-evolutionary dynamics at the altitudinal limit of a transcontinental boreal conifer

Pothier Guerra, Laura et de Lafontaine, Guillaume ORCID: https://orcid.org/0000-0001-6889-1733 (2024). Eco-evolutionary dynamics at the altitudinal limit of a transcontinental boreal conifer. Evolutionary Ecology .

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Résumé

Understanding ecological and evolutionary processes driving species range expansion is essential to assess extirpation risks and reduce future biodiversity loss. During range expansion, spatial sorting eco-evolutionary model predicts enhanced dispersal rate in leading-edge populations through local accumulation of phenotypic traits related to dispersal. This process may result in a transient trade-off, whereby local fitness is temporarily sacrificed for the benefit of dispersal during range expansion. Here, we empirically tested the spatial sorting model and its fitness cost by assessing dispersal ability of 8138 white spruce (Picea glauca) winged seeds and seed viability along altitudinal gradients in two eastern Canadian mountain ranges with different dynamics according to contrasted historical disturbance regime, as well as in a lowland site representative of the species geographical range core. In the Uapishka mountains, stand-replacing wildfires have opened the forest cover and leading-edge populations are currently expanding upslope. Dispersal ability was enhanced at the expansion front whereas germination potential decreased. Treeline populations exhibit a trade-off maximizing dispersal over fitness, as expected from the spatial sorting model. By contrast, in the McGerrigle mountains where there is no evidence of wildfire activity, treeline populations established several millennia ago and there is currently no upslope range expansion. In these mountains, no trait variation was found along the altitudinal gradient, suggesting that a local optimum was reached for the traits involved in the trade-off between dispersal ability and seed viability. In the geographical core of the range, dispersal ability reaches its lowest values while germination potential is maximal, suggesting absence of a spatial sorting mechanism, but natural selection as the primary evolutionary process operating to increase local fitness. This study sheds light on the importance of intraspecific trait variation related to the dispersal ability of individuals and its transient impact on life-history in tree populations located at the expansion front.

Type de document :	Article
Validation par les pairs :	Oui
Mots-clés :	Toundra alpine ; Extension de l'aire de répartition ; Forêt montagnarde ; Dispersion des graines ; Triage spatial ; Ligne d'arbres subalpine / Alpine tundra ; Range expansion ; Montane forest ; Seed dispersal ; Spatial sorting ; Subalpine treeline.
Départements et unités départementales :	Département de biologie, chimie et géographie
Date de dépôt :	09 oct. 2024 18:51
Dernière modification :	09 oct. 2024 18:51
URI :	https://semaphore.uqar.ca/id/eprint/2997