Islands of land on islands of ice: climate continentality, Pleistocene history, and oases size explain plant species and phylogenetic diversity of Arctic polar desert vegetation

Le résumé fourni par la source

Arctic polar deserts (Arctic Bioclimate Subzone A) are the northernmost biome, characterized by a single-layer vertical structure, discontinuous vegetation cover, absence of woody plants and the leading role of cryptogams in plant communities. With ongoing Arctic amplification, the climatic conditions of polar deserts are changing, raising the question of the stability of polar desert plant diversity.Based on 499 complete geobotanical plots from Eurasian and Canadian polar islands in Arctic Bioclimate Subzone A, we estimated the impact of palaeogeographic legacies on polar desert plant and lichen species richness and vascular plant phylogenetic diversity by assessing the influence of Late Pleistocene to Holocene climate, isolation and glacial history.Existing research links phylogenetic diversity (Faith’s phylogenetic diversity; PD) and relatedness metrics (mean pairwise distance and mean nearest taxon distance; MPD and MNTD, respectively) to global latitudinal and elevational gradients, showing declines under harsher conditions. However, our analysis of Arctic vascular plant communities shows no strong differences in phylogenetic relatedness between bioclimate subzone A and other Arctic subzones, nor any consistent trends across bioclimatic subzones, but only high metric variation within each subzone. While latitudinal and temperature gradients show weak but significant statistical associations, differentiation in phylogenetic diversity and relatedness are primarily driven by local habitat conditions (temperature, continentality, glaciation history and soil types).Our results demonstrate that ancient climate has a significant impact on modern plant and lichen species richness, with Last Glacial Maximum temperature being the strongest predictor (R² = 0.35) among all factors tested.We found that, in contrast to lower-latitude islands, island size and distance from the mainland are weak predictors of polar desert plant and lichen species richness, while ’oasis’ size (size of ice-free area) and proportion of land within a 1000 km buffer are more important, suggesting the influence of both glaciation and Pleistocene land-bridge connections.Our results reveal the strong, lasting influence of glaciation history and ancient climate suggesting that polar desert ecosystems may be resilient to plant diversity shifts driven solely by current climate change. However, the importance of islands’ isolation indicates the potential for species colonization that could change the diversity of the biome. Therefore, we suggest that future research prioritize niche modeling of potential colonizing species and the study of dark diversity, the group of potential colonizers, on polar islands.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.