Vatanparast, M. | Search bioRxiv

bioRxiv2022

Tracing the origin of Oriental beech stands across Western Europe and reporting hybridization with European beech - implications for assisted gene flow

Human-aided translocation of individuals within the species range, assisted gene flow (AGF), has been suggested as a climate change mitigation strategy, especially for foundational species, such as forest trees. The benefits and risks of AGF largely depend on the genetic divergence between host and donor populations, their rate and direction of hybridization, and the climate distance that the transfer involves. In this study, we explored the use of Oriental beech (Fagus sylvatica subsp. orientalis), growing from Iran to the Balkans, for AGF in populations of European beech (F. sylvatica subsp. sylvatica), which grow throughout Europe and are increasingly affected by climate warming. Using 16 microsatellite loci and samples from 13 and 6 natural populations of Oriental and European beech, respectively, we identified 5 distinct genetic clusters in Oriental beech with a divergence (FST) of 0.15 to 0.25 from European beech. Using this knowledge, we tracked the origin of 11 Oriental beech stands in Western Europe, some established in the early 1900s. In two stands of Greater Caucasus origin, we additionally genotyped offspring and found evidence for extensive hybridization, with 41.3% and 17.8% of the offspring having a hybrid status. Further, climate data revealed a higher degree of seasonality across the Oriental beech growing sites than across the planting sites in Western Europe, with some sites additionally having a warmer and drier climate. Accordingly, in one of these stands, we found evidence that bud burst of Oriental beech occurs four days earlier than in European beech. These results suggest that AGF of Oriental beech could increase the genetic diversity of European beech stands and may even help the introgression of variants that are more adapted to future climatic conditions. Our study showcases an evaluation of the benefits and risks of AGF and calls for similar studies on other native tree species.

evolutionary biology↗

bioRxiv2021

The diversification of Pterocarpus (Leguminosae: Papilionoideae) was influenced by biome-switching and infrequent long-distance dispersal

AimPhenotypes which evolved for dispersal over ecological timescales may lead to significant macroevolutionary consequences, such as infrequent long-distance dispersal and diversification in novel biomes. We aimed to reconstruct the phylogenetic history of Pterocarpus (Leguminosae/ Fabaceae) to assess whether seed dispersal phenotypes and biome switching explain the current biogeographical patterns of this group. LocationPantropical TaxonThe Pterocarpus clade, particularly Pterocarpus (Leguminosae/Fabaceae) MethodsWe sequenced ~300 nuclear loci captured using Angiosperms-353, a genomic bait set for flowering plants, from which we generated a time-calibrated phylogenomic tree. To corroborate this, we also generated a time-calibrated phylogenetic tree from data-mined Sanger-sequencing data. We then collated distribution data and fruit dispersal morphology traits to compare trait-dependent and trait-independent biogeographical models, allowing us to assess whether dispersal traits influenced the spatio-temporal evolution of Pterocarpus. Finally, using the results of these model tests, we estimated the ancestral ranges and biomes of Pterocarpus species to better understand their biogeographical history, and assessed the degree and direction of biome switching over the course of Pterocarpus diversification history. ResultsWe recovered well-supported phylogenetic relationships within Pterocarpus, within which there were two subclades - one Neotropical and the other Palaeotropical. Our divergence date estimates suggested that Pterocarpus largely diversified from around 12 Ma, during the Miocene. Trait-dependent biogeographical models were rejected for both range and biome evolution within Pterocarpus, but models parameterising dispersal were supported. Pterocarpus ancestral node shared a range across the new-world and old-world tropics, followed by divergence into two clades, one palaeotropical and one neotropical. Biome switching occurred most frequently into rainforest and grassland. Main conclusionsOverall, our analyses suggest that Pterocarpus underwent infrequent cross-continental dispersal and establishment into novel biomes. While this was minimally impacted by fruit dispersal syndromes, biome switching precipitated by long-distance dispersal and environmental change have played an important role in diversification within Pterocarpus since the Miocene.

evolutionary biology↗