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English yew (Taxus baccata) is one of the few gymnospermous species present in the Hyrcanian forests, and it is listed as a rare and endangered species prone to extinction in Iran. This study aims to determine the ecological capability of Taxus baccata in the Hyrcanian region by identifying the diversity of plant communities dominated by this species, and to compare their floristic composition with the Taxus communities of southern Europe (Sicily, Corsica, Sardinia). We collected 408 relevés in the central and eastern part of the Hyrcanian forests. The classification of plant communities was performed using TWINSPAN. Phi-coefficient index, constancy ratio, and the ratio of average cover were used to determine diagnostic species in each vegetation unit. The expert system language of the JUICE program was applied to create formal definitions for syntaxa. The relationship between species and environmental factors were investigated with DCA. The environmental differences among the syntaxa were also tested with one-way ANOVA. Sums of constancy and average species cover of the diagnostic species of classes according to the EuroVegChecklist were computed. We distinguished five associations within three alliances. Of these, two associations and one alliance are new for science. Annual precipitation, elevation and annual temperature which are affected by elevational as well as longitudinal gradients were found to be important factors affecting the diversity of Hyrcanian Taxus communities. The constancy sum of diagnostic species was the highest for the class Carpino-Fagetea sylvaticae in all Hyrcanian and European units except for one Taxus community in Sardinia. We conclude that the Hyrcanian and southern European Taxus communities are similar in their floristically and ecological properties. Yew communities in the central Hyrcanian forests are associated with humid temperate diagnostic species, while semi-humid temperate plants are frequent in the eastern Hyrcanian forests, similar to the yew communities in southern Europe. [ABSTRACT FROM AUTHOR]

Deciduous forests form the dominant natural vegetation of Europe today, but were restricted to small refugia during Pleistocene cold stages, implying an evolutionary past shaped by recurrent range contractions and expansions. Cold-stage forest refugia were probably widespread in southern and central Europe, with the northwestern Balkan Peninsula being of particular importance. However, the actual number and location of deciduous forest refugia, as well as the connections between them, remain disputed. Here, we address the evolutionary dynamics of the deciduous forest understorey species Euphorbia carniolica as a proxy for past forest dynamics. To do so, we obtained genomic and morphometric data from populations representing the species' entire range, investigated phylogenetic position and intraspecific genetic variation, tested explicit demographic scenarios and applied species distribution models. Our data support two disjoint groups linked to separate refugia on the northwestern and central Balkan Peninsula. We find that genetic differentiation between groups started in the early Pleistocene via vicariance, suggesting a larger distribution in the past. Both refugia acted as sources for founder events to the southeastern Alps and the Carpathians; the latter were likely colonised before the last cold stage. In line with traditional views on the pre-Pleistocene origin of many southeastern European deciduous forest species, the origin of E. carniolica was dated to the late Pliocene. The fact that E. carniolica evolved at a time when a period of continuous forestation was ending in much of Eurasia provides an interesting biogeographical perspective on the past links between Eurasian deciduous forests and their biota., (© 2023 The Authors. Molecular Ecology published by John Wiley & Sons Ltd.)

A central hypothesis of ecology states that regional diversity influences local diversity through species-pool effects. Species pools are supposedly shaped by large-scale factors and then filtered into ecological communities, but understanding these processes requires the analysis of large datasets across several regions. Here, we use a framework of community assembly at a continental scale to test the relative influence of historical and environmental drivers, in combination with regional or local species pools, on community species richness and community completeness. Using 42,173 vegetation plots sampled across European beech forests, we found that large-scale factors largely accounted for species pool sizes. At the regional scale, main predictors reflected historical contingencies related to post-glacial dispersal routes, whereas at the local scale, the influence of environmental filters was predominant. Proximity to Quaternary refugia and high precipitation were the main factors supporting community species richness, especially among beech forest specialist plants. Models for community completeness indicate the influence of large-scale factors, further suggesting community saturation as a result of dispersal limitation or biotic interactions. Our results empirically demonstrate how historical factors complement environmental gradients to provide a better understanding of biodiversity patterns across multiple regions.