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Mires or peatlands host unique biodiversity and provide many valuable ecosystem services. Mires often undergo different development phases during their evolution. Two mire phases that have clearly divergent hydrological regimes and characteristic biotas are minerotrophic fen and ombrotrophic bog. Open mires can be overgrown by trees and develop into peatland forests. Mire development trajectories are expected to be associated with three major factors—post‐glacial isostatic uplift, autogenic succession and climate‐induced changes. Understanding long‐term mire development is important for the conservation planning of these threatened habitats.We use data from modern pollen samples to characterize differences between the pollen signal and to identify indicator pollen taxa for three mire development phases—open fens, forested fens and bogs. The modern reference samples are then used to support the interpretation of the sediment records in terms of mire development phases and related biodiversity changes in six mires within a 20 × 30 km area in western Saaremaa, Estonia. Palynological richness and phylogenetic diversity (PD) as well as Ellenberg indicator values are compared throughout the 10,000‐year history of the Saaremaa mires.Pollen of herbaceous taxa discriminates between open fens, forested fens and bogs, and indicator pollen taxa can be associated with each mire phase. In general, the fen phases of the mires show higher richness and PD than the bog phases but there is considerable variation between the sites. The mire diversity peaks are often associated with transitional periods when high local community heterogeneity allows the coexistence of high numbers of taxa from different phylogenetic lineages.Synthesis. When the initiation of mires in isostatic land uplift areas is closely related to water‐level changes and the position of the sites in relation to the sea, the development of mires and their biodiversity in the late Holocene is associated with local conditions but mediated by climate. The ongoing rapid climate change is likely to accelerate changes in existing mires, and while the transitional periods are characterized by high diversity, these periods are temporary, and the overall diversity of mires can be expected to decrease. [ABSTRACT FROM AUTHOR]

Question How do pollen-based functional and phylogenetic diversity help to explain post-glacial vegetation change in relation to climate and human influence? Location Estonia and Latvia, NE Europe. Methods We used a data set of 1062 pollen samples from 20 sites covering the last 14 500 yrs to estimate plant richness, evenness, functional and phylogenetic diversity (community-weighted mean and mean pair-wise distance). We adjusted existing functional and phylogenetic diversity measures for the pollen data and tested the methods with a simulation study. The simulations showed that species-based and pollen-based diversity estimates were all significantly positively correlated. Results The Late Glacial (14 500-11 650 cal. yr BP) and the mid-Holocene (8000-4000 cal. yr BP) periods showed contrasting values for most of the diversity components, and several diversity estimates were strongly associated with climate. The cold climate during the Late Glacial led to high phylogenetic diversity, and relatively low functional diversity. Climate warming during the transition from the Late Glacial to the Holocene was followed by a decrease in phylogenetic diversity but an increase in functional diversity based on plant height and seed weight. Increasing human impact in the late Holocene was associated with an increase in plant richness and decreases in functional diversity based on plant height and seed weight and in phylogenetic diversity of herbs. Conclusions Pollen-based functional and phylogenetic diversity provide novel insights into post-glacial vegetation change and its drivers. Both functional and phylogenetic diversity were closely related to climatic conditions, suggesting that trait differences play an important role in long-term community response to climate change. Our results indicate that human impact during the last two millennia has influenced functional and phylogenetic diversity negatively by suppressing plants with certain traits (functional convergence) and giving advantage to plants from certain phylogenetic lineages. We see great potential in the further development of functional and phylogenetic diversity methods for pollen data. [ABSTRACT FROM AUTHOR]