Aim: The regional co-occurrence of contrasting bioclimatic elements (warm-temperate, continental, boreal, arctic-alpine) may be shaped by the distribution of their glacial or post-glacial refugia. We tested this hypothesis using pollen proxies in a region where such refugia are expected, but not unequivocally demonstrated.Location: East-Central Europe (Western Carpathians and adjacent regions).
Methods:We compiled pollen spectra from 112 sites distributed across various landscapes for six time-periods from the Late Glacial to the present. Compositional patterns were assessed by principal coordinates analyses (PCoA) with a sensitivity analysis based on a bootstrap technique. Site PCoA scores were interpolated geographically and correlated with palaeoclimatic models.Results: Consistently over the last 15,000 years, the first ordination axis sorted samples according to the proportion of deciduous temperate trees, while the second axis consistently followed an altitudinal gradient that coincided with temperature.The principal gradient was more important than the altitudinal gradient except for the Late Glacial and Bronze & Iron Ages, when both gradients were of similar importance. The fine-grained pattern in the present mountain landscape was formed as late as during early modern colonization.Main conclusions: Since the Late Glacial, the landscape has been differentiated into temperate, continental and cold regions. This finding supports the hypothesis that refugia are a key factor for understanding current biogeography in Central Europe.The Late Glacial occurrence of temperate trees is unlikely to be explained only by gradual migrations from southern Europe. Humid but relatively warm mountains hence might have acted as glacial refugia of temperate forest species, while lowlands and leeward basins might have acted as post-glacial refugia of steppe grasslands. The strong contrast between forested (temperate) and more open continental landscapes during the Early Holocene seems to correspond with recent diversity patterns. Our results highlight the relevance of integrating past landscape trajectories into modern biogeographical models.
The relevance of environmental and spatial processes for species distributions varies among environments and types of metacommunities. Here, for the first time, we use modern statistical approaches to test the contribution of these two processes in structuring ecologically unique and threatened biotas of insular spring fens. We applied two species categorisations, common/rare and generalists/specialists, to disentangle the roles of dispersal capacity and habitat specialisation.
In accordance with current understanding of headwater ecosystems, we found that environmental processes played a major role in most of the spring fen taxonomic and functional groups. However, we observed significant spatial structure in passive dispersers (Clitellata, a class of annelid worms), common species and habitat specialists.
Spatial processes played the leading role in structuring the metacommunity of passively dispersing specialists. In contrast, all analysed insect groups, even those known to be poor dispersers, were able to reach virtually all favourable sites.
We conclude that dispersal mode (active versus passive) and, to a lesser extent, habitat specialisation are the main factors determining the mechanism of spring fen metacommunity structuring.
The aim was to identify the main drivers of aquatic macroinvertebrate species richness in spring‐fen habitats (i.e. groundwater seepage wetlands) because these habitats are among the most threatened temperate biodiversity hotspots.
Isolated spring fens in the western Carpathian Mountains.
Assemblages of Tricladida, Clitellata, Mollusca, Ephemeroptera, Plecoptera, Trichoptera and Diptera were sampled at 48 fens distributed evenly along a gradient of water mineral richness and grouped according to habitat specialization and dispersal mode. Several physicochemical parameters that have been reported to be the main drivers of species distribution were recorded for each site, along with radiocarbon measurements of the absolute age of the sites. The numbers of species in the taxonomic groups analysed were modelled as a function of the predictors via multiple linear regressions.
We achieved a notably higher sampling efficiency than had been used in previous spring aquatic macroinvertebrate studies. In total, we collected and identified 255 species within 331 taxa from > 235,000 individuals. The number of species in all taxonomic groups increased with water discharge but the highest predictive power was obtained with water redox potential, which explained as much as 55.7% of the specialist species richness variance. We found contrasting and systematic differences in the importance of predictors related mainly to the level of species habitat specialization. Species richness of spring‐fen specialists was strongly determined by the main environmental gradient of change in groundwater chemistry, while generalists primarily reflected habitat stability linked to higher water discharge, habitat size and absolute age.
Isolated island‐like spring fens can harbour unusually species‐rich assemblages of aquatic macroinvertebrates, the species richness of which is shaped by contrasting mechanisms dependent mainly on habitat specialization and also partly on dispersal mode. The richness of habitat specialist species seen at calcareous fens indicates their conservation priority.
Question: Mosses are important ecosystem engineers in mires. Their pH optima and tolerances presented in the literature differ between regions, even though the high dispersal ability of mosses should prevent local adaptations. Nutrient availability is sometimes suggested as a reason for local niche differentiation. Are patterns in moss niche diversification, optima and tolerance with respect to pH consistent between regions differing in nutrient availability and abundance of calcareous bedrock?Location: Western Carpathians (Slovakia, a predominantly calcareous P-and K-poor region), Bohemian Massif (Czech Republic, a predominantly crystalline, P-and K-rich region).Methods: Analyses of an original stratified data set and a large database using species response curves.Results: Although the above two regions differ in abundance of calcareous fens, species pH optima (either original or adjusted according to calcium level) were consistent between the regions and data sets. Calcium-tolerant peat mosses (Sphagnum warnstorfii, S. contortum, S. teres) showed an optimum at pH 6 and rather narrow niches. Sphagnum fallax was the most acidophilous, and both S. palustre and S. flexuosum had rather wide intermediate niches. The pH amplitudes were largely consistent between the regions (especially when adjusted pH was used), but S. fallax and Aulacomnium palustre exhibited wider niches in the Bohemian Massif. Despite no significant difference in niche optimum and width, some more nutrient demanding and more generalist species occurred at higher frequency in specific parts of the pH gradient in the Bohemian Massif, while some fen specialists showed the opposite pattern.
Conclusions:The small stratified data set and the database data set yielded rather consistent results regarding fen moss niches in the Bohemian Massif and the Western Carpathians. The consistency in pH niches corresponds to the lack of large-scale genetic differentiation in moss species. The observed inter-regional differences in species response curves may thus reflect an increased frequency of competitively strong species in certain parts of the pH/Ca gradient in the nutrient-richer Bohemian Massif rather than genetically conditioned niche shifts. Expansion of these species was probably triggered by potassium enrichment that took place in the 1970s-1980s. Inter-regional differences in species response curves were observed in both data sets, but in the large database data set they were more frequently statistically significant.
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