Frontiers of Biogeography

The factors determining regional adaptation in salmonids are still unclear, but it is known that changes in their habitat imply changes in their population structure. In this preliminary study we integrate habitat data, molecular analyses (from both nuclear microsatellite and mitochondrial loci) and life-history traits (measured on archaeological vertebrae and modern scales) of two sympatric salmonid species: Atlantic salmon and brown trout. We propose that water temperature and geological characteristics changed the biogeographic patterns of these species through asymmetric migration and different (but complementary) population growth rates. As a consequence, differences in a life-history trait (mean number of years at sea) and population sizes were detected between regions, suggesting a process of substitution of Atlantic salmon by brown trout.

Assessing the impact of climate change on range dynamics is difficult in the absence of large-extent distribution data. We developed a novel two-step approach as an instrument for biodiversity risk assessment. First, we established relationships between modelled loss of occupied grid cells (‘range loss’, R²=0.29), or gain of currently unoccupied grid cells (‘range gain’, R²=0.30), for 195 plant species with distributional data under the A1FI climate change scenario up to 2080, and ecological and life history traits (life form, leaf persistence, ecological strategy, pollen vector, Ellenberg indicator values and characteristics derived from species’ ranges). Secondly, we used the resulting coefficients to predict climatic sensitivity for 688 plant species without spatially explicit distributional information. The models predicted range losses of 34±20 % (mean±standard deviation) and range gains of 3±4 %. Specifically, measures of species’ distribution, such as range size, were significantly related to both range loss and range gain. Other traits associated with range loss (e.g. life form, number of floristic zones) were not necessarily related to range gain (instead related to Ellenberg temperature indicator), indicating that two distinct sets of ecological processes govern range expansion and contraction. We found interaction effects between moisture indicator values and life form for range loss, and between moisture and temperature indicator values for range gain. The responses of species to climate change are complex and context dependent. Thus, our results highlight the importance of incorporating trait interactions in models to assess risks of climate change.

The processes underlying species’ dominance patterns and community composition are insufficiently investigated for springs, yet these systems, which are believed to be very stable environments, represent an important interface between aquatic and terrestrial habitats contributing significantly to local and regional diversity. We studied the dominance patterns and plant community composition of 238 springs in Central Europe. According to the conventional ecological belief we hypothesized (1) a positive relationship between local abundance and regional distribution of spring plant species, as well as between species commonness and species’ realized breadth and (2) the occurrence of oligarchic species similar to other stable environments like tropical forests. Based on previous studies on this springs, we furthermore hypothesized (3) that water pH—essentially a proxy for nutrient availability—is the major driver of spatial compositional dissimilarity, i.e. beta-diversity. We tested these three hypotheses by using species commonness estimates, realized niche space and generalized dissimilarity modelling based on hydrochemistry. In line with conventional wisdom, we report a positive relationship between local abundance, species commonness and regional distribution for the majority of the species. In contradiction to other systems, we found both specialist and generalist species to be locally dominant and regionally widespread, thus common, while species with intermediate niche breadth showed the lowest commonness values. However, we detected three oligarchic species, exceeding all other species in local abundance and regional distribution, which did not follow these relationships. Both dominance relations (oligarchy) and community composition were mainly driven by water temperature and concentration of elements related to acidity regime (Al, Cd, Ca and Mg), although much of the variation in both remained unexplained. Thus, further research should focus on biotic interactions, which are likely to be important drivers of plant community composition in springs.

PCPS is an R package for exploring phylogenetic eigenvectors across metacommunities. It offers a set of functions for analyzing principal coordinates of phylogenetic structure (PCPS), allowing analysis of phylogenetic signal in ecological traits of species at the metacommunity level, and the association between each PCPS and environmental, spatial and historical factors. The package is a flexible solution for exploring the distribution of major phylogenetic lineages across ecological or biogeographic gradients. The package is freely available on the CRAN official web server for R.

Cliffs of the National Park of Porto Conte, Sardinia (Italy), habitat and breeding site to the last European Rock dove populations. See Skandrani's article in this issue for more information about the Rock dove. Picture by Zina Skandrani.