The highly variable tufted hairgrass Deschampsia cespitosa is a tussock-forming plant especially of cool and humid environments. Although common and widespread, its phylogeographic structure and the significance of polyploidy for its evolution are poorly understood. Here we used a phylogenomic approach to study the genetic structure of this species in Europe and how the polyploid cytotypes/subspecies are related to the diploids. Using genomic data (RADseq and whole plastid sequencing) we found a highly divergent Iberian group, including the Spanish Deschampsia cespitosa subsp. cespitosa (diploid and tetraploid) and the Macaronesian island endemic diploid Deschampsia argentea. Moreover, we found substantial divergence of pseudoviviparous tetraploids (Deschampsia cespitosa subspp. neoalpina and rhenana) from seminiferous tetraploids (except Deschampsia cespitosa subsp. littoralis) and all diploids of the remaining European samples. The divergent pseudoviviparous tetraploids (D. cespitosa subspp. neoalpina and rhenana) and the seminiferous tetraploid D. cespitosa subsp. littoralis probably represent periglacial and relict lineages of unknown origin regarding auto- and/or allo-polyploidy, whereas other seminiferous tetraploid variants of D. cespitosa are always nested in the diploid D. cespitosa, suggesting multiple autopolyploid origins. An analysis after excluding the Iberian Group and the highly divergent tetraploids revealed five genetic groups with overlapping geographical patterns. However, the recovered geographical structure, the overall low genetic divergence and the diffuse genetic structure point to recolonization from various refugial areas and secondary contact. Effective wind dispersal of pollen and seeds in an open early post-glacial tundra landscape and, finally, increasing human impact on dispersal of this grass since the Neolithic, may have enhanced admixture and resulted in the complex patterns detected today.

The grass Deschampsia cespitosa is a variable taxon out of which many varieties, subspecies and endemic species have been separated. In this paper, the variation in genome size (GS) and ploidy of this grass including several of its subspecies and two related species in Eurasia was investigated by flow cytometric (FCM) measurements. GS and ploidy data were also related to specific environments and reproduction mode. Ploidy levels found by FCM were confirmed by chromosome counts of diploid (2n = 28) and tetraploid (2n = 52) samples. Seminiferous (seed bearing) D. cespitosa was mainly diploid (GS between 3.754 and 5.438 pg/1C). GS variation in diploids showed a geographic pattern with a significant difference (H = 41,441, P < 0.001) between European (median = 4.377 pg) and Asian (median = 4.881 pg) accessions. Genome size (1C) in tetraploids ranged from 7.9426 to 9.0399 pg. Tetraploid seminiferous D. cespitosa was found mostly in disturbed habitats in western and southern Europe, while tetraploids in Asia were registered in wet Arctic habitats. Genome size (1C between 8.3278 and 8.8603 pg) of the pseudoviviparous plants (spikelets produce plantlets asexually) of wet habitats in central and northern Europe indicated tetraploidy. A putative triploid (GS 6.6817 pg) was detected in Iceland. Summing up, we found a high variation in GS on the geographic scale with significant regional differences in diploid D. cespitosa. Among the tetraploids, the asexually reproducing plants were bound to specific habitats, while the seminiferous plants showed a habitat preference similar to the diploids.

Abstract Species losses and local extinctions are alarmingly common, frequently as a consequence of habitat destruction. Nevertheless, many intact habitats also face species losses, most likely due to environmental changes. However, the exact drivers, and why they affect some species more than others in apparently intact habitats, are still poorly understood. Addressing these questions requires data on changes in occurrence frequency of many species, and comparisons of the responses of those species to experimental manipulations of the environment. Here, we use historic (1911) and contemporary (2017) data on the presence–absence of 42 plant species in 14 seemingly intact Molinia meadows around Lower Lake Constance to quantify changes in occurrence frequency. Then, we performed a common‐garden experiment to test whether occurrence frequencies in 1911 and changes therein by 2017 could be explained by responses of the 42 species to nutrient addition and competition with the acquisitive generalist grass Poa pratensis. Within the 14 still intact Molinia meadows, 36 of the 42 species had declined since 1911. As expected, nutrient addition generally led to increased biomass production of the 42 target species, and competition with P. pratensis had a negative effect. The latter was stronger at high nutrient availability. The more frequent species were in 1911 and the more they declined in frequency between 1911 and 2017, the less above‐ground biomass they produced in our experiment. Competition with P. pratensis magnified this effect. Our work highlights that environmental change can contribute to local extinction of species in otherwise intact habitat remnants. Specifically, we showed that increased nutrient availability negatively affected formerly widespread Molinia‐meadow species in competition with P. pratensis. Our study thus identified a likely mechanism for the decline in occurrence frequency of species in the remaining Molinia meadows.

Abstract Habitat loss leading to smaller patch sizes and decreasing connectivity is a major threat to global biodiversity. While some species vanish immediately after a change in habitat conditions, others show delayed extinction, that is, an extinction debt. In case of an extinction debt, the current species richness is higher than expected under present habitat conditions. We investigated wetlands of the canton of Zürich in the lowlands of Eastern Switzerland where a wetland loss of 90% over the last 150 years occurred. We related current species richness to current and past patch area and connectivity (in 1850, 1900, 1950, and 2000). We compared current with predicted species richness in wetlands with a substantial loss in patch area based on the species‐area relationship of wetlands without substantial loss in patch area and studied relationships between the richness of different species groups and current and historical area and connectivity of wetland patches. We found evidence of a possible extinction debt for long‐lived wetland specialist vascular plants: in wetlands, which substantially lost patch area, current species richness of long‐lived specialist vascular plants was higher than would have been expected based on current patch area. Additionally and besides current wetland area, historical area also explained current species richness of these species in a substantial and significant way. No evidence for an extinction debt in bryophytes was found. The possible unpaid extinction debt in the wetlands of the canton of Zürich is an appeal to nature conservation, which has the possibility to prevent likely future extinctions of species through specific conservation measures. In particular, a further reduction in wetlands must be prevented and restoration measures must be taken to increase the number of wetlands.

AimsReintroduction has become an important tool for the management of endangered plant species. We tested the little-explored effects of small-scale environmental variation, genotypic composition (i.e. identity of genotypes) and genotypic diversity on the population survival of the regionally rare clonal plant Ranunculus reptans. For this species of periodically inundated lakeshores, genetic differentiation had been reported between populations and between short-flooded and long-flooded microsites within populations.MethodsWe established 306 experimental test populations at a previously unoccupied lakeshore, comprising either monocultures of 32 genotypes, mixtures of genotypes within populations or mixtures of genotypes between populations. In 2000, three years after planting out at the experimental site, a long-lasting flood caused the death of half of the experimental populations. In 2003, an extreme drought resulted in the lowest summer water levels ever measured.Important FindingsDespite these climatic extremes, 27% of the established populations survived in December 2003. The success of experimental populations largely differed between microsites. Moreover, the success of genotype monocultures depended on genotype and source population. Genetic differentiation between microsites played a minor role for the success of reintroduction. After the flood, populations planted with genotypes from different source populations increased in abundance, whereas populations with genotypes from single source populations and genotype monocultures decreased. In 2014, several small patches of Ranunculus clones were still present, but plants were strongly intermingled, which precluded their assignment to the original treatments. We conclude that sources for reintroductions need to be selected carefully. Moreover, mixtures of plants from different populations appear to be the best choice for successful reintroduction, at least in unpredictably varying environments.

Disturbance events shape plant communities depending on the disturbance regime as well as on the properties of the species constituting the community. We studied a lakeshore community at Lake Constance, a pre-alpine lake in Central Europe, where disturbance by flooding has a strong impact as the water level is almost not regulated by man. The lakeshore habitats are shaped by annual summer flooding during the vegetation period of plants, with seasonal course and magnitude of water-level fluctuations varying considerably between years. By a combination of field work and modelling we examined (1) whether flooding tolerance and interactions between individuals can explain zonation and species coexistence at lakeshore, (2) how strongly invasive species are affecting habitat specific species, and (3) whether changing flooding regimes due to potential climate changes will affect species composition.The study was based on a long-term monitoring record (23 years; 1988-2005) of presence/absence of six species along two transects in a species-poor community at Lake Constance and on detailed records of annual flooding. We succeeded in parameterizing a spatially explicit individual-based life-cycle model of community dynamics on a pattern-oriented basis. This gave results on species demography, dispersal, and interactions. The parameterized model could be verified along additional data recorded in 2011.The results of model parameterization showed that the habitat specialists (characteristic species for the studied lakeshore community) will be able to coexist with stable zonation over the coming decades, mainly due to a contrast between flood tolerance and strength of competitive interactions forming a variant of the competition-colonization trade-off model of coexistence. As a consequence, long-term shortening of the average flooding period, as predicted for the future, should negatively affect flood-tolerant but weakly competing habitat specialists. Here, an avoiding strategy, a shift of flood-tolerant plant species to lower parts of the lakeshore beyond transect boundary and hence beyond present model range, is to be expected.The modelling results revealed that two native but invasive species will have an increasing impact on the community, and they are predicted to endanger habitat specialists on a long run. This was verified already by the re-examination in 2011. Following the parameter values, invasive species threatening the lakeshore community are both flood-tolerant and competitive. Their expected importance for the fate of the community even exceeds that of possible changes in flood duration.The study demonstrates that an individual-based model can be developed on the basis of nonstationary, temporally and spatially changing local abundance data. Such a model goes beyond conventional matrix modelling by the inclusion of nonlinear features as a consequence of individual interactions, and such features turn out to be decisive factor for dealing with species coexistence and displacement in a plant community. (C) 2013 Elsevier B.V. All rights reserved.

As ploidy level and mating system can affect genetic diversity and differentiation, we conducted population genetic analyses of two closely related mosses, Scorpidium cossonii (Schimp.) Hedenas, and S. revolvens (Sw. ex Anonymo) Rubers which differ in ploidy level and sexual system. We collected 315 specimens in total from five populations of S. cossonii and four populations of S. revolvens in the Swiss Alps. Ploidy level, genetic diversity within populations, and genetic differentiation between populations and species were estimated using nine microsatellite markers. In each S. cossonii sample, each locus bore only one allele, while in S. revolvens, seven out of the nine loci were fixed or nearly fixed for two alleles per locus per individual. These findings are consistent with a gametophytic haploid S. cossonii and allodiploid S. revolvens. The haploid and dioicous S. cossonii was genetically more diverse than the (allo) diploid and monoicous S. revolvens. Differences in genetic diversity between the two species may be explained by different mating systems, different population sizes, and different population histories. Genetic differentiation among populations of S. cossonii was higher than among those of S. revolvens. The low genetic differentiation among populations of the monoicous species was not unexpected, since monoicous species frequently produce sporophytes, long- distance spore dispersal is more likely and leads to low differentiation.

Deschampsia littoralis is an endemic tetraploid Poaceae occurring on the shores of pre-Alpine lakes. It is closely related to the diploid and widespread D. cespitosa. Several D. littoralis populations from Lake Constance are vegetatively propagating through pseudoviviparous spikelets. These latter populations were formerly described as a separate species, D. rhenana. Still, the species status of D. rhenana has been questioned since, apart from pseudovivipary, no morphological differentiation from D. littoralis is observed. Both species are highly endangered and accurate assessment of taxon status is needed for conservation management. We used amplified fragment length polymorphism fingerprinting to assess whether D. rhenana from Lake Constance (43 specimens) was genetically differentiated from D. littoralis (11 specimens collected at Lac de Joux, incl. Lac Brenet) and the widespread D. cespitosa (48 specimens). An analysis of molecular variance (AMOVA) showed that 12 % of the genetic diversity occurred among the three species, 7 % occurred among populations within species and 81 % within populations. Principal coordinate analysis and fuzzy c-means clustering showed that D. rhenana was genetically distinct from D. littoralis. In addition, both species differed in levels of genetic diversity and clustering, with D. rhenana being the most divergent and structured species. D. littoralis appeared as genetically intermediate between D. rhenana and D. cespitosa. These results suggested that (1) all species are closely related, (2) genetic variation within populations is high even in the asexually propagating D. rhenana and (3) D. rhenana is more distinct from D. cespitosa than is D. littoralis. We therefore suggest to treat D. rhenana from Lake Constance and D. littoralis from Lac de Joux as independent evolutionary units in conservation management.

PREMISE OF THE STUDY:Nuclear microsatellite markers were developed in the fen specialist moss, Scorpidium cossonii, to study genetic diversity and genetic structure of this species in relation to land-use types, habitat fragmentation, and habitat conservation measures.METHODS AND RESULTS:The polymorphisms of 14 microsatellite markers were characterized. All primers were tested on 140 gametophytes collected from four populations in Switzerland. The primers amplified di- and trinucleotide repeats with three to 26 alleles per locus. The primers worked also in the two other species of the genus: 14 and 12 primers successfully amplified in S. revolvens and S. scorpioides, respectively.CONCLUSIONS:In future studies, our primers have the potential to provide valuable information on genetic diversity, genetic structure, and on historical and recent gene flow in S. cossonii; they should also enable related research in other Scorpidium species.

By Markov simulation modelling we analysed an almost continuous monitoring series over 27years of the abundance of the highly endangered amphibious plant species Myosotis rehsteineri at the shore of Lake Constance (Germany). The habitat is characterized by yearly floodings of variable magnitude that produce a zonation of species with different flood tolerances. A transect was established in 1983, perpendicular to the shoreline, and divided into segments (2m×2m) of different flood durations. Population sizes, expressed as the number of inflorescences, were determined per segment and year. Additionally, we had detailed data on flooding and knowledge on the dynamics of competing species. A Markov model fitted by nonlinear least squares against the time series of spatially structured abundance data proved to be a useful tool to evaluate population dynamics and to assess the effects of varying environmental conditions that are not accessible to experimental control. Water-level fluctuations and competition by Agrostis stolonifera were both found to affect the population dynamics of M. rehsteineri, but without causing a long-term change in population size under present conditions. The modelling enabled us to evaluate different flooding scenarios and thus providing support for future conservation measures, and we found that extinction risk will increase under changing flooding regimes. Our data and the results of the Markov model simulations showed that under strong abundance fluctuations long-term monitoring is indispensable to explore population dynamics of rare and endangered species in their natural context.

Many ecosystems of high conservation value have been shaped by human impacts over centuries. Today, traditional management of semi-natural habitats is a common conservation measure in Europe. However, despite traditional management, habitat remnants may still loose specialist species due to surrounding land-use change or atmospheric nitrogen deposition. To detect trends in species density (2-m2 plot scale) and habitat quality in calcareous fens in the pre-Alps of Switzerland, we surveyed 36 traditionally managed fens in 1995/97 and again in 2005/06 (five plots per fen). The fens occurred at three altitudinal levels (800–1000, 1000–1200, 1200–1400masl) and were either extensively grazed or mown once a year. Despite these traditional management regimes, species density of fen specialists and of all bryophytes decreased during this decade (vascular plant specialists: −9.4%, bryophyte specialists: −14.9%, all bryophytes: −5.7%). Management had no effect on the number of Red-List species and habitat specialists of vascular plants per plot. However, bryophyte species density was more strongly reduced in grazed fens. Species density of vascular plant generalists increased between the two surveys (+8.2%) but not of bryophytes. Among vascular plants, Red-List species decreased from 1.01 to 0.78 species per plot. Furthermore, between the two surveys aboveground plant biomass, mean plant-community indicator values for nutrients and species density of nutrient indicators increased, whereas mean plant indicator values for soil moisture, light and peat, and species density for peat indicators, decreased. We attribute these changes and the loss of specialist species over the past decade mainly to land-use change in the surrounding area and to nutrient inputs. Thus, despite traditional management, calcareous fens in the pre-Alps suffer from ongoing habitat deterioration and endangered plant species remain threatened. For their long-term protection, we suggest to reduce nutrient inputs and, where necessary, to restore hydrology and adjust grazing management.

Mooring areas are a common form of berthing in many of Germany's inland waters for the growing number of sporting boats. A circular swinging zone around the anchor zone is formed, in which the submerged macrophyte vegetation is destroyed to a large extent, and the sediment surface is eroded. We investigated the effects of two types of buoy (conventional and so-called hook-buoys) in comparison with undisturbed reference sites nearby. The aim of the study was to identify possible harmful consequences of mooring sites to lake littoral habitats in Lake Constance-Untersee, and to provide information to managers to aid them in the formulation of mooring management plans with the least ecological impact. The study focused on submerged vegetation, surface sediments and macro-invertebrate colonisation. In the swinging circle of conventional buoys (87 m2) we observed a significant sediment matter erosion of 0.9 tonnes and a reduction of organic matter amount by 4.5% of the undisturbed reference. The vegetation free area increased by 122%, and the phytomass (mainly Chara div. spp.) was reduced by 14.6% per berth. The psammophilous macro-invertebrate numbers were not significantly affected (−3%) in contrast to the phytophilous taxa which were reduced by 12.7% per berth. The mayfly larvae were the most negatively affected taxon. Oligochaetes profited from the clearing of the sediment surface in the swinging circles. The ecological effects of the hook-buoys were more minor, mainly due to the smaller swinging circle (6 m2). We concluded that the detrimental effects of mooring can be significantly reduced by mooring systems, e. g. the hook-buoy system as it was used in this study, which reduce the area disturbed and cleared by the anchor chain. We argue that these results can be generalised to mooring areas with soft bottom and dense macrophyte vegetation in Lake Constance and other large lakes.

The shores of Lake Constance in southwest Germany inhabit an endemic and highly endangered lake-shore community. In spring 2004, a so far unknown Cardamine (Brassicaceae) was detected at the lake-shores. In the subsequent years, this taxon has spread rapidly, 95 locations have been recorded until spring 2007. We tested the utility of DNA sequences to distinguish between two alternative hypotheses regarding the appearance of this new invasive taxon: a local formation via hybridization between native species versus an introduction of a non-native taxon. The relative DNA contents was analysed as an additional independent character. DNA sequences provided substantial evidence that the unknown Cardamine taxon, recently discovered at Lake Constance in southwest Germany, is a non-native species introduced from abroad. Sequences of the internal transcribed spacer of the large subunits of nuclear ribosomal DNA and two noncoding regions of chloroplast DNA (trnL intron, trnL/F spacer) were distant from sequences of all native Cardamine species providing evidence against a hybridization hypothesis. In contrast, DNA sequences of the unknown Cardamine were identical to one accession of Cardamine flexuosa auct. non With. (Asian C. flexuosa) from Japan. The introduction history of Asian C. flexuosa at Lake Constance and the potential threat to the native lake-shore vegetation is discussed. Our study highlights the potential of DNA sequences to identify invasive genotypes and source regions.

In Central Europe, massive losses in species richness of breeding birds have been documented in the last decades, but the question arises whether species richness is currently still decreasing or again increasing due to conservation efforts. In this study, we investigated regional and local species richness as well as mean number of breeding pairs and mean biomass per tetrad over a period of some 20 years at Lake Constance. Three quantitative censuses of 303 tetrads (2 × 2 km 2 ) repeated at 10-year intervals (1980–1981, 1990–1992, 2000–2002) revealed an increase in regional species richness (total number of breeding species). At the same time, however, a strong decline in local species richness (number of breeding species per tetrad), number of breeding pairs, and estimated biomass were observed. Changes of species richness differed markedly between Nonpasserine and Passerine birds. Whereas species richness of Nonpasserines remained constant from 1980 to 1990, and even increased between 1990 and 2000, that of Passerines decreased in both periods. This indicates that effects of conservation efforts apparently eclipse more general effects of climate and habitat change in Nonpasserines. The massive abundance and biomass losses observed in formerly common Passerine species are not compensated by gains in populations of Nonpasserine species. The results of the three bird censuses at Lake Constance imply that ongoing habitat degradation and human impacts as well as increasing effects of climate change are the main drivers of the observed population changes.