Ted von Proschwitz

Conservation status of freshwater mussels in Europe: state of the art and future challenges.

Freshwater mussels of the Order Unionida provide important ecosystem functions and services, yet many of their populations are in decline. We comprehensively review the status of the 16 currently recognized species in Europe, collating for the first time their life‐history traits, distribution, conservation status, habitat preferences, and main threats in order to suggest future management actions. In northern, central, and eastern Europe, a relatively homogeneous species composition is found in most basins. In southern Europe, despite the lower species richness, spatially restricted species make these basins a high conservation priority. Information on freshwater mussels in Europe is unevenly distributed with considerable differences in data quality and quantity among countries and species. To make conservation more effective in the future, we suggest greater international cooperation using standardized protocols and methods to monitor and manage European freshwater mussel diversity. Such an approach will not only help conserve this vulnerable group but also, through the protection of these important organisms, will offer wider benefits to freshwater ecosystems.

Evaluation of ITS rDNA as a complement to mitochondrial gene sequences for phylogenetic studies in freshwater mussels: an example using Unionidae from north-western Europe

Mitochondrial inheritance in the Unionidae is complex since mitochondria can be inherited from both parents. An increased rate of recombination could lead to erroneous homology assessments, which could cause problems for phylogenetic reconstruction. For this reason we investigated the possibility of using a nuclear marker, the ribosomal internal transcribed spacer region, for phylogenetic studies in the Unionidae, as a complement and comparison to two of the most widely used mitochondrial genes today. The nuclear ribosomal internal transcribed spacer region (ITS1, 5.8S, ITS2) was sequenced from 72 specimens representing six of the seven species of Unionidae mussels occurring in NW Europe: Unio pictorum, U. tumidus, U. crassus, Anodonta anatina, A. cygnea and Pseudanodonta complanata. Sequences from Margaritifera margaritifera were used as an outgroup. The ITS sequences of all species were found to have low intragenomic and infraspecific variation. Compared to mitochondrial genes (16S and COI) they show an intermediate genetic diversity. Phylogenetic analyses produce tree topologies that are congruent with those resulting from analyses of the mitochondrial sequences. Likewise, an incongruence length difference (ILD) test showed no significant incongruence between data sets, indicating that if recombination has occurred it has not produced any conflicting patterns. Best‐resolved and supported trees are obtained when gaps are treated as a fifth character state. A combined analysis of the three gene regions shows that Unio crassus and U. pictorum are more closely related than either to U. tumidus. Pseudanodonta is nested within Anodonta as sister taxon to A. cygnea. Advice on how to best preserve mussel material for DNA studies is provided.

Introgression and Differentiation of the Invasive Slug Arion vulgaris from Native A. ater

ABSTRACT The large arionid slug Arion vulgaris is an invasive pest dispersing through large parts of Europe and causing considerable damage in gardens, horticulture and agriculture. It is also possible that this so-called “Iberian slug” has an impact on Norwegian ecosystems, displacing or hybridizing with the native black slug Arion ater. The taxonomy of the large arionids is complex and confusing, encompassing different anatomical forms and colour varieties. The present study integrates, for the first time, coloration, ligula morphology, genital morphometry, nuclear and mitochondrial DNA in order to differentiate the large arionids found in Norway, A. vulgaris, A. ater and A. rufus. These data revealed a clear separation between A. vulgaris and A. ater based on the morphology of the genitalia and mtDNA. However, introgression with the red slug A. rufus was apparent in approximately half of the A. ater specimens analysed, evidenced by ligula morphology, mitochondrial and nuclear DNA. In addition, the mitochondrial COI gene and the nuclear ITS1 gene suggested introgression between A. ater and A. vulgaris. Phylogenetic analyses that included A. vulgaris, A. ater and A. rufus from other parts of Europe, together with A. flagellus, A. fuscus, A. lusitanicus and A. nobrei suggest that A. vulgaris is more closely related to A. ater and A. rufus than to A. lusitanicus. This study confirms the uncertainty of identification based solely on coloration and stresses the importance of integrating several approaches to differentiate these large arionids, allowing a better appreciation of their invasive potential, ecological impact and current distribution.

Conservation Thinning in Secondary Forest: Negative but Mild Effect on Land Molluscs in Closed-Canopy Mixed Oak Forest in Sweden

Secondary succession is changing the character of many temperate forests and often leads to closed-canopy stands. In such forests set aside for conservation, habitat management alternatives need to be tested experimentally, but this is rarely done. The Swedish Oak Project compares two often debated alternatives: minimal intervention and non-traditional active management (conservation thinning) on plots of each type replicated at 25 sites. We study responses of several taxa, and here report results for land molluscs. They are considered to be sensitive to more open, drier forest and we predicted a negative effect of the thinning (26% reduction of the basal area; mean value for 25 experimental forests). We sampled molluscs in the litter in ten 20 x 25 cm subplots, and by standardised visual search, in each plot. In total, we recorded 53 species of snails and slugs (24 369 individuals) and the mean species richness in plots was 17. Two seasons after thinning, mean (± SE) species richness had decreased by 1.4 (± 0.9) species in thinning plots, but increased by 0.7 (± 1.0) species in minimal intervention plots, a significant but small change with considerable variation among sites. In matched comparisons with minimal intervention, thinning reduced the overall abundance of molluscs. Most species responded negatively to thinning – but only five of the 53 species were significantly affected, and reproduction seemed to be negatively affected in only one species. An ordination analysis did not reveal any particular change in the species community due to thinning. Thus, the negative effect of conservation thinning on land molluscs was apparently mild – one reason was that many trees, shrubs and other forest structures remained after the treatment. Conservation thinning may be recommended, since other taxa are favoured, but minimal intervention is also a useful form of management for molluscs and saproxylic taxa.

A phylogenetic overview of the genus Vertigo O. F. Müller, 1773 (Gastropoda: Pulmonata: Pupillidae: Vertigininae)

ABSTRACT We document global phylogenetic pattern in the pupillid land snail genus Vertigo by analyses of nDNA (ITS1 and ITS2) and mtDNA (CytB and 16S) sequence from 424 individuals representing 91 putative specific and subspecific Vertigo taxa. nDNA and mtDNA data were separately subjected to neighbor-joining, minimum evolution, maximum likelihood and Bayesian reconstruction methods, with conclusions being drawn from shared topological structures. Six highly supported, reciprocally monophyletic subgeneric level clades were identified: Vertigo, Alaea, Boreovertigo new subgenus, Isthmia, Staurodon and Vertilla. 88 species or subspecies were also confirmed, nine of which are new and formally described herein: V. beringiana, V. chiricahuensis, V. chytryi, V. genesioides, V. kodamai, V. kurilensis, V. lilljeborgi vinlandica, V. pimuensis and V. pisewensis. Thirteen taxa were synonymized: V. arthuri basidens, V. arthuri hubrichti, V. arthuri paradoxa (= V. arthuri); V. allyniana (= V. modesta); V. andrusiana (= V. columbiana); V. conecuhensis (= V. alabamensis); V. dedecora tamagonari (= V. dedecora); V. elatior, V. idahoensis (= V. ventricosa); V. eogea (= V. ovata); V. modesta insculpta (= V. modesta concinnula), V. modesta microphasma, V. modesta sculptilis (= V. modesta castanea). Qualitative observations of conchological features, ecological preferences and geographic coverage were conducted for each subgenus and genetically supported species or subspecies-level taxon. These demonstrated that: (1) a suite of diagnostic shell features usually exists to demarcate each species-level taxon; (2) shell features were incapable of defining genetically validated subgenera; (3) all subgenera had transcontinental ranges; (4) ⅓ of all species possess continental or trans-continental ranges, with very few having range extents < 1,000 km; (5) all subgenera and fully ⅔ of global Vertigo species and subspecies are found in North America, more than 2.5 times the number found in central and eastern Asia, the second most diverse region. This is similar to several other molluscan groups, such as the polygyrid land snails and unionid bivalves for which North America is the global biodiversity hotspot.

Climate Warming as a Possible Trigger of Keystone Mussel Population Decline in Oligotrophic Rivers at the Continental Scale

The effects of climate change on oligotrophic rivers and their communities are almost unknown, albeit these ecosystems are the primary habitat of the critically endangered freshwater pearl mussel and its host fishes, salmonids. The distribution and abundance of pearl mussels have drastically decreased throughout Europe over the last century, particularly within the southern part of the range, but causes of this wide-scale extinction process are unclear. Here we estimate the effects of climate change on pearl mussels based on historical and recent samples from 50 rivers and 6 countries across Europe. We found that the shell convexity may be considered an indicator of the thermal effects on pearl mussel populations under warming climate because it reflects shifts in summer temperatures and is significantly different in viable and declining populations. Spatial and temporal modeling of the relationship between shell convexity and population status show that global climate change could have accelerated the population decline of pearl mussels over the last 100 years through rapidly decreasing suitable distribution areas. Simulation predicts future warming-induced range reduction, particularly in southern regions. These results highlight the importance of large-scale studies of keystone species, which can underscore the hidden effects of climate warming on freshwater ecosystems.