The Chinese pond mussel Sinanodonta woodiana demographically outperforms European native mussels

The effect of parasitism on boldness and sheltering behaviour in albino and pigmented European catfish (Silurus glanis)

Parasites can change the behaviour of their hosts, but little attention has been given to the relationship between parasite effects on host behaviour and colouration. The correlation between disrupted melanin production and alterations in various physiological and behavioural traits, e.g., aggression, shoaling behaviour, stress responsiveness and sensitivity to brood parasitism, has been reported in albino fish. We hypothesized that parasitism would affect the behaviour of albino and pigmented conspecifics differently. In laboratory conditions, we infested a group of pigmented and a group of albino individuals of European catfish Silurus glanis with glochidia of two Uninoidea species, namely, the native species Anodonta anatina and the invasive species Sinanodonta woodiana, and investigated the effect of parasitization on the boldness and sheltering behaviour of the hosts. The behaviour of albino individuals differed from that of pigmented conspecifics both before and after parasitization. Parasitization with glochidia did not affect sheltering behaviour, but it increased boldness in pigmented individuals, whereas albino individuals did not exhibit any changes in behaviour. Sheltering results were consistent in both binomial and continuous variable analyses, whereas boldness was significant only in the binomial analyses. Our results demonstrate the reduced susceptibility of the albino phenotype to glochidia infestation, together with questions of the choice of analyses.

Disentangling structural and functional responses of native versus alien communities by canonical ordination analyses and variation partitioning with multiple matrices

Freshwaters are under accelerated human pressure, and mollusk communities are among its most sensitive, threatened, and valuable components. To the best of our knowledge, the overall effects of damming, environment, space, time, and invasive alien mollusk species, on structural and functional responses of native mollusk communities were not yet compared. Using historical information and recent data from a river, we aimed to investigate and disentangle these effects and evaluate the differences in structural and functional responses of natives and alien invasives to the same predictors. Variation partitioning showed that alien species were as important predictors as were environmental factors and time in explaining species composition of native freshwater mollusk communities. Aliens were more independent of environmental conditions than natives and responded to different drivers, partially explaining their invasion success. The increased abundance of some alien gastropods was positively related to taxonomic diversity, while certain alien bivalves were negatively associated with the functional diversity of native communities. We introduce a cumulative variation partitioning with multiple response (native and alien) and predictor matrices, along with a diagram to show their relations, advocating for a conceptual shift in future community ecology, from “variables to matrices” and from “multivariate analyses to multi-matrix statistical modeling”.

Distribution and potential impacts of non-native Chinese pond mussels Sinanodonta woodiana (Lea, 1834) in Bavaria, Germany

The Chinese pond mussel, Sinanodonta woodiana, is non-native to European freshwater systems. Originating from Asia, it was brought to Europe in the 1970s and is now spreading across many countries. Management of the species is currently limited by a lack of information on the actual distribution and population characterisation of S. woodiana as well as on the co-occurrence of native mussels potentially resulting in competition. For this paper, we examined nine water systems in the German federal state of Bavaria with randomly observed and anecdotally reported S. woodiana occurrences. We recorded the density and biomass of S. woodiana and of the co-existing mussel species as well as the habitat characteristics. We found S. woodiana in eight water systems, co-existing with other native and invasive mussel species in seven of them. The distribution of S. woodiana was geographically widespread throughout Bavaria, indicating great invasion potential. In one fish pond, S. woodiana was the only mussel species occurring with the highest mean biomass (1286.0 ± 1067.7 g m−2) and with the biggest specimen (25.0 cm and 1616.0 g). The wide range of habitat variables matched the expectation of a wide ecological niche for the species. This study provides evidence that S. woodiana has already become established in many water systems in Bavaria, with fish ponds and fisheries management practises being a likely vector. To counteract this species and to conserve native mussel species, it is important to implement effective legislation, to take measures to eradicate this invasive mussel transnationally, and to raise public awareness.