Joint species models reveal the effects of environment on community assemblage of freshwater mussels and fishes in European rivers

Abstract

Aim Given that riverine systems exhibit longitudinal environmental gradients from headwater to the mouth of a river, habitat heterogeneity appears to be a major driver of spatial variation in community composition among riverine localities. As freshwater ecosystems are amongst the most endangered ecosystems in the world, community‐based conservation and multiple‐species management are necessary to maintain ecosystem integrity. We used joint species distribution models (JSDMs) to investigate the relative importance of abiotic and biotic factors that are responsible for the distribution and co‐occurrence of species in riverine ecosystems. Location Central and northern Europe. Methods We examined the general patterns of species assemblage of two endangered freshwater mussel species (Margaritifera margaritifera and Unio crassus) and their associated fish communities. We examined the patterns of positive or negative co‐occurrence in mussel and fish species and identified shared abiotic responses between mussel–host pairs. Results We found that the relative importance of abiotic and residual factors and patterns of significant species correlations varied among taxa: significant residual correlations were prevalent among fish species, whereas mussel occurrences were exclusively explained by abiotic factors. Mussels and their fish hosts generally had shared abiotic responses with some mismatched responses between mussel–host pairs. Main conclusions Given that the composition of communities were tightly linked with abiotic factors and residual correlations, the results have significant implications for the conservation and restoration of aquatic communities. This study highlights the necessity to simultaneously consider environmental factors and species co‐occurrences in the modelling of species distributions and assemblages of riverine communities. Such a holistic community conservation approach can reveal ecological similarities and differences among species, which can help us avoid conflicts among target‐species conservation plans.

From individual to joint species distribution models: A comparison of model complexity and predictive performance

“…Tikhonov et al, 2017). Studies applying joint models to freshwater communities suggest that shared responses to environmental conditions may be more important in determining community composition than residual correlations between taxa (Inoue, Stoeckl, & Geist, 2017;Pollock et al, 2014;Royan et al, 2016).…”

A spatially explicit approach to prioritize protection areas for endangered freshwater mussels

“…As most populations of M. margaritifera are already associated with some kind of protected area, albeit with typically weak levels of protection, the most useful strategy is to increase protection by upgrading the respective protection categories to provide stricter protection for the landscape. This is likely to mitigate further habitat degradation and population loss because M. margaritifera populations are adversely affected by even slight changes in the substrate conditions of streams (Geist & Auerswald, 2007) and in stream nutrient levels (this study ;Bauer, 1988;British Standards Institution, 2017;Inoue et al, 2017). In contrast, the greater tolerance of U. crassus to substrate conditions and nutrient input, as well as the greater spectrum of host fish species, will in most cases not require an extremely strict legal protection category.…”

“…A previous study found associations between the occurrence of mussel species and their fish hosts, as well as a relationship between environmental factors and mussel occurrences (Inoue, Stoeckl, & Geist, ). The same study hypothesized that mussel distributions are nested within the host fish distributions and that the presence of mussels at a given site is primarily driven by local abiotic conditions.…”

“…Lopes‐Lima et al () recommended applying species‐specific conservation strategies for endangered mussel species. This approach is needed for M. margaritifera and U. crassus given their differences in habitat requirements and fish hosts (Inoue et al, ).…”

“…Such information is important when implementing effective conservation strategies and prioritizing conservation areas. Furthermore, although many protected areas have been designated primarily for their terrestrial ecosystems (Nel et al, 2009) This approach is needed for M. margaritifera and U. crassus given their differences in habitat requirements and fish hosts (Inoue et al, 2017).…”