Climate-induced range shifts of the American jackknife clam Ensis directus in Europe

Abstract

Mapping the future potential distribution of alien species has become an issue of great concern. Ecological niche models are increasingly used to forecast the spatial range of introduced species in the context of climate warming. Here, we studied the potential spread of the American jackknife clam Ensis directus into European waters. E. directus, a marine bivalve native to the American coasts, was observed in Europe for the first time in the German Bight at the end of the 1970s. Afterwards, the clam quickly colonized the surrounding waters of the North Sea. Although many studies focused on its biology, ecology and colonization, the extent to which E. directus may invade European and Nordic seas remained poorly known. In this study, we used two ecological niche models (ENMs), calibrated on the native area of the mollusk, to evaluate the potential distributional range of the bivalve over European seas. Under current environmental conditions, E. directus should continue to progress towards the southern coasts of France and may also invade new areas in the Adriatic Sea. Projections for the end of the century suggest that the probability of occurrence of E. directus increases from Denmark to France with both ENMs. The Tunisian coasts may also become a new suitable area for the mollusk but the results of the two ENMs differ for this region. Therefore, contrary to what is often observed, a southward range expansion of E. directus is probable, especially as climate will get warmer.

Modelling present and future global distributions of razor clams (Bivalvia: Solenidae)

“…Predicted present (top models in red) and future (2100) (bottom models in blue) distribution models of environment suitability for 14 Solen species with a probability of occurrence >0.5 150 m, wave height of 5-7 m, mean SST of 12-28 °C, and primary productivity of 400-700 mg C m −2 day −1 cell −1 ). The suitable environments for Solenidae species were similar to the temperate razor clam Ensis directus (Pharidae) [50]. They also found high probabilities of occurrence for E. directus at depths between 0 and 67 m, minimum annual SSTs between 3 and 18 °C and maximum annual SSTs between 20 and 26.5 °C [50].…”

“…The suitable environments for Solenidae species were similar to the temperate razor clam Ensis directus (Pharidae) [50]. They also found high probabilities of occurrence for E. directus at depths between 0 and 67 m, minimum annual SSTs between 3 and 18 °C and maximum annual SSTs between 20 and 26.5 °C [50].…”

Evidence of horizontal transmission of the cancer-associated Steamer retrotransposon among ecological cohort bivalve species

“…It is evident that there is markedly greater genetic diversity for Steamer among E. directus specimens The invasive Atlantic razor clam E. directus is now well established in the North Sea, where it is outcompeting the endemic razor clam, E. ensis (see Raybaud et al 2015). In addition to its presence in M. arenaria in the northwest Atlantic, here we have shown the presence of Steamer in the North Sea invasive E. directus and in the North Sea endemic M. balthica.…”

“…Other than what is implied for these disseminated neoplasia of bivalves, the only other known cross-species transmission of cancerous cells concerns the establishment of a tapeworm malignancy in the lungs of a highly immunocompromised patient (Muehlenbachs et al 2015). Mechanisms similar to DFTD and CVTV may be at play in bivalves insofar as the putative infective cells are hemocytes responsible for non-self recognition via agglutination and aggregation factors (Moreira et al 2012).It is evident that there is markedly greater genetic diversity for Steamer among E. directus specimens The invasive Atlantic razor clam E. directus is now well established in the North Sea, where it is outcompeting the endemic razor clam, E. ensis (see Raybaud et al 2015). In addition to its presence in M. arenaria in the northwest Atlantic, here we have shown the presence of Steamer in the North Sea invasive E. directus and in the North Sea endemic M. balthica.…”

“…In addition to its presence in M. arenaria in the northwest Atlantic, here we have shown the presence of Steamer in the North Sea invasive E. directus and in the North Sea endemic M. balthica. The presence or absence of this retrotransposon in the genome of E. ensis, and other mud-dwelling bivalves, deserves scrutiny, particularly as the distribution of E. directus suggests near-term expansion into the Adriatic (Raybaud et al 2015).Acknowledgements. We thank the staffs of the Ambrose Monell Cryo Collection and the Canadian Centre for DNA Barcoding for providing tissues from their collections.…”