The faunal Ponto-Caspianization of central and western European waterways

Abstract

As alien invasive species are a key driver of biodiversity loss, understanding patterns of rapidly changing global species compositions depends upon knowledge of invasive species population dynamics and trends at large scales. Within this context, the Ponto-Caspian region is among the most notable donor regions for aquatic invasive species in Europe. Using macroinvertebrate time series collected over 52 years (1968–2020) at 265 sites across 11 central and western European countries, we examined the occurrences, invasion rates, and abundances of freshwater Ponto-Caspian fauna. We examined whether: (i) successive Ponto-Caspian invasions follow a consistent pattern of composition pioneered by the same species, and (ii) Ponto-Caspian invasion accelerates subsequent invasion rates. In our dataset, Ponto-Caspian macroinvertebrates increased from two species in 1972 to 29 species in 2012. This trend was parallelled by a non-significant increasing trend in the abundances of Ponto-Caspian taxa. Trends in Ponto-Caspian invader richness increased significantly over time. We found a relatively uniform distribution of Ponto-Caspian macroinvertebrates across Europe without any relation to the distance to their native region. The Ponto-Caspian species that arrived first were often bivalves (46.5% of cases), particularly Dreissena polymorpha, followed secondarily by amphipods (83.8%; primarily Chelicorophium curvispinum and Dikerogammarus villosus). The time between consecutive invasions decreased significantly at our coarse regional scale, suggesting that previous alien establishments may facilitate invasions of subsequent taxa. Should alien species continue to translocate from the Ponto-Caspian region, our results suggest a high potential for their future invasion success highly connected central and western European waters. However, each species’ population may decline after an initial ‘boom’ phase or after the arrival of new invasive species, resulting in different alien species dominating over time.

Intercontinental invasion dynamics of Cercopagis pengoi, an IUCN-listed planktonic invasive species

“…In recent decades, a range of brackish and freshwater habitats in Europe and North America, including the Baltic Sea and the Laurentian Great Lakes, have experienced numerous invasions by species native to the Azov, Black and Caspian Seas. This phenomenon is known as the Ponto-Caspian invasion (Soto et al, 2023). Despite the environmental conditions and shipping frequencies in these regions, these invasions are far more prevalent than expected (Casties and Briski 2019).…”

Taming the terminological tempest in invasion science

“…Often, a species' impacts are evaluated at a local scale (e.g. within a specific lake or a forest patch), whereas broader large-scale impacts are inferred by extrapolating local-scale measurements of ecological effects and/or invader abundance across regions or even broader spatial scales, thereby ignoring the spatial variation in the type and severity of impacts that is expected to increase with spatial scale (Haubrock et al, 2022;Ahmed et al, 2023;Soto et al, 2023b). Furthermore, designating a species as 'nonnative' is commonly reported at the national scale (the typical spatial entity for which regulations are established) depending on the perspective of each jurisdiction, but in reality, nativeness is determined at the biogeographic scale, thereby de-emphasising sub-national or regional differences and biogeographic boundaries.…”

Climatic niche differentiation between native and non‐native ranges is widespread in Ponto‐Caspian amphipods

“…The Ponto-Caspian region (the Black, Azov, Caspian, and Aral seas as well as adjacent lagoons and river mouths) harbours a unique and diverse endemic aquatic fauna (Copilaș-Ciocianu & Sidorov, 2022;Cristescu & Hebert, 2005;Naseka & Bogutskaya, 2009;Wesselingh et al, 2019) characterised by a broad environmental tolerance (Borza et al, 2018;Dobrzycka-Krahel et al, 2023;Paiva et al, 2018;Pavel et al, 2021;Reid & Orlova, 2002;Šidagytė & Arbačiauskas, 2016). The adaptability of these species coupled with numerous anthropogenic factors (shipping, canals, and deliberate introductions) has transformed the Ponto-Caspian area into a major source of invasive species throughout the inland waters of the northern hemisphere (Bij de Vaate et al, 2002;Copilaș-Ciocianu, Sidorov, & Šidagytė-Copilas, 2023;Soto et al, 2023). The spread of many of these species is still ongoing (Copilaş-Ciocianu & Šidagytė-Copilas, 2022), generating significant ecological and economical impacts (Arbačiauskas et al, 2017;Dermott et al, 1998;Gaye-Siessegger et al, 2022;Strayer, 2009;Vanderploeg et al, 2002).…”