The role of freshwater connectivity in facilitating the range expansion of invertebrate invasive species

Invasive non-native species (INNS) are a significant threat for the diversity of freshwater ecosystems, often disrupting the structure and functioning of native communities (Jackson et al. 2014). 47 of 194 identified INNS in the UK have invaded freshwater ecosystems, with future increases in their establishment predicted (Gov.uk, 2023). Freshwater invertebrate INNS in the UK include a range of crustaceans (e.g., signal crayfish, demon, and killer shrimps) and bivalves (e.g., Asian clam and zebra mussel) (Harrower et al. 2021) which have been intentionally or unintentionally released into the natural environment through human activities such as fishing, aquaculture, and boating (Francis and Chadwick, 2021; Smith et al. 2020).

The mechanism of successful establishment of these invertebrates will differ depending on their functional characteristics, however the connectivity of waterbodies, such as anthropogenically constructed links between rivers, lakes, canals, drains/ditches, and reservoirs, is likely to facilitate their movement across the landscape (Wohl, 2017).

Increasingly, evidence is suggesting that anthropogenic waterbodies such as canals and reservoirs are highly invaded ecosystems (Keller et al. 2011; Mathers et al. 2023) which may act as stepping stones for future expansion into adjacent, connected water-bodies (Clavero and Hermoso, 2011). Despite this, little research has examined the role of waterbody connectivity in facilitating freshwater invasions and range expansion in the UK despite some limited international evidence (e.g., River Rhine - Leuven et al. (2009) and the USA Great Lakes - Pimentel, 2005).

Moreover, the role of barriers (e.g., weirs) and direct connections (e.g., locks) has been largely overlooked internationally but may impact the structure of macroinvertebrate communities (Walker and Hassall, 2021). The limited knowledge regarding the spatial and temporal effect of freshwater connectivity on the potential containment and/or expansion of invasive species presents a major knowledge gap in freshwater ecology.

As a result, this project aims to: (1) quantify temporal trajectories in the distribution of INNS in highly connected waterbodies using available secondary data, (2) quantify the spatial distribution of INNS within a range of highly connected waterbodies via field investigations and secondary data; and (3) explore whether linkages or barriers between connected waterbodies facilitate or limit the invasion process.