Predicting the influence of river network configuration, biological traits and habitat quality interactions on riverine fish invasions

Abstract

Aim: The relationships between species and their landscape are important for understanding migration patterns. In fluvial systems, the complexity of the river network can strongly influence the dispersal and colonization rates of invading alien fishes, but habitat quality, species’ biological traits and their location of introduction are also potentially important. However, understandings of how these factors interact in the wild to influence the spatial distribution of invasive species over time are limited from empirical studies. Location: “Virtual” and “real-world” rivers from England and Wales. Method: We developed an individual-based model (IBM) to predict how these different factors influenced the invasion dynamics and population growth rates (as abundances) of nine “virtual” alien fishes over two timeframes (10 and 30 years). The alien fishes differed in their demographic (r- to K-selected) and dispersal (fast to slow) characteristics and the rivers in their network complexity. Results: Irrespective of river type, species and timeframe, the main drivers of both dispersal and population growth were the location of the introduction and the mean habitat quality of the patch into which the species were released. The introduction location determined whether dispersal was mainly passive in a downstream direction (faster) or active in an upstream direction (slower), with higher habitat quality then enabling faster population growth rates. Over 30 years, invasion rates were predicted to increase as the complexity of the river network increased, as this opened multiple invasion fronts where the invader traits favoured faster dispersal. Main conclusions: This novel IBM revealed how the complexity of the physical environment interacts with the biological traits of alien species to influence invasion outcomes, with the location of the introduction and its habitat quality being the most important factors. These results thus substantially increase understanding of the factors that influence the dispersal and colonization rates of alien freshwater fishes.