Inference of local invasion pathways in two invasive crayfish species displaying contrasting genetic patterns

Abstract

The efficient management of invasive alien species (IAS) requires the identification of their introduction pathways. Genetic assessments have proven useful to inform invasion pathways at large (national to worldwide) scales, but studies at local scales are still rare, despite their importance for guiding management. In this study, genetic analyses were used to identify local invasion pathways of two invasive crayfish species (the spiny‐cheek crayfish Faxonius limosus and the red swamp crayfish Procambarus clarkii) in a dense network of artificial lakes. We first characterized the spatial patterns of genetic variability, effective population sizes (Ne) and among‐lakes recent migration events for each species using neutral microsatellite markers. We then identified the environmental factors affecting genetic variability and inferred the potential local invasion pathways. Results revealed different patterns of genetic variability between the two species: F. limosus displayed very low levels of genetic diversity, Ne and spatial structuring compared to P. clarkii, which displayed high genetic diversity, Ne and spatial genetic structuring. We also demonstrated context‐dependent effects of different environmental factors (fishery management, spatial distribution and lake size) on genetic variability indices. We did not identify local invasion pathways for F. limosus due to limited genetic variability, likely caused by a strong founder effect and potential parthenogenetic reproduction. Contrastingly, multiple invasion pathways (release, contaminant, unaided/corridor spread and stowaway) were identified for P. clarkii. Synthesis and applications. Although limited in some particular cases (e.g. for species having experienced strong shaping events and/or displaying asexual reproductive modes), neutral genetic variation assessments can provide important insights for inferring local invasion pathways in complex landscapes for invasive alien species displaying short generation times and complex invasion histories.

Stocking practices shape the taxonomic and functional diversity of fish communities in gravel pit lakes

“…Knowledge of the composition of fish communities at the start of our study was limited, with no information about management history. Fish could have been introduced legally, illegally, or as stowaways during fish releases (Paz-Vinas et al, 2021), before our study, so we focused on recent stocking practices and their effects on current communities. Our results are consistent with a predictable shift in community composition previously observed in gravel pit lakes (Zhao et al, 2016) and confirm the influence of fishery management and stocking on the trajectory of community assembly in these ecosystems.…”

“…The study area included 34 gravel pit lakes located in the central part of the Garonne floodplain, Haute‐Garonne, France (Figure 1). These gravel pit lakes were located within a 55‐km radius and disconnected from the hydrographical network and other gravel pit lakes (Alp et al, 2016; Paz‐Vinas et al, 2021; Zhao et al, 2016) (Figure 1 and Table S1). Study lakes were distributed along a gradient of maturity (from 17 to 56 years following excavation), maximum depth (ranging from 1.7 to 22.4 m), and surface area (ranging from 0.73 to 47.43 ha; Colas et al, 2021; Table S1).…”

“…This process is likely to be complex and variable depending on lake age, lake history, lake location, and also fish species. Multiple pathways can act simultaneously to explain the colonization of gravel pit lakes, including legal and illegal stocking or introduction as stowaway during the stocking of other species (Paz‐Vinas et al, 2021). For this reason, we focused our investigations on recent stocking events and current fish communities.…”

Genetic-based inference of densities, effective and census sizes of expanding riverine meta-populations of an invasive large-bodied freshwater fish (Silurus glanis L.)

“…The considerable levels of genetic diversity and the high effective meta-population sizes observed in S. glanis populations at the hydrographical basin scale could be the result of multiple introduction events involving individuals from different genetic sources, as is the case for other aquatic invasive species inhabiting the study area (e.g. the spiny-cheek crayfish Procambarus clarkii; Paz-Vinas et al, 2021). This was also (i) suggested by a previous study having conducted a broader genetic survey at the European scale (Castagné et al, 2023), (ii) evidenced by our genetic clustering analyses, which revealed the presence of four genetically distinct groups of individuals (clusters), and (iii) confirmed by the ABC-RF model-choice procedure we conducted, which provided higher support for demo-evolutionary models involving four genetically-distinct sources of individuals instead of one single source.…”

“…Although being generally conducted from a conservation standpoint (e.g. to identify at-risk populations), joint Ne and Nc assessments may also have an important practical value in the context of biological invasions monitoring and management, as they may help identify, monitor and prioritize invasive populations requiring active population control actions at local scales (Blanchet, 2012;Paz-Vinas et al, 2021). For instance, introduced populations with Ne<50 can be expected to be less likely to establish, be maintained and become invasive compared to introduced populations with Ne>500, due to the expected pervasive genetic effects associated with low effective population sizes and genetic diversities (e.g.…”