Invasive crayfish alter the long‐term functional biodiversity of lotic macroinvertebrate communities

Abstract

Invasive species represent one of the primary threats to global biodiversity. Despite acknowledged implications for taxonomic properties of ecological communities following invasion, functional measures remain poorly understood. We examined the long‐term implications of invasion by a crayfish species, Pacifastacus leniusculus, on functional alpha and beta diversity properties of lotic macroinvertebrate communities in three English regions. The dataset comprised 477 samples collected predominantly between 1990 and 2013. Unlike many invasion studies, we employed before and after invasion comparisons, in association with control rivers not invaded by crayfish. Functional richness and divergence metrics displayed the strongest responses to invasion, highlighting that P. leniusculus may alter the range of functional niches and extreme trait values (likely reflecting resistance and resilience mechanisms) displayed by macroinvertebrate communities. Interestingly, in one region, biodiversity gains seen in control rivers were not mirrored in invaded rivers, potentially suggesting that invasion inhibited ecological improvements. Invasion by signal crayfish resulted in functional compositional changes in two of the three English regions studied, with these rivers yielding greater ecological differences between pre‐ and post‐invasion periods relative to control rivers. This change was primarily driven by higher nestedness values in invaded rivers, with communities containing functional subsets relative to control rivers. The third region demonstrated no functional compositional changes or alterations in functional beta diversity associated with invasion. Our findings indicated that in most instances, the functional properties of macroinvertebrate communities responded to crayfish invasion and may therefore represent a complementary means to monitor the ecological condition of lotic ecosystems. Given their spatial transferability, functional traits could provide a platform to guide regional management practices in the face of biological invasions. A free Plain Language Summary can be found within the Supporting Information of this article.

Response of freshwater snails to invasive crayfish varies with physiochemical exposure cues and predator experience

“…This is particularly true for P. antipodarum , which typically burrow into fine sediments but also Physella acuta, with both species being documented to display increased use of subsurface substrates in the presence of the fish species, Gobiomorphus (Holomuzki & Biggs, 2012; Holomuzki et al., 2009). However, although vertical migration into substates has been observed as an anti‐predator response for other taxa (Mathers et al., 2020) in addition to gastropod species, migration towards the waterline is the most widely documented response for Gastropoda.…”

“…Where invasive populations become established, they can have far‐reaching consequences for aquatic ecosystems (Doherty‐Bone et al., 2019). Signal crayfish ( Pacifastacus leniusculus ; Dana) are widespread and abundant across much of Europe and have been documented as having negative effects on the structure of macroinvertebrate assemblages where populations have successfully established (Galib et al., 2021; Mathers et al., 2016, 2020; Nilsson et al., 2012). Gastropods are one of the most common prey taxa of crayfish, with many in situ studies documenting a reduction in richness, abundance and/or biomass associated with crayfish presence (Mccarthy et al., 2006; Wilson et al., 2004).…”

Ecosystem effects of invasive crayfish increase with crayfish density

“…Their impacts on ecosystem processes (e.g. primary productivity and leaf litter decomposition: Charlebois & Lamberti, 1996; Jackson et al., 2014), and on biota, including amphibians (Axelsson et al., 1995; Gamradt & Kats, 1996), fishes (Findlay et al., 2015; Wood et al., 2017), various bivalves (Machida & Akiyama, 2013; Meira et al., 2019), and other macroinvertebrates (Mathers et al., 2016, 2020; Nyström et al., 1996) have been studied, mostly in laboratory environments. Nevertheless, our understanding is limited with regard to how crayfish density affects multiple ecosystem components in natural habitats.…”

Invasive species influence macroinvertebrate biomonitoring tools and functional diversity in British rivers

“…Functional responses have been increasingly tested in bioassessment and primary ecological research (e.g. Belmar et al., 2019; Mondy et al., 2012), being recently identified as a promising approach for the assessment of impacts associated with biological invasion (Colin et al., 2018; Mathers, White, Guareschi, et al., 2020), but to date rarely used (Flood et al., 2020). To integrate environmental management and invasive species research better, wide‐ranging studies considering multiple components of communities have been proposed (e.g.…”