Stable resource polymorphism along the benthic littoral–pelagic axis in an invasive crayfish

Abstract

Although intraspecific variability is now widely recognized as affecting evolutionary and ecological processes, our knowledge on the importance of intraspecific variability within invasive species is still limited. This is despite the fact that understanding the linkage between within‐population morphological divergences and the use of different trophic or spatial resources (i.e., resource polymorphism) can help to better predict their ecological impacts on recipient ecosystems. Here, we quantified the extent of resource polymorphism within populations of a worldwide invasive crayfish species, Procambarus clarkii, in 16 lake populations by comparing their trophic (estimated using stable isotope analyses) and morphological characteristics between individuals from the littoral and pelagic habitats. Our results first demonstrated that crayfish occured in both littoral and pelagic habitats of seven lakes and that the use of pelagic habitat was associated with increased abundance of littoral crayfish. We then found morphological (i.e., body and chelae shapes) and trophic divergence (i.e., reliance on littoral carbon) among individuals from littoral and pelagic habitats, highlighting the existence of resource polymorphism in invasive populations. There was no genetic differentiation between individuals from the two habitats, implying that this resource polymorphism was stable (i.e., high gene flow between individuals). Finally, we demonstrated that a divergent adaptive process was responsible for the morphological divergence in body and chela shapes between habitats while difference in littoral reliance neutrally evolved under genetic drift. These findings demonstrated that invasive P. clarkii can display strong within‐population phenotypic variability in recent populations, and this could lead to contrasting ecological impacts between littoral and pelagic individuals.

Patterns and determinants of phenotypic variability within two invasive crayfish species

“…Faxonius limosus is also known to experience two peaks of mating activity throughout the year with long‐term storage of sperm (Aklehnovich & Razlutskij, 2013; Buřič et al., 2013; Holdich & Black, 2007). In the studied system, previous works highlighted the existence of substantial phenotypic variability (morphology, trophic ecology) among (Evangelista, Lecerf, et al., 2019; Jackson et al., 2017) and within populations of P. clarkii (Lang et al., 2020; Raffard et al., 2017). This suggests contrasting impacts of invasive individuals on ecosystem functioning among populations of P. clarkii (Alp et al., 2016; Evangelista, Lecerf, et al., 2019).…”

“…For each species, crayfish abundance was estimated in each lake as the number of individuals trapped over 24 hr (catch per unit effort expressed in ind trap −1 hr −1 ; Table 1). The predation pressure in each lake was assessed as the biomass of predator fish trapped in a set of gillnets randomly distributed, over 1 hr (biomass per unit effort expressed in g gillnet −1 hr −1 ; Table 1; see further details in Lang et al., 2020 and Zhao et al., 2016).…”

“…PCRs were performed following the procedure described in Lang et al. (2020) (see Figure S1 for the description of the multiplex used in this study). Amplified fragments were analysed on an ABI PRISM 3730 capillary sequencer (Applied Biosystems) at the Génopole Toulouse Midi‐Pyrénées.…”

Invasion and distribution of the redclaw crayfish, Cherax quadricarinatus, in Martinique

“…Although no documented impacts have been reported on the ecosystem in Martinique, invasive crayfish are known to have profound impacts on freshwater communities (plants and animals) due to their opportunistic, omnivorous and predatory nature. This can affects the trophic chain at all levels, by competing with autochthonous species or predating them and perturbating the entire ecosystem functioning (Loureiro et al, 2015;Jackson et al, 2017;Lang et al, 2020). For example, several studies have shown that P. clarkii (Jackson et al, 2014;Loureiro et al, 2015;Lang et al, 2020), P. leniusculus (Jackson et al, 2014;Vaeßen and Hollert, 2015) and Faxonius virilis (formerly Orconectes virilis) (Jackson et al, 2014) can cause strong decreases in species richness of insect larvae and mollusks through predation after their introductions to a new location.…”

“…This can affects the trophic chain at all levels, by competing with autochthonous species or predating them and perturbating the entire ecosystem functioning (Loureiro et al, 2015;Jackson et al, 2017;Lang et al, 2020). For example, several studies have shown that P. clarkii (Jackson et al, 2014;Loureiro et al, 2015;Lang et al, 2020), P. leniusculus (Jackson et al, 2014;Vaeßen and Hollert, 2015) and Faxonius virilis (formerly Orconectes virilis) (Jackson et al, 2014) can cause strong decreases in species richness of insect larvae and mollusks through predation after their introductions to a new location. Studies also suggest a decrease in the abundance and diversity of aquatic plants and animals is directly related to crayfish density (Gherardi and Acquistapace, 2007;Rodríguez-Pérez et al, 2015).…”