In a Pinch: Mechanisms Behind Potential Biotic Resistance Toward Two Invasive Crayfish by Native African Freshwater Crabs

Abstract

South et al. Biotic Resistance Toward Invasive Decapods factors such as closing force actually translate to resource holding potential in a contest scenario. We thus provide evidence that African freshwater crabs may exhibit biotic resistance toward invasion and the first measurements for C. quadricarinatus closing force strength.

Invasive crayfish outperform Potamonautid crabs at higher temperatures

“…macrophytes and algae) (Matsuzaki et al., 2009) altering trophic cascades and changing ecosystem structure and function through indirect effects (Twardochleb et al., 2013). The results presented here confirm the necessity to use relevant comparison species, indeed in terms of trait performance (closing force) P. clarkii was outperformed by the same two focal species (South et al., 2020), as well as consider a broader range of resources when assessing impact. The documented impacts in field and laboratory experiments may be related to resource availability in the field (i.e.…”

“…As such, any differences detected in the consumption rates and FR parameters between these decapods are unlikely to be due to major differences in their trophic ecology nor functional traits. Using trophically analogous native species as comparison species can provide ecologically meaningful inferences, which allows the results to be interpreted in a contextually relevant manner (Dick et al., 2013; Dickey et al., 2020; South et al., 2020). In all laboratory experiments, there is some degree of confinement effect for both predator and prey behaviour.…”

“…The documented impacts in field and laboratory experiments may be related to resource availability in the field (i.e. density dependent consumption) (Bondar et al., 2005; Veselý et al., 2020), feeding specialisations via functional traits and chelae dentition (West et al 1991; South et al., 2020), or even some degree of survivorship bias with regards to ethical barriers to using live vertebrate prey in laboratory experiments. Our results highlight that in some cases invasion history, especially Palearctic results, might not be robust to transplant into Afrotropical settings.…”

“…Given the absence of native crayfish on mainland Africa, it is predicted that negative impacts on native trophic analogous decapods, such as freshwater crabs from the genus Potamonautes are likely to be strong (Jackson et al., 2016; de Moor, 2002; Nunes et al., 2016), but see South et al. (2020) regarding trait inferred measures of biotic resistance. Potential impacts by freshwater crayfish on African freshwater crabs are a cause for concern because freshwater crabs are the major shredder species present in African freshwaters, forming the vital intermediate trophic link between detritus and predatory species such as fish, otters, and birds (Cumberlidge, 2011).…”

First record of the Australian redclaw crayfishCherax quadricarinatus(von Martens 1868) in Hong Kong, China

“…A study in South Africa demonstrated that biotic resistance to C. quadricarinatus by native, trophically analogous, freshwater crabs was size and sex-dependent. For example, the female Potamonautes perlatus native to Southern Africa, have significantly stronger maximum chela force than female C. quadricarinatus and both sexes of another introduced crayfish species Procambarus clarkii (South et al 2020). In Hong Kong, C. quadricarinatus may compete with functionally similar native decapods such as Macrobrachium hainanense , M. nipponense , and Nanhaipotamon hongkongense .…”