4. Functional biogeography of invasive species: the case of two widely-distributed omnivorous crustaceans
Biological invasions are to date acknowledged as significant environmental and economic threats, yet the identification of key ecological traits determining species invasiveness has remained elusive. One unappreciated source of variation concerns dietary flexibility and the ability to shift trophic position within invaded food webs. Trophic plasticity may greatly influence invasion success as it negates resource availability as a functional constraint for introduced individuals; in addition, the impact of an invader might increase with its dietary plasticity since a greater proportion of the resident assemblage of species and multiple trophic levels are affected.
The present validation case will focus on two invasive crustaceans widely distributed in marine and freshwater European waters, i.e., the Atlantic blue crab Callinectes sapidus and the Louisiana crayfish Procambarus clarkii. Key questions that will be addressed are:
a) does the trophic position of C. sapidus vary between invaded Mediterranean and native west Atlantic habitats, testifying the occurrence of significant post-invasion shifts in dietary habits?
b) does the trophic position of P. clarkii vary in invaded habitats, and which are the main ecological factors involved?
c) do bioclimatic drivers influence broad‐scale spatial patterns of variation in the trophic position of C. sapidus and P. clarkii?