One of the most imperiled taxonomic groups in North American freshwaters is that of crayfish ( Decapoda: Astacoidea): over 30% of the 390 species are threatened or endangered. This situation is globally significant because 80% of the world's crayfish species are North American. Few studies have examined the environmental changes that most threaten crayfish biodiversity, but competition and hybridization with non‐native crayfis...