Factors Structuring the Biogeography of Cosmopolitan and Endemic Crayfishes

Crayfishes are important components of aquatic biodiversity, with species distributions and abundances influenced strongly by competition and habitat quality.  Spatial influences on crayfish distributions, such as stream connectivity, may be locally mediated by habitat- and competition-induced species sorting, patch dynamics, and stochastic demographic processes.  We hypothesized that observed distributions of endemic crayfishes will be more influenced by local stream characteristics relative to other species, and that connectivity will be an important explanation for both endemic and cosmopolitan species distributions.  To address these hypotheses, we will perform a stratified probabilistic survey of crayfishes in five major Louisiana watersheds, focusing on three endemic species:  Orconectes hathawayi hathawayi, O. h. blacki and O. maletae.  We will trap and electrofish 10 streams in each watershed to collect relative abundance and alpha diversity data.   We will also examine stream characteristics, including land development (commercial, agricultural, and non-industrial forest), vegetation cover, geographical connectivity, stream depth, water quality, substrate type, habitat heterogeneity, and evidence of local anthropogenic disturbance, and compare the variability of these characteristics to crayfish diversity and abundance.  Results of this study will be collated into species distribution maps that will update lacking literature on Louisiana crayfish distributions for state land and aquatic conservation agencies.