Conservation biogeography of Headwater Catfish (Ictalurus lupus) in the United States

Authors: Stephanie George, Joshuah Perkin, Megan Bean, Dijar Lutz-Carrillo

Year: 2019

Abstract

Our aim was to review the conservation status of Headwater Catfish, Ictalurus lupus, in the United States with emphasis on Texas populations. Our status assessment included evaluating change in geographic distribution over time and measuring introgression and hybridization with Channel Catfish, Ictalurus punctatus, to inform conservation prioritization. We used machine learning methods (random forest and boosted regression tree) to construct species distribution models based on historical and contemporary presence-absence data using 13 environmental predictors based on remotely sensed stream network data. We measured introgression and hybridization with the widely introduced Channel Catfish using external morphology and molecular markers. The sub-basin (8-digit hydrologic unit code) from which collections were made was the most important predictor variable across all models. Species distribution models illustrated temporal shifts in Headwater Catfish occurrence. Historically, Headwater Catfish occurrence was higher among streams with steeper slopes, greater distances from spring outflows, broader ranges of annual precipitation, and with greater portions of the network catchment classified as water. These shifts are likely related to both range contraction of the species and temporal variation in sampling locations. Morphological and molecular data revealed four genetically pure and isolated locations where conservation of Headwater Catfish phenotypes and genotypes are likely to be most successful. Species distribution models provide critical assessments of where a species might persist, but they require careful validation and cannot account for genetic introgression. Combining targeted sampling efforts with locations highlighted by SDMs and genetic analyses can be used to promote systematic conservation planning for rare and threatened species.