The fundamental and realized niches of a rare aquatic beetle in an extreme environment

Rare animals are difficult to study, but understanding their habitat preferences and comparative physiology is essential for conservation in the face of climate change. Extreme environments often have high proportions of rare species and low biodiversity. We challenge the notion that these species are physiologically adapted to such habitats. Hygrotus diversipes is a rare aquatic beetle known from Wyoming's intermittent streams. Little is known about the species despite multiple petitions for its listing under the US Endangered Species Act. These beetles experience harsh conditions like drought, flash floods, and high salinity. We hypothesized a disparity between H. diversipes’ fundamental and realized niches, suggesting the species selects for more extreme habitats to avoid negative biotic interactions, but experiences low fitness as a result. This disparity is concerning if rapid environmental changes outpace the beetles' limits.

Our study combined physiological experiments with habitat selection analyses to evaluate the beetle’s fundamental and realized salinity niches. We had a greater chance of detecting H. diversipes in habitats with conspecifics, higher salinity, lower pH, and greater species richness. In a controlled laboratory setting without biotic interactions, H. diversipes preferred fresher water and had lower long-term survival at high salinities. Understanding this rare species' physiological tolerances before climate change exacerbates these harsh habitats is crucial for species persistence. Insects in extreme environments are under-researched; conservation efforts should integrate habitat preferences and controlled physiological experiments to develop more comprehensive management strategies for threatened species facing climate change.