Evolutionary history and sex are significant drivers of crayfish demography in resource-limited cave ecosystems

Abstract

Obligate and facultative cave species both play significant functional roles in cave ecosystems. Unlike obligate cave species, facultative cave species can persist in habitats both within and outside of caves. However, no comparative demographic model explaining the sustained presence of both obligate and facultative cave species has been provided. We developed a multi-state capture–mark–recapture (CMR) analysis based on 5 years of data collected from caves in northern Alabama, USA to explore differences in survival and reproductive transition probabilities between obligate (Orconectes australis and Cambarus hamulatus) and facultative (C. tenebrosus) cave crayfish. Multi-state CMR analyses revealed that male obligate cave species showed significantly higher rates of transitioning to a reproductive state than male C. tenebrosus, while no differences among species were observed for females. Transitioning into a non-reproductive state, however, was higher for obligate cave species regardless of sex. Apparent survival rates between cave obligates and C. tenebrosus did not differ, suggesting that the larger population sizes of obligate cave species within our study sites may be driven by more successful male reproductive strategies. Our results suggest that obligate cave crayfishes have evolved unique sex-specific reproductive strategies not shared by C. tenebrosus that likely represent a specialized adaptation to the cave environment. Conversely, persistent immigration by surface populations is likely crucial for the sustained presence of facultative species within cave environments.