ABSTRACT
Freshwater crayfish occur in a wide variety of habitats. Comparison of how these habitats shape population structure can lead to a better understanding of crayfish evolution and diversification. Both biotic and abiotic factors impact species distributions, with different species responding differently to changes in habitat/climate. Crayfish inhabit streams, caves, lakes, or burrows and have a variety of physiological requirements associated with these habitats. Yet few studies have examined how these different habitats and physiological requirements impact population structure. In this study, population connectivity of a stream crayfish Procambarus spiculifer is compared to that of a tertiary burrowing crayfish, Procambarus paeninsulanus, using two mitochondrial genes, 16S and COI. Procambarus spiculifer is dependent on habitat with moving water with high oxygen content. The habitat requirements for Procambarus paeninsulanus are less stringent, and it can be found nearly anywhere water has pooled or periodically pools within its native range. Not only is P. spiculifer dependent on moving water with higher oxygen content, it also has a lower heat tolerance than P. paeninsulanus. These physiological attributes of P. spiculifer limit the amount of habitat that can support this species. In contrast, P. paeninsulanus has higher heat tolerance and lower oxygen requirements, which opens a wider range of available habitat. Comparing population connectivity of these species across the same geographic region allows us to examine how physiological attributes have affected the population structure of each species. We hypothesize that the species with the more stringent physiological needs, P. spiculifer, would have more population substructure resulting in less genetic diversity within subpopulations compared to among subpopulations. On the other hand, P. paeninsulanus, with fewer physiological constraints, would have less population structure and, therefore, more similar levels of genetic diversity both within and among subpopulations. Our genetic data support the hypothesis that physiological attributes have affected the population structure of these species, with the more physiologically constrained species showing greater population structure.
