Determining diagnostic characteristics of the nonmarine Ostracoda (Crustacea) and their habitat selection with unique functional traits in the Kastamonu province (Türkiye)

Nonmarine ostracods are widely distributed in a variety of aquatic habitats, from mountain lakes to underground waters, where each species tends to show species-specific habitat preferences with unique functional traits to increase their survival chances. To understand the patterns of such a relationship between habitat preferences and functional traits of the species, 101 different aquatic sites in the Kastamonu province (Türkiye) were randomly sampled during August 2023. A total of 39 ostracods (20 species, 19 unnamed taxa) were encountered from 49 sites. Seventeen species are new reports for the province. Among them, six species are the most common species with cosmopolitan (or cosmoecious) characteristics. The contribution of these species to the diversity of alpha species (p < 0.05) was more than 90 %. The species with relatively high ecological tolerances generally unveiled low-optimum estimates. Canonical correspondence analysis explained 62.5 % of the correlation between environmental variables and species in which redox potential, electrical conductivity, calcium, and pH were found to be the most related variables to the species (p < 0.05). Fundiversity analysis showed that the presence of swimming setae was correlated with high values of functional diversity, functional richness, and functional distribution of species among five elevation ranges. The results of the habitat selection index and the standardized selection index coincided with the functional traits of the most common species. The species characterized by their habitat selection can be considered as diagnostic species of those specific habitats. Among them, Neglecandona neglecta, reported primarily from dams, springs, and troughs, is considered a typical diagnostic species of these habitats, while Cypridopsis vidua found in lakes and dams can be used as an indicator species for these types of lentic habitats. Similarly, three species (Heterocypris incongruens, Ilyocypris bradyi, Psychrodromus olivaceus) can play a critical role as diagnostic species in troughs but reporting them from different habitats such as ditches and rivers / lakes (I. bradyi) and dams (P. olivaceus and H. salina) indicated their wide range of habitat preferences. Hence, the results suggest that the occurrence of diagnostic species seems to correspond to certain habitat types and their functional traits.