Distribution, co-occurrence, and habitat characteristics of non-marine ostracods (Crustacea) in lentic and lotic waters of Eskişehir province, Türkiye

This study sought to examine the co-occurrence patterns and ecological traits of ostracod species in Eskişehir province. During the period of July 11–17, 2020, a total of 118 sampling sites were surveyed, and 36 ostracod species were collected from 94 sampling sites. Of these, 24 species were newly reported for the province. With the addition of the 20 previously known species, the total number of ostracod species in the area has increased to 44. The most influential ecological variables on species occurrences identified by Canonical Corresponding Analysis (CCA) were elevation, nitrite, and pH. The first two axes of CCA explained about 51% of the relationships between the species abundance and the environmental variables investigated. Species co-occurrence test showed different patterns based on habitat types in the area. Accordingly, Potamocypris arcuata co-occurred with Heterocypris salina , and Ilyocypris bradyi co-occurred with Herpetocypris intermedia and Prionocypris zenkeri across the entire sampled area. However, H. salina and I. bradyi were generally found together in the lentic waters while P. zenkeri was found with I. bradyi in the lotic habitats. According to the C2 analysis, which uses weighted averaging regression, the ecological tolerance levels of some species appeared to differ between lentic and lotic habitats, except for a few cosmopolitan species. Results suggested that cosmopolitan species tend to co-occur in a variety of habitats due to their similarities in functional characteristics. This observation can be useful in determining typical habitat characteristics of species both in contemporary and paleontological studies.