Ecological characteristics of the freshwater Ostracoda in Bolu Region (Turkey)

Abstract

Total of 40 ostracod taxa obtained from 141 different sampling locations in Bolu were examined to determine relationships between habitat preferences of species and their ecological characteristics from June to August 2006. According to the first axis of Canonical Correspondence Analysis (CCA), 52% of the relationships between species and five most influential environmental variables with 36.2% of variances were explained. Although the first four variables, air temperature, water temperature, pH, and electrical conductivity had significant influence (P < 0.05) on species composition, the effect of dissolved oxygen (P = 0.47) was relatively low. Spearman correlation analyses indicated that some species had weak to strong positive correlation with electrical conductivity, whereas some others had a significant negative correlation with pH and redox potential. Only two species (Herpetocypris chevreuxi and Ilyocypris inermis) had strong correlation to the habitat type (P < 0.05). Unweighted Pair-Group Method using Arithmetic averages (UPGMA) clustered species into four groups based on their occurrences. Species with cosmopolitan characteristics displayed higher tolerances to environmental variables than noncosmopolitans or rare species. Indeed, four cosmopolitan species (Heterocypris incongruens, I. bradyi, Candona neglecta, and C. candida) had high Environmental Tolerance Index (ETI) values for at least six different environmental variables. Thus, cosmopolitans are highly adaptable within a wide range of environmental conditions and geographical distribution.