Changes in Phylogenetic and Functional Diversity of Ciliates along the Course of a Mediterranean Karstic River

Ciliates are a group of phagotrophic protists found in a wide variety of ecosystems. This study builds on recent studies of ciliates in the Krka river and investigates changes in the phylogenetic and functional diversity of ciliates in biofilm to predict the phylogenetic and functional structure of ciliates in other karstic rivers. Biofilm samples were collected from four representative locations: upstream (Krka spring), midstream (Marasovine), and downstream (Roški slap, Skradinski buk) of the Krka river to test for differences in phylogenetic and functional diversity of ciliates in relation to location and positioning on tufa stones (light/dark-exposed side of tufa stone). Our results showed that Krka spring had higher phylogenetic species variability, lower phylogenetic diversity, and lower functional richness than Skradinski buk, suggesting phylogenetic overdispersal at Krka spring. This could be due to environmental filtering, competitive exclusion, or a combination of these factors. As the first study of its kind in the Mediterranean, our results shed light on the phylogenetic and functional diversity of ciliates in karst ecosystems and provide a basis for future ecological and conservation efforts.