Abstract

Diatoms are important organisms in aquatic ecosystems due to their position as primary producers and, therefore, analyzing their communities provides relevant information on ecosystem functioning. Diatoms have been historically identified based on morphological traits, which is time-consuming and require well-trained specialists. Nevertheless, DNA barcoding approach offers an alternative to overcome some limitations of the morphological approach. Unfortunately, however, only a few studies have compared beta diversity patterns for both DNA barcoding and morphological approaches. Here, we derive a new take on this issue and assess the ecological mechanisms underlying spatial variation in epiphytic diatom metacommunities using a comprehensive dataset from 22 Mediterranean ponds at different taxonomic resolutions. Our results suggest a relatively poor correspondence in the compositional variation between morphology--based and molecular--based approaches. We speculate that the incompleteness of the reference database and the bioinformatics processing are the biases most likely related to the molecular approach whereas the limited counting effort and the presence of cryptic species are presumably the major biases related to morphological approach. On the other hand, we found that both approaches were strongly related to the environmental template, suggesting that epiphytic diatom communities were mainly controlled by species sorting at regional extents. Overall, this work suggests that both molecular and morphological approaches provide complementary information on diatom metacommunity organization and emphasizes the importance of DNA barcoding to addressing empirical research questions of community ecology in freshwaters.