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.