Diatoms are microalgae, known to present several characteristics that
make them excellent bioindicators. In this study, we analyzed the
epiphytic diatom communities of shallow lakes, with the aim of exploring
the genetic variability explained by physical, chemical or geographical
variables. We selected 77 lakes within the Spanish part of the Duero
River Basin characterized by wide chemical variability. In each lake,
physical parameters were measured in situ and water samples were taken
to determine nutrient levels in the laboratory. Diatom communities were
collected and identified by both microscopy and DNA-metabarcoding,
amplifying a genetic barcode of rbcL gene. We analyzed the phylogenetic
signal for several environmental parameters at the genus level for the
three most representative genera of these lakes. Our results indicate
significant phylogenetic signals that differ from a genus to another.
Processes related to spatial scales appear to be the main predictors
controlling the genetic diversity of diatom communities in these ponds,
with genetic variants deffering among geographical areas for a given
species. These molecular studies confirm the enormous diversity present
in the diatom communities that inhabit these ecosystems, but further
research is needed to apply diatom-based techniques in shallow lakes
monitoring or conservation programs. Our results reinforce the view that
considering not only morphological but also molecular and ecological
characters is necessary to describe new diatom species, especially given
the high number of species described each year.