# A Comparative Analysis of DNA Metabarcoding and Morphological Identification in Diatoms Reveals Similar Patterns of Environmental Response

## TL;DR

The study compares DNA metabarcoding and traditional morphological methods for identifying diatoms in high mountain mires, finding similar environmental patterns but differences in diversity estimates.

## Contribution

The study demonstrates that DNA metabarcoding and morphological identification yield similar environmental response patterns but highlights limitations in molecular methods for alpha diversity estimation.

## Key findings

- Beta diversity patterns from DNA metabarcoding and morphological identification strongly correlate.
- Molecular methods underestimate alpha diversity metrics like species richness and Shannon index.
- Environmental factors like pH, Mg, and temperature drive diatom community patterns in both methods.

## Abstract

Diatoms are widely used as environmental sentinels and are commonly studied through morphological identification. However, this method requires specialist knowledge, which is becoming increasingly scarce, resulting in species identification becoming costly, time‐consuming, and difficult. DNA metabarcoding offers an alternative method to semiautomate some identification processes to circumvent these difficulties, thus minimizing identification costs while providing objective and reliable information. However, discrepancies between marker genes and morphological identification remain unsolved. This study investigated the 66 diatom communities on 26 high mountain mires in the Pyrenees by identifying morphological species and sequencing the Cytochrome c oxidase I (COI) and 18S rRNA markers. We assessed whether morphological and molecular approaches reveal the same patterns of alpha and beta diversity. Our results showed a strong correlation between beta diversity patterns of diatoms obtained by morphological identification and genetic markers. In contrast, alpha diversity calculated through molecular studies underestimated species richness and the Shannon index. The diatom community was chiefly driven by pH, Mg, and temperature, reflecting these patterns in morphological and molecular data. DNA metabarcoding also proved to represent diatom community patterns and the roles of the environmental drivers as clearly as in morphological identifications in high mountain mire diatom communities.

This study compares the use of two universal molecular markers (COI and 18S rRNA) with morphological identification to evaluate patterns in diatom communities from high mountain mires. The results revealed a strong correspondence in beta diversity and environmental response across beta and alpha diversity. However, these molecular markers were found to be inadequate for achieving accurate taxonomic resolution and diversity assessment, as they tend to underestimate alpha diversity, which could potentially lead to misinterpretation of the data.