A phylogenetic classification of diatoms (Bacillariophyta)

Overview

Diatoms represent a morphologically diverse eukaryotic lineage characterized by silicified cell walls and constitute a dominant component of aquatic primary productivity. Traditional taxonomic frameworks spanning nearly two centuries have relied on morphological interpretation of silica wall architecture; however, molecular phylogenetic investigations have demonstrated substantial incongruence between these established classifications and evolutionary relationships. This work presents a comprehensive phylogenetic reclassification synthesizing contemporary molecular evidence with morphological data to establish a natural classification system.

Methods and approach

The classification was constructed by integrating recent advances in diatom phylogenomics and molecular systematics. The authors evaluated phylogenetic relationships across the Bacillariophyta and delimited monophyletic groups at multiple hierarchical levels. The resulting framework recognizes only clades supported by phylogenetic evidence, establishing explicit taxonomic ranks from genus through class. The classification encompasses 431 genera distributed across subordinate ranks, with formal nomenclatural designation of novel taxa where phylogenetic analyses support recognition of previously unrecognized lineages.

Key Findings

The proposed classification recognizes 10 classes, 44 orders, 68 families, and 431 genera. Seven classes, 13 orders, three families, and one genus are described as new taxa. The hierarchical structure demonstrates congruence with previous systematic frameworks in numerous instances; however, significant departures exist regarding class-level organization. Notably, morphologically defined groups historically treated as single classes, including centric diatoms and araphid diatoms, are resolved as polyphyletic assemblages. The revised classification recognizes these as multiple discrete classes, reflecting the actual diversity of lineages within these traditionally circumscribed groups.

Implications

The phylogenetic framework substantially revises the higher-order taxonomy of Bacillariophyta by reflecting evolutionary relationships rather than relying exclusively on morphological features. This reclassification provides a more robust foundation for comparative biological studies, as taxonomic units now correspond to genuine evolutionary lineages. Phylogenetic classification facilitates accurate inference of ancestral traits, enables rigorous assessment of character evolution, and supports investigation of ecological and functional diversity within appropriately circumscribed clades. Enhanced taxonomic precision strengthens interpretations regarding the evolutionary origins of morphological complexity and metabolic diversity in diatoms.

Scope and limitations

This summary is based on the study abstract and available metadata. It does not include a full analysis of the complete paper, supplementary materials, or underlying datasets unless explicitly stated. Findings should be interpreted in the context of the original publication.