Restructuring higher taxonomy using broad-scale phylogenomics: The living Ophiuroidea.

Area of Science:

• Marine invertebrate biology
• Evolutionary biology
• Phylogenetics
• Taxonomy

Background:

• Next-generation sequencing (NGS) advances understanding of life's evolution and classification.
• Ophiuroids (brittle stars) represent a diverse class of marine invertebrates with an incompletely understood higher classification.

Purpose of the Study:

• To construct a robust phylogeny of living ophiuroids.
• To revise the higher classification of ophiuroids based on phylogenetic data.
• To establish a new taxonomic framework for the class Ophiuroidea.

Main Methods:

• Utilized an exon-capture system to generate a large DNA data-matrix (1484 exons, 273kbp).
• Sequenced DNA from 576 ophiuroid species, achieving an average of 90% target sequence recovery.
• Employed phylogenetic distinctiveness and temporal-banding to guide classification revisions, setting a family crown age limit of 110±10 million years ago.

Main Results:

• Generated a comprehensive phylogeny of living ophiuroids, robust to variations in sampling and analytical methods.
• Node age estimates showed considerable imprecision (approx. 25% variation).
• The revised classification resulted in 32 families and six orders, expanding the number of higher taxa.

Conclusions:

• The new classification scheme provides a more accurate representation of ophiuroid evolutionary history.
• The revised ophiuroid taxonomy is generally widespread globally, with some families restricted to specific latitudes or depths.
• This work establishes a new benchmark for ophiuroid classification, integrating molecular data with evolutionary timescales.