Integrating genetic and morphometric data, a new study dismantles previous misconceptions about Ophiothrix angulata, revealing it as a species complex with significant cryptic diversity.

Ophiothrix angulata, a commonly found and widely studied ophiuroid species in the Western Atlantic, has been a subject of ongoing taxonomic debates due to its exceptional morphological diversity.

In a recent publication in the esteemed scientific journal PeerJ Life & Environment, a team of researchers from Universidad Nacional Autónoma de México, Universidad Católica del Maule, and Florida Natural History Museum has shed new light on the taxonomy of this species, leading to a significant breakthrough in the field.

With the goal of understanding species delimitation and geographical differentiation within O. angulata, the comprehensive study took an integrative approach.

Quetzalli Hernández, one of the study’s co-authors, emphasized the importance of this approach, stating, “We tried to unravel the genetic relationship between the various shapes and colorations of the arm in the ophiuroid species Ophiothrix angulata.”

Given its wide distribution across diverse latitudes and depths, this species has confounded taxonomists for nearly two centuries due to its plethora of colorations and subtle variations, which have perplexed alpha taxonomists relying solely on morphological characteristics.

To address this taxonomic challenge, they adopted an integrative approach, analyzing multiple types of genetic and morphological data separately before combining them.

By compiling extensive evidence and adhering to species definition criteria, they discovered that Ophiothrix angulata represents a species complex with concealed diversity, approximately delimited within large geographic regions. Although this task was undoubtedly challenging, it was equally exhilarating.

The study’s findings revealed remarkable insights into Ophiothrix angulata, which had long been recognized as a single species.

Hernández elucidated the discoveries, stating, “In the northwestern Atlantic distribution, we have identified two distinct genetic clades using the COI (mitochondrial) and ITS2 (nuclear) genetic markers.”

Significantly, this genetic differentiation aligns with the observed variations in ventral and dorsal arm plate shapes. By integrating genetic and morphometric data through comprehensive analyses, they accumulated substantial evidence supporting the existence of more than one species within the cryptic complex of Ophiothrix angulata. One of these genetic clades reveals that a group previously classified as O. angulata actually belongs to a newly discovered ophiuroid species.

Furthermore, an exhaustive analysis of arm coloration patterns scientifically demonstrated that coloration alone is an unreliable morphological characteristic for distinguishing the different genetic clades identified in this study. This finding holds immense significance for the O. angulata species complex, as it challenges the validity of subspecies described solely based on coloration patterns in the 19th century, which remain influential today.

The identification of multiple species within the Ophiothrix angulata complex highlights the crucial role of integrating diverse data types in taxonomic investigations. This breakthrough not only enriches our understanding of the species’ evolutionary history but also has implications for conservation efforts and management strategies.

The study marks a significant milestone in ophiuroid research, underscoring the value of interdisciplinary approaches. It opens up avenues for further exploration into the ecology, behavior, and distribution patterns of these newly identified species within Ophiothrix angulata.

Source: Florida Museum of Natural History & University of Florida

Image Credit: 10.7717/peerj.15655