Evolution of brachiopod symbiosis in the early Paleozoic

ABSTRACT

The evolution of brachiopod symbiosis is closely tied to the evolution of brachiopod faunas and their partner groups during the early Palaeozoic. Brachiopod groups with a larger number of taxa had more symbiotic associations, and there was no specific group that was more prone to symbiosis during this time interval. The first symbiotic associations appeared soon after the emergence of certain brachiopod groups, with Cambrian brachiopods partnering with typical representatives of the Cambrian fauna. Bryozoans and tentaculitoid tubeworms, which became important partners during the Ordovician and Silurian, first diversified in the Ordovician. The gradual decrease in the number of brachiopod partner groups from the Cambrian to the Silurian was likely due to specialisation. However, the number of symbiotic associations did not increase faster than the number of brachiopod taxa. The GOBE-induced diversification of brachiopod taxa did not lead to an escalation in symbiotic relationships. Symbiotic associations involving brachiopods continued after the end-Ordovician mass extinction. Although early Palaeozoic brachiopods were vulnerable to kleptoparasites, the harm caused by these parasites was not enough to drive their associated brachiopods to extinction.

KEYWORDS:

• Brachiopods
• symbiosis
• encrustation
• borings
• bioclaustrations
• cambrian
• ordovician
• silurian

Acknowledgments

We are grateful to G. Baranov, Department of Geology, Tallinn University of Technology for digital photographing of some figured specimens. This paper is a contribution to the IGCP project 653 ‘The Onset of the Great Ordovician Biodiversification Event’ and the IGCP project 735 ‘Rocks and the Rise of Ordovician Life’. O.V. was supported by a research grant from the Institute of Ecology and Earth Sciences, University of Tartu, and a Sepkoski Grant, Paleontological Society. Lars Holmer’s work was supported by a grant from the Swedish Research Council (VR 2018-03390). We are grateful to two anonymous reviewers for their constructive comments on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Institute of Ecology and Earth Sciences, University of Tartu [Research Grant]; Paleontological Society [Sepkoski Grant].