Comparison of sclerobiont communities between three brachiopod host species from the Upper Ordovician Fairview Formation, Eastern USA

Sclerobionts are organisms that encrust onto or bore into a hard substrate. They are valu-able sources of palaeoecological data as they often preserve the skeletonized portion ofin situ communities from which evidence of host-sclerobiont or sclerobiont-sclerobiontinteractions can be extracted. Sclerobiont data also provide useful information relatedto the life habits of their hosts. Although much work has been done on sclerobionts,those from the Ordovician are understudied. The sclerobiont communities on three bra-chiopod host species from the Ordovician Fairview Formation (Eastern United States),Rafinesquina alternata, Vinlandostrophia sp., and Hebertella occidentalis, were tested fordifferences in community structure and distribution using scores derived from PolarOrdination. The sclerobiont communities on R. alternata and Vinlandostrophia sp. showsignificant differences, and diversity indices show that Vinlandostrophia sp. hosted aless speciose and less diverse assemblage of sclerobionts. Bookstein shape coordinatelocation data show sclerobionts clustering near the hinge line of H. occidentalis, suggest-ing that encrustation occurred after the host’s death. Sclerobionts on Vinlandostrophiasp. clustered on the sides and avoided the central fold/sulcus, potentially because theywere utilizing the lateral inhalant current produced by a living Vinlandostrophia’s lopho-phore. The sclerobionts on R. alternata showed no clustering patterns, but the sclerobi-ont communities are different between the dorsal and ventral valves of this host. Theseresults demonstrate the importance of host identity and morphology to the structure ofsclerobiont communities. Some sclerobiont taxa may have preferred a living host at thetime of settlement.
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