Coevolution of post‐Palaeozoic arthropod basibiont diversity and encrusting bryozoan epibiont diversity?

Abstract

We hypothesize that the diversification of motile marine arthropods with hard carapaces resulted in a concurrent increase in the diversity of encrusting marine bryozoans whose larvae exploited those substrates through the Mesozoic and Cenozoic. To test this, family‐level data were tabulated from the literature on the post‐Palaeozoic diversity of motile marine arthropod basibionts and sessile marine bryozoan epibionts. We found strong temporal correlation from general to more specific basibiont‐epibiont relationships (i.e. arthropods and bryozoans in general to decapods and encrusting gymnolaemates to robust decapods and encrusting cheilostomes in particular). We compared the diversification of bryozoans to another common group of basibionts (i.e. molluscs) and found weaker correlations. This suggests that the diversification of motile arthropods with hard carapaces (e.g. brachyuran crabs) may have played a role in the diversification of sessile bryozoans (e.g. encrusting cheilostomes) in the post‐Palaeozoic.

Bryozoan Fouling of the American Lobster (Homarus americanus) Following the 1999 Die-Off in Long Island Sound, USA

“…Hard substrate space has been a limiting factor for bryozoans, especially encrusting bryozoans (Jackson 1977, Lidgard & Jackson 1989, McKinney 1995, Taylor 2016). Therefore, any increase in hard substrate space (e.g., motile host lobster) should have reduced competition for substrate space and increased bryozoan diversity as documented by Balazy and Kuklinski (2013) and Key and Schweitzer (2019). Living on a motile host provided the sessile bryozoans with free transport for avoiding predators, improved gamete dispersal, and increased geographic range.…”

“…By the end of the Cretaceous period, more epibionts (i.e., brachiopods, oysters, and serpulid worms) were fouling mecochirid, nephropid, palinurid, and pemphicid lobsters (Bishop 1981, 2016, Tshudy & Feldmann 1988, Robin et al 2016). The diversification of motile arthropods with hard carapaces (e.g., lobsters) played a coevolutionary role in the diversification of sessile bryozoans (e.g., encrusting cheilostomes) over the last 250 Myr (Key & Schweitzer 2019).…”