Competition between encrusters on marine hard substrates and its fossil record

Abstract

Many animals and plants that colonize hard surfaces in the sea are sessile and either bore into, or cement themselves permanently to the substrate surface. Because they retain their life positions after fossilization, these sclerobionts offer scope for studying biotic interactions in the fossil record. Encrusting sclerobionts compete actively for living space, with dominant competitors overgrowing the edges of subordinates. In addition to such marginal overgrowths, spatial competition may also occur through fouling in which larvae recruit directly onto the living surfaces of established sclerobionts. Spatial competition has been studied extensively in modern marine communities but there has been little research on competition between encrusters in ancient communities. This reflects poor knowledge of the taxonomy of the sclerobionts involved, as well as problems in distinguishing between overgrowth in vivo and post-mortem. Nevertheless, if carefully interpreted, the fossil record of sclerobionts can provide an as yet largely unexploited resource for studying the long-term ecological and evolutionary dynamics of competition.

Size, weapons, and armor as predictors of competitive outcomes in fossil and contemporary marine communities

“…However, these post-mortem instances likely contribute to noise rather than signal, not least because we do not expect live colonies to discriminate the traits of dead colonies. As in Liow et al (2016Liow et al ( , 2017, we disregarded fouling (the settlement on top of an existing colony of a larva and its subsequent metamorphosis and growth to form a new colony), as this does not entail a marginal encounter and has a greater probability of occurring when the underlying colony is moribund or dead (Taylor 2016). Our data consist of 6,195 overgrowth battles among 82 cheilostome bryozoan species, where both partners in battles are identified to species level.…”

“…, Huntley and Kowalewski ), graze‐marks created by herbivores on leaves and other plant fossils (Labandeira , Labandeira and Currano ), and evidence of spatial overgrowth competition in benthic communities (Liow et al. , Taylor ), to document changing patterns of such interactions. The second is the use of phylogenetic hypotheses based on data from extant organisms to model diversity‐(in)dependent diversification (Rabosky ) or the evolution of traits that affect biotic interactions (Manceau et al.…”

“…). However, not only is there variation in the outcomes of such spatial competition not fully explained by zooid size, but other traits are also thought to affect spatial competition (Centurion and Gappa , Taylor ). Hence, in the current study, we model overgrowth interactions (termed battles hereon to avoid confusion with explanatory variable interactions) among 82 cheilostome bryozoan species in the Wanganui Basin of the North Island of New Zealand (Rust and Gordon ).…”

Alcyonacea awakens: Palaeobiology and palaeoecology of Palaeozoic octocorals known from their sclerites

“…Regarding the relationships between Syringopora and Termieralcyon , several observations and inferences can be performed: The sclerites were fixed to the coral when it was alive (syn‐vivo overgrowth, meaning a live–live interaction), although Alcyonacea could also grow over some dead parts of the coral (post‐mortem overgrowths), as evidenced by the occurrence of sclerites inside some calyces. The sclerites are attached to the surface of the coral, but they do not penetrate deeply into the wall, suggesting that there was no direct relationship between the soft tissues of the two organisms. The sclerites cover all or much of the external surfaces of the Syringoporoid skeleton. Because of this disposition, Young and Noble () and Tourneur et al () regarded the organism that produced the sclerites as an epibiont, that is, an organism that attaches itself to and lives on the surface of a substrate. Sclerobionts are usually considered harmless to their hosts, but in most cases, they compete actively for living space (Taylor, ). In our samples, and apart from some slight dissolution and some scarce evidence of malformations, skeletal pathologies or growth anomalies that could be related to the development of the sclerobiont have not been observed.…”

Uncovering the holes and cracks: from anecdote to testable hypotheses in predation studies

“…The profound impact of biological interactions in modern communities (both marine and terrestrial) is well known. While Taylor () reviewed the importance of competition between organisms, this contribution focuses on the importance of predatory interactions in the marine realm.…”