The Evolutionary Ecology of Biotic Association in a Megadiverse Bivalve Superfamily: Sponsorship Required for Permanent Residency in Sediment

Peter Middelfart,Keith A. Crandall,Diarmaid Ó Foighil,Jingchun Li

doi:10.1371/journal.pone.0042121

Peter Middelfart, Keith A. Crandall + Show 2 more

Open Access

https://doi.org/10.1371/journal.pone.0042121

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Abstract

BackgroundMarine lineage diversification is shaped by the interaction of biotic and abiotic factors but our understanding of their relative roles is underdeveloped. The megadiverse bivalve superfamily Galeommatoidea represents a promising study system to address this issue. It is composed of small-bodied clams that are either free-living or have commensal associations with invertebrate hosts. To test if the evolution of this lifestyle dichotomy is correlated with specific ecologies, we have performed a statistical analysis on the lifestyle and habitat preference of 121 species based on 90 source documents.Methodology/Principal FindingsGaleommatoidea has significant diversity in the two primary benthic habitats: hard- and soft-bottoms. Hard-bottom dwellers are overwhelmingly free-living, typically hidden within crevices of rocks/coral heads/encrusting epifauna. In contrast, species in soft-bottom habitats are almost exclusively infaunal commensals. These infaunal biotic associations may involve direct attachment to a host, or clustering around its tube/burrow, but all commensals locate within the oxygenated sediment envelope produced by the host’s bioturbation.Conclusions/SignificanceThe formation of commensal associations by galeommatoidean clams is robustly correlated with an abiotic environmental setting: living in sediments (). Sediment-dwelling bivalves are exposed to intense predation pressure that drops markedly with depth of burial. Commensal galeommatoideans routinely attain depth refuges many times their body lengths, independent of siphonal investment, by virtue of their host’s burrowing and bioturbation. In effect, they use their much larger hosts as giant auto-irrigating siphon substitutes. The evolution of biotic associations with infaunal bioturbating hosts may have been a prerequisite for the diversification of Galeommatoidea in sediments and has likely been a key factor in the success of this exceptionally diverse bivalve superfamily.

Highlights

One of the classic questions in biology concerns the mechanisms that control the generation and maintenance of planetary biodiversity [1]
The Red Queen model [2,3] states that biotic factors play major roles in shaping lineage diversification, while the Court Jester model [4] places more emphasis on abiotic factors
Our result establishes that formation of commensal associations by galeommatoidean clams is robustly correlated with living in sediments (Pv0:001)

Summary

Introduction

One of the classic questions in biology concerns the mechanisms that control the generation and maintenance of planetary biodiversity [1]. The Red Queen model [2,3] states that biotic factors play major roles in shaping lineage diversification, while the Court Jester model [4] places more emphasis on abiotic factors Both sets of drivers operate on different spatial and temporal scales [4], they clearly play off each other [5] and their relative importance remains an active area of contention in fundamental biodiversity research [6,7,8]. To test if the evolution of this lifestyle dichotomy is correlated with specific ecologies, we have performed a statistical analysis on the lifestyle and habitat preference of 121 species based on 90 source documents

Methods

Results

Conclusion