Ecological interactions on macroevolutionary time scales: clams and brachiopods are more than ships that pass in the night

Abstract

Competition among organisms has ecological and evolutionary consequences. However, whether the consequences of competition are manifested and measureable on macroevolutionary time scales is equivocal. Marine bivalves and brachiopods have overlapping niches such that competition for food and space may occur. Moreover, there is a long-standing debate over whether bivalves outcompeted brachiopods evolutionarily, because brachiopod diversity declined through time while bivalve diversity increased. To answer this question, we estimate the origination and extinction dynamics of fossil marine bivalve and brachiopod genera from the Ordovician through to the Recent while simultaneously accounting for incomplete sampling. Then, using stochastic differential equations, we assess statistical relationships among diversification and sampling dynamics of brachiopods and bivalves and five paleoenvironmental proxies. None of these potential environmental drivers had any detectable influence on brachiopod or bivalve diversification. In contrast, elevated bivalve extinction rates causally increased brachiopod origination rates, suggesting that bivalves have suppressed brachiopod evolution.

Sex and the shifting biodiversity dynamics of marine animals in deep time

“…If so, however, this increased biomass did not translate into elevated diversity. Increased predation and seafloor disturbance may have helped drive down the diversity and abundance of some taxa, such as brachiopods (67)(68)(69), although competition may also have been important (70), consistent with diversity dependence.…”

The Evolution of Brachiopoda

“…However, two particular examples require mention: competition with bivalved molluscs and body size evolution. Because both bivalves and brachiopods have two valves, they are often assumed to occupy the same ecological niche, but in fact they do not now and have never really done so (although see Liow et al 2015). Some overlap exists, but bivalves are much more diverse in their feeding behavior and mode of life, and although it might be possible to argue that brachiopods are therefore inferior competitors, no competition for food or space in a particular location or habitat has been clearly documented.…”

Getting somewhere with the Red Queen: chasing a biologically modern definition of the hypothesis

“…We diverge from this proposal as this set of conditions is probably unachievable, because a period of constancy of any potential abiotic factors is virtually absent from the geological record [14]. Another challenge to evaluating the RQH is that biotic and abiotic factors can interact to drive macroevolution [54,55], making it hard to differentiate primary biotically driven evolution from secondary biotically driven evolution instigated by abiotic forcing. Because of these challenges, here we focus on an alternative method to assess the validity of the RQH sensu Van Valen [1].…”