Competition in benthic marine invertebrates: the unrecognised role of exploitative competition for oxygen

Authors: Nick Ferguson, Craig R White and Dustin J Marshall

Published in: Ecology, volume 94, issue 1 (January 2013) doi: 10.1890/12-0795.1

Abstract

Competition is a ubiquitous structuring force across systems, but different fields emphasize the role of different types of competition.

In benthic marine environments, where some of the classic examples of competition were described, there is a strong emphasis on interference competition: marine invertebrates are assumed to compete fiercely for the limiting resource of space. Much of our understanding of the dynamics of this system is based on this assumption, yet empirical studies often find that increases in density can reduce performance despite free space being available. Furthermore, the assumption that space is the exclusively limiting resource raises paradoxes regarding species coexistence in this system.

Here, we measure the availability of oxygen in the field and in the laboratory, as well as the tolerance of resident species to low-oxygen conditions.

We show that oxygen can be the primary limiting resource in some instances, and that exploitative competition for this resource is very likely among benthic marine invertebrates. Furthermore, growth form (and the associated risk of oxygen limitation) covaries with the ability to withstand oxygen-poor conditions across a wide range of taxa.

Oxygen availability at very small scales may influence the distribution and abundance of sessile marine invertebrates more than is currently appreciated. Furthermore, competition for multiple resources (space and oxygen) and trade-offs in competitive ability for each may promote coexistence in this system.

Full paper

Ferguson N, White CR, Marshall DJ (2013) Competition in benthic marine invertebrates: the unrecognised role of exploitative competition for oxygen. Ecology, 94(1) 126–135 PDFPDF 311 KB 311 doi: 10.1890/12-0795.1

Advantages and disadvantages of interference-competitive ability and resource-use efficiency when invading established communities

Authors: Simon P Hart and Dustin J Marshall

Published in: Oikos, volume 121, issue 3, doi: 10.1111/j.1600-0706.2011.19557.x

Abstract

Invaders into established communities must overcome low resource availability. To establish, invaders must either appropriate resources from existing individuals through interference competition or efficiently use the small amount of resource that remains. Although both strategies may be important, they are rarely considered together and, in particular, resource-use efficiency is often ignored in systems dominated by interference competition.

To identify the traits that confer invasion success, we experimentally invaded resource patches in established communities with multiple species from two functional groups that differ in interference competitive ability and resource-use efficiency.

In contrast to previous assessments, we show that resource-use efficiency can facilitate invasion in systems dominated by interference competition. Furthermore, large resource requirements can be a liability when establishing because interference competition is inherently costly and so cannot fully compensate for limitations in the primary resource.However, we also show that there is a tradeoff in performance among functional groups between small and large resource gaps.

Our results suggest we modify the way we view and manage species invasion in systems dominated by interference competition.

Full paper

Hart SJ, Marshal DJ (2012) Advantages and disadvantages of interference-competitive ability and resource-use efficiency when invading established communities. Oikos, 121: 396–402 PDFPDF 132 KB doi: 10.1111/j.1600-0706.2011.19557.x