Posted by: oikosasa | January 25, 2013

Surf and Turf 1

Yesterday, Randi Rotjan and Josh Idjadi introduced us to the Surf and Turf concept. Today, Howard V. Cornell gives a short background to his and Susan P. Harrison’s Surf and Turf paper “Regional effects as important determinants of local diversity in both marine and terrestrial systems”:

When Josh Idjadi and Randi Rotjan organized the Surf and Turf Symposium at the 2009 meeting of the Ecological Society of America, it was immediately clear that they had identified an important problem. Marine and terrestrial ecologists do not always follow each others’ work, and as a result, there is not enough cross-fertilization of ideas derived from the study of these two realms. When Josh and Randi invited Susan Harrison and me to participate in the symposium, it forced us to think hard about how large-scale biogeographic  and evolutionary processes affect the species diversity in marine vs. terrestrial communities. Because of differences in dispersal between atmospheric and aquatic media, the ease of identifying marine vs. terrestrial species pools, and the historical development of marine and terrestrial community ecology, marine ecologists have placed more emphasis on the importance of large-scale effects on community structure than terrestrial ecologists. Nevertheless, it became clear to us upon reflection that large-scale processes are important in both realms but such processes are studied in different ways. We were grateful for the opportunity afforded by the symposium to look at this issue more deeply and as a result, have come to a clearer understanding of the general importance of examining different spatial scales when trying to understand ecological patterns. Below is a short summary of our paper.

s&t1bs&t1Terry Hughes

One apparent difference between marine and terrestrial ecology is that the influence of regional processes on local populations and communities is better established in the marine literature. We examine three potential explanations: 1) influential early studies emphasized local interactions in terrestrial communities and regional dispersal in marine communities. 2) regional-scale processes are actually more important in marine than in terrestrial communities. 3) recruitment from a regional species pool is easier to study in marine than terrestrial communities. We conclude that these are interrelated, but that the second and especially the third explanations are more important than the first. We also conclude that in both marine and terrestrial systems, there are ways to improve our understanding of regional influences on local community diversity. In particular, we advocate examining local vs. regional diversity relationships at localities within environmentally similar regions that differ in their diversity either because of their sizes or their varying degrees of isolation from a species source.

s&t1

Figure: Scenarios for propagule supply in marine and terrestrial systems. (a) In marine systems, habitats are immersed in a homogeneous surrounding medium containing propagules of many species with few dispersal barriers, many of which pass through the fitness filter and are able to recruit to the habitat. (b) In terrestrial systems, topography and environmental heterogeneity erect larger dispersal and fitness barriers to arriving propagules and ‘seed banks’, confound arriving propagules with those already present in the habitat.

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