Inter‐hemispheric comparison of bottom‐up effects on community structure: Insights revealed using the comparative‐experimental approach

Abstract

The comparative‐experimental approach uses identically designed, replicated experiments at different sites along environmental gradients in order to gain insight into the changing dynamics of communities with changing environmental conditions. Such studies reveal how ecological processes vary in intensity and interact to produce community structure. Early emphases were on the community consequences of shifting top‐down impacts, competition and disturbance with environmental stress. Recent advances include the more precise quantification of gradients and thus a better understanding of species responses to the environment, and the revelation that bottom‐up forces can vary significantly on within‐region scales, with major consequences for the impact of top‐down forces and thus community dynamics. Here the use of the method to examine the role of geographic location (coastal ecosystems in different hemispheres) and oceanographic conditions (upwelling vs downwelling) on these bottom‐up/top‐down linkages is advanced. We show that a bottom‐up factor (prey recruitment) and a top‐down effect (predation rate) vary consistently with oceanographic conditions within each coastal ecosystem, and also between geographic locations (New Zealand, Oregon). In general, both recruitment and predation rates are higher in Oregon. It is postulated that these differences are common responses to oceanographic variation, and that between‐hemisphere differences result from the stronger and more persistent upwelling in the California Current ecosystem.

Comparative Ecology of North Atlantic Shores: Do Differences in Players Matter for Process?

“…Indeed one of the few comparative ecological studies across the Atlantic demonstrated the strong effects of productivity in mediating the effects of consumers on local diversity (Worm et al 2002). Despite the recognition of the importance of productivity there have been few attempts to relate larger-scale patterns in community structure to inter-regional differences in productivity (but see Bustamante et al 1995, Menge et al 2002, Worm et al 2002. Global images of ocean color show consistent areas of high and low pelagic productivity along the coastlines of America and Europe, but no clear overall differences between the two regions (images available online).…”

Scientific families: Dynasty

“…Lubchenco and Menge wanted to probe other environmental impacts on coastal ecosystems, and so began a decades-long world tour that took Paine's experimental approaches to Chile, South Africa and New Zealand. Their studies showed 4 , for example, that the intermittent upwelling of nutrient-rich water can intensify competition, predation and other interactions between marine species.…”

Variability and community organization in moderately exposed tropical rocky shore algal communities as influenced by different consumer groups

“…This experiment was therefore started to examine micro and medium scale variability of grazing and the influence of slow moving and fast moving consumers in tropical rocky shore algal communities at Cape d' Aguilar and Stanley shores, Hong Kong. It is hoped that by separating the effects of different consumer groups using the comparative experimental approach (Dayton 1971;Menge 1986a;Menge 1999;Menge et al 2002) this will help us identify the major groups of consumers and species that can directly or indirectly impact the settlement, growth and distribution of algae. This approach allows us to directly compare sites, shores and treatments over a large area and to generalize results to similar shores.…”