Dominance and Diversity Maintenance in an Oceanic Ecosystem

Abstract

1-bstract . . Disturbance-pe~urbation, dispersal-reaction, and contemporaneous disequilibrium are Simi~a: theon~s used ~o explam the maintenance of species diversity in communities. These theories explicitly pre.dict that m patches, on certain time-space scales, there should be substantial shifts in the ?rder of s~ecies domi~ance. There is good evidence that these theories may explain species coexistence m terrestnal and manne systems of sessile organisms. We have tested this set of theories in a mobile pelagic system by examining the order of dominance of copepod species in samples separated in time a~d space, collected from "='30 min to 16 yr apart, and from hundreds of metres to thousands of k.ilometr~s ~pai_t. We cou~d not detect significant changes among the samples in rank order or in p~rcent simrlanty of spe~Ies abundance on any time scale, or on any space scale up to "='800 km, either when all 175 species or when only the 30 most abundant were considered. There was smallscale, mesoscale, seasonal, and interannual heterogeneity in physical properties during the time we ~ade ~ur measurements. Although the theories are satisfactory explanations of diversity maintenance m .sessile syst~m~, our results fail to validate them in our mobile pelagic system. Because there were episodes of significant physical variability and because of the long-term species equilibrium and constanc~ of dominance, we believe our highly diverse community to be resilient and robust, rather than fragrle_. Th~ regulatory forces are strong and almost certainly biological, rather than physical, but we cannot Identify them.

A multivariate approach to large‐scale variation in marine planktonic copepod diversity and its environmental correlates

“…The latitudinal distribution of modeled copepod diversity reflected the high diversity values already reported around 20-30uN globally (Rombouts et al 2009) and in the South Atlantic anticyclonic gyre (Piontkovski et al 2003). High diversity in oligotrophic regions has been related to a complex network of biological interactions (McGowan and Walker 1985;Piontkovski et al 2003). Low food resource availability for copepods in oligotrophic regions could result in competition for resources and hence, if species are to coexist in a community, efficient division of resources would be essential.…”

Cytometric diversity in marine ultraphytoplankton

“…It remains to be considered whether phytoplankton communities are governed by similar principles. In the copepod (McGowan and Walker 1985) and phytoplankton (Venrick 1990) communities of the central North Pacific, the observational evidence does not indicate that comparable mechanisms are operative (McGowan and Walker 1993). Experimental work is lacking.…”

“…Moreover, future cytoscales at which the plankton were sampled. McGowan and metric descriptions could be extended beyond properties Walker (1993) remarked that diversity patterns are most measured here; and the importance of cells could be rated clearly delineated at large climatic scales where habitat feaby other criteria, for example the cellular rate of photosynthesis (Li 199417).…”

“…The concept of biotic diversity is a central theme in community ecology, both in general (Pielou 1975;Magurran 1988) and in particular for marine communities (Frontier 1985;McGowan and Walker 1993). Diversity embodies two notions: richness, which indicates the number of different kinds of organisms; and evenness, which indicates the relative "importance" (e.g.…”

Spatial dependence of calanoid copepod diversity in the North Atlantic Ocean

“…Examination of a global scale map of planktonic foraminera diversity (Rutherford et al 1999) and maps of eddy kinetic energy (Stammer & Wunsch 1999, Ducet et al 2000 does not visually show a strong link in subtropical and equatorial areas. The central gyre of the North Pacific, which is characterised by high diversity (McGowan & Walker 1985, McGowan 1990, has a low average eddy kinetic energy (Ducet et al 2000). Thus, the link between diversity and eddy kinetic energy is not likely to be true at a global scale but may be a characteristic of the northern North Atlantic Ocean pelagic ecosystems.…”