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An empirical examination of consumer effects across twenty degrees of latitude
Author(s) -
Lavender James T.,
Dafforn Katherine A.,
Bishop Melanie J.,
Johnston Emma L.
Publication year - 2017
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1002/ecy.1926
Subject(s) - latitude , empirical examination , ecology , geography , environmental science , biology , economics , geodesy , classical economics
The strength and importance of consumer effects are predicted to increase toward low latitudes, but this hypothesis has rarely been tested using a spatially consistent methodology. In a consumer‐exclusion experiment spanning twenty degrees of latitude along the east Australian coast, the magnitude of consumer effects on sub‐tidal sessile assemblage composition was not greater at low than high latitudes. Across caged and control assemblages, Shannon's diversity, Pielou's evenness, and richness of functional groups decreased with increasing latitude, but the magnitude of consumer effects on these metrics did not display consistent latitudinal gradients. Instead, latitudinal gradients in consumer effects were apparent for individual functional groups. Solitary ascidians displayed the pattern consistent with predictions of greater direct effects of predators at low than high latitude. As consumers reduced the biomass of this and other competitive dominants, groups less prone to predation (e.g., hydroids, various groups of bryozoans) were able to take advantage of freed space in the presence of consumers and show increased abundances there. This large‐scale empirical study demonstrates the complexity of species interactions, and the failure of assemblage‐level metrics to adequately capture consumer effects over large spatial gradients.

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