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Apparent competition leaves no detectable imprint on patterns of community composition: observations from a natural experiment
Author(s) -
KAARTINEN RIIKKA,
ROSLIN TOMAS
Publication year - 2013
Publication title -
ecological entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.865
H-Index - 81
eISSN - 1365-2311
pISSN - 0307-6946
DOI - 10.1111/een.12048
Subject(s) - biology , herbivore , competition (biology) , ecology , parasitism , parasitoid , abundance (ecology) , food web , population , predation , host (biology) , demography , sociology
Indirect interactions mediated by natural enemies shared among herbivorous insects have recently attracted much interest. While many studies have predicted a high potential for apparent competition, only a few have rigorously tested predictions derived from the food web structure in terms of realised population and community dynamics. In this study, a quantified food web was used to identify pairs of herbivore species potentially tied by strong parasitoid‐mediated interactions. The host populations and their parasitism rates over two consecutive years were then followed, during which time the abundance of one dominant host crashed. Following this natural experiment, imprints of asymmetrical, long‐term apparent competition among hosts were sought in population growth rates. The population growth revealed no signs of apparent competition as mediated by parasitoids: the abundance and parasitism rates of less abundant herbivores were uncorrelated with the relative growth rate of four dominant herbivore species with which they shared a major part of their parasitoids. Likewise, the population crash of the dominant herbivore, Cynips longiventris , did not detectably affect the abundances or parasitism rates of other herbivores with which it shared a major fraction of its parasitoids. Overall, this case study fails to add evidence to previous suggestions that apparent competition may constitute a major force in structuring natural communities. However, it suggests that dynamics should not be inferred from static food web structure alone, but rather that predictions based on structure should be verified by empirical observations of realised population dynamics.