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Switching in the Parasitoid Nasonia Vitripennis and Its Effects on Host Competition
Author(s) -
Cornell Howard,
Pimentel David
Publication year - 1978
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1936375
Subject(s) - nasonia vitripennis , parasitoid , biology , host (biology) , parasitoid wasp , population , competition (biology) , ecology , pteromalidae , zoology , demography , sociology
Switching behavior of the parasitoid wasp Nasonia vitripennis was investigated for its effects on the competitive outcome of 3 fly host species, Phormia regina, Phaenicia sericata, and Musca domesticia, interacting in laboratory ecosystems. The investigation was carried out in 2 stages: (1) examination of factors which altered Nasonia's innate preference for each host species when hosts were offered in pairwise combinations, (2) examination of the effect of Nasonia's attack pressure on host competitive outcome. In stage (1), Nasonia showed a strong innate preference for P. regina (4.45:1) when offered with M. domestica, a weak innate preference for P. regina (1.41:1) when offered with P. sericata, and a weak innate preference for P. sericata (2.71:1) when offered with M. domestica. In all 3 tests, Nasonia's preference for a given host was increased if Nasonia had a previous feeding experience on that host. In the switching tests, Nasonia concentrated its attacks on the most abundant host as its ratio in the diet increased from 1:7 to 7:1. Both strong and weak preference combinations showed similar switching effects. Increasing parasitoid density was found to obscure gradually the expression of switching. At maximum parasitoid densities the parasitoid population became host limited, and all host individuals were attacked regardless of host ratio offered. In stage (2), parasitoid host interaction systems were established with Nasonia attacking the 3 competing host species. Under some conditions, Nasonia attack pressure can induce a reversal of dominance in the competitive outcome, but stable coexistence between the host species was not achieved in these tests. The results of these investigations partly confirm previous conclusions about switching and partly expand the switching concept to include more situations.