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Host genotype affects the relative success of competing lines of aphid parasitoids under superparasitism


Vorburger, C; Eugster, B; Villiger, J; Wimmer, C (2010). Host genotype affects the relative success of competing lines of aphid parasitoids under superparasitism. Ecological Entomology, 35(1):77-83.

Abstract

1. In solitary parasitoids, only one individual can complete development
in a given host. Therefore, solitary parasitoids tend to prefer unparasitised hosts for
oviposition, yet under high parasitoid densities, superparasitism is frequent and results
in fierce competition for the host’s limited resources. This may lead to selection for
the best intra-host competitors.
2. Increased intra-host competitive ability may evolve under a high risk of
superparasitism if this trait exhibits genetic variation, and if competitive differences
among parasitoid genotypes are consistent across environments, e.g. different host
genotypes.
3. These assumptions were addressed in the aphid parasitoid Lysiphlebus fabarum
(Hymenoptera: Braconidae: Aphidiinae) and its main host, the black bean aphid, Aphis
fabae (Scopoli) (Hemiptera: Aphididae). Three parthenogenetic lines of L. fabarum
were allowed to parasitise three aphid clones singly and in all pairwise combinations
(superparasitism). The winning parasitoid in superparasitised aphids was determined
by microsatellite analysis.
4. The proportions of singly parasitised aphids that were mummified were similar
for the three parasitoid lines and did not differ significantly among host clones.
5. Under superparasitism, significant biases in favour of one parasitoid line were
observed for some combinations, indicating that there is genetic variation for intra-host
competitive ability. However, the outcome of superparasitism was inconsistent across
aphid clones and thus influenced significantly by the host clone in which parasitoids
competed.
6. Overall, this study shows that the fitness of aphid parasitoids under superparasitism
is determined by complex interactions with competitors as well as hosts,
possibly hampering the evolution of improved intra-host competitive ability.

Abstract

1. In solitary parasitoids, only one individual can complete development
in a given host. Therefore, solitary parasitoids tend to prefer unparasitised hosts for
oviposition, yet under high parasitoid densities, superparasitism is frequent and results
in fierce competition for the host’s limited resources. This may lead to selection for
the best intra-host competitors.
2. Increased intra-host competitive ability may evolve under a high risk of
superparasitism if this trait exhibits genetic variation, and if competitive differences
among parasitoid genotypes are consistent across environments, e.g. different host
genotypes.
3. These assumptions were addressed in the aphid parasitoid Lysiphlebus fabarum
(Hymenoptera: Braconidae: Aphidiinae) and its main host, the black bean aphid, Aphis
fabae (Scopoli) (Hemiptera: Aphididae). Three parthenogenetic lines of L. fabarum
were allowed to parasitise three aphid clones singly and in all pairwise combinations
(superparasitism). The winning parasitoid in superparasitised aphids was determined
by microsatellite analysis.
4. The proportions of singly parasitised aphids that were mummified were similar
for the three parasitoid lines and did not differ significantly among host clones.
5. Under superparasitism, significant biases in favour of one parasitoid line were
observed for some combinations, indicating that there is genetic variation for intra-host
competitive ability. However, the outcome of superparasitism was inconsistent across
aphid clones and thus influenced significantly by the host clone in which parasitoids
competed.
6. Overall, this study shows that the fitness of aphid parasitoids under superparasitism
is determined by complex interactions with competitors as well as hosts,
possibly hampering the evolution of improved intra-host competitive ability.

Citations

3 citations in Web of Science®
3 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Uncontrolled Keywords:Aphis fabae, genotype-by-genotype interaction, Hamiltonella defensa, Lysiphlebus fabarum, parasitoids, superparasitism, symbiosis.
Language:English
Date:2010
Deposited On:24 Jan 2010 11:25
Last Modified:05 Apr 2016 13:45
Publisher:Wiley-Blackwell
ISSN:0307-6946
Additional Information:The definitive version is available at www.blackwell-synergy.com
Publisher DOI:https://doi.org/10.1111/j.1365-2311.2009.01159.x

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