Direct vs. inclusive fitness in the evolution of aphid cornicle length

By comparing the relative sizes of anatomical structures among phenotypes, selective pressures that shape species' morphologies can be evaluated. Aphids emit droplets containing an alarm pheromone/defensive secretion from unique anatomical structures called cornicles, upon being attacked. As ap...

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Bibliographic Details
Published in:Journal of evolutionary biology 2007-03, Vol.20 (2), p.807-812
Main Authors: MONDOR, E.B, MESSING, R.H
Format: Article
Language:English
Subjects:
Adaptation, Physiological
alarm pheromone
Animal Communication
Animals
Aphididae
Aphids - anatomy & histology
Aphids - classification
Aphids - physiology
Biological Evolution
Female
Flight, Animal
Homoptera
kin selection
Male
Phenotype
Phylogeny
polyphenism
predation risk
Selection, Genetic
Species Specificity
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Summary:By comparing the relative sizes of anatomical structures among phenotypes, selective pressures that shape species' morphologies can be evaluated. Aphids emit droplets containing an alarm pheromone/defensive secretion from unique anatomical structures called cornicles, upon being attacked. As aphids live in colonies of high relatedness, it is uncertain whether direct or inclusive fitness benefits have chiefly promoted cornicle evolution. Morphological measurements for apterous parthenogen, alate parthenogen, female sexual and male sexual morphs of 43 species (21 genera, one subfamily) were assessed to distinguish between the hypotheses that: (1) cornicles evolved for mechanical defence against natural enemies (direct fitness); (2) cornicles evolved for alarm signalling (inclusive fitness); or (3) cornicle length has been largely constrained by flight aerodynamics. Our results generally support the inclusive fitness hypothesis; cornicle length decreases as the relative number and relatedness of offspring decreases. As cornicle length is greatest in apterous parthenogenetic morphs, inclusive fitness benefits of protecting highly related kin may have been a key factor selecting for cornicles, and increased cornicle length, in aphids.
ISSN:1010-061X
1420-9101
DOI:10.1111/j.1420-9101.2006.01271.x