Resource tracking in aphids: programmed reproductive strategies anticipate seasonal trends in habitat quality |
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Authors: | A F G Dixon R Kundu |
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Institution: | (1) School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK Fax: 01603 592250; e-mail: a.f.dixon@uea.ac.uk, GB;(2) Department of Entomology, Institute of Postgraduate Studies in Agriculture, PO IPSA, Salna, Gazipur, Bangladesh, BD |
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Abstract: | Most aphids show cyclical parthenogenesis, have short generation times and complete several generations each season. Two
hypotheses have been proposed to account for the adaptive seasonal trends observed in the reproductive strategies of aphids.
Firstly, individuals of each generation modify their reproductive strategy in direct response to the conditions they experience
during their development. Secondly, the reproductive strategies of the different generations are to a large extent programmed
and anticipate seasonal trends in habitat quality. These hypotheses were tested by rearing individuals of three generations
of the host-alternating willow-carrot aphid, Cavariella aegopodii, on both willow and carrot. This revealed that the way this aphid allocates resources to gonads and lipid reserves is independent
of an aphid's weight and the host plant on which it is reared. In addition each generation shows a specific relationship between
offspring size and adult size, which tends to keep the absolute investment in individual offspring relatively constant from
generation to generation, inspite of the big differences in adult size between generations. That is, through programmed allometric
engineering aphids anticipate the predictable seasonal trends in habitat quality and so more closely track their resources,
investing relatively more in gonads when food quality is high and relatively more in lipoidal reserves when food quality is
poor.
Received: 25 August 1997 / Accepted: 19 October 1997 |
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Keywords: | Body size Cavariella aegopodii Gonad size Habitat quality Lipoidal reserves |
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