Acta Phytopathologica et Entomoligica 25. (1990)

1-4. szám - ECOLOGY - N. A. C. Kidd: Why is aphid flight density-dependent?

Acta Phytopathologica et Entomologica Hungarica, 25 /1-4/, pp. 105-112 /1990/ WHY IS APHID FLIGHT DENSITY DEPENDENT? N.A.C. Kidd School of Pure and Applied Biology, University of Wales, Cardiff, U.K. ABSTRACT This paper explores one possible reason why aphid populations commonly produce migrant alatae in a density dependent fashion, namely, that it may be the best strategy for maximising the number of migrants produced during the life of the colony. Evidence in support of this hypothesis was obtained using a simulation model of a generalized aphid population. On short-lived plants, the best density-dependent strategy produced about 50% more dispersants than the best density-independent one, with no greater net cost to the resident population. On longer-lived plants, such as trees, the advantage of density-dependence is removed where stable environmental conditions prevail, but returns when environmental variations induce fluctuations in aphid numbers. INTRODUCTION During spring and summer adult aphids generally appear in two parthenogenetically reproducing forms, winged alatae and wingless apterae. Apterous adults are usually produced when the number of aphids in a colony is low, while alatae are characteristic of densely populated colonies. Academiai Kiadó, Budapest

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