Reproductive Strategies of the Alate Morphs of the Bird Cherry-Oat Aphid Rhopalosiphum padi L.

Abstract

Emigrants have the greatest fecundity but do not reproduce for as long, or live as long as the smaller alate exules. Alate exules also live longer, reproduce longer and produce more offspring than the heavier gynoparae. Large emigrants and gynoparae do not live longer than small individuals of these morphs. In each morph large aphids are more fecund than small aphids. Gynoparae have the highest reproductive rate on the 1st day of adult life followed by the emigrants and then the alate exulex. By day 2 the emigrants have achieved the same reproductive rate as the gynoparae but the alate exules have a reproductive rate of only 63% of the other two. Emigrants contain more embryos with pigmented eyes than the gynoparae which contain more than the alate exules. Gynoparae only develop another 6% more embryos before dying; the emigrants and alate exules develop another 51 and 67%, respectively. The offspring of gynoparae are significantly lighter at birth than the offspring of emigrants and alate exules. The morph of the mother, i.e., whether apterous or alate, influences the weight of her offspring at maturity. Emigrants contain less fat than gynoparae and alate exules. The differences between the alate morphs are associated with seasonal changes in the aphids'' way of life.