Habitat quality and the reproductive strategies of the migratory morphs of the bird cherry-oat aphid, Rhopalosiphum padi (L.), colonizing secondary host plants
Emigrants and alate exules of Rhopalosiphum padi were kept on good and poor quality hosts. Alate exules on good hosts were more fecund than those on poor hosts. Host quality did not affect the fecundity of the emigrants. The number of ovarioles in the gonads of the emigrants varied from 10-16, alate exules from 4-10 and was not correlated with weight in either morph. On poor quality hosts the aphids with most ovarioles suffered the greatest mortality. There was no significant difference in the time of wing muscle autolysis of emigrants on good or poor hosts. However, alate exules on poor hosts retained their flight capability for longer than those on good hosts. On poor hosts alate exules retained their flight capability for longer than emigrants. It is concluded that the ability of alate exules to retain their flight capability for longer and reduce their reproductive rate when they colonize poor hosts is an adaptation to the generally poor habitat conditions this morph usually experiences compared with emigrants.
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