Habitat quality and reproductive investment in aphids

Abstract

ABSTRACT. Genetically identical vetch aphids, Megoura viciae (Buckton), showed a weak but significant positive relationship between reproductive investment (number of ovarioles) and weight, here used as an indicator of habitat quality. Apterae reared on poor quality plants showed the same range in numbers (twelve to twenty‐two) but on average fewer ovarioles than those reared on high quality plants. The variability in ovariole number was determined prior to birth. Under constant conditions the age of a mother does not affect the range of ovariole numbers or the proportion of her offspring in each ovariole class. Apterae reared on poor quality host plants gave birth to proportionately fewer offspring with a high ovariole number than apterae reared on high quality plants. Winged individuals gave birth to proportionately more offspring with a high number of ovarioles than apterae. The control and ecological significance of the intramorph variation in reproductive tactics shown by many species of aphids is discussed in the light of these results.