Influence of temperature on reproductive biology and phenotype of a ladybird, Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae)

摘要

Body melanisation in insects is polygenic, resulting from genetic polymorphism or phenotypic plasticity, with diverse implications ranging from thermal budgeting to reproductive success. In this study, we assessed the, mate choice, reproductive success, and offspring colouration of typical (T) and melanic (M) morphs of the ladybird Menochilus sexmaculatus paired at three temperatures 15 degrees C, 25 degrees C and 35 degrees C. Mating success of the two morphs and the consequences for offspring fitness and offspring phenotype under these temperature regimes were evaluated. Melanic adults of both sexes achieved significantly higher mating success at 15 degrees C and 25 degrees C, but at 35 degrees C no influence of adult morph on mate selection was observed. Melanic females were more fecund than typical females at all temperatures. Offspring of melanic parents developed faster than those of typicals at 15 degrees C and 25 degrees C, but not at 35 degrees C. Evidence was also found of phenotypic plasticity in colour form at 15 degrees C and 35 degrees C. At 25 degrees C the parents of pure (T) and (M) morphs produced offspring of the same morph. However, low temperature induced partial melanisation among the offspring of typical parents (T). Whereas at 35 degrees C the offspring of (T) parents became paler in colour with very fine zigzag lines on elytra, i.e. they decrease the degree of melanisation. Pure melanics (M) compensated for elevated temperature stress by producing offspring that were either pure melanic but small or large with reduced melanisation. Our results on offspring phenotype variation indicate that the degree of melanism in morphs is a result of environmentally regulated expression of the parental genotype. (C) 2016 Elsevier Ltd. All rights reserved.