The evolution of alternative morphs: density-dependent determination of larval colour dimorphism in a butterfly
2009 (English)In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 98, no 2, 256-266 p.Article in journal (Refereed) Published
Understanding the ultimate causes for the presence of polymorphisms within populations requires knowledge of how the expression of discrete morphs is regulated. In the present study, we explored the determination mechanism of a colour dimorphism in larvae of the butterﬂy Pararge xiphia (Satyrinae: Nymphalidae) with the ultimate aim of understanding its potential adaptive value. Last-instar larvae of P. xiphia develop into either a green or a brown morph, although all individuals are invariably green during the preceding three instars. A series of laboratory experiments reveal that morph development is strongly environmentally dependent and not the result of alternative alleles at one locus. Photoperiod, temperature, and in particular larval density, all inﬂuenced morph determination. The strong effect of a high larval density in inducing the brown morph parallels other known cases of density-dependent melanization in Lepidopteran larvae. Because melanization is often correlated with increased immune function, this type of determination mechanism is expected to be adaptive. However, the ecology and behaviour of P. xiphia larvae suggests that increased camouﬂage under high-density conditions may be an additional adaptive explanation. We conclude that the colour dimorphism of P. xiphia larvae is determined by a developmental threshold that is inﬂuenced both by heredity and by environmental conditions, and that selection for increased immune function and camouﬂage under high-density conditions may be responsible for maintaining the dimorphism. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 256–266.
Place, publisher, year, edition, pages
2009. Vol. 98, no 2, 256-266 p.
developmental threshold, melanization, morph, nymphalidae, pararge, plasticity, polymorphism, polyphenism, satyrinae, threshold trait.
Research subject Animal Ecology
IdentifiersURN: urn:nbn:se:su:diva-31115DOI: 10.1111/j.1095-8312.2009.01290.xISI: 000269801100002OAI: oai:DiVA.org:su-31115DiVA: diva2:275278
ProjectsThe evolution of developmental plasticity in insects