Temperature-dependent phenotypic plasticity in wing pattern of Utetheisa ornatrix bella (Erebidae, Arctiinae).

A. Sourakov

Abstract


Utetheisa ornatrix exhibits geographic and intrapopulational variability in wing pattern. Here, evidence is presented that temperature-dependent phenotypic plasticity exists in north Florida populations of the subspecies U. ornatrix bella. On six different occasions, experimental groups of late instar larvae and pupae were reared at lower temperatures (15-16°C) and short-day photoperiod, while control groups of sibling larvae were raised through to adult stage at 22°C. Resultant moths from the two groups had different wing pattern phenotypes. Increased melanization is the probable cause of the observed differences, as the cold-affected individuals had more extensive black markings on both surfaces of forewing and hindwing. Cold-induced melanization affected both wings simultaneously, in which it differed from normal genetic variation in melanic markings found in U. ornatrix, which inherits separately for fore- and hindwing. Additionally, cold-induced reduction of red/orange pigmentation on the upper forewing surface was sometimes observed. The expression of this phenotypic plasticity varied depending on the brood used in the experiment. Possible adaptive significance of cold-induced melanization in bella moth is discussed in the context of our knowledge of similar phenotypic plasticity found in many butterfly species.

Keywords


adaptation; reaction norm; polyphenism; polymorphism; Lepidoptera; thermal biology; camouflage; aposematism; bella moth; ornate moth; chemical ecology; melanin accumulation; seasonal forms

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