Wing Scale Morphology of a Sexually Dimorphic Color Pattern Element in the Butterfly Co-Mimics Heliconius melpomene and Heliconius erato
Moore, Megan Elizabeth
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Heliconius, a Neotropical genus of butterfly, has served as a model organism for the study of mimicry since the 19th century. Despite the extensive research conducted on this organism, very little is known about sexually dimorphic elements of their wing patterns. In this study, I examined the characteristics of the overlap band, an area of shiny, silvery/brown scales on the posterior ventral forewing and the anterior dorsal hindwing. Males and females are sexually dimorphic in regards to the length and breadth of the area covered by these scales. Males also have sex-specific, pheromone-releasing scales known as androconia within this region. In order to determine if sexual dimorphism existed on the level of the wing scales, beyond the presence or absence of androconia, I extensively sampled the overlap band of four specimens: a male and female from each of the co-mimics Heliconius melpomene and Heliconius erato. By analyzing the distributions of classes of scale shapes, I found strong trends in how scale shape changes across the overlap band. These trends, with variations, are present in both species, male and female, which raise questions about the control and organization of wing scale development in two relatively distant members of the genus.