PATTERNS OF QUANTITATIVE VARIATION IN LEPIDOPTERAN WING MORPHOLOGY: THE CONVERGENT GROUPS HELICONIINAE AND ITHOMIINAE...

Wing morphology has historically been a major focus in taxonomic and evolutionary studies of lepidopterans. However, general patterns of quantitative variation and diversification in wing sizes and shapes and the factors underlying them have been unexplored. A morphometric study of wing variation in the convergent heliconine and ithomine butterflies reveals remarkable similarities, both in their morphologies at a given size and in their patterns of allometry and variability. The groups differ primarily in the relative lengths of inner and outer forewing margins, with larger species being more similar across groups than smaller ones. Allometric size-scaling variation accounts for more than 90% of the total morphological variation in the two groups and thus seems to be the major determinant of wing shape. Forewings and hind wings are isometric in size (area) with respect to one another; however, wing shape within and among groups is significantly allometric, resulting in considerable shape differences between small and large species. A strong trend of increasing variability from anterior to posterior along the wings is consistent with hypotheses of aerodynamic constraint. Wings and bodies represent classical morphological "character suites" in that size and shape variation are more tightly correlated within suites than among them. Such complexes argue against the overriding importance of aerodynamic factors, such as wing load and muscle development, in constraining gross morphology.