Presenter Information

Stephanie ParkerFollow

Presentation Type

Presentation - Campus Access Only

Abstract

In many butterfly species, males and females often differ in striking ways. Sexual dimorphism in body size and shape, coloration, behavior, physiology, and life history traits evolve when natural selection or sexual selection acts differently on males and females. The Squinting Brown-Bush butterfly (Bicyclus anynana) is one such example with females larger than males. Additionally, this species is phenotypically plastic - the temperature experienced during larval development will determine the adult phenotype. During the warm, wet, season, these males and females are short-lived, colorful, and active. During the cool, dry, season both sexes are long-lived, cryptically-colored, and inactive. Regardless of the season, the females are always larger than the males. The mating system differs dramatically between the two seasons: in the wet season, males actively court females and females are choosy; in the dry season, females actively court males and males are choosy. Here, we examine the extent of, and differences in, sexual dimorphism of wing size and shape between seasons. Two laboratory populations of B. anynana, originally from Malawi, were reared in 18°C and 27°C, typical temperatures of the two seasonal environments. Approximately 800 eggs were reared at each temperature through adult emergence, for a total of about 400 adult males and 400 adult females. I conducted a geometric morphometric analysis of the wings by identifying homologous landmarks on the forewings and hindwings based on vein-vein intersections, vein-margin junctions and color pattern landmarks. With these data, we are exploring the differences in wing size and shape between the sexes across different temperatures to better understand the relationship between sexual dimorphism and the forms of natural and sexual selection shaping female and male life history and behavior within each seasonal environment.

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Life Sciences

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Apr 15th, 9:20 AM Apr 15th, 9:40 AM

Phenotypic Plasticity & Sexual Dimorphism of the Squinting Brown-Bush Butterfly (Bicyclus anynana)

In many butterfly species, males and females often differ in striking ways. Sexual dimorphism in body size and shape, coloration, behavior, physiology, and life history traits evolve when natural selection or sexual selection acts differently on males and females. The Squinting Brown-Bush butterfly (Bicyclus anynana) is one such example with females larger than males. Additionally, this species is phenotypically plastic - the temperature experienced during larval development will determine the adult phenotype. During the warm, wet, season, these males and females are short-lived, colorful, and active. During the cool, dry, season both sexes are long-lived, cryptically-colored, and inactive. Regardless of the season, the females are always larger than the males. The mating system differs dramatically between the two seasons: in the wet season, males actively court females and females are choosy; in the dry season, females actively court males and males are choosy. Here, we examine the extent of, and differences in, sexual dimorphism of wing size and shape between seasons. Two laboratory populations of B. anynana, originally from Malawi, were reared in 18°C and 27°C, typical temperatures of the two seasonal environments. Approximately 800 eggs were reared at each temperature through adult emergence, for a total of about 400 adult males and 400 adult females. I conducted a geometric morphometric analysis of the wings by identifying homologous landmarks on the forewings and hindwings based on vein-vein intersections, vein-margin junctions and color pattern landmarks. With these data, we are exploring the differences in wing size and shape between the sexes across different temperatures to better understand the relationship between sexual dimorphism and the forms of natural and sexual selection shaping female and male life history and behavior within each seasonal environment.