Date of Award

Spring 2021

Document Type

Open Access Thesis

Department

Biological Sciences

First Advisor

Carol Boggs

Abstract

Visual signals in the form of wing color, size, shape, pattern, and UV reflectance play an important role in the mating and reproductive strategies of diurnal butterflies. Wing-based visual signals are linked to different functions and can be acted on by a variety of selective pressures. In a comprehensive look at the literature on the visual communication strategies of lepidopteran species, I look at how visual signals, most notably color, are used, generated, and perceived. I discuss the costs and benefits of those strategies for the fitness of butterflies and moths and look at lepidopteran visual communication through the lens of life history and resource allocation. Previous dietary restriction studies in other species demonstrated that larval food stress affects adult morphological traits essential for lepidopteran visual communication. Gonzalez (2018) discovered differences in such traits in field collected Speyeria mormonia (Lepidoptera: Nymphalidae) across years that differed in drought stress. Here, I asked if the effects of larval nutrient stress on wing and eye morphology could explain the variation Gonzalez found. To address that question, I performed a larval starvation experiment, where S. mormonia in the 5th instar of larval development were divided into a control group, fed ad libitum, and a semi-starved, larval food stress treatment group. I measured adult wing length, spectral reflectance on three points of the wing, and facet number, facet area, and eye surface area. Larval food stress significantly decreased wing length and average facet area for both males and females, and only affected the dorsal wing reflectance of females, with treatment females having less red-shifted reflectance curves than control females. Females had longer wing lengths, while males had larger eye surface areas, more facets, bigger facets, and more red-shifted wing reflectance curves. The results reveal the presence of sex-specific resource allocation strategies and tradeoffs within Speyeria mormonia, with males favoring investment into their visual system and wing coloration and females investing more into their overall size. Also, results reveal the possibility of genetic heritability playing a role in the resource allocation strategies of this species.

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Biology Commons

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