Date of Award

5-1-2023

Degree Type

Thesis

Degree Name

Honors Thesis

Department

Biology

First Advisor

Andrew Stoehr

Second Advisor

Carmen Salsbury

Abstract

Dealing with the wide ranges of temperatures throughout the year can be a challenge for ectothermic animals like insects. Phenotypic plasticity, the development of different phenotypes depending on the environment, is one way that animals can combat this problem. However, traits are often integrated and share developmental or genetic mechanisms which can limit the adaptive response of an individual trait. Modules, groups of traits that vary together but are independent of other traits, often share developmental mechanisms and therefore can facilitate the evolution of these adaptive traits. The seasonally variable melanistic wing patterns elements of the Colias butterfly are an ideal model to study modularity because of their homologies and shared developmental requirement of the pigment, melanin. The seasonal variation of the ventral hindwing is adaptively advantageous for thermoregulation, but the variation of other melanistic traits has received far less attention. This goal of this project was to identify which melanistic traits vary seasonally and examine how they correlate with each other and with the ventral hindwing in Colias butterflies using statistical analyses. The results show that melanistic wing pattern elements are seasonally plastic and modular. Furthermore, these modules align with elements of the nymphalid groundplan. Because melanized basal trait elements show similar patterns of seasonal plasticity as the ventral hindwing, they may share its thermoregulatory function. Additionally, the potential underlying mechanisms of the seasonal plasticity and modularity of these melanistic wing pattern elements are discussed.

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