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Title:Developmental timing of pupation and analysis of color pattern response to thermal stress in Bombus impatiens (Hymenoptera: Apidae)
Author(s):Dean, Charles-Antoine Edouard
Advisor(s):Cameron, Sydney A.
Department / Program:Entomology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Mullerian mimicry
color pattern
Abstract:Bumble bees comprise a genus of approximately 250 species that exhibit high diversity in color pattern phenotypes, colony sizes, and habitats across the globe. Nearly two centuries of research have investigated the biological factors leading to their widespread distribution and ecological adaptability. As purported members of Müllerian mimicry complexes, the evolution of divergent and convergent color patterns within and among species appears to play an important role in bumble bee speciation. Distantly related species that share a common geographic range sometimes converge on similar aposematic coloration to presumably increase the efficacy of learned predator avoidance. However, the extent to which other selective pressures affect color pattern evolution remains largely untested. Temperature is an important environmental component known to impact the development rate, metabolism, and color pattern formation of many insects. As yet, the extent to which environmental temperatures affect the physiological development underlying color pattern phenotypes in bumble bees is unknown. To that end, I examined thermal stress on late instar larvae to determine whether developmental temperatures alter adult color pattern phenotypes. I selected a species that is monomorphic in color pattern, Bombus impatiens, and demonstrated that individuals are able to withstand a wide range of temperatures and retain their characteristic adult color pattern. In performing this experiment, I found that the developmental staging of bumble bee pupation had not been properly characterized. A biologically accurate description of bumble bee life stages was needed for the testing of color pattern response to developmental temperatures. I therefore analyzed histological changes throughout pre-adult development to determine the onset and duration of pupation. I analyzed epidermnal cellular activity and structural changes in the overlying cuticle, both dissected from the first and second metasomal tergites of Bombus impatiens, throughout development and showed that pupation begins roughly two days after silk-spinning and lasts approximately 40 hours prior to the onset of pharate adulthood. I found that the length of pupation is much shorter than previously maintained delimitations of this developmental stage. Ultimately, I both quantified the pupal stage and demonstrated that color pattern development appears to be resistant to thermal stress in Bombus impatiens. Future experimentation should determine if these results are consistent across polymorphic bumble bee species.
Issue Date:2016-07-14
Rights Information:Copyright 2016 Charles-Antoine Dean
Date Available in IDEALS:2016-11-10
Date Deposited:2016-08

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