Abstract

Fireflies are some of the most captivating organisms on the planet. Because of this, they have a rich history of study, especially concerning their bioluminescent and visual behavior. Among insects, opsin copy number variation has been shown to be quite diverse. However, within the beetles, very little work on opsins has been conducted. Here we look at the visual system of fireflies (Coleoptera: Lampyridae), which offer an elegant system in which to study visual evolution as it relates to their behavior and broader ecology. They are the best-known case of a terrestrial organism that communicates through the use bioluminescence. The molecular basis for this communication is relatively simple: one gene-family (opsins) controls the detection of the signal, and one gene family (luciferase) controls the production of the signal. We use a transcriptomic approach to sample for and investigate opsin evolution in fireflies. We also present the first total evidence approach using both an extensive molecular matrix and a robust morphological matrix to reconstruct the lampyrid phylogeny. We then use this phylogeny to assess the hypothesis that adult use of bioluminescence occurred after the origin of Lampyridae. We find evidence for only two expressed opsin classes in each of the nine firefly species studied, one in the ultra-violet sensitive and one in the long-wavelength sensitive areas of the visible spectrum. Despite the need for most adult fireflies to respond to a clearly sexual and colorful visual signal (bioluminescence) to maximize fitness, their visual system is relatively simple, and does not match the trend for opsin duplication found in other insect groups. All subfamilies except for Lampyrinae are recovered as monophyletic; Pterotinae and Ototretinae are recovered within the Lampyridae. The ancestral state of adult bioluminescence is suggested to be non-bioluminescent, with at least three gains and at least three losses.

Degree

College and Department

Life Sciences; Biology

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