Date of Award

Summer 8-5-2017

Degree Type

Dissertation/Thesis

Department

Biological Sciences

Faculty Advisor

Dr. Markus Friedrich

Abstract

Insects of the order Diptera are a popular biological model for understanding morphological trait evolution. One area of particular interest is the development of the compound eyes. While the development of ommatidia and photoreceptors has been thoroughly studied in this case, little attention has been paid to the interommatidial bristles (IOBs) present on the eyes of some dipteran families. A preliminary survey suggested that these bristles exhibit high variability among IOB families on multiple taxonomic levels and are not uniformly present or absent in any suborder of the Diptera. To confirm this observation, I conducted a literature search to quantify how many dipteran families uniformly possessed IOBs, lack IOBs, or include species with both trait states. This effort revealed a slight bias towards lack of IOBs in the Diptera. Parsimony and maximum likelihood ancestral state reconstructions showed that IOBs are likely to have been present on the eyes of early dipteran ancestors, despite the bias towards lack of IOBs in the extant families. The absence of IOBs is therefore speculated to be the result of frequent evolutionary losses. Finally, the comparison with the 371 other previously studied traits suggests that IOBs have experienced the highest number of loss events among known fly traits.

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