CUTTING EDGE INNOVATION: DISSECTING THE GENETIC BASIS OF A PLANT-PIERCING OVIPOSITOR IN AN HERBIVOROUS FLY

• Main Author: RAY, JULIANNE FLORENCE
• Other Authors: Whiteman, Noah K.
• Language: en_US
• Published: The University of Arizona. 2016
• Online Access: http://hdl.handle.net/10150/613574; http://arizona.openrepository.com/arizona/handle/10150/613574

The evolution of herbivory within an insect lineage is often enabled by novel morphological innovations. The ancestor of Scaptomyza flava developed a serrated ovipositor nearly six million years ago, associated with an evolutionary transition to herbivory, that allows these flies to cut into mustard plants deposit eggs into the wound. We aim to identify candidate genes associated with ovipositor peg development in S. flava using a genome-wide association study (GWAS). GWAS methods are only appropriate for heritable, variable traits. Dissection and photographic profiling of ovipositors from over 700 female flies revealed variation in the number of serrated pegs within natural populations. Mother-daughter profiling showed this variation was heritable (h2 = 46%). Peg number variation among individuals followed a normal distribution, suggesting multiple genes likely influence this trait. Sequencing genomes of pools of individuals with the most and fewest ovipositor pegs from two populations identified four candidate loci affecting ovipositor peg number in S. flava. Many of these loci contribute to neural development in Drosophila melanogaster, consistent with the hypothesis that ovipositor pegs are hardened, innervated bristles. Overall, this project sets the stage for understanding the genetic and developmental basis of a key evolutionary innovation – a leaf-cutting ovipositor – in herbivorous insects.