A population-level approach investigating sea slug species in the genus Julia

The genus Julia is a group of Sacoglossan heterobranch sea slugs belonging to the family Juliidae (E.A. Smith, 1885), which is composed of morphologically unique gastropods possessing bivalve shells. Several species of Julia have unusually large, pan-Pacific geographic ranges, stretching from the Hawaiian Islands to East Africa. The taxonomy of Julia was traditionally investigated using shell morphological characteristics, and more recently improved by incorporating molecular and internal anatomical data. Based on these data, McCarthy (2017) conducted a phylogenetic analysis of Julia that revealed the existence of three possible new species within Julia. In this project I will examine the geographic structure of species of Julia using a population-level approach, and investigate the degree of genetic variation between and within populations using CO1 and 16S primers designed specifically for the genus Julia in addition to the universal primer for the nuclear gene H3. I will investigate the demographic characteristics of populations and estimate the amount of gene flow that is maintained among species with large distributions. I expect to identify the three candidate species as well as research the existence of a species complex, both essential in constructing a more conclusive taxonomy.