50 Shades of Red:
An analysis of biodiversity in the nudibranch genus Goniobranchus
By: Lynn Bonomo
Coral reefs are biological hotspots of the marine environment, with the most biodiverse reefs occurring in the Indo-Pacific Coral Triangle. Recent expeditions to the most biodiverse area of the Coral Triangle have discovered over 300 new marine species, including at least 70 new species of nudibranchs, an extremely diverse group of sea slugs. Nudibranchs are the one of the most diverse molluscs, with a wide range of colors and feeding behaviors. These adaptations allow them to defend, reproduce, and to live in disparate ecosystems. Phylogenetic analysis of the diversity of color and movement in nudibranchs allow a reconstruction of how convergent or divergent evolutionary processes lead to the diversity seen today. However, the number of nudibranch species is unknown due to cryptic species, making it difficult to compare diversification among different families of nudibranchs without doing genetic studies.
In the last several years, the family tree of Chromodorididae has been undergoing refinement due to molecular work, indicating new relationships between taxa. The genus Goniobranchus is one clade of the Chromodorididae and used to be included within Chromodoris. Chromodoris was determined to be non-monophyletic and Goniobranchus was separated out. Since separation, molecular work to resolve the internal relationships in Goniobranchus has not been undertaken and over half of the proposed species in this genus are still undescribed. My goals are to create a molecular phylogeny with morphological support, to refine this phylogeny with egg types and larval development, and to analyze whether certain behaviors and color variations are predominantly a behavioral adaptation to the habitat or are genetically determined. Through genetic sequencing, we have sequenced 151 Goniobranchus specimens representing 39 previously defined species. We have used two mitochondrial (COI and 16s) genes and one nuclear gene (H3) to begin to resolve the genetic relationships between Goniobranchus species. Next steps include adding morphological analyses of each species of nudibranchs and starting to look at egg types and larval development of Goniobranchus. Through genetic sequencing and morphological analysis, I can elucidate the evolutionary history of Goniobranchus by determining the emergence of particular morphological characteristics.