Biological invasions cause significant economic and ecological damage, representing the second greatest threat to biodiversity. Once introduced, non-native species can alter natural communities and result in considerable economic losses to the aquaculture industry.

One group often introduced to new regions is the sea squirts, also known as ascidians. As our closest invertebrate relatives, ascidians are often utilized as models to study chordate development and evolution. Despite their ecological and evolutionary importance, identifying ascidian species remains a challenge as morphological differences are often microscopic and the DNA barcode commonly used in animals cannot always easily define ascidian species.

Finding a new reliable set of DNA regions will allow researchers to accurately identify ascidian species and address important questions in invasive species spread and chordate evolution. In particular, microbial symbionts appear to play a significant role in the evolution of chordate hosts.

We are developing new molecular markers from across the nuclear genome and the ascidian tree of life to benefit the entire ascidian research community, which currently relies on limited markers with variable resolution for phylogenetics and species identification. We will apply these novel markers to create the first catalog of ascidian diversity in artificial (harbor) and natural (reef and mangrove) Belizean habitats. This inventory will not only extend and update our knowledge of ascidian biodiversity and distribution along the Mesoamerican Barrier Reef System, but will also document the prevalence of introduced ascidian species, and provide identification based on integrated molecular and morphological data for over 40 species never sequenced before. We are also characterizing ascidian microbiomes and map variation in structural (taxonomic groups) and functional (specific gene) features across the ascidian tree of life to provide insight into the role of microbial symbionts in ascidian evolution.

By combining traditional morphology with newly developed molecular markers, then applying this integrative approach to introduced species identification and the investigation of microbial symbiosis as a driver of ascidian evolution, results obtained here will significantly advance our understanding of ascidian diversity and phylogenetics, biological invasions, and chordate evolution.

Work funded by the National Science Foundation (NSF) under Grant No. DEB-2122475. PIs: Drs. Lauren Stefaniak, Marie Nydam, Patrick Erwin and Susanna Lopez-Legentil.