Date of Award

Summer 8-1-2024

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

Lauren Stefaniak

Second Advisor

Michelle Barthet

Third Advisor

Erin Burge

Additional Advisors

Marie Nydam

Abstract

Ascidians are our closest invertebrate relatives and comprise nearly 3,000 species separated into three orders: Aplousobranchia (most speciose), Stolidobranchia, and Phlebobranchia (least speciose). Ascidians can be classified as either solitary or colonial organisms. Species delimitation using morphological characters alone has had varied results. Well known, widely distributed, morphological species have turned out to be catch all species comprised of several cryptic species. Molecular markers can help mitigate some of the issues presented by strictly using morphological observations, including resolving the status of cryptic species, and accessing the expert knowledge required to identify a species. By incorporating molecular markers and pairing them with morphological observations, more species may be correctly identified by the scientific community. This project focuses on comparing the utility of the molecular markers mitochondrial cytochrome oxidase 1 (mtCO1) and 18S rRNA, both commonly used to barcode marine invertebrates, in terms of successfully delimitated species within families. Members of the ascidian families Ascidiidae, Pyuridae, and Styelidae were collected from Belize in July 2022 and July 2023 and were sequenced for CO1 and 18S and identified using morphological techniques. Additional sequences were obtained from GenBank. Species delimitation methods used for this project include Assemble Species by Automatic Partitioning (ASAP) and Bayesian Poisson Tree Process (bPTP). Morphological identifications tended to line up well when using CO1 with ASAP while 18S and ASAP lumped species together. bPTP tended to split species relative to morphological identifications for both genes. Future work includes implementation of the Bayesian input of bPTP into this analysis to see how it compares alongside ASAP. In addition to this, morphological identification of the Belizean samples down to the species level will also be completed.

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