PhD: Unravelling early teleost relationships: diversification at the dawn of the most successful fish radiation

Project Highlights:
- Teleost fishes are a staggeringly diverse and abundant group that include 99% of the more than 30,000 living species of ray-finned fishes: nearly half of all bony fish diversity.
- Focussed study on exceptionally preserved fossils will improve our understanding of relationships leading to the living radiation
- Using this revised hypothesis of relationships as a backbone, new insights can be gained into patterns of evolution and diversification at the dawn of this hugely successful group

Overview:
With over 30,000 living species ubiquitous in all aquatic environments, teleost ray-finned fishes represent the largest living vertebrate group. This hugely successful radiation, familiar to us from the fishmonger and aquarium and comprising everything from cod to bream and seahorses to goldfish, is of vast scientific, economic and ecological importance. Despite an abundance of exceptional three-dimensional fossils, the anatomy of the early members of this exceptionally important group is poorly constrained. Compounding this is a series of conflicting hypotheses of relationships between and within a range of groups thought to branch just outside of the living teleost radiation. These fossil assemblages display high levels of taxonomic diversity and morphological disparity, offering a rather neglected source of anatomical data with intrinsic links to ecological signal. CT scanning techniques will be used to target key representatives of these radiations in order to resolve questions of phylogenetic affinity, clarifying the morphological innovations leading to the living teleost radiation. Quantifying morphological change in inner ear structure in these lineages has the potential to provide insight into patterns of diversification and ecological expansion. A firm hypothesis of relationships among stem and early crown teleosts will provide a framework upon which to examine macroevolutionary patterns such as biogeographic dispersal. This research will answer fundamental questions concerning the origin of half of vertebrate life, providing new insights into the driving factors underlying the staggering diversity of teleosts.

Methodology:
This project will use a variety of techniques in order to investigate early teleost evolution in a synthetic manner. Specimen description will be carried out mostly through computed tomography (CT) scanning, which allows the internal and external anatomy to be investigated in a non-destructive manner. Key taxa will be targeted for CT scanning, with supplemental anatomical data provided by traditional descriptive techniques where CT scanning is not feasible. These anatomical data will be used to revise our understanding of relationships on the teleost stem through a range of phylogenetic methods, including maximum parsimony and Bayesian analysis. Quantitative methodology will be used to investigate broader patterns of evolution. Landmarking of segmented CT scans and 3D geometric morphometrics will be used to quantify patterns of morphological evolution within the group. Databasing methods will be used to collect occurrence, stratigraphic and environmental data, which will be interrogated to understand patterns of biogeographic dispersal.

Training and skills:
The student will be trained in CT scanning and segmentation, comparative anatomy and description, systematics and phylogenetic techniques (including parsimony and Bayesian analyses), database construction and comparative biology. The student will also receive training in how to write and illustrate scientific papers, apply for grants and prizes, present work at conferences and scientific meetings, and network with peers and other scientists. There may also be opportunities for undergraduate teaching and research supervision. These form the basis of an outstanding skill set, combining traditional and state- of-the-art techniques, that will facilitate a successful research career for an outstanding student.

Partners and collaboration:
This project will be carried out in collaboration with the Natural History Museum, London. Dr Zerina Johanson will provide additional supervision. The collections at the NHM represent a world-leading resource, with exceptionally preserved material that is of key importance to this project. Dr Johanson has extensive experience of CT scanning and anatomical interpretation and will assist the student in these areas.

Possible timeline:
Year 1: Literature review, CT scanning and segmenting, database construction.
Year 2: Comparative anatomy, phylogenetic analysis, database analysis.
Year 3: Morphospace analysis, synthesis, completing thesis, writing manuscripts (although manuscripts will be written throughout project).

Further reading:
Arratia, G. (2013). ‘Morphology, taxonomy, and phylogeny of Triassic pholidophorid fishes (Actinopterygii, Teleostei)’, Journal of Vertebrate Paleontology, 33 (sup1), 1–138. https://doi.org/10.1080/02724634.2013.835642.
Friedman, M. (2015). ‘The early evolution of ray‐finned fishes’, Palaeontology, 58 (2), 213–228. https://doi.org/10.1111/pala.12150.
Giles, S., Rogers, M. and Friedman, M., (2016). ‘Bony labyrinth morphology in early neopterygian fishes (Actinopterygii: Neopterygii)’, Journal of Morphology, 279 (4), 426–440. https://doi.org/10.1002/jmor.20551.
Giles, S., Xu, G. H., Near, T. J., & Friedman, M. (2017). Early members of ‘living fossil’ lineage imply later origin of modern ray-finned fishes, Nature, 549 (7671), 265–268. https://doi.org/10.1038/nature23654.
Sallan, L. C. (2014). Major issues in the origins of ray‐finned fish (Actinopterygii) biodiversity, Biological Reviews, 89 (4), 950–971. https://doi.org/10.1111/brv.12086.