Date of Award

5-2017

Culminating Project Type

Thesis

Degree Name

Biological Sciences - Ecology and Natural Resources: M.S.

Department

Biology

College

College of Science and Engineering

First Advisor

Matthew Davis

Second Advisor

Matthew Tornow

Third Advisor

Matthew Julius

Fourth Advisor

Heiko Schoenfuss

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Keywords and Subject Headings

Myctophiformes, Systematics, UCE, Phylogenetics, Fishes, Heterodonty

Abstract

Mechanisms of speciation in the deep-sea, an environment with few physical isolating barriers, are relatively understudied in deep-sea fishes. This research focuses on the lanternfishes (Myctophiformes ~250 species) as a study system to investigate speciation in deep-sea environments and to test new phylogenomic approaches at resolving contested phylogenetic relationships. Previous phylogenetic hypotheses of lanternfishes identify two monophyletic families (Myctophidae and Neoscopelidae) and two monophyletic subfamilies within Myctophidae (Myctophine and Lampanyctinae), based on morphological and molecular data. Although subfamily relationships have generally remained the same, hypotheses of higher order (tribe, genus, species) relationships lack resolution. This study is the first to infer the evolutionary relationships of lanternfishes with a genome scale target-enrichment approach with ultraconserved elements (UCEs), which are noncoding areas of the genome that are highly conserved across distantly related taxa. Our results infer a phylogeny of lanternfishes that includes a monophyletic Neoscopelidae, a monophyletic Myctophinae, and a paraphyletic Lampanyctinae. We elevate two tribes to subfamilies (Gymnoscopelinae and Diaphinae both previously within Lampanyctinae) in addition to Lampanyctinae and Myctophinae. Gymnoscopelinae was resolved as the stem myctophid group and Diaphinae as sister to Myctophinae. Little is known regarding how lanternfish achieved such high species richness in the deep sea, and many studies have focused on their bioluminescence. This study also focuses on the evolution of feeding structures in lanternfishes and the potential for niche differentiation in this group. Geometric morphometrics were performed on 955 lanternfish specimens, and an ancestral character-state reconstruction was used to examine patterns of evolution in mouth size in lanternfishes. We identify that mouth size in lanternfishes is highly variable, with general trends towards larger mouths in Lampanyctinae and Gymnoscopelinae and shorter mouths in Myctophinae. Of particular note, Diaphinae was found to occupy a large range of morphospace, with broad plasticity in mouth size among the examined species. To further investigate the evolution of feeding structures, we examined 229 lanternfish specimens within Myctophiformes, assessing variation in tooth anatomy, presence on tooth bearing bones, and presence of heterodonty. An ancestral character-state reconstruction was also used to examine the evolution of heterodonty in this group. Our results support at least four separate evolutions of heterodonty in lanternfishes. Once in the common ancestor of the tribe Lampanyctini, once in Diogenichthys, once in Centrobranchus, and possible multiple evolutions in Diaphus. Heterodonty tooth types are expressed by four different anatomical variations around a global ‘hook’ shape, which have allowed for specialization in feeding.

Comments/Acknowledgements

I would like to thank the following people and institutions for providing specimens, facilities, and equipment used in this study: W. Leo Smith, A. Bentley (University of Kansas), K. Hartel and A. Williston (Museum of Comparative Zoology), J. Sparks (American Museum of Natural History), C. McMahan, K. Swagel, and S. Mochel (The Field Museum), J. Williams and G. D. Johnson (Smithsonian Institution), H.J. Walker (Scripps Institution of Oceanography), A. Graham (Commonwealth Scientific & Industrial Research Organization), and H. Ho (National Museum of Marine Biology and Aquarium). I would also like to thank the following individuals for discussions on UCE analysis: A. Alexander (University of Kansas); K. Barker, S. Jansa, P. Hundt and A. Simons (University of Minnesota). Funding for this work was provided by the National Science Foundation (DEB 1258141, 1543654), the University of Kansas, The Field Museum, and the American Museum of Natural History Lerner-Grey Marine Research Grant. I also thank the American Society of Ichthyologists and Herpetologists for the Edward C. Raney award, and St. Cloud State University for Student Research Funds and for the use of facilities and equipment, including the ISELF Integrated Research Space. An additional thank you goes out my family, friends, and to my advisor Matthew Davis for introducing me to deep-sea research and pushing me to strive for excellence in all of my work.

Available for download on Thursday, May 03, 2018

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