Culminating Project Title
Date of Award
Culminating Project Type
Biological Sciences - Ecology and Natural Resources: M.S.
College of Science and Engineering
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
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.
Martin, Rene P., "Phylogenomics of Lanternfishes and the Evolution of Feeding Structures" (2017). Culminating Projects in Biology. 21.