Dissertation/Thesis Abstract

Investigating Patterns and Processes of Evolution, Ecology, and Diversification in Carangiform Fishes
by Glass, Jessica Rose, Ph.D., Yale University, 2019, 178; 27541666
Abstract (Summary)

Fishes comprise the largest diversity of vertebrate animals, with over 35,000 species currently recognized and hundreds more described each year. Advances in molecular genetics have propelled the identification of new lineages of fishes and, more broadly, have changed our understanding of the tempo and pattern of evolution of vertebrate animals. In order to better understand the diversity of fishes, a detailed examination of each clade is necessary. This dissertation focuses on a group of approximately 180 species of fishes, the Carangiformes, whose taxonomy has been contentious. Carangiform fishes include species commonly known as jacks, trevallies, scads, billfishes, remoras, and dolphinfishes, many of which are economically important for commercial, recreational, and artisanal fisheries. This dissertation bridges the fields of phylogenetics, biogeography, population genetics, and trophic ecology by quantifying the patterns and processes of evolution for representative members of carangiform fishes at multiple taxonomic scales. It is composed of three chapters, each of which addresses a different aspect of the evolution and ecology of carangiform fishes.

Chapter one addresses the phylogenetic relationships of Carangiformes and patterns of biogeography. Given past uncertainty about the taxonomic composition of carangiform member clades and the relationships between them, I use multiple analytical methods to construct phylogenies of Carangiformes that are rich in both taxonomic representation and genomic coverage. I use a prominent genomic method for phylogenetic inference, ultraconserved elements, and sequence 80% of the recognized taxonomic members of Carangiformes. I construct well-supported carangiform phylogenies using maximum likelihood and multispecies coalescent approaches. These phylogenies reveal multiple paraphyletic genera, calling for a morphological and taxonomic revision of Carangiformes and, specifically, Carangoidea. I then address patterns of biogeography by examining 41 sister species pairs and calculating the extent to which range overlap and range symmetry relate to node age. I find widespread sympatry amongst sister species pairs (73%), regardless of age. Moreover, sister species that are sympatric have greater differences in body length and depth in the water column compared to allopatric sister pairs. This suggests ecological partitioning enables the maintenance of diverse evolutionary lineages in spite of extensive range overlap.

Chapter two narrows in on two carangiform species in the genus Caranx, the giant trevally (Caranx ignobilis) and bluefin trevally (Caranx melampygus). I analyze hundreds of individuals of both species collected from thirteen localities throughout the Indian and Pacific Oceans to address patterns of population genetic structure and phylogeography. Using double digest restriction site associate DNA (ddRAD) sequencing to analyze thousands of single nucleotide polymorphisms, I find a distinct population of C. ignobilis in the central Pacific, specifically Hawaii and Kiribati, and a stepping-stone pattern of isolation by distance moving from the western Pacific to the Indian Ocean. Caranx melampygus, however, is genetically panmictic across its range. Although these two species are associated with coral reefs and coastal habitats, the patterns of genetic diversity they display resemble those of open-ocean pelagic fishes such as sharks and large tunas. These results have implications for fisheries management, particularly given a history of overfishing of C. ignobilis in Hawaii.

Finally, chapter three addresses spatial variation in trophic niche breadth in the giant trevally, Caranx ignobilis. Giant trevallies are considered top predators on coral and rocky reefs, yet their trophic ecology has not been well-studied throughout their Indo-Pacific range. I use compound specific amino acid stable isotope analysis to quantify isotopic ratios of carbon (δ13C/ δ12C) and nitrogen (δ15N/ δ14N) at four sampling sites in the western Indian Ocean that comprise three habitat types: coral atolls, coastal reefs, and granitic islands. I find considerable variation in trophic niche breadth between sampling sites and an offshore to coastal gradient in carbon, reflecting a carbon isotopic landscape that varies between sites only a few hundred kilometers apart. My analyses also expand the trophic range of C. ignobilis compared to prior studies, placing it at the same trophic position as many large sharks and confirming its role as a top predator in reef and coastal ecosystems.

By utilizing novel methodologies spanning multiple fields of biology, this dissertation provides important insight on an economically significant yet severely understudied clade of marine fishes. I show how a robust phylogeny opens the door to address questions on the maintenance of biodiversity and the importance of biogeographic barriers. I also demonstrate that novel methods characterizing genetic connectivity and trophic niche breadth, when analyzed in combination, collectively enhance our understanding of the ecological and evolutionary history of a marine top predator.

Indexing (document details)
Advisor: Near, Thomas J.
Commitee: Post, David M., Hull, Pincelli M., Baldwin, Carole C.
School: Yale University
Department: Ecology and Evolutionary Biology
School Location: United States -- Connecticut
Source: DAI-B 81/10(E), Dissertation Abstracts International
Source Type: DISSERTATION
Subjects: Evolution and Development, Ecology
Keywords: Biogeography, Carangidae, Fisheries, Phylogenetics, Population genetics, Western Indian Ocean
Publication Number: 27541666
ISBN: 9798607316211
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