Dissertation/Thesis Abstract

High Seas Hitchhiker and Sea Turtle Symbiont: Global Genetics and Ecological Interactions of Oceanic Crabs
by Pfaller, Joseph Bryce, Ph.D., University of Florida, 2016, 181; 13847498
Abstract (Summary)

Oceanic crabs of the genus Planes are common and conspicuous members of the community of organisms that occupy the surface of the open ocean. Unlike other crabs that occupy intertidal or benthic habitats, Planes crabs spend their entire lives rafting on surface-drifting oceanic flotsam or as symbionts of sea turtles. This lifestyle has important implications for the global genetic structure and ecological interactions of these crabs.

Using mitochondrial and genomic data, I test the prediction that the ability of Planes to disperse widely, not only as pelagic larvae, but also as adults associated with oceanic flotsam and sea turtles, should limit species diversification and population differentiation. I found low species diversity and weak population differentiation among rafting Planes and Pachygrapsus laevimanus, an intertidal species found to be closely related to Planes. Global genomic analyses indicate that there is no differentiation within ocean gyres, weak differentiation between gyres and moderate differentiation between ocean basins.

Using ecological data from crabs collected on sea turtles and oceanic flotsam, I test the predictions that (1) Planes major shows long-term social monogamy on sea turtles and (2) sea turtle symbiosis facilitates social monogamy via constraints imposed by refuge size. I found strong evidence that Pl. major is socially monogamous on sea turtles, but that pairing is not necessarily long-term. Moreover, I found that refuge area, not total area, on turtles and flotsam modulate group size and composition of adult crabs and therefore facilitates social monogamy by crabs on turtles.

Using ecological data from crabs collected from three different turtle species captured in neritic and epipelagic habitats, I use crabs as indicators of epipelagic habitat use and surface-dwelling behavior to evaluate two questions: (1) Do turtles display variable/flexible epipelagic-neritic transitions? and (2) Do turtles display similar surfacedwelling behavior in epipelagic habitats? I found evidence that loggerhead and olive ridley turtles display variable/flexible epipelagic-neritic transitions, while green turtles do not. Moreover, I found evidence that epipelagic loggerheads (Caretta caretta) tend to spend more time at or near the surface than epipelagic olive ridley ( Lepidochelys olivacea) and green turtles (Chelonia mydas ).

Indexing (document details)
Advisor: Bjorndal, Karen
Commitee: Bjorndal, Karen, Bolten, Alan, Branham, Marc, Brockmann, Jane, Lillywhile, Harvey, Pavlay, Gusiav
School: University of Florida
Department: Biology
School Location: United States -- Florida
Source: DAI-B 80/07/(E), Dissertation Abstracts International
Subjects: Biology, Ecology, Genetics
Keywords: Crab, Mating system, Phylogeography, RADseq genomics, Sea turtle, Social monogany
Publication Number: 13847498
ISBN: 978-0-438-94753-5
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