Dissertation/Thesis Abstract

Cryptic Tales in the Siphonous Green Algae (Bryopsidales, Ulvophyceae)
by Sauvage, Thomas, Ph.D., University of Louisiana at Lafayette, 2016, 235; 10163348
Abstract (Summary)

Cryptic species are defined as species-level entities masked within taxonomically accepted morphospecies that may be fully convergent in habit. Cryptic species complexes represent an important issue impeding the progress and/or accuracy of ecological, taxonomic, and evolutionary studies, and the overall efforts to conserve, track/detect, or utilize important biological species. In the present dissertation, I explored the molecular diversity of siphonous green algae (Bryopsidales) with the chloroplast gene tufA with a focus on species complexes tied to marine invasion in the genus Caulerpa and substratum bioerosion by the genus Ostreobium. My approach consisted in resolving the extent of cryptic diversity underlying a given morphology linked to a generic or specific epithet by maximizing sequencing efforts from known biodiversity hotspots in order to create molecular diversity ‘roadmaps’ as a basis for further study and future taxonomic revisions, as well as resolving temporary clade names (with nomina nuda) or those firmly based on the sequencing of historical material from type locality when possible. To complete these projects, I developed a toolbox of primers and summarized tufA sequence frameworks for comprehensive phylogenetic analyses. For historical specimens, I designed a set of primers allowing amplification of short fragments and reconstruction of tufA from century-old degraded DNAs in Caulerpa. I also designed highly degenerate primers targeting the algae sensu lato to realize metabarcoding assays from environmental mixtures with novel sequencing technologies as a shortcut to phototrophic biodiversity characterization, here applied to endolithic communities rich in ‘Ostreobium’ species in marine calcium carbonate substrata. Aside from these methodological aspects, the present dissertation reveals an overall evolutionary trend of diversification from microscopic simple siphons (i.e. ‘Ostreobium’ spp. and ‘Pseudochlorodesmis’ spp.) to macroscopic families with complex morphologies (e.g. Halimedaceae, Rhipiliaceae), as well as the widespread use of the endolithic niche by the Bryopsidales, either transiently and/or perennially.

Indexing (document details)
Advisor: Fredericq, Suzanne
Commitee: Albert, James, Chistoserdov, Andrei, Neigel, Joseph, Norris, James
School: University of Louisiana at Lafayette
Department: Biology
School Location: United States -- Louisiana
Source: DAI-B 78/04(E), Dissertation Abstracts International
Subjects: Biology, Evolution and Development
Keywords: Biodiversity, Caulerpa, Cryptic species, Ostreobium, Siphonous, Ulvophyceae
Publication Number: 10163348
ISBN: 978-1-369-18040-4
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