A molecular systematic and taxonomic assessment of the Rhodymeniales

Abstract

The assessment of biological diversity and understanding the evolutionary history of organisms is integral to understanding life on earth. The Rhodymeniales is a well-defined red algal order for which interfamilial relationships are incompletely understood and species identification is complicated by the inability of traditional morphology-based approaches to reconcile convergent features and phenotypic plasticity. In this thesis, I used an integrative taxonomic approach combining molecular and morphological techniques to address rhodymenialean phylogenetic relationships and species diversity. I implemented multi-gene phylogenetics and site-stripping analyses to uncover reasonable support for interfamilial relationships within the Rhodymeniales for the first time. As part of that study, I established the phylogenetic assignment of some taxa (Binghamiopsis, Chamaebotrys, Minium) previously missing from molecular analyses, restored monophyly to notoriously polyphyletic genera by establishing Perbella gen. nov. and Fushitsunagia gen. nov., and described three novel Australian species of Drouetia (D. aggregata sp. nov., D. scutellata sp. nov., D. viridescens sp. nov.) after clarifying tetrasporangial development for that genus. Identification of recently collected material from Australia as the generitype of Leptofauchea facilitated a re-examination of that genus and its constituent species. Multigene phylogenetics provided support for Leptofauchea as a monophyletic genus for the first time. Additionally, inconsistencies with published accounts of some Leptofauchea species were clarified and two novel species (L.cocosana sp. nov., L. munseumica sp. nov.) assigned to that genus were recognized. A molecular-assisted alpha taxonomic approach employing the 5’ end of the mitochondrial cytochrome c oxidase subunit I (COI-5P) DNA barcode was implemented to reassess species diversity and redefine inaccurate or inadequate species concepts for rhodymenialean taxa in British Columbia. I resolved 16 species in 10 genera where 13 species in 11 genera were previously reported, uncovering underestimated diversity for the genera Botryocladia, Faucheocolax, Fryeella, Gloiocladia and Rhodymenia. The previous necessitated a taxonomic transfer (Fryeella callophyllidoides comb. nov. for Rhodymenia callophyllidoides), the resurrection of a previously synonymized species epithet (R. rhizoides) and the establishment of novel taxa (B. hawkesii sp. nov., R. bamfieldensis sp. nov.). That study also included reassessment of anatomical development for the monospecific genus Minium. Lastly, a comprehensive floristic survey of the genus Rhodymenia from Australia was performed using molecular-assisted alpha taxonomy with COI-5P and ITS sequence data as the genetic markers. Whereas five species were previously reported, I resolved 12 genetic groups. Four of those groups were attributed to previously recognized species, whereas some collections were attributed to a New Zealand species, R. novazelandica, expanding its biogeographical range. The remaining seven genetic groups were inconsistent with existing species of Rhodymenia and established as novel taxa (R. compressa sp. nov., R. contortuplicata sp. nov., R. gladiata sp. nov., R. insularis sp. nov., R. lociperonica sp. nov., R. norfolkensis sp. nov., R. womersleyi sp. nov.).