Phylogeny and biogeography of the toxic dinoflagellate Alexandrium
Lilly, Emily L.
MetadataShow full item record
The incidence and known distribution of paralytic shellfish poisoning (PSP) have both increased dramatically in recent decades. A concurrent rise in bloom frequency and geographic range of PSP toxin-producing Alexandrium dinoflagellates explains the increase in PSP, but the reasons for changes in Alexandrium occurrence are unknown. This thesis explores the phylogeny, taxonomy, and biogeography of Alexandrium in light of this recent expansion. Alexandrium phylogeny was reconstructed through rDNA sequence analysis and compared to traditional morphological taxonomy. Alexandrium split into two groups, termed the α and ß clades. Interspecific relationships did not correlate with the morphological traits traditionally used to identify and group species, although other traits appeared phylogenetic ally conserved. The ability to produce toxins has been acquired and/or lost multiple times during Alexandrium evolution. Because most PSP events are caused by either the tamarensis or minutum complexes, the phylogeny, species definitions, and biogeography of each complex was examined. The morphospecies of the tamarensis complex, A. catenella, A. tamarense, and A. fundyense, did not represent valid species by the phylogenetic, biologic or morphological species concepts. Instead, five cryptic species were identified through phylogeny and mating incompatibility. A. universa and A. toxipotens contain all toxic strains, while A. mediterra, A. tamarensis and A. tasmanense contain only non-toxic isolates. Within the minutum group, A. lusitanicum and A. angustitabulatum were also not distinct species based on morphology and phylogeny while A. insuetum and A. tamutum were clearly distinct. Three new minutum group species were identified on the basis of morphology, phylogeny and prior research. Unlike the pattern found for the tamarensis complex, toxic and non-toxic A. minutum strains cannot be segregated based upon LSU sequences. The reconstructed biogeography of the tamarensis and minutum complexes indicate that both natural dispersal and human-assisted transportation of Alexandrium have caused the geographic spread. Human-assisted transport of toxic A. catenella-type cells from Asia to the Thau Lagoon, France, was demonstrated in chapter iv. This thesis demonstrates the importance of human action in the recent PSP increase, better defines species boundaries and provides an invaluable genetic database for tracking future Alexandrium spread and distinguishing between harmful and non-toxic Alexandrium blooms.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2003
Suggested CitationThesis: Lilly, Emily L., "Phylogeny and biogeography of the toxic dinoflagellate Alexandrium", 2003-09, DOI:10.1575/1912/2455, https://hdl.handle.net/1912/2455
Showing items related by title, author, creator and subject.
Phenotypic diversity within two toxic dinoflagellate genera : environmental and transcriptomic studies of species diversity in Alexandrium and Gambierdiscus Pitz, Kathleen (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2016-09)Dinoflagellates are a diverse group of single-celled eukaryotic phytoplankton that are important for their unique genetics and molecular biology, the multitude of ecological roles they play, and the ability of multiple ...
Blooms of the toxic dinoflagellate Alexandrium fundyense in the Gulf of Maine : investigations using physical-biological model Stock, Charles A. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2005-02)Blooms of the toxic dinoflagellate Alexandriumfundyense are annually recurrent in the western Gulf of Maine (WGOM) and pose a serious economic and public health threat. Transitions between and vital rates within the life ...
Physiological and behavioral diagnostics of nitrogen limitation for the toxic dinoflagellate Alexandrium fundyense Poulton, Nicole J. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2000-09)One challenge in phytoplankton ecology is to measure species-specific physiological responses to changes in environmental conditions. Of particular importance in this regard are harmful algal bloom (RAB) species such as ...