Phylogeny and Biogeography of the Toxic Dinoflagellate Alexandrium
Abstract
The incidence and known distribution of paralytic shellfish poison-producing Alexandrium dinoflagellates have both increased dramatically in recent decades. This thesis explores the phylogeny, taxonomy, and biogeography of Alexandrium in light of this expansion. Alexandrium rDNA sequence phylogeny did not correlate with morphological traits traditionally used to identify and group species. 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, A. toxipotens, A. mediterra, A. tamarensis, and A. tasmanense. Within the minutum group, A. lusitanicum and A. angustitabulatum were not distinct species based on morphology and phylogeny while A. insuetum and A. tamutum were clearly distinct and three new species were identified. The ability to produce toxins has been acquired and/or lost multiple times during Alexandrium evolution. Each species of the tamarensis complex appears to contain either all toxic or non-toxic isolates, while 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. (56 refs.)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2003
- Accession Number
- ADA418376
Entities
People
- Emily L. Lilly
Organizations
- Massachusetts Institute of Technology