TAXONOMY, DIVERSITY AND ECOLOGY OF FUSARIUM SPECIES ASSOCIATED WITH INFECTIONS OF MARINE ANIMALS
Open Access
- Author:
- Smyth, Christopher W
- Graduate Program:
- Plant Pathology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 11, 2018
- Committee Members:
- David Michael Geiser, Dissertation Advisor/Co-Advisor
Seogchan Kang, Committee Chair/Co-Chair
Maria Del Mar Jimenez Gasco, Committee Member
Gretchen Anna Kuldau, Committee Member
Maryann Victoria Bruns, Outside Member - Keywords:
- Fusarium
Fungi
Sea Turtle
Conservation
Mycology
Taxonomy
Sea Turtle Egg Fusariosis
Marine Fungi - Abstract:
- Fungal diseases of wildlife are increasingly common, with devastating consequences for biodiversity and ecosystem health. Two closely related members of the Fusarium solani species complex, Fusarium keratoplasticum (Fk) and Fusarium falciforme (Ff), have been associated with mass mortalities in the nests of sea turtles. These are common, cosmopolitan species of filamentous fungi that are known opportunistic pathogens of immunosuppressed, and sometimes healthy, humans. While Ff is a known soil inhabitant, Fk is only known from clinical infections and the built environment (i.e. sink drains). Both species show high levels of genetic diversity, and known anthropogenic isolates of Fk are dominated by an expanding clone complex. This research aims to answer the following questions: 1) What is the diversity of Fusarium species found in Florida sea turtle nesting sites? 2) Are Fk and Ff present at these sites, and if so, are they associated with nest mortality? 3) Are isolates of Fk from nesting sites genetically diverse, or are they a part of the widespread clonal complex associated with clinical infections and sink drains? Selective sampling for Fusarium was conducted at three nesting sites in Florida in cooperation with a sea turtle nest health assessment program. Fungi were isolated from unhatched eggs, hatched eggshells, and samples of sand inside and outside of 24 nests already being excavated for assessment of hatching success. An established three-locus multilocus sequence typing procedure was used to identify Fusarium isolates to species level and assess the genetic diversity of sea turtle nest isolates. The Fusarium solani species complex (FSSC) species Fk, undescribed phylogenetic species FSSC 12 and Ff, in order of frequency, are the most common causative agents of veterinary fusarioses in the United States. Unlike Fk and Ff, however, FSSC 12 has never been isolated from human infections. Rather, all isolates of FSSC 12 are derived from, or associated with, infections of captive marine animals. FSSC 12 was originally identified via Genealogical Concordance Phylogenetic Species Recognition (GCPSR), which has resolved at least 60 phylogenetic species within three clades in the FSSC. The prevalence of FSSC 12 in association with captive marine animal infections highlights the need for a formal species recognition and description. In addition, an assessment of the characteristics that may impact its pathogenicity in marine animals, such as osmotic stress tolerance, is necessary to understand its exclusive association to date with marine animals. This study uses morphological and molecular data to formally recognize and describe this taxon as Fusarium aquariorum Smyth, O’Donnell and Geiser sp. nov.. In addition, F. aquariorum isolates were assessed for their ability to tolerate osmotic stress compared to other closely related species within the FSSC.