Abstract
Pilularia globulifera, or pillwort, is a semi-aquatic fern which belongs to the heterosporous order Salviniales and Marsileaceae family. It is considered endangered due population decline across native habitats of Western and Central Europe. Conservation efforts have been undertaken in the past, however, success has not been cohesively quantified at any level. Implementing genomic data to support these initiatives, notably reintroduction and translocation of populations, is hopeful as they can provide useful insight into species diversity; the evolutionary history of fern organelle genomes in particular, and respective usefulness as phylogenetics tools, has made them ideal candidates for sequencing. However, ferns have a complex genetic makeup which has contributed to the severe lack of data that still exists for some families.This study aimed to lay the foundations for such work; next generation sequencing and bioinformatics methods were utilised to assemble the whole chloroplast genome of pillwort as a novel species, alongside identify putative mitochondrial regions and tRNAs. With the aim of resolving conflicting phylogenetic relationships, Bayesian inference and maximum likelihood analyses for Marsileaceous ferns were conducted, with incorporation of published data. Subsequently, primers were designed to target four chloroplast regions believed to be of phylogenetic and conservational significance.
Findings revealed a typical quadripartite structure with gene complement similar to other leptosporangiates and Salviniales and a length of 153,051 bp. However, ndhB notably spanned the inverted repeat region boundaries in pillwort, seemingly unreported for heterosporous ferns. Phylogeny results at family level favoured Regnellidium as sister to both Pilularia and Marsilea,and also led to an incidental finding of a possible erroneous P. americana GenBank entry following unusual clustering patterns and a high degree of sequence similarity to P. globulifera. Further work is suggested in light of these results, and there is hope continued sequencing will provide valuable insight into fern populations, with implementation into conservation and phylogenetic studies.
| Date of Award | 4 Apr 2024 |
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| Original language | English |
| Supervisor | Martin Carr (Main Supervisor) & Simon Rout (Co-Supervisor) |