Genetic diversity evaluation of rare endemic plant species Braya longii and Braya fernaldii

MacNeil, Nathan (2024) Genetic diversity evaluation of rare endemic plant species Braya longii and Braya fernaldii. Masters thesis, Memorial University of Newfoundland.

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Abstract

Braya longii and B. fernaldii are two endangered vascular plants endemic to Newfoundland's (Canada) Northern Limestone Barrens. Currently, there is no firm understanding of the genetics of either species. To date, these two species are managed together under the same Braya Action and Recovery Plans due to their shared habitat and close taxonomic relationship. However, an improved understanding of the genetics of both B. longii and B. fernaldii would improve the future management and survival of these two species, as the use of genetically appropriate source populations in restoration, is a high-priority recovery measure. Genomic analysis is a valuable tool for delineating conservation units and can be performed by next-generation sequencing methods such as genotype-by-sequencing. This research aims first to identify the genetic diversity and structure of the B. longii and B. fernaldii populations, and second, to provide insight into the relationship between the two species' population genetics and the implications for management/conservation units. I leverage phylogenetic results using SplitsTree4, population structure analysis using STRUCTURE and discriminant analysis of principal components, and SNP analysis using the R package Hierfstat to gain insights into the relationships between each species and within populations. The results support the separation of each species. I propose six divergent lineages as evolutionarily significant units, three for Braya longii and three for B. fernaldii. I also propose eight management units, with each population managed separately, while Sandy Cove 1 and Savage Cove share a single management unit. These management units can be referenced for making restoration decisions, such as when sourcing individuals. While this research provides new insight into the population genetics of B. longii and B. fernaldii for the conservation and management of these species, future research could use this dataset to estimate past and current gene ow, effective population sizes and test population expansion or contraction.

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