Reciprocally formed Tragopogon allopolyploids and their diploid parents : a comparative study : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Biology, School of Natural Sciences, Massey University, Palmerston North. Embargoed until 19 December 2025

Abstract

Allopolyploidy has been a significant evolutionary force across the eukaryotic tree of life, particularly in plants. Newly formed polyploids inherit traits from their progenitors but may also show transgressive characters that allow them to inhabit different areas and/or outcompete their parents in similar habitats. In this thesis, multiple approaches were used to study differences between reciprocally formed allopolyploids (Tragopogon miscellus) and their diploid parents (T. dubius and T. pratensis) in the genus Tragopogon. This system was chosen because the parentage of the allopolyploids is known and the polyploids were recently (within the last 100 years) formed. These four species were analysed for: growth parameters under variable temperature and water conditions; physiology and cellular characteristics; and variations in plastid genomes. Both reciprocally formed polyploids were found to have different growth profiles from each other, with short-liguled Tragopogon miscellus being potentially more robust. Leaf physiology revealed T. dubius had low water use efficiency, but a higher transpiration capacity than the other diploid T. pratensis and the polyploids. Comparison of whole plastid genomes revealed variations in both DNA sequence and base modifications, including methylation patterns, among the four species. Collectively, these results help further our understanding of phenotypic and genotypic evolution in young allopolyploids.