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Project: 348/2022

Title: The evolution and diversification of the Australian Diurideae: Understanding the influence of genome size and chromosome number 

Applicant: Ryan O’Donnell

Institution:  The Australian National University  Acton ACT 2601

The evolution and diversification of the Australian Diurideae: Understanding the influence of genome size and chromosome number

Encompassing approximately 1,010 species, the tribe Diurideae (Orchidaceae; Orchidoideae) contains the majority of Australian terrestrial orchid species. Recent phylogenomic work has begun to detangle the evolutionary history of this diverse tribe of orchids; however, our understanding of the genomic evolution of the group is still in its infancy. While genome size, ploidy, chromosome count, and nucleobase composition (GC content) have been implicated in diversification rate shifts and climatic adaptive potential across the Orchidaceae, the Diurideae have historically been underrepresented in previous investigations.

Recent genomic studies of the Diurideae have revealed substantial levels of genomic variation and diversity, which challenges the assumptions presented by previous studies. Nevertheless, there are still few genome size estimates across the Diurideae, which render a comprehensive understanding of genome size evolution within the group non-viable with existing datasets.

This Australian Orchid Foundation research grant will be used to perform flow cytometry to obtain genome size, ploidy, and GC content estimates for a subset of the Diurideae representing genera with known chromosome counts. We will then analyse these data within an evolutionary framework to gain a preliminary perspective into how genome size and chromosome number may be phylogenetically structured in the Diurideae, and whether there may be any correlation with environmental and climatic variables. The identification of which orchid groups are more or less susceptible to climatic change and fluctuations at a genomic level will allow for the development of more nuanced conservation and management plans that target orchid taxa most at risk.