The Role of Biome Shifts in Lineage Diversification
The Role of Biome Shifts in Lineage Diversification Esther Elizabeth Dale Submitted in fulfilment of the requirements for the degree of Doctorate of Philosophy Department of Botany, University of Otago November 2018 II Abstract This thesis examines the role of biomes in lineage diversification. It explores whether biome conservatism, the tendency to remain in ancestral biomes, constrains diversification, and tests whether biome shifts are linked to characteristics of particular biomes, clades or traits. This work focuses on a series of radiations in Australia and New Zealand. Using the hyper-diverse genus Acacia in Australia, Species Distribution Models (SDM) were used to predict distributions and niche traits of 481 species in 19 clades across two biome typologies. Diversification was not constrained to any biomes, with most species (94%) occupying multiple biomes, but diversification was greatest in those biomes currently occupying larger areas. New Zealand groups (Poaceae, Melicytus, Myrsine and Pseudopanax) with small scale radiations (< 25 species) were then investigated in relation to occupancy of the three main biomes (Forest, Open and Alpine). A temporal sequence of biome availability in New Zealand allowed an examination of diversification in the context of the directional transition from forest to more open biomes. A combination of methods including SDM, biogeographical models, and trait measurements of plants grown in a common garden were utilised to explore the importance of biome shifts during diversification, the relationship between trait shifts and biome shifts, and ask if biome conservatism was prevalent in the different clades. Biome conservatism did not constrain diversification in New Zealand lineages. Biome shifts were generally frequent and more closely related to extrinsic biome factors like biome age, biome availability and relative environmental similarity between biomes, rather than to intrinsic features of lineages, such as clade size, diversification rate or age.
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