The distribution of plants and animals across the globe raises a key question: why are species found where they are, and why not elsewhere? To attempt this roughly 200-year-old question requires the study of different ‘levels’ – for instance, from how the population density (the abundance) of a species is structured across its range to how the extent of a species’ occurrence (the range) influences large-scale patterns of species richness. This PhD aims to understand the macroecological patterns and processes of species diversity and distribution using a three-layered approach.

At the largest level, what drives patterns of species richness? For the first two chapters, we build simulation models to understand i) the influence of range properties on cross-taxa species richness patterns and ii) how eco-evolutionary processes drive extant range and richness patterns.

Given that species can be rare along two dimensions, namely abundance and range size, which traits determine rarity? In the third chapter, we study how the interactions between habitat specificity, habitat availability and competition affect the abundance and range sizes of woody plants of the Western Ghats.

At the smallest level, what influences the distribution of abundance across a species’ range? In the final chapter, we attempt to understand the spatial patterning of abundance of select woody plants of the Western Ghats using a combination of modelling and field surveys.

Overall, this thesis will provide new insights into patterns of richness, range size and abundance and their underlying drivers in tropical biodiversity hotspots.