The macroecology of island floras

Patrick Weigelt

doi:10.21425/f5fbg25073

Abstract

Islands are key model systems in biogeography and ecology. However, standardized data on environmental characteristics of the large number of islands worldwide have so far been lacking, and the effects of these characteristics on island ecology and biodiversity remain insufficiently understood. In my PhD thesis, I presented the first comprehensive environmental characterization of the world’s islands, covering past and present bioclimatic and physical island characteristics (including the spatial setting of islands and archipelagos). I used these data to investigate how island characteristics influence the diversity and assembly of island floras at different spatial scales and across major plant groups. To this end, I assembled a global database of vascular plant species composition including 45,000 species and covering 1,070 islands. I showed that different aspects of island environments affect different facets of insular diversity (species richness, turnover, phylogenetic diversity) across scales and major plant groups, in accordance with their predominant dispersal- and speciation-related traits and adaptations to climate. The results contribute to a better understanding of the environmental and evolutionary drivers of plant assemblage composition, on islands as well as on mainlands.

Highlights

Islands have intrigued biogeographers since the beginning of biogeographic research (e.g. Wallace 1880) and have inspired some of the most influential theories in ecology and evolution (e.g. MacArthur and Wilson 1967)
I hypothesized that the proportion of variation in species richness explained by isolation is higher when considering large source islands, stepping stones, climatic similarity, wind and ocean currents and the total area of surrounding landmasses, as opposed to considering only the commonly used metric of distance to the nearest mainland
We developed a set of predictors describing the intra-archipelagic spatial structure, including mean inter-island distance, connectivity, total archipelago area, range in island areas and the environmental volume occupied by an archipelago’s islands as defined by the global bioclimatic and physical principal components analysis from Weigelt et al (2013)

Summary

Introduction

Islands have intrigued biogeographers since the beginning of biogeographic research (e.g. Wallace 1880) and have inspired some of the most influential theories in ecology and evolution (e.g. MacArthur and Wilson 1967). To address the roles of different aspects of island isolation in determining insular species richness I compared ecologically meaningful metrics of island isolation in models of vascular plant species richness (Weigelt and Kreft 2013).

Results

Conclusion