Abstract
The theory of island biogeography predicts that area and age explain species richness patterns (or alpha diversity) in insular habitats. Using a unique natural phenomenon, pumice rafting, we measured the influence of area, age, and oceanic climate on patterns of species richness. Pumice rafts are formed simultaneously when submarine volcanoes erupt, the pumice clasts breakup irregularly, forming irregularly shaped pumice stones which while floating through the ocean are colonized by marine biota. We analyze two eruption events and more than 5,000 pumice clasts collected from 29 sites and three climatic zones. Overall, the older and larger pumice clasts held more species. Pumice clasts arriving in tropical and subtropical climates showed this same trend, where in temperate locations species richness (alpha diversity) increased with area but decreased with age. Beta diversity analysis of the communities forming on pumice clasts that arrived in different climatic zones showed that tropical and subtropical clasts transported similar communities, while species composition on temperate clasts differed significantly from both tropical and subtropical arrivals. Using these thousands of insular habitats, we find strong evidence that area and age but also climatic conditions predict the fundamental dynamics of species richness colonizing pumice clasts.
Highlights
The globe is experiencing its sixth mass extinction event, and considerable evidence suggests that native biodiversity is being lost as a result of human activities
The theory of island biogeography (TIB) predicts that richness of biodiversity in isolated environs or habitats at the local scale are explained by species turnover as a function of area and through processes of immigration, speciation, and extinction that will eventually reach a dynamic equilibrium of species, because resources and space become saturated (Keppel, Buckley, & Possingham, 2010; MacArthur & Wilson, 1967; Simberloff & Wilson, 1969; Whittaker, 1960), while beta diversity allows us to compare the differences between species composition between similar and different habitat types in a broader landscape or oceanic context (Anderson, Ellingsen, & McArdle, 2006; Whittaker, 1960)
3.2 | How does the influence of area and age change for pumice clasts that were collected from different climatic zones?
Summary
The TIB predicts that richness of biodiversity (or alpha diversity) in isolated environs or habitats at the local scale are explained by species turnover as a function of area and through processes of immigration, speciation, and extinction that will eventually reach a dynamic equilibrium of species, because resources and space become saturated (Keppel, Buckley, & Possingham, 2010; MacArthur & Wilson, 1967; Simberloff & Wilson, 1969; Whittaker, 1960), while beta diversity allows us to compare the differences between species composition between similar and different habitat types in a broader landscape or oceanic context (Anderson, Ellingsen, & McArdle, 2006; Whittaker, 1960). As beta diversity is a measure of community similarity or dissimilarity among sampling units that are grouped based on the point of collection (climatic zone), we would expect that clasts of similar area and age from the same climatic zone would be comprised of similar communities (Anderson et al, 2006)
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