Is there a robust effect of mainland mutualism rates on species richness of oceanic islands?

TL;DR

This paper questions whether the proportion of mutualists on the mainland significantly influences species richness on oceanic islands, challenging previous claims and re-analyzing existing data to assess this potential effect.

Contribution

The study critically re-examines prior claims about mutualist effects on island species richness, providing new insights into island biogeography and the factors influencing biodiversity.

Findings

No strong evidence supporting a robust effect of mutualism rates on island species richness.

Re-analysis casts doubt on previous conclusions about mutualist influence.

Highlights the importance of considering multiple factors in island biodiversity studies.

Abstract

In island biogeography, it is widely accepted that species richness on island depends on the area and isolation of the island as well as the species pool on the mainland. Delavaux et al. (2024) suggest that species richness on oceanic islands also depends on the proportion of mutualists on the mainland, based on the idea that mutualists require specific interaction partners for their survival and thus have lower chances of establishment after successful immigration. As the proportion of mutualists increases towards the tropics, this effect could explain a weaker latitudinal diversity gradient (LDG) for oceanic islands. However, after re-analyzing their data, we have doubts if these conclusions are supported by the available data.