Why tropical island endemics are acutely susceptible to global change

Abstract

Tropical islands are species foundries, formed either as a by-product of volcanism, when previously submerged seabed is thrust upwards by tectonics, or when a peninsula is isolated by rising sea level. After colonisation, the geographical isolation and niche vacancies provide the competitive impetus for an evolutionary radiation of distinct species-island endemics. Yet the very attributes which promote speciation in evolutionary time also leave island endemics highly vulnerable to recent and rapid impacts by modern people. Indeed, the majority of documented human-driven extinctions have been exacted upon island endemics. The causes include over-exploitation, invasive species brought by people and destruction of island’s naturally constrained habitats. Imminent threats include inundation by rising sea levels and other adaptive pressures related to anthropogenic global warming. We review recent work which underscores the susceptibility of island endemics to the drivers of global change, and suggest a methodological framework under which, we argue, the science and mitigation of island extinctions can be most productively advanced.