The cover shows several islands of Teti’aroa atoll, French Polynesia. Atolls are large, ring-shaped coral reef structures that grow in the tropical Indo-Pacific. Atolls have both a marine part – the coral reefs –, and a terrestrial part – the islands along the rim. While the reefs can be massive and tens of millions of years old, the islands of atolls are no more than a few hundred hectares in size and just few thousand years old. Because each atoll houses many individual islands, each one can be thought of as an archipelago of small islands. The islands, even though small, young, and dynamic, can house remarkably different species communities. Together, atolls like Teti’aroa can offer unique windows into the limits and boundary conditions of biogeographic properties, which inherently cannot be examined through the study of larger islands. Full open access paper here.