Island species as models for small population biology and conservation

Islands provide unparalleled natural laboratories for understanding how small, isolated populations persist and evolve. Our synthesis of island population studies reveals that 50–70% report effective population sizes below 100, yet many taxa have sustained such small populations for millions of years. Strikingly, only 4% and 27% of studies examined genetic load and genomic diversity, exposing major blind spots in our understanding of genomic erosion. We argue that island systems offer critical insights into how limited populations retain viability and adaptive potential. Future work should expand taxonomic and geographic coverage, exploit temporal genomic data, and integrate genomic, demographic, and fitness information to link evolutionary resilience on islands to the conservation of increasingly fragmented populations worldwide.