Climate-induced coral loss is causing declines in abundance and diversity of coral reef fishes. Thus far, these impacts have been greatest on those fishes which depend on live coral for food or shelter, with the most specialized species showing the greatest declines in abundance following coral mortality. As the frequency, intensity and magnitude of disturbance events on coral reefs increase, many such fishes may be at considerable risk of extinction. Establishing the extinction risk, and more importantly the factors that increase extinction risk among vulnerable species groups, is therefore critical in prioritizing conservation efforts aimed at preventing and reversing biodiversity loss. This study will investigate the capacity of large-range butterflyfishes to withstand large-scale disturbances through variation in ecological versatility, and/or recolonisation of disturbed habitats by remnant populations. The specific aims of the project are (1) to investigate geographic variation in the feeding ecology of wide-ranging butterflyfishes and determine whether specialisation is a local or regionalised phenomenon; (2) to investigate the influence of diet and resource availability on the abundance and distribution of butterflyfishes; (3) to determine genetic population structure and quantify population connectivity among geographically separated populations of large-range butterflyfishes; and (4) to investigate the effects of ecological specialisation on the genetic population structure of butterflyfishes. This research will provide a greater understanding of the relationships between abundance, specialisation, geographic range, population connectivity and extinction risk in coral reef fishes.