Recent years have seen a surge in interest in island biology and the theory of island biogeography (IBT; Losos & Ricklefs, 2010; Santos et al., 2016; Patino et al., 2017; Whittaker et al., 2017), partly motivated by the 40 th and 50 th anniversaries of the Core IBT model (MacArthur & Wilson, 1963) and the monograph that expanded on this model with related ideas (MacArthur & Wilson, 1967). We were involved in one such initiative, a working group on island biogeography funded by the Centre for the Synthesis and Analysis of Biodiversity (CESAB). A major output of the group was a collective perspective on how key attributes of islands surrounded by water provide prospects for improving our understanding of the ecology and evolution of biological communities in general (Warren et al., 2015; see Box 1 for a detailed distinction of IBT and Core IBT). In the process of organising our ideas, interesting issues arose that were tangential to this aim. One example is that over the decades since 1967, IBT has inspired numerous ecological theories and schools of thought. Although IBT is focussed on islands surrounded by water, even in the opening chapter of the 1967 monograph, MacArthur and Wilson emphasized that such island biomes are an extreme example of fragmented or insular environments (isolated by geography or ecology) that are common worldwide. Consistent with this view, not only has IBT proven relevant to a wide variety of insular environments that are not islands surrounded by water (e.g., Brown, 1971; Drake et al., 2002; Wagner et al., 2014), but it also has links to important ecological theories and concepts, the implications of which stretch far beyond such islands. Here we highlight some of the main links between IBT and subsequent developments in ecology and conservation biology. The elegance of Core IBT stands in its ability to model complex phenomena with few