History of island biogeography, new directions, and the emerging unifying theory

Background/Question/Methods

The field of island biogeography has a long history.  Occupying the minds of such founding fathers as Darwin, Wallace and von Humboldt, early considerations of the biogeography of island laid the ground for diverse fields, including the theory of evolution by natural selection, Pleistocene climate cycles, plate tectonics, and adaptive radiations. From the mid-1960s, the equilibrium theory of island biogeography developed by MacArthur and Wilson had an equally strong impact, initiating a paradigm change in ecological biogeography that moved the focus away from traditions of historical ‘story telling’ inferences and towards testable quantifiable hypotheses, evaluated mainly through analyses of emergent diversity properties (i.e. macroecological analysis). Most recently, developments in gene sequencing and in methods of historical biogeography and phylogeography have initiated a new more analytical phase of historical biogeography of classic oceanic island systems.

A more coherent theory of island biogeography is emerging, which aims to incorporate the multitude of processes that affect island biotas into a single framework. The basis of this unified understanding comes from two lines of research. One is the development of robust, timed phylogenies for several island taxa, which make it possible to reconstruct colonisation and speciation patterns across archipelagos, integrating ecological and evolutionary theory.  The other is a growing appreciation for the importance of geological dynamics on the evolution of island biota. Because many oceanic islands are volcanic in origin, they exhibit a characteristic life cycle of building, maintenance and erosion, which affects the rates of speciation and extinction on the islands.

Results/Conclusions

The integration of ecological, evolutionary and geological dynamics is likely to lead to significant advances in our understanding of island biogeography. Yet, there remain many poorly explored elements of island biology. These new directions include a) the variation in geological history and sea-level dynamics among islands; b) the role of archipelago-wide dynamics and the emergence of neighbouring islands in forming island radiations; c) the relationship between island-scale and local community dynamics; d) global variation in islands characteristics and climate; e) functional trait variation and ecosystem functioning in impoverished island faunas; d) the application of the interplay between geological and evolutionary dynamics to other island-like systems, such as sea mounts and mountain tops. We give examples of these emergent directions, and describe the shape of the new paradigm of island biogeography.