Abstract

The biota of the Juan Fernández Islands (SE Pacific) provides important information on key evolutionary and biogeographical phenomena. However, a long-standing matter of contention concerns how the archipelago’s various lineages arrived there. Was it via former landbridges/exotic terranes, or did it involve long-distance dispersal? We address the issue through a two-pronged review-synthesis, one focusing on the geology, the other on the biology (using 207 clades from four key groups: angiosperms, ferns, landbirds, and coastal fishes). Regarding the first, a critical observation relates to the archipelago’s emergence history as only since c. 4.7 Mya has there been an uninterrupted sequence of land-surfaces in the Juan Fernández region. The biota reflects this with the bulk of the clades having definitely arrived in the last few million years. That said, c. 5% of the groups have ‘colonization intervals’ that extend back >20 Mya, but these are probably artefacts caused by the loss of intervening off-archipelago lineages, which results in their notably old stem ages. Concerning sourcing, the landbirds and plants are mainly from South America, whereas the fishes have strong connections to the western and insular Pacific. Collectively, the geological and biological evidence indicates that the ancestors of the various clades colonized geologically recently, and exclusively by long-distance dispersal.

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