Emerson BC

Kitson JJN

Strasberg D

Thébaud C

Warren BH

Aim To test a prediction derived from island biogeographic theory that in situ speciation should make an increasingly important contribution to community assembly as islands age. This prediction is tested on estimated biogeographic histories from Mauritius (approximately 9 Ma) and Reunion (approximately 5 Ma). We additionally investigate the evolutionary dynamics of insect flight loss, since the loss of flight in island lineages can influence patterns of diversification. Location Mascarene Islands; Southwest Indian Ocean. Taxon Weevils. Methods Up to five individuals of each taxonomically described species sampled within each sampling site were sequenced for the mitochondrial gene Cytochrome Oxidase II to delimit operational taxonomic units (OTUs). OTUs were further sequenced for the nuclear genes Arginine Kinase, Histone 3, and ribosomal 28s, to reconstruct the phylogenetic history of the group. Timings of colonisation and in situ speciation events were estimated with BEAST2. Results Our results support the hypothesis that present-day species richness on the older island of Mauritius is largely the result of in situ speciation, with few colonisation events, of which all but the most basal are recent. In contrast, Reunion presents a more uniform temporal spectrum of colonisation times. Flight loss has evolved convergently at least five times, and speciation events associated with flight loss are significantly younger than speciation events that have not resulted in flight loss. Main conclusions Patterns of community assembly on the islands of Mauritius and Reunion fit a model where the addition of new species and species turnover is increasingly dominated by in situ speciation as an island community matures. Repeated flight loss indicates selection for flightlessness, with the young age of flightless lineages suggesting higher extinction rates over longer evolutionary time scales and little influence on present-day species richness

Community assembly and diversification in a species-rich radiation of island weevils (Coleoptera: Cratopini)

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