Molecular evidence for multiple origins of woodiness and a New Would biogeographic connection of the Macaronesian Island endemic Pericallis (Asteraceae : Senecioneae)

The prevalence of woody species in oceanic islands has attracted the attent ion of evolutionary biologists for more than a century. We used a phylogeny based on sequences of the internal-transcribed spacer region of nuclear ri bosomal DNA to trace the evolution of woodiness in Pericallis (Asteraceae: Senecioneae), a genus endemic to the Macaronesian archipelagos of the Azore s, Madeira, and Canaries. Our results show that woodiness in Pericallis ori ginated independently at least twice in these islands, further weakening so me previous hypotheses concerning the value of this character for tracing t he continental ancestry of island endemics. The same data suggest that the origin of woodiness is correlated with ecological shifts from open to speci es-rich habitats and that the ancestor of Pericallis was an herbaceous spec ies adapted to marginal habitats of the laurel forest. Our results also sup port Pericallis as closely related to New World genera of the tribe Senecio neae.