The Azores diversity enigma : diversity and evolution of the genus Pericallis (Asteraceae) in Macaronesia

• Main Author: Jones, Katy Elizabeth
• Published: University of Bristol 2014
• Subjects: 583
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680378

Oceanic archipelagos are famous for their rich endemic biota and island lineages have played a central role in biogeography. Macaronesia is a region of archipelagos in the Atlantic Ocean and 22% of native flowering plants are endemic to the region. Diversity in Macaronesia is unevenly distributed. Darwin first recognized the paucity of richness and Single Island Endemics (SIBs) in the Azores compared to other archipelagos and this pattern is now known as the' Azores Diversity Enigma'. This PhD explores hypotheses to explain the 'Enigma' related to taxonomy and diversity patterns. Analyses of herbarium collections of endemic plants suggest that our current understanding of the Azores endemic flora may be insufficient to establish a robust taxonomic framework. The taxonomically complex genus Pericallis (Asteraceae) exhibits a diversity pattern that reflects the' Enigma', it therefore provides an ideal focus for testing hypotheses to explain the 'Enigma'. A dated phylogenetic analysis of Pericallis is established. Comparisons of diversity and evolutionary processes of Pericallis in both the Azores and Canaries enable two key hypotheses for the 'Enigma' to be tested: (i) taxonomic artefact and (ii) lack of ecological diversity in the Azores. Taxon delimitation issues are also resolved. The study umavels a complex evolutionary history involving both habitat and geographic shifts. Furthermore, in both the Canaries and Azores much ofthe diversity is recent (ca. 1.7 Myr). Analyses of Pericallis suggest that taxonomic artefact does not satisfactorily explain the 'Enigma'. Ecological diversification has played a significant role in both archipelagos; therefore hypothesis (ii) can be rejected. Novel molecular and morphological diversity patterns are revealed. One new species is described in Madeira and four new subspecies are recognized in the Canaries. The results of this PhD reveal novel patterns of diversity and evolution that are significant for exploring and challenging the assumptions of island biogeography studies.