Phylogeography and speciation of Lomatia and Telopea (Proteaceae)

Abstract

One of the most frequently asked questions by evolutionary biologists is what determines a species distribution, and can it be explained by vicariance or dispersal processes? This is particularly intriguing in the case of disjunct distributions, and requires an understanding of what came first - the populations or the barriers that separate them. Proteaceae is a diverse family of plants, distributed across most of the southern continents, making it an ideal group to test hypotheses of biogeographical processes in plants at an intercontinental and continental scale. Two genera within the Proteaceae, Lomatia and Telopea, are closely related, and share a similar distribution across eastern Australia, with Lomatia also occurring in South America. This provides an ideal study system to investigate biogeography in eastern Australia and the hypothesis of vicariance across Gondwanan continents. This study uses phylogenetic, phylogeographic and molecular clock analyses to determine the cause of divergence and distribution in Lomatia and Telopea. Both genera have undergone allopatric speciation, followed by secondary contact resulting in hybridisation and introgression. Lomatia displays Gondwanan vicariance biogeographical patterns, however within Australia species with overlapping distribution are not monophyletic, and instead reflect geographical rather than morphological relationships. The study shows that genetic divergence in the genera is related to known historical events, including continental drift, increasing aridity in Australia during the Miocene and glacial cycles during the Quaternary. This study has provided evidence for several important biogeographical barriers within eastern Australia, notably the Hunter River Valley, which is known to affect a number of fauna species but is rarely investigated for flora. Show more