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Molecular dating of the ‘Gondwanan’ plant family Proteaceae is only partially congruent with the timing of the break-up of Gondwana

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Abstract:

Abstract Aim 

The flowering plant family Proteaceae is putatively of Gondwanan age, with modern and fossil lineages found on all southern continents. Here we test whether the present distribution of Proteaceae can be explained by vicariance caused by the break-up of Gondwana. Location 

Africa, especially southern Africa, Australia, New Zealand, South America, New Caledonia, New Guinea, Southeast Asia, Sulawesi, Tasmania. Methods 

We obtained chloroplast DNA sequence data from the rbcL gene, the rbcL-atpB spacer, and the atpB gene from leaf samples of forty-five genera collected from the field and from living collections. We analysed these data using Bayesian phylogenetic and molecular dating methods, with five carefully selected fossil calibration points to obtain age estimates for the nodes within the family. Results 

Four of eight trans-continental disjunctions of sister groups within our sample of the Proteaceae post-date the break-up of Gondwana. These involve independent lineages, two with an Africa-Australia disjunction, one with an Africa–South America disjunction, and one with a New Zealand–Australasia disjunction. The date of the radiation of the bird-pollinated Embothriinae corresponds approximately to the hypothesized date of origin of nectar-feeding birds in Australia. Main conclusions 

The findings suggest that disjunct distributions in Proteaceae result from both Gondwanan vicariance and transoceanic dispersal. Our results imply that ancestors of some taxa dispersed across oceans rather than rafting with Gondwanan fragments as previously thought. This finding agrees with other studies of Gondwanan plants in dating the divergence of Australian, New Zealand and New Caledonian taxa in the Eocene, consistent with the existence of a shared, ancestral Eocene flora but contrary to a vicariance scenario based on accepted geological knowledge.

Keywords: AtpB; Bayesian dating; Gondwana; Proteaceae; atpB-rbcL spacer; dispersal; historical biogeography; molecular dating; rbcL; vicariance

Document Type: Research Article

DOI: https://doi.org/10.1111/j.1365-2699.2007.01749.x

Affiliations: 1: Royal Botanic Gardens and Domain Trust, Mrs Macquaries Rd, Sydney, NSW 2000, Australia 2: Institute of Systematic Botany, Zollikerstrasse 107, CH-8008, Zurich, Switzerland

Publication date: 2007-12-01

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