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

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.

The conservation of mitochondrial genome sequence in Leucadendron (Proteaceae)

“…Using molecular dating, it was reported that Leucadendron evolved 40 millions year ago. (Barker et al 2007). Actinidia is dated even younger, approximately 20-26 million year ago (Qian and Yu 1991).…”

New Caledonia: a very old Darwinian island?

“…The same applies for Placostylus land snails, the sister group of which involves both the recently emerged Lord Howe Island and New Zealand ( Trewick et al in press). The New Caledonian sandalwood, Santalum austrocaledonicum, also differentiated recently, in this case from Vanuatu species 1-1.5 Ma (Harbaugh & Baldwin 2007 (Barker et al 2007). The New Caledonian freshwater shrimp genus Paratya (Page et al 2005) and galaxiid fishes (Waters et al 2000), sisters respectively to an Australian and a New Zealand group, are dated as younger than 12 and 9 Ma, respectively.…”

“…Another example is the radiation of the cricket genus Agnotecous ( Eneopterinae), which includes many species with peculiar stridulatory apparatuses that emit songs in unusually high frequencies and with harmonic shifts (Robillard & Desutter-Grandcolas 2004;Robillard et al 2007). The cockroach subfamily Tryonicinae (Blattidae) includes the speciose genus Lauraesilpha, the members of which exhibit a unique combination of Araucaria (Setoguchi et al1998) Angustonicus (Murienne et al 2005) geckos (Bauer et al 2006) Sapotaceae (Bartish et al 2005) Proteaceae (Barker et al 2007) Paratya (Page et al 2005) diving beetles (Balke et al 2007a, b) galaxiid (Waters et al 2000) Tasmantis Scincidae (Smith et al 2007) sandalwoods ( behavioural traits, wood eating, intestinal ciliates and solitary habits (Grandcolas 1997;Murienne 2006; in press a, submitted). These characteristics recall those of panesthiine cockroaches (Blaberidae), which include many wood-eating species in Australasia and throughout the southwest Pacific (including Vanuatu and Lord Howe Islands), but with the exception of New Caledonia (Roth 1991).…”

International Code of Area Nomenclature

“…Distribution patterns are corroborated as 'Gondwanan' if they are considered old enough (e.g. Gamble et al, 2008), and rejected as 'Gondwanan' if they are not (Barker et al, 2007).…”

“…Gondwana is an ancient supercontinent that existed from approximately 250-170 Ma, comprising what we now know as Australia, New Guinea, New Zealand, sub-Saharan Africa, Madagascar, India, Arabia, South America and Antarctica. The name 'Gondwana' has been used for all or just part of the once vast land-mass that began to break up in the mid-Jurassic: the 'Gondwana' of Philippe et al (2003) includes India, whereas the 'Gondwana' of Barker et al (2007) does not. Distribution patterns are corroborated as 'Gondwanan' if they are considered old enough (e.g.…”