Biogeography of the Gondwanan genus Lomatia (Proteaceae): Vicariance at continental and intercontinental scales

Abstract

Aim: We tested whether the divergence of South American and Australian Lomatia was the result of the breakup of Gondwana, and assessed the date of divergence between Tasmania and mainland Australia, and across the Hunter River Valley. Location: South America (Chile and Argentina) and eastern Australia (Tasmania, Victoria, New South Wales and Queensland). Methods: We sequenced one chloroplast (psbA-trnH intergenic spacer) and two nuclear (PHYA and ITS) markers across all 12 species of Lomatia, five species of Telopea and Embothrium coccineum, and included sequences from GenBank for the rest of the tribe Embothrieae. Species relationships were inferred using Bayesian and maximum likelihood analyses, then divergence times estimated using the random local clock in beast. Results: The chronogram is congruent with geological events: SAm (SAm (SAm (Tas (NEQld (SEAus north of the Hunter + SEAus south of the Hunter))))). South American and Australian species of Lomatia diverged between 35 and 64 Ma. Tasmanian species of Lomatia diverged from mainland Australian taxa c. 32 Ma. Mainland Australian species of Lomatia are mostly not corroborated as monophyletic but show a divergence either side of the Hunter River Valley, dated at 17 Ma. Main conclusions: The divergence date between South American Lomatia ferruginea and Australian species cannot exclude Gondwanan vicariance; however, divergences within South America occurred prior to separation of South America and Australia from Antarctica. Tasmanian species diverged from mainland Australia in the early Oligocene. Mainland Australian species of Lomatia are not resolved but form two clades representing populations north and south of the Hunter River Valley, confirming the Hunter River Valley as a significant barrier to gene flow for plants. We suggest that drying events that divided northern and southern floras at the Hunter River Valley occurred at the same time as those that divided eastern and western floras.