Trans-Atlantic, trans-Pacific and trans-Indian Ocean dispersal in the small Gondwanan Laurales family Hernandiaceae

Aim: To investigate the historical biogeography of the pantropical flowering plant family Hernandiaceae (Laurales), which today comprises 62 species in five genera. Location: Hernandiaceae occur in Africa (9 species), Madagascar (4), the Neotropics (25), Australia (3), southern China, Indochina, Malesia, and on numerous Pacific Islands (32). These numbers include two widespread species, Hernandia nymphaeifolia, which ranges from East Africa to the Ogasawara Islands and New Caledonia, and Gyrocarpus americanus, thought to have a pantropical range. Methods: We sampled 37 species from all genera, the widespread ones with multiple accessions, for a chloroplast DNA matrix of 2210 aligned nucleotides, and used maximum likelihood to infer species relationships. Divergence time estimation relied on an uncorrelated-rates relaxed molecular clock calibrated with outgroup fossils of Lauraceae and Monimiaceae. Results: The deepest split in the family is between a predominantly African-Madagascan-Malesian lineage comprising Hazomalania, Hernandia and Illigera, and an African-Neotropical lineage comprising Gyrocarpus and Sparattanthelium; this split may be 122 (110-134) Myr old. The stem lineages of the five genera date back at least to the Palaeocene, but six splits associated with transoceanic range disjunctions date only to the Oligocene and Miocene, implying long-distance dispersal. It is inferred that Hernandia beninensis reached the West African islands of São Tomé and Bioko from the West Indies or the Guianas; Hernandia dispersed across the Pacific; and Illigera madagascariensis reached Madagascar from across the Indian Ocean. Main conclusions: The disjunct ranges and divergence times of sister clades in the Hernandiaceae are partly congruent with the break-up of West Gondwana, but mostly with later transoceanic dispersal. An exceptional ability to establish following prolonged oceanic dispersal may be largely responsible for the evolutionary persistence of this small clade.