Thursday, January 22, 2015

[Ornithology • 2015] Dispersal and Speciation in Purple Swamphens (Rallidae: Porphyrio)

Location (top) and genetic relationship between different swamphen populations. The genetic relationships were found using two types of DNA: mitochondrial (bottom left) and nuclear (bottom right). Circles with multiple colours show interbreeding between populations.

Dispersal, when accompanied by reduced gene flow and natural selection, influences speciation rates among groups of organisms. We used molecular phylogenetics, divergence time estimates, and population genetics to reconstruct the mode, pattern, and tempo of diversification within the wide-ranging purple swamphens (genus Porphyrio), with emphasis on the “supertramp” P. porphyrio. Our results suggest that the Porphyrio clade arose during the Middle Miocene in Africa, with a single colonization in the Americas and several other colonizations in Southeast Asia and the Indo-Pacific around 10 mya. We found that the widespread P. porphyrio is not monophyletic. Indeed, several subspecies and subspecies groups may represent species-level lineages. The P. p. melanotus lineage probably reached Australasia during the Pleistocene (600 kya), although some islands were colonized only in the past few hundred years. New Zealand, and some other islands, had previously been colonized (∼2.5 mya) by flying Porphyrio that evolved into flightless endemic species. Early and recent lineages are now sympatric. Widespread occupation of oceanic islands implies high dispersal and colonization rates, but gene flow probably occurs episodically and follows varying routes at different times. This pattern of colonization enables populations to differentiate and, ultimately, speciate.

Keywords: biogeography, dispersal, phylogeny, speciation


Juan C. Garcia-R. and Steve A. Trewick. 2015. Dispersal and Speciation in Purple Swamphens (Rallidae: Porphyrio) [Dispersión y especiación en las gallinas de agua (Rallidae: Porphyrio)]
The Auk. 132(1):140-155. DOI: 10.1642/AUK-14-114.1

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