The land-bird family Rallidae is cosmopolitan and global in distribution. An intriguing of this biodiversity is that there are many instances where islands support populations of widespread species, and derived island endemics. Several exampes of diversity arising from multiple colonisation events are known (see below). Despite this clear indication that individuals of at least some rail lineages are adept at dispersing and establishing new populations, even across oceans, there is also evidence that different regions of the world have distinct combinations of rail lineages.

Global Diversity
Genus level diversity of rails around the world (García-Ret al 2014a).

Age of the rails
Rail diversity dates to Eocene time about 40 million years ago but the stem of the rail clade dates back (according to genetic data) to about 50mya.

Multiple Invasions
Several bird lineages have each contributed to New Zealand avifauna by multiple colonisation. Most prominent are the rails (Rallidae), whose diversity illustrates this process of species accumulation. Only genera found in New Zealand are represented here; flying species by winged-bird icon and flightless by walking-bird icon. Right-facing flying-birds indicate breeding populations, left-facing ones indicate vagrants. Each flightless-bird icon indicates a different endemic species in the location indicated, and each different flying-bird colour/pattern represents a different species of;  Porphyrio blue, Gallirallus red, Fulica black, Porzana grey, Gallinula yellow. Several of the flightless species became extinct after human colonisation.

Swamphen diversity
Recent analysis of genetic variation shows that diversity of Porphyrio swamphens (blue icons above) is geologically young in age(<3mya). Nevertheless this includes populations of widespread flying swamphens and flightless island endemic species such as takahe (below). More on swamphens

References (Go to Publications page)

Trewick SA, Worthy T. 2000 Origins and prehistoric ecology of takahe: flightless Porphyrio (Aves: Rallidae). Chapter 4, Pp: 31-48. In: William G.L. and I.G. Jamieson (eds) The Takahe: 50 Years of Conservation Management and Research. Otago University Press, Dunedin.

Trewick SA. 2011. Vicars and vagrants: Assembly of the New Zealand avifauna. Australasian Science 32: 24-27.

García-R JC, Trewick SA. Dispersal and speciation in purple swamphens (Rallidae: Porphyrio). The Auk 132: 140-155

García-R JC, Gibb G, Trewick SA. 2014a. Eocene diversification of crown group rails (Aves: Gruiformes: Rallidae). PLoS ONE, 9:e109635.

García-R JC, Gibb G, Trewick SA. 2014b. Deep global evolutionary radiation in birds: diversification and trait evolution in the cosmopolitan bird family Rallidae. Molecular Phylogenetics and Evolution. 81: 96-108.

Trewick SA, Morgan-Richards M. 2014. New Zealand Wild Life. Penguin, New Zealand. ISBN-13:9780143568896 ISBN-10:0143568892