MODES OF ORIGIN 17Box 2.2 The splitting of Gondwanaland and the debate between vicariant and dispersalist
explanations in island biogeography
The origin of many contemporary continental-
fragment islands is directly linked with the
breakup of Gondwanaland, the southern
supercontinent that split apart from Pangaea, the
last unique landmass, some 160 Ma. At the start
of the Cretaceous period (c.140 Ma)
Gondwanaland was still intact. By the Late
Cretaceous (c.80 Ma), however, South America,
Africa, and peninsular India were already discrete
entities (Stanley 1999). It was during the
Cretaceous that first Madagascar, and later the
Seychelles and Kerguelen micro-fragments, began
their trip to their present isolated geographic
locations in the south-west, north-west, and
south of the Indian Ocean, respectively. Australia
and New Zealand rifted from Antarctica about
100 Ma, and subsequently, New Zealand broke
first from Australia and then from Antarctica
about 80 Ma (Lomolino et al. 2005). While other
elements of Gondwanaland drifted toward the
lower latitudes, the Antarctic slowly moved
poleward, so that by about 24 Ma it was located
over the South Pole, triggering the development
of a great icecap.
Although Kerguelen is too far south (50
latitude) to possess a diverse biota, other ancient(a)(c) (d)(b)
Arabian
PeninsulaArabian
PeninsulaArabian
PeninsulaArabian
Peninsula200 my130 my 100 my160 myAustraliaAustraliaAustraliaAustraliaAfrica AfricaAfricaSouth
AmericaSouth
America
South
AmericaSouth
AmericaIndiaIndiaIndiaIndiaAntarcticaAntarcticaAntarcticaNew ZealandNew Zealand New ZealandNew ZealandSouth PoleSouth Pole South PoleSouth PoleMadagascarMadagascarMadagascarMadagascarAntarcticaAfricaThe stages in the breaking up of Gondwanaland. Bold lines show zones of sea-floor spreading. (From Storey 1995.)