If the island of Madagascar separated from the African continent about 130 million years ago, and from India between 65 and 80 million years ago, after the dismemberment of the supercontinent Gondwana, how did the diverse and exotic fauna that inhabit it got there? at the moment? An international investigation in which the Higher Council for Scientific Research (CSIC) has participated has concluded thatMost of the Malagasy fauna reached the island through repeated ocean dispersals after the separation from the mainland.
To reconstruct the history of the colonization of Madagascar, the team of researchers sequenced several genes from the main groups of vertebrates on the island and from the closest species from Africa, Asia and South America. Then, to date the divergence periods, they applied the so-called “molecular clock”, which allows estimating the evolutionary time from the number of differences between two DNA sequences. The results show that the origin of most of the Malagasy groups is relatively recent, geologically speaking, and that they colonized the island by oceanic dispersal, mainly from Africa, according to the researchers reported today in the journal PNAS. “Most likely, strong cyclones would drag large logs or small floating islands of vegetation to the mainland with what would be the first colonizers.“, explains the CSIC researcher David Vieites, from the National Museum of Natural Sciences.
At the end of the Cretaceous period there was a mass extinction across the planet. According to this study, only two groups of the vertebrate species that then lived in Madagascar survived this wave of extinctions: freshwater turtles and iguanas. The rest of the fauna present on the island later reached it by crossing the ocean in various periods. The Mozambique Channel that separates Madagascar from Africa has a depth of almost 3,000 meters, too deep for a drop in sea level to have allowed dispersal by land.
According to this study, subsequent diversification within the island was favored by the existence of humid forests, which allowed groups adapted to that habitat to diversify until Madagascar became one of the world’s biodiversity hotspots. Today, this island is home to unique fauna and vegetation, both for its high number of endemic species and for the great biodiversity it houses.
Despite everything, the CSIC researcher points out, the future of Madagascar’s biodiversity is uncertain. “ We humans have been on the island for only 2,000 years and 90% of the original surface of its natural habitats has already disappeared. It is necessary to stop the destruction of the forest and manage it properly so that this diversity is not lost shortly, ”he concludes.
