'Sea of Dimeria' along the lowland region of Western Ghats
In Dimeriinae, about 90% of the known world species can be found in the following three areas, viz. Peninsular India, Sri Lanka and Southern China. Most of the species are having restricted distribution in one of these 3 regions.
The distribution pattern inferred from the literature and herbarium data indicates that subtribe Dimeriinae was naturally distributed in the southern erstwhile Gondwanaland region, an area composed of Madagascar, India, Sri Lanka, Australia and South East Asia, especially the Malesian region.
Three species are restricted to Madagascar, and all of them are endemic. This geographical isolation of Malagasy species from other species of Dimeria by approximately 2000 km, indicate an interesting direct phytogeographical link between Peninsular India and Madagascar. Some species are also found in volcanic soils of Mascarene Islands. This distribution supports the geological data which indicated that the archipelagic connections existed between the Indian plate, the Mascarene plateau, Madagascar and Africa until 75 million YBP!
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