Phytogeographical Distribution of  Rare, Endangered, Threatened and Endemic Taxa of India

    Biodiversity is the totality of genes, species and ecosystems in a region and can be divided into three main categories, viz. genetic diversity, species diversity, cultural diversity. Genetic diversity is the variation of genes within species. Species diversity refers to the variety of species within a region, and can be defined as a group of inter-breeding or potentially inter-breeding natural populations that are reproductively isolated from other such groups. Cultural diversity of human society includes diversity in language, religious beliefs, social structure, food habits, etc.

    The loss of biological diversity and the degradation of habitats and ecosystems may at its most be irreversible, ultimately resulting in extinction of species. The loss may be due to hunting, collection, persecution, habitat destruction and modification due to natural calamities as well as human activities, environmental and genetic uncertainty and also demographic uncertainty.

    Of the 3,00,000 estimated angiospermic species of the world, about 2,50,000 has been described till now. India is one of the megadiversity region of the world and has 18,000+ species of flowering plants occupying ca. 7% of world species. Out of the total twelve biodiversity hotspots in the world India has two, one is the north east region and other is western ghats. The rich and diverse vegetation of India is due to its varying climate and geographical conditions with varied ecological habitats. The geographical area of India is about 329 million ha and its coastline stretches to over 7000 km.

    Many plant species are becoming extinct or vulnerable to extinction due to various reasons like population crash, loss of specific pollinators, loss of reproduction and seed germination capacity, habitat destruction both natural and human induced, and also genetic variability. About 70 Indian plants are possibly / presumed extinct. Endemic flora of a country on the biogeography of the region, centres of speciation, areas of extinction, vicariance and adaptic evolution of the flora occurring in the country. Endemic species are of two types , viz. palaeoendemic – remnants of  older floras occurring in geologically old landmasses and, neoendemic – newly evolved endemic species of relatively recent origin from an actively evolving genetic stock occurring in a particular ecotone.

    India  ranks 7^th regarding agriculture species and has been a primary centre of domestication for rice, sugarcane, banana, tea, mango, cucumber, citrus, jute, minor millets, vignas, brassicas, jackfruit, alocasia, colocasia, cardamom, black pepper, ginger, turmeric, cucurbits, bamboos, etc., and asecondary centre of domestication for sesame, tomato, potato, maize, soyabean, etc. About 167 cultivated species of plants are estimated to have originated in India. It is also estimated that about 335 species of wild relatives of crop plants have originated in India of which about 60 are endemic.

 Plant Groups/Species in India

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