India is one of the 12 mega diversity countries

by siddharth sanghvi

for NEETPLAY.COM

Nearly 45,000 species of plants and twice as many of animals have been recorded from India

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How many living species are actually there waiting to be discovered and named?

If we accept May’s global estimates, only 22 per cent of the total species have been recorded so far. 

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Applying this proportion to India’s diversity figures, we estimate that....

  There are probably more than 1,00,000 plant species and more than  3,00, 000 animal species yet to be discovered and described

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 Nature’s biological library is burning even before we catalogued the titles of all the books stocked there.

Patterns of Biodiversity

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1. Latitudinal gradients

Patterns of Biodiversity

Species diversity decreases as we move from equator towards the poles.  Tropics (23.5° N to 23.5°S) harbour more species than temperate or polar areas.

  Colombia located near the equator has nearly 1,400 species of birds while New York at 41° N has 105 species and Greenland at  71° N only  56 species.

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 India, with much of its land area in the tropical latitudes, has more than 1,200 species of birds.

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A forest in a tropical region like Equador has upto 10 times more vascular plants, as a forest of equal area in temperate midwest of USA.

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The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth

40,000 species of plants ,  3,000 of fishes 1,300 of birds  427 of mammals. 427 of amphibians   378 of reptiles More than 1,25,000 invertebrates

Amazonian rain forest

40,000 species of plants ,  3,000 of fishes 1,300 of birds  427 of mammals. 427 of amphibians   378 of reptiles More than 1,25,000 invertebrates

Amazonian rain forest

Scientists estimate that in Amazonian rain forests there might be at least two million insect species waiting to be discovered and named.

Amazonian rain forest

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Diversity in Tropics

Diversity in Tropics

Ecologists and Evolutionary biologists have proposed various hypotheses to explain greater biological diversity at the tropics.

(a) Speciation is generally a function of time, unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification

Hypothesis-1

(b) Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable Such "constant environments promote niche specialisation" and lead to a greater species diversity 

hypothesis-2

(c) There is more solar energy available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity.

Hypothesis-3

Species-Area relationships

Patterns of Biodiversity-2

Species-Area relationships

Patterns of Biodiversity-2

 Alexander von Humboldt .

German Naturalist & Geographer 

During his pioneering and extensive explorations in the wilderness of South American jungles, the great German naturalist and geographer Alexander von Humboldt observed that ..

 "Within a region species richness increased with  increasing explored area, but only up to a limit

The relation between species richness and area for a wide variety of taxa (angiosperm plants, birds, bats, freshwater fishes) turns out to be a Rectangular hyperbola

On a logarithmic scale, the relationship is a straight line  described  by the equation  log S = log C + Z log A  where S= Species richness A= Area Z = slope of the line (regression  coefficient)  C = Y-intercept

Ecologists have discovered that the value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group or the region (whether it is the plants in Britain, birds in California or molluscs in New York state, the slopes of the regression line are amazingly similar). 

But, if you analyse the species-area relationships among very large areas like the entire continents, you will find that the slope of the line to be much steeper  (Z values in the range of 0.6 to 1.2). 

Z values in the range of 0.6 to 1.2 For example, for frugivorous (fruit-eating) birds and mammals in the tropical forests of different continents, the slope is found to be 1.15 What do steeper slopes mean in this context?