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Biodiversity of India

  • Biodiversity of India

India has a rich and varied heritage of biodiversity, encompassing a wide spectrum of habitats from tropical rainforests to alpine vegetation and from temperate forests to coastal wetlands. India figured with two hotspots – the Western Ghats and the Eastern Himalayas.

India contributes significantly to latitudinal biodiversity trend. With a mere 2.4% of the world’s area, India accounts for 7.31% of the global faunal total with a faunal species count of 89,451 species.

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Bio-geographical regions of India

India has two major realms called the Palaearctic and the Indo-Malayan, and three biomass, namely the tropical humid forests, the tropical dry/deciduous forests, and the warm desert/semi-deserts. India has ten biogeographic regions including the Trans-Himalayan, the Himalayan, the Indian desert, the semi-arid zone(s), the Western Ghats, the Deccan Peninsula, the Gangetic Plain, North-East India, and the islands and coasts. India is one of the 12 centres of origin of cultivated plants. India has 5 world heritage sites, 12 biosphere reserves, and 6 Ramsar wetlands. Amongst the protected areas, India has 88 national parks and 490 sanctuaries covering an area of 1.53 lakh sq. km. India’s record in agro-biodiversity is equally impressive. There are 167 crop species and wild relatives. India is considered to be the centre of origin of 30,000-50,000 varieties of rice, pigeon-pea, mango, turmeric, ginger, sugarcane, gooseberries etc and ranks seventh in terms of contribution to world agriculture.

what is Gradient in biodiversity

Gradients in Biodiversity       (please subscribe and share our YouTube channel Science World)                  

Latitudinal Gradients in Biodiversity

The word ‘tropical’ usually evokes images of a dense jungle packed with all sorts of different creatures, or a coral reef full of fishes of many different colours. However, ‘the tropics’, i.e. the zone extending approximately 30º north and south of the Equator (Pringle 2000), includes also huge extents of desert and savannah which appear, on the contrary, to contain low numbers and diversities of living organisms.

Are then, the tropics, more biologically diverse than other climatic zones? In fact, this is the most universally accepted and oldest recognized pattern in ecology. The tropics have extraordinarily high species richness or, viewed from a different perspective, areas outside the tropics have extraordinarily low species richness (Blackburn and Gaston 1996).

Generality of latitudinal diversity gradients

Despite this recognition of the generality of latitudinal diversity gradients, our knowledge is biased towards some taxonomic groups, regions and ecosystems. First, studies have been biased towards vertebrates, which make up less than 5% of species on Earth. For example, many mammals peak in species richness in the tropics (Kaufman 1995), while some insect groups show reversed latitudinal gradients (Kouki et al. 1994).
Second, diversity gradients described for the northern hemisphere seem to be invalid for the southern hemisphere (Platnick 1991, Boyero 2002). For example, terrestrial vertebrates are more species rich in Central America than North America, but that is not the case in tropical versus temperate Australia (Schall and Pianka 1978). Species richness of Odonata per unit area is similar in tropical and temperate South America, while it is about 29 times greater in Central America than in North America. The so-called ‘boreal bias’ (Platnick 1991) exists because the vast majority of studies have been performed by ecologists from North America and Europe.

Third, most of the available information comes from terrestrial or marine ecosystems, while fresh waters have received little attention, even though they contain 20% of the Earth’s vertebrate species (Rohde 1998). Nevertheless, available data show that freshwater fish and macro invertebrates are more diverse in the tropics. For example, the number of fish species in tropical lakes far exceeds that of temperate lakes (e.g. 1450 species in the lakes Victoria, Tanganyika and Malawi versus 212 species in the North American Great Lakes and Lake Baikal; Rohde 1998).

A similar pattern is found in rivers (e.g. 2000 species in the Amazon and 700 in the Congo, versus 250 species in the Mississippi and 70 in the Danube, Pringle 2000). Some stream macro invertebrates are more diverse in the tropics in Australia  and America (e.g. 25 species of Odonata and 32 of Ephemeroptera per unit area (106 km) in North America, versus 717 Odonata and 206 Ephemeroptera in Central America; Boyero 2002).

The causes for latitudinal gradients in biodiversity

The determinant of biological diversity is, clearly, not latitude per se, but the environmental variables correlated with latitude. More than 25 different mechanisms have been suggested for generating latitudinal diversity gradients, but no consensus has been reached yet (Gaston 2000).

One of the factors proposed as a cause of latitudinal diversity gradients is the area of the climatic zones. Tropical land masses have a larger climatically similar total surface area than land masses at higher latitudes with similarly small temperature fluctuations (Rosenzweig 1992). This may be related to higher levels of speciation and lower levels of extinction in the tropics Moreover, most of the land surface of the Earth was tropical or subtropical during the Tertiary, which could in part explain the greater diversity in the tropics today as an outcome of historical evolutionary processes (Ricklefs 2004).

The higher solar radiation in the tropics increases productivity, which in turn is thought to increase biological diversity. However, productivity can only explain why there is more total biomass in the tropics, not why this biomass should be allocated into more individuals, and these individuals into more species (Blackburn and Gaston 1996). Body sizes and population densities are typically lower in the tropics, implying a higher number of species, but the causes and the interactions among these three variables are complex and still uncertain (Blackburn and Gaston 1996).

Higher temperatures in the tropics may imply shorter generation times and greater mutation rates, thus accelerating speciation in the tropics (Rohde 1992). Speciation may also be accelerated by a higher habitat complexity in the tropics, although this does not apply to freshwater ecosystems. The most likely explanation is a combination of various factors, and it is expected that different factors affect differently different groups of organisms, regions (e.g. northern versus southern hemisphere) and ecosystems, yielding the variety of patterns that we observe.

The importance of understanding latitudinal gradients in biodiversity
Understanding the global distribution of biodiversity is one of the most significant objectives for ecologists and bio geographers (Gaston 2000). But, beyond purely scientific goals, this understanding is essential for applied issues of major concern to humankind, such us the spread of alien invasive species, the control of diseases and their vectors, and the likely effects of global environmental change on the maintenance of biodiversity (Gaston 2000).

Tropical areas, usually located in developing countries, play a prominent role in this picture, as their rates of habitat degradation and biodiversity loss are exceptionally high. Just as very little information existed on ‘natural’ conditions of temperate ecosystems before they were dramatically altered, this information is very scarce today for the tropics. The difference is that, today, it is not too late to collect this information

how we can characterized Community biodiversity

  • Community Diversity (You can visit my educational YouTube channel Science World)

 Ecologists have developed ways to characterize species diversity in a given area:

  • Within-habitat diversity or alpha-diversity: refers to a group of organisms interacting and competing for the same resources or sharing the same environment. Measured as # of species within a given area.
  • Between-habitat diversity or beta-diversity: refers to the response of organisms to spatial heterogeneity. High beta-diversity implies low similarity between species composition of different habitats. It is usually expressed in terms of similarity index between communities (or species turnover rate) between different habitats in same geographical area (often expressed as some kind of gradient).
  • Geographical diversity or gamma-diversity: This term is used for the rate of turnover or replacement of species b/w similar habitat in different geographical areas. Such as difference in species. Diversity of habitat are the total landscape or geographical area is called GAMA DIVERSITY.

What are possible level of Biodiversity? (with examples)

  • Level of Biodiversity (For more Educational topics click on Science World)

Biodiversity is said to have three level or components that are:

  1. Ecological diversity: Indian ecosystem biodiversity is described at each three levels (biogeographical region, biotic province &biome.) largest identified ecosystem is biogeographical zone. The vast area covered by biogeographical zone contains a wide diversity of smaller units called biotic provinces. Finally in each biotic province various kinds of biomes. Biome classification follows the following terminology, distinguishing b/w forest, grasslands, wetlands, desert and other such ecosystems on the basis of their physical appearance & dominant biotic or Abiotic element. Vast range of terrestrial and aquatic environment on earth has been classified into no. of ecosystem. Such as: TROPICAL RAIN FOREST, GRASSLAND & WETLANDS.
  2.  Species diversity: It refers to variety of species in a region. With increase in fortunately, genetic diversity can be estimated by species diversity, and this has become the standard unit of measurement in most biodiversity surveys. Species have the advantage of being natural biological divisions and easily identifiable; their diverging appearances were the basis by which they were classified in the 18th century, and modern phylogenetic techniques more often than not produce species divisions similar to those of classical taxonomic divisions. For many groups of organisms, such as birds and flowers, public interest means that identification of many species is already known by large numbers of people. The degree of genetic variability at the species level, and indeed at any taxonomic level, can be maximized by taking species that differ by one another by as many characters as possible. If these characters represent different genetic elements, then the divergent species should represent greater genetic diversity.
  3. Genetic diversity

It refers to the variation of genes in species. Some argue that the fundamental unit of biodiversity is the gene. Genetic diversity is the degree of variability of the genetic material of an organism. Species are defined by the differences in their genes. High genetic diversity indicates populations that can more easily adapt to changing situations and environments, and also a greater assortment of materials that can be found, increasing the chances of finding a useful compound.  However, exact assessment of genetic diversity is both time-consuming and prohibitively expensive, requiring modern laboratories and expensive chemicals. We have so far been able to account for all the genes in just one species of bacteria! Realistically, investigators could only examine a minute fraction of the genetic diversity to be found using this approach, and time is often a constraint.