Biodiversity is the outcome of evolutionary and ecological processes. Biodiversity causes biodiversity. Environmental factors have significant effect on genetic diversity. Evolution is the center of genetic processes. New spp. via micro-evolution or destruction via macro evolution or diversity via mutation.
Factors for Biodiversity Creation
(A) Primary factor
(B) Ecological Templates
(C) Interactive intimate factors
(A) Primary factors
Physical & geographical reasons, determinant of environments in certain regions of world, creates wide & regional set up.
The primary reasons for causing biodiversity are:
a. History and age of particular ecosystem: Older the ecosystem higher the biodiversity.distribution of present day biodiversity is the result of two historical events of the earth.
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- creation & existence of single super-continent and the subsequent split and continental drift of fragments
- Second major historical influence are creation of ‘refugia’ or natural sanctuaries because of extreme environmental pressure on spp.
b. Gradients: Biodiversity did not occur scatteredly but harmonically with range of different climatic factors.
- Significantly gradual increasing trend of biodiversity from polar to equatorial region like latitudes, other factors such as altitude, oceanic depth, salinity, aridity, etc. also control biodiversity.
- In arid region, diversity poor, whereas with increasing rainfall diversity increases.
- In coral reef, diversity rich; it decreases with increase in depth. Deeper part of ocean supports little or less biodiversity; reasons: less light, low diffusible gases, low heat and high pressure.
- Aquatic biodiversity high in freshwater and ocean water, low in mixed region i.e. in brackish water (estuaries).
- Two places situated in equal distance and altitude from sea enjoys low diversity in arid but high in wet regions.
- Geological era also control gradients of biodiversity, i.e. Pleistocene glacier destroyed biodiversity in nearest temperate zone which has not yet been recovered because of time gap; however, undisturbed equatorial region got longer time for creation of new species to make its biodiversity richer. For this reason equatorial tropics richer in biodiversity compared to Tundra.
c. Habitat heterogeneity: Environmental factors suitable or unsuitable for community determines heterogeneity. Coral reefs and tropical forests: suitable environment for diversity. Causes:
- Climate not so harsh, not unpredictable.
- Seasonality not so much distinct, waterlogging absent; these favouring creation of high biodiversity and biological productivity.
- Desert: Unsuitable environment, less diversity and less productivity because of extreame climate factors, invaded spp. can not multiply and survive vigorously.
- Tropics: Higher spp. diversity, total productivity high; help rare spp. to sustain and multiply and easily saved from getting extinct. When biological productivity low, rare spp. and spp. growing in restricted small area, they may get suddenly extinct, so called “spp.-energy hypothesis”.
“Speciesarea relationships”: higher the area higher the biodiversity, but valid only between two comparable ecosystems Such as tropical rainforest of Brazil & Indonesia.
However, biodiversity must be dissimilar between 2 incomparable ecosystems e.g. large desert and small part of tropical rain forest or large area of tropical forest. Usually large area can give support to large number of species.
- Isolated habitats support low diversity; habitat dissected into smaller parts biodiversity will also be less.
- Biodiversity of islands depends upon pattern of immigrants.
- If chance of immigrants little, spp. diversity will be lesser.
- Isolation & area creates ‘source habitats’ place where a sp. multiplies just to survive.
- Isolation & area also creates ‘sink habitats’ where spp. can not keep its population survived without help of immigrants. When immigrant arrives in sink habitat, it is called ‘rescue effect’.
- When population of different dissected parts connected by immigrants called ‘metapopulation’, i.e. a metapopulation is a set of populations in separate patches but linked by immigration.
(B) Ecological template
- Productivity: Low productivity showing ecosystems can not show high biodiversity; because some special spp. can not survive with low productivity; high productivity can also support some time very low diversity e.g., water bloom formation by some spp., some dominant grass spp. in grass land ecosystem.
- Scaleless pattern: caused because of body size, population abundance, number of species, rules for the structure of food webs and interrelationships among species.
- Habitat Complexity : The more complex the architecture of a habitat the greater the diversity of species.
(C) Interactive intimate factors
- Succession: Ecological processes by which spp. reaches to climax community; cause diversity.
- Interaction between spp. may increase or decrease diversity; competition, mutualism, exploitation, engineering i.e. one sp. allows physical and functional facilities for others etc.
- Disturbance: natural calamities may cause or destroy biodiversity e.g., fire, storm, landslide, etc. may cause immediate death or destruction of spp. or may create denuded land & invite succession. In disturbed part some spp. may become superior to nutrient, light, etc. Disturbance in patchy distribution may cause unsuitable for dominant spp.
- Dispersal: dispersing strength of sp. may be related to diversity. It depends upon behavior & salient features of spp.” carrying of reproductive parts of a species to different places” is its dispersal. It is done by means of spores, seeds, fruits, etc. Almost every sp. does have some capacity of dispersal. When dispersal crosses big barriers called ‘jump dispersal’. Sp. become diffusive to its adjacent regions via dispersal.