ByPRANAVATHIYANI GB.Sc Bioinformatics

Biodiversity is the degree of variation

of life.

This can refer to genetic variation,

species variation, or ecosystem

variation within an area, biome, or

planet.

ѻ Diversity is a function of

two factors: number of

species (Species

Richness) and number of

specimens belonging to

these species (Evenness).

ѻ Several indices

measuring diversity have

been proposed, giving

more or less weight to

either of these two

factors.

PATTERN OF DISTRIBUTION

Both species occupy the same tree.(A) Apteryx australis occupies thefloor (B) Rhipidura fuliginosaoccupies the canopy branches

(A)

(B)

MICROHABITAT concept

Geological history

Climate

Availability of food

Chemistry of Environment

Competition

Global patterns of terrestrial vertebrate diversity analysed in the study.Each of the 32 bioregions is coloured by its vertebrate species richness (amphibian,reptile, bird, mammal richness combined; dark green represents the lowest valuesand dark red represents the highest values) (Jetz & Fine, 2012)

Species introduction led to new patterns of distribution

Macropus eugenii was thought to be extinct in

Australia for 100 years. But it has been

rediscovered in an island in New Zealand (2000

species) where a former governor of that country

introduced the species in 1862.

Introduction of mahogany species in the Philippines

led to hectares of biodiversity-dead zones.

Spatial and temporal isolation leads to

speciation

Migration constitutes a special kind of dynamic pattern

Ancient human migration patterns as derived from mitochondrial DNA

analysis

The tropics have the highest species diversity

Latitudinal gradients of species richness for swallow tail butterflies in three parts of the world. (Collin & Morris, 1985)

High species diversity is due to:

a. high productivity and food availability

b. high biomass and hence complex structure

c. past patterns of evolution

d. survival of fragments of habitats through the cold episodes of the last

2 million years.

e. degree of small-scale disturbance mosaic of successional processes

Diversity involves species richness and evenness and

generally increases during the course of succession

Species

Regulation

The patterns of species diversity

in an area or at any one time

are set by some combination of

three factors:

Chance

History and

Necessity.

Chance: random processes of birth, death and migration. A lizard

might arrive unpredictably on a remote island, for example, because

the log it was on happened to float in the right direction.

History: correlation through time as a function of reproduction. In

other words, if a species was abundant in the near past, chances are

that it will be abundant today. Also, progeny tend to cluster near the

parents, therefore, we tend to find organisms in "pockets" rather than

evenly distributed in space.

Necessity: The laws of growth, competition and interaction.

Different species flourish in different conditions. The number of

species that can coexist will depend on how complex the

environment is and on how strongly they compete with one another.

And, of course, the number of species of herbivores, predators and

parasites will depend on the number of plants, prey and hosts.