Biogeography the factors responsible for the distribution of


Biogeography is the branch of geography in which we study the
past and present distribution of organisam

It is an integrative field because it collects a lot of
information from different field such as ecology,evolutionary biology,geology
and physical geography.

There are three main branches of biogeography

The branch of biogeography in which we study the distribution
of plant over geological time is called phytogeography

The branch of biogeography in which we study the
distribution of animals over geological time is called zoogeography

Similarly the branch of biogeography in which we study the
distribution of microbes is called microbial geography

Areas of

There are three main areas of biogeography

Historical area is the broader classification of organisam
which help us in studing past and evolutionary history of species or organisam

Ecological biogeography shows the factors responsible for the
distribution of species, this is the short term distribution within species

Conservation focuses on protection of flora and fauna

Major concept of biogeography




Evolution, endemic area and speciation


The three basic events that shape the geography distribution
includes dispersal vacariace and extinctions events

These are the basic of biogeography


In this event individual move from an existing population

It may be ecological dispersal or geological dispersal

Ecological events mean move away from

BIOGEOLOGICAL EVENT: the shifting of species range by moving
over long distance across large barriers

MECHANISM OF DISPERSAL: when an organism move from one place
to another by its own mean . this movement may be active or passive ( move by
external force)

VICIERANCE EVENT: in this event geographical isolation of
population occurs. This isolation occurs due to some barriers, climate change
,formation of mountains and also due to some human activities.

Vicierance event can give rise to different but related
species. This event also leads to reproductive isolation.

EXTINCTION EVENT: in this event disappearance or termination
of specie occurs due to some factors. For example the change in climate, due to
epidemics , spreading of invasive species, deforestration ,hunting ,pollution
and global warming .

BARRIERS: barriers may be biotic and abiotic .the barriers restrict
movement of genes or individuals. They induce a specie to get tolerant


Physiological barrier: these barriers are outside of the
range of species for example land water, temperature and salinity

Ecological barriers: dispersing organisms must be able to
resist ecological hazards. For example predation and competition

Behavioral barriers: some organisms have the ability to
select suitable habitat can have the ability to disperse across the barrier

CONTINUOUS DISTRIBUTION: this is also known as cosmopolitan
distribution. In this distribution a species is found over a wide area . they
can cross barrier by fighting, rafting and swimming etc.

DISCONTINUOUS DISTRIBUTION: in this type of distribution the
continuity is broken. A specie living in different part on the earth.

DISJUNCT DISTRIBUTION: in this type of distribution a specie
having two groups but they are isolated from each other geographically due to
the range fragmentation, habitat fragmentation, production of fragmented
population and by different barriers.

RASP: the word RASP stands for reconstruct ancestral state
in phylogenies. This software mainly focus on historical biogeography by
constructing ancestral geographic distribution on phylogenetic tree

RASP software have different models

S DIVA: statistical dispersal vicarience analysis

DEC: dispersion extinction cladogenesis

S DEC: statistic DEC mode

BBM: boyesean benay MCMC

S DIVA: this is mostly used method for interfering
biogeographical histories,  rapid
results, high results and exportable graphics

In this method we can calculate the occurance of ancestral
range at a node

Original DIVA algorithm encodes 4 types od biogeographic
events i.e duplication, extinction, dispersal and vicierance

RASP: requires tree files, a final tree and distribution