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Biodiversity Introduction
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Biodiversity
What is it?
How do we measure it?
Why is it important?
"A definition of biodiversity that
is altogether simple,
comprehensive, and fully
operational ... is unlikely to be
found." (Noss, 1990)
History
The term was introduced as Biological
Diversity in 1968.
It was not used by the general scientific
community before the early 1980’s.
The term ‘Biodiversity’ was first used in a
scientific publication in 1988.
The term incoporates what was
earlier called natural diversity or
natural heritage.
It has, rather unfortunately,
displaced the more precise terms
of species diversity and species
richness, which have a long
history of scientific use.
Species Diversity
The effective number of species
represented in a collection of
individuals.
Species Richness
quantifies how many different
types the dataset of interest
contains.
Definitions
There are at least several definitions of the
term:
"totality of genes, species, and ecosystems of a
region;“ (Larsson 2001)
"Biological diversity is the variety of life
forms...at all levels of biological systems
(Wilcox 1982)
Four levels of biodiversity are generally
considered to exist:
species
ecosystem
genetic
molecular
Measuring diversity at one level
in a group of organisms may not
precisely correspond to diversity
at other levels
For species and ecosystem levels
the following may be applied.
How do we measure
biodiversity?
The oldest method is to merely to count the
number of species in the area of interest.
Sounds simple?
How and what do we count?
Accounting for differences in
percentages
Indices of Diversity - Used with nominal
scale data
(Which have no mean or median). Most
based on information theory which
considers uncertainty synonymous with
diversity.
Shannon-Weaver Index
Shannon-Weaver index, H'= (n log n – the
summation of k, from i=1 of fi log fi)/n.
Further, H'max=log k, and, J'=H'/H'max.
J' has been called evenness, homogeneity or
relative diversity. 1-J' can then be considered
as a measure of heterogeneity or dominance.
Brillouin’s Index
where H=(log n! – summation of the log
fi!)/n;
Hmax=(log n! - (k-d)log c! -
dlog(c+1)!)/n;
and, J=H/Hmax
There are numerous indices
Simpson’s Index
Inverse Simpson’s Index
Gini-Simpson Index
Berger-Parker
The methodology you use to
count the species in your samples
can dramatically alter your
findings.
Some simple methods
Meter square
Line transect
Line transect with sidelines
Other more exotic methods may
include arial photography, direct
count by snorkling or scuba,
canopy ‘rides,’ etc.
Gotelli & Colwell 2001
Quantifying biodiversity: procedures
and pitfalls in the measurement of
species richness. Ecology Letters
4:379-391
“Species richness is a
fundamental measurement of
community and regional
diversity, and
it underlies many ecological
models and conservation
strategies.”
“In spite of its
importance, ecologists have not
always appreciated the effects of
abundance and
sampling effort on richness
measures and comparisons.”
Magurran, A. 2004. Measuring
Biodiversity.
Genetic Biodiversity
Genetic diversity, the level of biodiversity,
refers to the total number of genetic
characteristics in the genetic makeup of a
species.
It is distinguished from genetic variability,
which describes the tendency of genetic
characteristics to vary.
Genetic diversity serves as a way
for populations to adapt to
changing environments. With
more variation, it is more likely
that some individuals in a
population will possess variations
of alleles that are suited for the
environment.
This is, in essence, a new name
for population genetics
Measuring population
biodiversity
Gene Diversity is the proportion of
polymorphic loci across the genome.
Heterozygosity is the mean number of
individuals with polymorphic loci.
Alleles per locus is also used to demonstrate
variability.
Centers of Genetic Biodiversity
A center of diversity is an area that
has a high degree of genetic variation
for a particular species or genus of
plants that can also be the center of
origin for that species.
It works for animals as well, e.g.
salmon
The importance of genetic
biodiversity
Genetic diversity is the sum of genetic
information contained in the genes of
individual plants, animals, and micro-
organisms.
Each species is the storehouse of an immense
amount of genetic information in the form of
traits, characteristics, etc.
The number of genes ranges
from about 1000 in bacteria to
more than 400 000 in many
flowering plants.
Each species consists of many
organisms and virtually no two
members of the same species are
genetically identical.
This is technically not true!
An important conservation
consequence of this is that even if
an endangered species is saved
from extinction it has probably
lost some of its internal diversity.
Subsequent inbreeding in small
populations may result in:
a) reduced fertility and
b) increased susceptibility to
disease.
Genetic diversity is usually
mentioned with reference to
agriculture and maintaining food
security.
This is because genetic erosion of
several crops has already occurred
leading to the world's dependence
for food on just a few species.
However, aquaculture is
approaching this state at a far
quicker pace that traditional
aquaculture has done. E.G. Salmon
Currently, a mere 100-odd
species account for 90% of the
supply of food crops, and three
crops – rice, maize, and wheat –
account for 69% of the calories
and 56% of the proteins that
people derive from plants.
Poulson et al 2012
‘…biodiversity is of tremendous
global importance, being central
to the well-being and
development of
millions of people in developing
countries.’
“In June 2012, at the UN
Conference on Sustainable
Development (or “Rio+20”),
global leaders from governments
and civil society reaffirmed the
intrinsic value of biological
diversity and recognised the
severity of global biodiversity loss
and degradation of ecosystems”
While aimed at dryland
biodiversity conservation, this
book contains relevant
information for any biodivesity
conservation effort, particularly
on the necessary efforts of
governments and policy makers
at all levels, as well as science.