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.