DST-NRF CENTRE OF EXCELLENCE
FOR INVASION BIOLOGY
Ecology and Biodiversity
Energy and Food webs
What is biodiversity
The biodiversity crisis
The Convention for Biological Diversity
How to measure biodiversity
Links
WHAT IS ENERGY?
Energy is the property of a system that
enables it to do work
Several forms of energy: kinetic, potential,
heat, chemical, nuclear and radiant energy.
Common measures of energy: joules (SI
Unit), calories and kilowatt-hours
SOURCES OF ENERGY
Sun: primary source of energy on earth
Fossil fuels: coal, oil
Nuclear energy
LAWS OF ENERGY
1st law of energy: Energy cannot be created or
destroyed but can be transferred from one form
to another
2nd law of energy: When one form of energy is
transferred into another form, some useful
energy is always lost as heat, therefore, energy
cannot be recycled.
In nature systems go from order to chaos - Entropy
is the amount of disorder in a physical system
Closed system: entropy remains constant or
increases
In an open system: entropy can decrease, at a local
scale - by using energy, this tendency can be
“reversed” - Think of a teenager’s bedroom
FLOW OF ENERGY
Solar
energy
herbivores
carnivores
top carnivores
HEAT ENERGY RETURNED TO THE ATMOSPHERE
death and decay
plants
ENERGY & NUTRIENT FLOW IN A
FOOD CHAIN
Solar
energy
Plants
Inorganic
nutrient pool
Energy
Nutrients
Consumers
(herbivores and carnivores)
Decomposers
MARINE FOOD CHAIN
TERRESTRIAL FOOD CHAIN
EXAMPLES OF A FOOD CHAIN
EXAMPLE OF A FOOD WEB
Definition of Biodiversity
“Biological Diversity or BiodiversityThe variety of life in all its forms, levels
and combinations. Includes ecosystem
diversity, species diversity, and genetic
diversity.”
Ecosystems
River, forest, high alpine, …
Species
Fir, spruce, oak, …
Genetic diversity
Different alleles in
a population
More Definitions
Visualise the Earth as being made up of
building blocks
We start with an INDIVIDUAL
An organism is an individual from any
kingdom
A group of individuals from the
same species together in
an area is known as
a POPULATION
More Definitions
Populations of different
species are usually found
living together making up
a COMMUNITY
The grouping of both living communities
and their non-living surroundings form an
ECOSYSTEM
River, forest, high alpine, …
More Definitions
A BIOME consists of many different
ecosystems together
Map taken from:
http://www.environment.gov.za/enviroinfo/nat/biome.htm
Species diversity
Chordates incl.
vertebrates
Plants
Insects
After Purvis & Hector 2000
Nature 405: 212-219
Many studies have focused on a few groups
of organisms; mostly plants and vertebrates.
Ecologists should also investigate the effects
of environmental change on invertebrates.
Biodiversity in South Africa
South Africa is home
to an unique selection
of species. This even
includes the worlds
smallest floral kingdom.
South Africa is a signatory to
the Convention for Biological
Diversity that aims to reduce
the loss of biodiversity.
Capensis
The Cape Floral Kingdom
The smallest of the six floral kingdoms
(the Western Cape province).
With a very rich flora including many
endemic plant families.
Like Australis, Capensis is regarded as a
segregated remnant of an ancient
Antarctic Floral Kingdom (Gondwana).
Fynbos traditionally thought to be less
rich in insects than other habitats.
Seeds of many fynbos plants are ant –
dispersed (myrmechory)
Cape Floristic Biodiversity Hotspot
One of the world's five Mediterranean hotspots
Characterised by evergreen fire-dependent
shrublands
The greatest non-tropical concentration of
higher plant species in the world
The only hotspot that encompasses an entire
floral kingdom,
5 of South Africa’s
12 endemic plant
families and 160
endemic genera.
The Succulent Karoo Biodiversity
Hotspot
Richest succulent flora on earth
69% of plants are endemic
Reptiles show relatively high levels of endemism
One of only two entirely arid ecosystems to earn
hotspot status
Home to the mysterious tree-like succulent, the
“halfmens”, as well as many unique species of
lizards, tortoises and scorpions
Threats: Grazing,
agriculture and mining,
especially for diamonds
and heavy metals
Maputaland-Pondoland-Albany
Biodiversity Hotspot
Highest tree richness of any temperate forest on
the planet (nearly 600 tree species)
Important centre of plant endemism
The celebrated, bird-of-paradise flower is a
distinctive hotspot endemic
Rescue of the white rhino from extinction (took
place in this hotspot) one of the best-known
success stories in African conservation
Threats: industrial and
local farming and the
expansion of grazing lands
Why should we care about
biodiversity?
Why we should worry about biodiversity is debated
Intrinsic value
Ethical value (e.g. god’s creation)
Economic value (e.g. medicines)
Ecosystem services (one of the
most important reasons from a
scientific perspective) The Earth’s
organisms and ecosystems maintain
our planet’s life support system
■
Increased stability
■
Increased adaptability
■
Increased productivity
Recreation
But …
Man only uses a small number of species
directly for food, medicines, building
materials, recreation, … (90% of human
food sourced from plants comes from just
30 species)
Many species seem to fulfil similar
functions.
Some monocultures are more productive
than diverse systems (under ideal
conditions).
However, healthy functioning ecosystems
are vital to ensure that there essential
resources (e.g. air and water) for life on
Earth
What determines local biodiversity
Area
Connectivity
Productivity
Disturbance
History
…
Species-area relationship
Larger areas harbour more
species.
(MacArthur & Wilson 1967 Theory of Island
Biogeography, Princeton Univ. Press)
■ less extinctions
■ more immigrations
■ more diverse habitats
■ etc.
Same book also
explain why more
isolated areas are
less diverse.
Diversity-productivity relationship
Overall areas with higher productivity
seem to have larger diversity as well.
However, some monocultures seem
to be very productive (under ideal
conditions).
Highly productive systems may have
reduced diversity through increased
competition. The diversity-productivity
relationship is scale-dependent.
Intermediate disturbance
Under stable conditions some species will outcompete others.
Disturbance creates free space for establishment by
removing strong competitors. Thus disturbance
creates a more patchy environment with different
successional stages coexisting.
However, in strongly disturbed habitats only a few
specialists can survive.
Disturbance events can vary in frequency
and severity.
Cattle: cow pads,
grazing, trampling
Tractor: opening of bare
Ground, aeration, …
Fire: ash,
removal of litter
INDICATORS OF BIODIVERSITY
Assumption: indicator is correlated
with overall biodiversity.
Indicators can be taxa or abiotic
variables
Cost effective
Time savings
Easy and accurate to measure
Biodiversity Indices
Problem how to decide what is a
diverse site/ which site has a higher
diversity
Simplest method: Species richness
Other Indices contain more information
about the species composition than just
richness
Equitability or evenness
Evenness
Site dominated by one species
If you select an individual at random it is
likely to be a grasshopper
Site with even species distribution
If you select an individual at random it is
equally likely to be any of the four species
# Individuals
30
25
Site dominated by
single species
Site with more even
species distribution
20
15
10
5
0
Species
Biodiversity Indices
Shannon-Wiener Diversity: H
Shannon-Wiener Equitability: EH
Simpson’s Diversity: D
Simpson’s Equitability: ED
S
total number of species in
the community (richness)
Useful for questions
like:
pi
proportion of S made up of
the ith species
“Which site is the most
diverse?”
“Are school grounds
impoverished?”
Biodiversity Indices
Renkonen index
Sørensen index
p1i = Frequency of species i in site 1
p2i = Frequency of species i in site 2
a = Number of shared species
b = Number of species only in site 1
c = Number of species only in site 2
Useful for questions like:
“Is ant species composition within a habitat type (e.g. fynbos)
more similar than ant species composition between sites from
different habitats?”
“Are school grounds more similar to each other than nature
reserves are to other nature reserves?”
Links (Biodiversity)
Convention on Biological Diversity
Handbook (the 3rd Edition)
http://www.biodiv.org/handbook/defa
ult.asp
IUCN Red lists
http://www.redlist.org/
Biodiversity Hotspots
http://www.biodiversityhotspots.or
g/Pages/default.aspx
Links (General)
Air photograps
http://earth.google.com/
can be linked with antbase
http://www.antweb.org/google_earth.jsp
Control sites:
South Africa National Parks
http://www.sanparks.org/
Cape Nature Conservation managed
reserves
http://www.capenature.org.za