What is biodiversity and its global distribution

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What is biodiversity and its global distribution
Part 1
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Major themes of todays lecture 1) What is
biodiversity?2) What is a species?3) How many
species are there?4) How is biodiversity
distributed?5) What to preserve? 5) How to
pay for biodiversity ?
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What is Biodiversity?The term biodiversity was
coined by W.G. Rosen in 1985 while planning the
National Forum on Biological Diversity a
conference examining the loss of biological
diversity
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Definition of biological diversity Biological
diversity encompasses all species of plants,
animals, and microorganisms, the genes they
contain and the ecosystems and ecological
processes of which they are a part.It is an
umbrella term for the degree of natures variety.
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Biodiversity encompasses everything that is alive
on Earth, from microbacteria growing on rocks in
Antarctica to giant river otters in the Amazon
Basin.Ecological and evolutionary processesOn
a finer scale it also includes the genes and
genetic variation contained with in species
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It may be considered at three different levels

• Genetic diversity -- the sum of total genetic
  information contained in the genes of animals
  that inhabit the earth.

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• Species diversity, which refers to all the
  species -- somewhere between 10 and 100 million
  (only about 1.4 million have been described).

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• Ecosystem diversity -- the variety of habitats,
  biotic communities,

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4. Ecological and evolutionary processes that
produce and maintain biotic diversity
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What is a Species? Biologists classify life on
Earth into a hierarchical system which tries to
reflect evolutionary relationships, i.e., who
evolved from whom?
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In descending orderKingdom - Animalia,
Eubacteria, Protista, Archaebacteria, Fungi,
PlantaePhylum - Chordata (about 100
others)Class - MammaliaOrder - PrimatesFamily
- HominidaeGenus - HomoSpecies - sapiens
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The last two designations are referred to
together as the Latin binomial and are used to
identify an organism. Homo sapiens
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Biological species concept Species are
generally thought of as a population or group of
populations which share genes, interbreed, and
are reproductively isolated from other species.
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Anagenesis
Cladogenesis
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Classical Allopatry the steps...

• 1) species range is divided in
• to two
• 2) populations evolve independently - genetic
  divergence accrues as a result of adaptation and
  by sampling drift and/or selection
• 3) If these forces are strong enough then
  reproductive isolation evolves
• 4) Once reproductive isolation is achieved
  speciation is complete

Geographic barrier
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Types of speciation
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While the Biological Species Concept is useful it
has many problemsIt does not take into account
the fact that many species have an evolutionary
history
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Example Australian quail-thrushes (Cinclosoma)
(Cracraft 1982)
interbreed
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Other species conceptsPhylogenetic species --
Joel Cracraft --concept combines phyletic
approach with biological reproduction.Cohesion
-- Alan Templeton -- where genetic processes are
important.Morpho-species -- based only on
morphology
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Adaptive radiations
Darwins finches
Hawaiian Honeycreepers
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How Many Species Are There?
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We know how many molecules are in a drop of
water and the size of the universe. The
approximate number of stars in the universe is
about 100 billion.But we cannot answer the
question of how many species exist on Earth by an
order of magnitude.
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Estimates range from 10 to 100 million. The
fact of the matter is that very few of the world
species have been described -- perhaps as little
as 2 of them.
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Reptilia (Reptiles)6,300 Echinodermata
(Starfish, etc.)6,100 Porifera (Sponges)5,000
Monera (Bacteria, Blue-green Algae)4,760
Amphibia (Amphibians)4,184 Mammalia
(Mammals)4,000 described species
Described species
Algae26,900 Pisces (Fish)19,056 Platyhelminthes
(Flatworms)12,200 Nematoda (Roundworms)12,000
Annelida (Earthworms etc.)12,000 Aves
(Birds)9,040 Coelenterata (Jellyfish, Corals,
Comb Jellies)9,000
Insecta 751,000 Plantae (Multicellular
Plants) 248,428 Non-insect Arthropoda
(Mites,Spiders,Crustaceans etc.) 123,151
Mollusca (Mollusks)50,000 Fungi 46,983
Protozoa 30,800
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Bacteria -- most lists include only 4,000
species but the actual number is probably in the
millions.
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Keystone species and resources

• Certain species maybe more important that others
  with respect to ecological function

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Terms describing biodiversity

• Alpha diversity - species richness
• Beta diversity - degree to which species
  composition changes with distance (i.e. along an
  environmental gradient)
• Gamma diversity - refers to the number of species
  in a large area
• Endemism - when species are restricted to
  particular region

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Theory of Island Biogeography
The relationship between species abundance
area and distance
Robert H. MacArthur
Edward O. Wilson
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species
AREA
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Large areas tend to hold more species.
S CAzS number of speciesA areaZ type
of island (0.15-0.35)C type of species
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For a bird of prey on a number of islands,
whereC1 and z0.25area species10km2 210
0 31000 610,000 10Note a ten-fold
increase in island area does not result in a
ten-fold increase in number of species.Here a
ten-fold increase leads to an increase by a
factor of two.
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Islands
a
Imagine a row of newly emerged islands all an
equal distance from the mainland but differing in
size.Islands will fill up at the same rate
because immigration rates are the same.
Mainland
b
c
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Islands
However, extinction rates will be slower on the
larger islands because a larger island means more
space and larger populations of any given
species.Over time the larger islands will
contain more species.
a
Mainland
b
c
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Distance effectsThe farther an island is from
the mainland, the fewer number of species will be
able to colonize it.
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Islands
Imagine islands of the same size but at
increasing distances from the mainland.
Extinction rates will be the same as they fill
up, but because immigration rates will be lower
on the distant islands they will end up at an
equilibrium, with fewer species than nearby
islands.
Mainland
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These dynamics can be described for a single
island
Species per unit time
Number of present species
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These same principals may be applied to habitat
islands on the mainland and are useful to
biologists in studying the effects of
fragmentation.
Good
Poor
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Vast majority of reserves are small
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Minimum Critical Size of the Ecosystem Project
-MCS (started in Brazil in the early 1970s)
By isolating a replicated series of 1, 10, and
100ha forest patches and studying the presence
and absence patterns of biota before and after
isolation, predictions could be generated on what
size forest patches are needed to maintain given
percentages of the original diversity.
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lt10 hectare fragmentsArmy ants require more than
plotsLost also were 5 species of ant birds
which follow them
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A keystone species in tropical forests are dung
beetles. They bury dung and carrion as food for
their larva which means that nutrients are
recycled more rapidly and many pathogens which
reside in the dung are killed.
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Small forest fragments had fewer species of dung
beetle than large forests - as a result dung
decomposed at a slower rate in smaller forest
fragments
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Why where there fewer beetles in smaller
fragments? 1) fewer vertebrates -- less
dung 2) climate of smaller fragments is
hotter and dryer 3) rarer beetle may go
extinct in smaller fragments because of chance
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On smaller plots monkeys that ate fruit
disappeared (because not enough fruit ripens at
any given time) while leaf- eating monkeys
survived.
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In sum, these studies suggest that forest
fragmentation can have a widespread effect on
community interactions and ecosystem processes.
This information is essential for designing
reserves.
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How is biodiversity distributed?Where are most
species found?
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RainforestsMuch of the attention has focused on
tropical rainforests because of the great
diversity of species found there.
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Rainforests cover only 7 of the Earth's land
area but are believed to contain over 50 of the
worlds species.
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On a single tree in the lowland forests of
Amazonia Ed Wilson found 43 species of ants
comprising 26 genera that was equivalent to the
entire ant fauna of the British Isles.
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In a one-hectare plot 584 species of large
trees,200 species of lizards and snakes,600
species of birds.
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The first step is to establishing conservation
priorities.1) by region (Hotspots) classified
by species richness and endemism and levels of
threat2) by country
Mapping Biodiversity
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Endemic Bird Areas and Centers of Plant Diversity
in Forests (source http//earthtrends.wri.org/)
World Resources Institute
WRI
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Species Richness and Endemism by River Basin
WRI
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Conservation Internationals Hot
spots (http//www.biodiversityhotspots.org)
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Long-wattled umbrella bird
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Others have proposed identifying Megadiversity
Countries.
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Although basic scientific information on
biodiversity and endangered ecosystems should be
our first step in conservation decisions,
conservation programs are developed by
countries.Biodiversity is not evenly
distributed among countries.A very small
number of countries lying partly or entirely
within the tropics account for a very high
percentage of the worlds biodiversity and these
countries require special attention.About 12
countries fit this criteria, including Brazil,
Columbia, Ecuador, Peru, Mexico, Zaire,
Madagascar, Australia, China, India, Indonesia,
and Malaysia. These countries hold between 60
and 70 of the worlds biodiversity.
This concept recognizes that
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The focus on individual countries is not a triage
approach rather, it simply sees the reality of
political boundaries.The megadiversity
approach does not solve all of the problems. To
be effective one still needs to work within
countries.
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How well do the maps overlap?
Often poor overlap among different taxa
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Orme et al. 2005 Nature (readings)use a new
global database on the breeding distribution of
all known extant bird species to test for
congruence across three types of hotspot.
demonstrate that hotspots of species richness,
threat and endemism do not show the same
geographical distribution. only 2.5 of
hotspot areas are common to all three aspects of
diversity, with over 80 of hotspots being
idiosyncratic. low overall congruence of
biodiversity indices, with any one index
explaining less than 24 of variation in the
other indices. These results suggest that, even
within a single taxonomic class, different
mechanisms are responsible for the origin and
maintenance of different aspects of diversity.
Consequently, the different types of hotspots
also vary greatly in their utility as
conservation tools.
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Other problems with focusing only on species
richness and endemismmay miss regions important
in ecological and evolutionary processes - the
ones that produce and maintain biodiversity-mov
ements patterns-elevational gradients
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Ecological processes
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Swainsons Thrush (Catharus ustulatus)
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