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Global Biodiversity
We examine
biodiversity at
several levels.
It has
evolutionary
and ecological
aspects.
Populations of species sometimes include
distinguishable subspecies with
nonoverlapping geographic ranges.
Subspecies typically differ morphologically
or behaviorally.
There may be many subspecies. Some
people recognize 30 subspecies of cougars.
There are 31 subspecies of the house
sparrow. Often unclear just what constitutes
a subspecies.
Evolutionarily Significant Unit:
a geographically isolated portion of the species
population that also has a high level of genetic
difference from other subpopulations of the species,
whether or not this difference is recognized
taxonomically.
The black sea turtle
Chelonia mydas agassizii ?
Of particular interest are endemic taxa.
Restricted to a particular region.
One aspect of biodiversity that we are concerned with is
the degree of endemicity of the biota of a region. If a
region has high endemicity, then it has many taxa that
are found nowhere else.
Areas with high endemicity include oceanic islands,
freshwater lakes in rift basins, and land areas bounded
by mountain ranges.
Some long-isolated
areas have
particularly high
levels of
endemicity.
Animal Info - Madagascar
Lemurs
Madagascar’s fossa
The Galapagos Islands
Marine iguana
Galapagos tortoise
Flightless cormorant
Darwin’s
Finches
What is a species?
Several concepts:
Biological species – a group of actually or
potentially interbreeding individuals that are
reproductively isolated from other such
groups.
Phylogenetic species – a group of individuals
that is distinct in its characteristics and has a
common ancestry.
Application of the phylogenetic species concept
will likely increase the number of recognized
species, with some current some subspecies
being elevated to species status.
So, how many species are there?
Around 1.5 million described. Many more undescribed.
How many remains in doubt. As many estimates as
there are biologists.
Terry Erwin fogged trees in the canopy of tropical
forests. From 19 trees belonging to one species, he
found 1,200 species of beetles. He estimated 162 to be
restricted to that tree species. Through a series of
extrapolations, he estimated that there were some
30,000,000 species of organisms on earth.
Biodiversity hotspots
Russia’s Lake Baikal
Nerpa
Golomyanka
Omul
Baikal lake Web World - Ichthyofauna of Baikal lake
African Rift Lakes
Lake Malawi
There are at least 280
cichlids in Lake Malawi,
perhaps as many as 1000.
The Cichlid Fishes of Lake
Malawi, Africa
California’s Vernal Pools
VernalPools.Org California Vernal Pools
In addition to biodiversity hotspots, we can see some
global trends in biodiversity:
Diversity tends to be higher in the tropics than at
higher latitudes. Why?
In terrestrial habitats, diversity tends to be higher in
mountainous regions. Why?
In marine habitats, diversity tends to be higher in
systems like coral reefs or mangrove swamps. Why?
There is also great variation above the species
level. The variety of interactions leads to a great
number of ecosystems.
However, there’s not really a good way of
recognizing distinct ecosystems. It’s probably
pretty much continuous.
We do, however, need a way of
designating ecosystems for conservation
purposes. Several have been developed.
Bailey developed a hierarchical system:
Domains
Divisions
Provinces
Baileys' Eco-Regions (July 1995)
Udvardy developed a classification of
biogeographic provinces based on 14 major
land and fw biomes and 8 biogeographic
realms. Biomes are ecosystem types defined
by dominant plant life forms, biogeographic
realms correspond to major continental units.
Altogether, his system identifies 193
biogeographic provinces. This has become the
basis for global conservation planning.
Udvardy's biogeographic regions
Measures of Diversity
alpha diversity –describe (richness and evenness)
beta diversity – degree of change in species from one
community type to another. Changes from region to region.
gamma diversity – for a region as a whole, the overall
richness in species reflects the number of community types
present, the alpha diversity of each, and the pattern of beta
diversity (change) from one type to the next type.
n
 p ln( p )
H'
i
i
i 1
Formula for one index of alpha diversity (Shannon Index)
What determines diversity? Who knows.
Some ideas…
Time
Stability
Productivity
Habitat heterogeneity
Predation, competition, etc.
Joe Connell
developed the
intermediate
disturbance
hypothesis.
Catastrophism
hypothesis.
How long has it
been since the
last
catastrophe?