SPECIES RICHNESS
READINGS:
FREEMAN, 2005
Chapter 54
Pages 1265-1277
CONSERVATION BIOLOGY
• Conservation biology is a new science that
has developed in response to concerns about
decreasing biodiversity.
• It seeks to understand the effects of human
activities on populations, species,
communities and ecosystems.
• It intends to develop practical approaches to
preventing declines in biodiversity and to
restore species into functioning ecosystems.
What is Biodiversity?
• Biodiversity is the full range of living
things on earth and their surroundings
and their heritage (genes).
• “Everything from genes to ecosystems”
• The millions of plants, animals, fungi
and microbes that inhabit earth; the
genes they contain; and the ecosystems
they help build.
Biodiversity Is Reflected In:
• Ecosystem (Community) Diversity as
described by community composition and
environmental conditions.
• Species Diversity as measured by species
richness (number of species) and relative
abundance of each species (species
evenness).
• Genetic (Populational) Diversity as
determined by morphological traits and DNA
comparisons.
ECOSYSTEM DIVERSITY
The diversity of life within the biosphere can be
seen at global, regional and local scales:
1. Biomes (Global) -- marine, freshwater,
terrestrial;
2. Life Zones (Regional) -- marine [littoral
(shore), pelagic (open water), benthic
(bottom), abyssal (dark), reef (shallow)];
3. Habitats (Local) -- prairie [wet, mesic, dry].
ECOSYSTEM DIVERSITY
• Preserved as National Parks.
• Natural areas owned by the Federal
Government.
• Preserved for scientific, educational and
recreational activities.
• Showcases of nature including a wide
spectrum of ecosystems.
NATIONAL PARKS
NATIONAL PARKS
NATIONAL PARKS
GENETIC DIVERSITY
The diversity of life is fundamentally genetic. A
variety of genetic methods have been used
to investigate diversity both within and
between species. Here are a few:
1. Morphological variation -- a good clue, but
does not correlate perfectly with genetics;
2. Chromosomal variation -- inversions,
translocations and polyploidy;
3. Soluble proteins -- blood groups, soluble
enzyme polymorphism’s;
4. DNA markers -- microsatellites, “fingerprint”
loci.
Morphological Variation
• Morphology
(appearance or
phenotype) provides
clues to the genetic
diversity that underlies
species differences.
• But, ‘looks can be
deceiving. The wolf and
coyote show distinct
mussel lengths. The red
wolf is in fact a hybrid
between these two
species; thus, has an
intermediate mussel
length
Chromosomal Variation
• This ideogram
(arrangement of
chromosome photos)
shows variation in
genetic material from a
species of Brazillian fish
species.
• This is a striking
example of genetic
variation within a
morphological species.
Soluble Protein Variation
• The human ABO blood
groups are an example
of soluble proteins that
demonstrate genetic
variation.
• Prior to DNA
technology, soluble
proteins provided some
of the first material for
studying heterozygosity,
a measure of genetic
variation.
SPECIES DIVERSITY
• Species Richness is a measure of the total
number of species in an area or taxonomic group.
A simple count of number of species.
• Species Evenness is a measure that indicates
how evenly the total number (abundance) of
individuals is apportioned among species. The
Simpson Index and Shannon-Weaver Index are
measures of evenness.
• Species Difference (Taxonomic Diversity) is a
measure of phenotypic differences among
species. A rough over-view of this concept is
seen in classification schemes.
SPECIES DIFFERENCE
(TAXONOMIC DIVERSITY)
• Classification system of Domains,
Kingdoms, Phyla or Divisions, Classes,
Orders, Families, Genera, Species.
• Two Domains - Prokaryotes &
Eukaryotes.
• Six Kingdoms - Archaebacteria,
Eubacteria, Protista, Plantae, Fungi,
Animalia.
SPECIES RICHNESS
• How many species on
earth?
• Only 1.5 million have been
classified.
• Best estimate places
number of species at 10
million.
• Birds, mammals and
butterflies are mostly
named and described by
science.
GROUP
SPECIES
PLANTS
307,000
ANIMALS
9,153,000
FUNGI
47,000
PROTISTS 30,000
BACTERIA 14,000
LICHENS
16,000
Global Distribution of Species Richness
• Highest species richness is found in tropical forests.
• Mammals and butterflies are often used as indicators
of species richness.
• Endemic species is found only in the local or regional
area. Numbers for Richness (Endemic).
COUNTRY
MAMMALS
Columbia
Indonesia
Peru
U. S.
New
Zealand
379(22)
547(182)
381(42)
347(96)
7(0)
BUTTERFLIES RANK
1,276(185)
988(417)
1,212(139)
292(22)
11(0)
1
2
3
21
135
SPECIES EVENNESS
• The Simpson Index (or Diversity Index) gives a
simple measure of evenness.
• It addresses the question: What is the probability that
two individuals encountered at random in a
community will belong to the same species?
• D = 1 - sum(pi)2
where D is the Diversity Index with values that vary
from 0 (all of same species) to 1 (myriads of species,
all equal in number);
sum over all species in community;
pi is the proportion of species i in the
community.
Simpson Index (or Diversity Index)
• For example, consider two communities
(1 and 2), each of which has 3 species,
A, B and C.
Species
A
B
C
Community Community
1
2
98
35
1
32
1
33
Simpson Index (or Diversity Index)
Species Community 1
Proportion (pi)
A
98
98/100 = 0.98
B
1
1/100 = 0.01
C
1
1/100 = 0.01
D = 1 - sum(pi)2 = 1 - [(0.98)2 + (0.01)2 + (0.01)2
= 1 - (0.96) = 0.04
Community 1 has very low species evenness.
Simpson Index (or Diversity Index)
Species Community 2
Proportion (pi)
A
35
35/100 = 0.35
B
32
32/100 = 0.32
C
33
33/100 = 0.33
D = 1 - sum(pi)2 = 1 - [(0.35)2 + (0.32)2 + (0.33)2
= 1 - (0.33) = 0.66
Community 2 has very high species evenness.
Diversity Increases Productivity (I)
• Hypothesis: More species result in
higher community productivity.
• Method: Plots with the same number of
plants, but with different numbers of
species were created. In the second
year of growth, the area of each plot
covered by plants was measured.
Diversity Increases Productivity (II)
60
TOTAL PLANT COVER (%)
• Results: Communities with
higher species richness had
a higher percentage of the
area covered by plants. See
Figures 53.24 and 55.4 in
Freeman (2005) for
description of the experiment
(page 1238) and definition of
functional groups (page
1271-1272).
• Conclusion: Diverse
communities are more
productive.
50
40
30
20
10
0
1
3
5
7
9
11
13
15
17
19
21
NUMBER OF PLANT SPECIES PER PLO T (S)
23
Biogeography and Species Richness
• Number of species on
an island is related to its
size.
• In general, a 10 fold
larger area will have
twice the number of
species in a given taxa.
• Conservation biologists
have used this
generalization to predict
species loss from
habitat destruction and
to determine optimum
preserve size.
Species-Area Relationships
(Lonsdale, 1999)
• The observation that
the number of species
in a sample plot
increases as a log-log
function of area is well
established.
• This graph indicated
data for native species
from 104 sites
throughout the world.
Species-Area Relationships
• To learn more about
species-area
relationships see the
laboratory on Biodiversity
and Nitrogen Deposition.
• Also, read section 53.3
on pages 1236-1239 and
1275-1276 in Freeman
(2005).
Species Loss in Local Communities
• Recensus of 54 Wisconsin
Prairies showed 8-60% loss of
native plant species after 32-52
years. Local extinction at a rate
of 0.5-1.0% per year.
• Annual rate of loss elsewhere:
Limestone out crop in England
(1.6%); Beech-Hemlock forest in
Pennsylvania (0.9-1.2%);
Calcareous grassland in Czech
Republic (1.1%); Seeps in
California (1.6%).
Declining Eastern U.S. Songbird Populations
• Migratory populations of
most songbird species
declined substantially sing
the 1940’s; those hardest hit
are scarlet tanager, wood
thrush, American redstart.
• Even some resident
populations have declined;
song sparrow, whitebreasted nuthatch.
• Others are stable; northern
cardinal, Carolina chickadee.
Causes of Decline in Native Populations
of Plants and Animals
• Habit Destruction: Conversion of natural areas into farms,
dwellings, industries, places of business and corridors for
transportation.
• Introduction of Exotic (Non-native) Plants and Animals: The
intentional or unintentional transport of a plant, animal, fungal,
protozoan or bacterial species into areas where they did not
previously occur.
• Overexploitation: Hunting, fishing, grazing, cutting, gathering,
collecting native plants and animals.
• Other: Pollution (particularly aquatic species); Unknown.
• Decline is often due to a combination of the above causes, as
well as demographic and other environmental factors.
Major Causes of Endangerment
Of 632 species listed as endangered in the 50 states,
the major causes of endangerment were:
Major Cause
Habitat Loss
Introduction of Exotics
(Predation)
(Competition)
(Pathogen)
Overexploitation
Unknown
Species
425
170
(120)
(45)
(5)
34
3
%
67
27
(19)
(7)
(1)
5
0.5
HABITAT DISTRUCTION
• Habitat loss and
fragmentation are the most
pervasive threats to the
conservation of biodiversity.
• Farming and logging prior to
the 1900’s were responsible
for most habitat loss in
eastern U.S.
• Residential and commercial
development are the primary
reasons for habitat loss in
recent times.
Loss of Forest Habitat
1620
1850
1920
• The rate of loss of
deciduous forest habitat
between the 1850’s and
early 1900’s is more
than 10 times faster
than after.
• In fact, today forest
acreage is increasing
due to abandonment of
farmland.
Edge Effects in Fragmented
Forests
•
•
•
•
Biologists recorded forest
fragmentation by following the fate of
66 study plots in Manaus, Brazil. There
were four 1-hectare fragments, 3 10hectare fragments and 2 100-hectare
fragments.
The graphed results indicate a decline
in biomass in 16 study plots along
forest edges.
The loss of large trees along edges
reduced the number of habitat layers;
thus, beetles, orchids and birds
disappeared.
See Freeman (2005) Figure 55.7 for
more.
EXOTIC SPECIES
• Exotic or invasive species are non-native plants
and animals introduced into an area by people.
• They are able to establish populations in the wild.
• They lack natural predators, competitors or
pathogens in the new place.
• They often have “boom and bust” population
dynamics.
• Currently more than 4,500 exotic species in U.S.
• They are arriving at a high rate due to accelerated
trade and travel.
Examples of Introduced
(Exotic) Animal Species
• Flathead catfish -Introduced as a “sport” fish
into rivers of the SE and SW
US from the Midwest US.
• Asian Longhorn Beetle -Arriving from China on
shipping pallets into New
York City and Chicago.
• Cherry Bark Tortrix -- arriving
from Asia via Europe into
ports in Washington state ,
currently spreading into
Oregon.
Examples of Introduced
(Exotic) Plant Species
• Purple Loostrife -Introduced from Europe as a
horticultural plant.
• Tamerix -- Newly
established in SW US desert
as an escaped ornamental
introduced from Eurasia.
• Old-World Climbing Fern -A nursery escape in Florida
from SE Asia.
Introduction of Zebra Mussel
• The geographical distribution
of the zebra mussel is being
extended rapidly in the US.
• First reported in the St.
Lawrence Seaway on 21
November of 1991 it had
spread throughout the
Missouri and Mississippi
drainage basin by the year
2000.
OVERHARVESTING OF
WHALES
• The whaling industry engaged
in harvesting almost to the
point of extinction of some
species.
• End of commercial harvest -Blue Whale 1969; Fin Whale
1975; Sei Whale 1977; Sperm
Whale 1982.
• International ban on whaling.
• Resumption of harvest will call
for a sustained yield harvest.
OVERHARVESTING OF
GINSENG
• Ginseng is used as
a herbal by people
throughout the
world.
• Harvesting natural
populations in
eastern U.S. has
endangered this
deciduous forest
plant.
SPECIES RICHNESS
READINGS:
FREEMAN, 2005
Chapter 54
Pages 1265-1277