Biodiversity
I.
What is Biodiversity?
A.
B.
C.
D.
II.
III.
IV.
V.
Levels of biodiversity
Characterizing biodiversity
Defining species
How many species are there?
Measuring Biodiversity
Patterns of Biodiversity
Ecological components of Biodiversity
Biodiversity Crisis
I. What is Biological Diversity?
“the millions of plants, animals, and
microorganisms, genes they contain, and the
intricate ecosystems they help build into the living
environment” (World Wildlife Fund, 1989)
“Biodiversity" also has served on occasion as a catch-all for "conservation" itself.
B. Characterizing Biodiversity
NOMENCLATURE:
Taxonomic Hierarchy
Kingdom
Animalia -- animals
Phylum
Arthropoda -- arthropods
Subphylum
Crustacea Brünnich, 1772 -- crustaceans
Class
Malacostraca Latreille, 1802
Subclass
Eumalacostraca Grobben, 1892
Superorder
Eucarida Calman, 1904
Order
Decapoda Latreille, 1802 -- crabs, crayfishes, lobsters, prawns, shrimp
Suborder
Pleocyemata Burkenroad, 1963
Infraorder
Superfamily
Family
Genus
Species
Stenopodidea Claus, 1872
Astacoidea Latreille, 1803
Cambaridae Hobbs, 1942 -- crayfishes
Fallicambarus Hobbs, 1969
Fallicambarus devastator Hobbs and Whiteman, 1987 -- Texas prairie crayfish
IDENTIFICATION AIDS
7(6). Coxa of fourth pereiopod lacking caudomesial boss (Fig. 6a)...................................................................
Coxa of fourth pereiopod with caudomesial boss (Fig. 6b-d) ...............................................................
8
9
8(7). First pleopods, in resting position, deeply withdrawn between bases of pereiopods and largely
concealed by dense setiferous mat extending from ventrolateral margins of sternum (Fig. 7a):
...............................................................................................................Hobbseus Fitzpatrick and Payne, 1968.
First pleopods, in resting position, never deeply withdrawn between bases of pereiopods and
never concealed by dense setiferous mat extending from ventrolateral margins of sternum
(Fig. 7b): ......................................................................................................Orconectes Cope, 1872 (part).
9(7). Opposable margin of dactyl of chela with abrupt excision in proximal ½ (Fig. 8a):............................
.....................................................................................................................Fallicambarus Hobbs, 1969b (part).
Opposable margin of dactyl of chela without abrupt excision in proximal ½ (Fig. 8b-e):...............
.......................................................................................................................Cambarus Erichson, 1846 (part).
Figure 6
Figure 7
Figure 8
1) Biological Species
Concept
2) Evolutionary/Phylogenetic
Species Concept
3) Morphospecies Concept
4) Evolutionary Significant
Unit
Testing an hypothesis that a set of populations is
a single species is important to conservation
management.
Sets of recognized species often form the basis
for surrogates for geographic priority setting.
1. BCS
• Proposed by Ernst Mayr, 1942
• Legal definition employed in the
Endangered Species Act
• Criteria =
• Confirms the lack of gene flow, thus
showing evolutionary independence
2. ESC
• First proposed by G.G. Simpson, 1961
• Criteria =
• Populations must have been evolutionarily
independent long enough for diagnostic
traits to emerge
• Species are named on the basis of
statistically significant differences in the
traits used to estimate the phylogeny
3. MSC
• Criteria =
• Good to use for fossil specimens
Problems:
Doesn’t account for behavioral or genetic differences
evident in cryptic species
The skull on the left is from the
Peloncillo Mts., west of the Rio
Grande in New Mexico near the
Arizona border. The skull on the
right is from the Franklin Mts. of
Texas, east of the Rio Grande.
Molecular evidence now indicates
that these are two separate species
despite the great morphological
similarity.
ESU & the genetic species concept
• Determining what to conserve (distinct
evolutionary units) is oftentimes very
difficult
• How do you account for genetic diversity
below the “species” level?
Natural selection
Phenotypic
differences
Historical Isolation
Genetic
differences
Canis latrans
Canis rufus
D. How many species are there?
Determining the actual # impossible…
Species richness in major groups of organisms. The main 'pie' shows the
species estimated to exist in each group; the hatched area within each slice
shows the proportion that have been formally described. Nature 2000 v405
II. Measuring Biodiversity
A.
B.
C.
D.
E.
Species richness
Alpha diversity
Beta diversity
Gamma diversity
Diversity Indices Shortcomings
A. Species richness [S]
• Number of different species
Endemism –
Ecological distinctiveness of different
species, e.g., functional differentiation
Evolutionary distinctiveness of different
species
B. alpha diversity
• # of species in a certain community, “the
species richness of standard sample sites”
Equitability, Evenness [E]
 Diversity index = mathematical measure of species diversity
in a community. Provides more information about community
composition than simply species richness
• Simpson Index - It takes into account the number of species
present, as well as the relative abundance of each species. It
represents the probability that two randomly selected
individuals in the habitat belong to the same species.
– 1 – D, the index represents the probability that two individuals
randomly selected from a sample will belong to different species
• Shannon Diversity Index – takes into account the proportional
abundance of different species and the eveness.
– [H’ = -∑i pi ln(pi)]
 most widely used index in community ecology
 The higher the number the greater the diversity
C. Beta diversity
• diversity associate with changes in sample
composition along an environmental
gradient
• Measures the rate of change in species
composition across a landscape
• S/α – 1
• Can determine the following
Site 1
Region X
Site 2
Site 3
Region Y
Site 4
D. Gamma diversity
• Used to compare large areas that
encompass diverse landscapes or a wide
area
• landscape scale where diversity also
controlled by site-to-site variation in
ecological controls, disturbance regime,
habitat diversity, dispersal
E. Diversity Indices Shortcomings
1) Richness & evenness can be inversely
related
2) Mathematical measures don’t
correspond to ecological importance
•
•
All species are treated as “equal”
value of the species in the ecosystem not
correlated
III. Patterns of Biodiversity:
A. Species-Area Relationship
• Direct relationship between species
richness and area
• The number of species on an island is a
constant power of the island’s area
Patterns of Biodiversity:
B. Global Patterns
• Species distribution affected by several
factors:
Lacustrine fishes
earthworms
bats
birds
Woody plants
Spatial Patterns in Species Richness
Nature 2000 v.405
Patterns of Biodiversity:
C. Regional Trends in Diversity
 Marine environments –
 Freshwater wetlands highest in
temperate landscape
 Edge –
Biodiversity “HOT SPOTS”
http://www.biodiversityhotspots.org/xp/Hotspots/
Additional Considerations
Habitat generalists
Habitat specialists
Endemism and rarity
Disturbance
Disturbance & Species Richness
• Habitat heterogeneity and disturbance
Higher heterogeneity =
• Diversity-Stability Rule –
• in a more variable environment selection forces
come from physical environment…more stable
environment, selection forces are largely biotic competition
Why do we need to study
biodiversity?
• Ecological Value:
– Biodiversity actually boosts ecosystem productivity &
functionality where each species, no matter how
small, all have an important role to play and that it is
this combination that enables the ecosystem to
possess the ability to prevent and recover from a
variety of disasters.
– Ecological components of biodiversity
IV. Ecological components of biodiversity
A. Functionality:
B. Productivity –
Biodiversity is linked to productivity is linked to
biodiversity????
 The more resources available (nutrients, plants or prey
species)
 The more energy
 A greater number of
VI. Biodiversity Crisis
• Part of the natural cycle, precedes
speciation events
• Problem?
• Rates of extinction v. speciation
• Current rates of extinction:
Mass extinctions through time –
(62 million year periodicity)
From the 2004 World Conservation Union Study:
Threatened animal species:
Fish
Invertebrates
Amphibians
Birds
Reptiles
http://www.iucnredlist.org/
Already extinct:
Mammals