Biodiversity I: meaning and
measurement
Bio 415/615
Questions
1. What are the major components of
‘biodiversity’ as broadly defined?
2. What is species evenness, and how is it
different from species richness?
3. How is the concept of biodiversity
related to the science of phylogenetics?
4. How do alpha and beta diversity differ?
5. What role do keystone species play in
ecosystems?
Historical Conservation Themes
• Individual species or groups (Intrinsic rights
and utilitarianism)
• Wild, pristine, human-free places
(Preservation Ethic)
• Wise use, sustained yield, sustainability
(Resource Conservation Ethic)
• Holism of Leopold, people in the equation
(Evolutionary-Ecological Land Ethic)
• And now: Biodiversity
Defining Biodiversity
• Definitions…measurement…monitoring
The variety of life in all its forms,
levels and combinations. Includes
ecosystem diversity, species diversity,
and genetic diversity.
IUCN, UNEP and WWF, 1991
Biodiversity is the variability among all
living organisms from all sources,
including, inter alia, terrestrial, marine
and other aquatic ecosystems and
ecological complexes of which they are
part; this includes diversity within
species, between species and of
ecosystems.
Convention on Biological Diversity
The totality of
the inherited
variation of all
forms of life
across all levels of
variation, from
ecosystem to
species to gene.
Edward O. Wilson
Biodiversity means the whole variety of
life on Earth.
Biodiversity is the grand diversity of life
on Earth and all the interconnections
that support these myriad forms of life.
Biodiversity…is perhaps most commonly
defined as "the full variety of life on
Earth."
"A definition of biodiversity that is
altogether simple, comprehensive,
and fully operational ... is unlikely to
be found.“
(Noss 1990)
Extremes
• Narrow definition: species richness
• Inclusive definition (Noss):
– Genes, species, ecosystems
– Composition, structure, function/process
Inclusive hierarchy
• Species diversity (numbers and
abundances of species)
• Genetic diversity (numbers and
abundances of genes, genotypes, genetic
material)
• Ecosystem diversity (biotic and abiotic
components)
Noss 1990
SCALE as
integral to
biodiversity
concepts
Species, MUs, and ESUs
• Species concepts
– Morphological
– Biological
– Phylogenetic
• MUs=Management units
• ESUs=Evolutionarily significant units
What’s a species?
Biological Species Concept: "species
are groups of interbreeding natural
populations that are reproductively
isolated from other such groups“
(Ernst Mayr)
Horse +
Donkey =
Mule
Morphological Species Concept: a
group of individuals that look like
each other, not necessarily due to
common ancestry
Oak
Trees,
Ducks
What’s a species?
Phylogenetics: use of genetic
information to identify shared
ancestry
Humans,
other apes
split 6-8
mya
Phylogenetic species: group of
individuals that shares a
common ancestor
Everyone
alive today
shares a
common
ancestor
from ca.
130,000
ybp
Also called cladistics
Cladistics / Phylogenetics
Integrated molecular tools
to quantify biodiversity
Taxonomy-free!
• Phylogeny
• Identity: DNA
barcodes
• Individual variation
Janzen’s biodiversity gadget: a
decade away?
Captain, I’m picking
up the hybrid
genotype of
Polystichum
acrostichoides and
lonchitis…
Types of species for conservation
•
•
•
•
•
•
Indicators
Keystones
Umbrellas
Flagships
Vulnerables
Foundation
Indicator species
• A species representative of an entire
ecosystem, habitat, ecological process,
or environmental condition
American dipper needs clear,
unsilted streams to
forage effectively for
food
Indicator species
Carnegia gigantea
Hastings and Turner, The Changing Mile
Keystone Species –
A species that has a significant effect
on the presence and abundance of many
other species in a community: far out of
proportion to its biomass
Starfish – Pisaster
Sea Otters
Trophic
Cascade
Urchin barren: no kelp!
Ecosystem Engineers / Transformers –
Organisms who build a structure (or
otherwise modify a habitat) that allows
an entire community to exist
Beaver dams & ponds
Animals nest
Foundational Species –
Organisms whose presence provides the
structure that allows an entire community
to exist
Trees in a forest
Kelp in a kelp forest
Pickleweed in an
estuary
‘Ecosystem Engineers – Transformers’
‘Foundational’
Other species concepts
• Umbrella species have ranges that
encompass many other (imperiled)
species: protect it’s habitat, and you
protect the rest
• Flagship species are
conservation icons:
charismatic, lots
have human-like
faces (esp. eyes) and
sometimes cuddly
Species diversity defined
• Species richness = number of species
• Species evenness or equitability = more
similar in relative abundance
Which has the highest
diversity?
Community 1
5 monkeys
5 lions
5 frogs
5 herons
5 cows
Community 2
1 monkey
2 lions
1 frog
18 herons
2 cows
1 reptile
Which community has the highest evenness,
which has the lowest?
Community 1:
10 toads, 10 rabbits, 10 lions, 10 fish
Community 2:
4 toads, 4 rabbits, 4 sheep, 4 elephants
Community 3:
7 toads, 3 rabbits, 3 sheep, 3 elephants
Community 4:
7 toads, 3 rabbits, 3 sheep, 1 elephant
Diversity indices
Emergent properties of communities,
integrating richness and evenness.
Example: Shannon diversity (H’):
pi = proportional abundance of species I
Consider transformation: e^H’ (easier to interpret)
Diversity indices
“A community’s diversity index is
merely a single descriptive
statistic, only one of the many
needed to summarize its
characteristics, and by itself, not
very informative” (Pielou 1975)
Rank-abundance Graph
Abundance
Community with 10 frogs, 7 rats, 4 chipmunks,
2 mice
10
8
6
4
2
0
1
2
3
4
Rank by abundance
A more realistic distribution of abundance generally
requires a log scale
889 oak trees, 100 bay trees, 10 maple trees, 1 birch
tree
% of individuals
100
10
1
.1
.01
1
2
3
4
Rank by abundance
Length of the line
changes with diversity
Slope generally
changes with diversity
Slope changes because
of the change in
evenness that
generally correlates
with system diversity
What would the slope
be in a perfectly even
community?
Alpha vs. beta diversity
Alpha diversity: single location. Eg, per area.
(within site)
Beta diversity: differentiation diversity;
change (between sites)
Alpha is simple. Beta is not!
Often tied to gradient analysis: ie, measuring diversity within and
among plots. But there are many ‘non-gradient’ forms.
Beta diversity (species turnover)
Community 1:
A, B, C, D
Community 3:
A, B, C, D
Community 2:
E, F, G, H
Community 4:
C, D, E, F
Species turnover between community 1&2 is 4
species, between 1&3 is 0 species, between 1&4
is 2 species