Biodiversity I: meaning and measurement
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Transcript of Biodiversity I: meaning and measurement
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)
Morphological Species Concept: a group of individuals that look like each other, not necessarily due to common ancestry
Horse + Donkey = Mule
Oak Trees, Ducks
What’s a species?
Phylogenetics: use of genetic information to identify shared ancestry
Phylogenetic species: group of individuals that shares a common ancestor
Also called cladistics
Humans, other apes
split 6-8 mya
Everyone alive today
shares a common ancestor from ca. 130,000
ybp
Cladistics / Phylogenetics
Integrated molecular toolsto 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
Hastings and Turner, Hastings and Turner, The Changing MileThe Changing Mile
Carnegia giganteaCarnegia gigantea
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
TrophicCascade
Urchin barren: no Urchin barren: no kelp!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
‘Foundational’‘Ecosystem Engineers – Transformers’
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?
5 monkeys 5 herons 5 lions 5 cows5 frogs
1 monkey 18 herons2 lions 2 cows1 frog 1 reptile
Community 1 Community 2
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)
Community with 10 frogs, 7 rats, 4 chipmunks, 2 mice
1 2 3 4Rank by
abundance
Ab
un
danc
e10
8
6
4
2
0
Rank-abundance Graph
889 oak trees, 100 bay trees, 10 maple trees, 1 birch tree
1 2 3 4Rank by abundance
% o
f in
div
idu
als
100
10
1
.1
.01
A more realistic distribution of abundance generally requires a log scale
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: Community 2:
A, B, C, D E, F, G, H
Community 3: Community 4:
A, B, C, D 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