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