Transcript Measuring Biological Diversity

Biological Richness,
An Introduction
James A. Danoff-Burg
Dept. Ecol., Evol., & Envir. Biol.
Columbia University
Today: Introduction to
Biological Richness
Designing Surveys – Review of assignment 1
Why Study Biological Diversity?
Types & Aspects of Diversity
Evenness
Species Richness Indices
Rarefaction
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Application of Techniques –
An Exercise
Design a study, avoiding pseudoreplication
Include visual representations of sampling method
Include:
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Experimental question
Manipulations
Hypotheses (null, alternatives)
Target organisms
Censusing design
Censusing method
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Last Week’s Assignment
Project of your own design
Write up a short (2-3 paragraphs) description of
your proposed study in normal scientific prose
Include question and hypotheses (including null
and all alternative hypotheses)
Include sampling design, sampling method
Be specific and thorough
Email to [email protected] before the start of
class next week
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Types of Censusing Designs
Grid
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Using regular intervals along a 2-dimensional design
Transect
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Sampling with reference to a straight line
Random
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Can be used to site point-quarters, quadrats, other
sampling methods
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Choosing Between
Censusing Designs
How to choose between sampling layouts?
Depends on experimental question
Gradients
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Probably best to use a transect
Ensures comparability
Relatively uniform sampling area
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Random probably best – if done frequently enough, get
equal representation of areas included
Grid may be useful when need to uniformly sample area
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Surveying Design
Need to equally capture / census entire
community (or subset) to be studied
Be consistent
Have equal sampling effort in different areas
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Time, area, quantity sampled
Appropriately represent area studied
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Equally sample disparate constituent areas
Random vs. orderly (grid, transect)?
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Surveying Techniques
In short: Any viable form of collecting or sampling
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Need to be sited at a level appropriate to the question
Examples:
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Point-Quarter
• Proximity to a central point within a cross
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Quadrat
• Sampling within a small area
Pitfall traps
 Beating Sheets
 Mist netting
 Seining
 Etc…
Lecture 2 – Introduction to Biological Richness
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© 2003 Dr. James A. Danoff-Burg, [email protected]
Pseudoreplication Example
Treatment A
Treatment B
Site 1
Site 3
Site 2
Site 4
Lecture 2 – Introduction to Biological Richness
 Question – What is
the affect of
treatments A & B?
 Pseudoreplication
= treating stars of
the same color as
replicates
 Replication =
include only a single
star of each color,
or their average
© 2003 Dr. James A. Danoff-Burg, [email protected]
Today: Introduction to
Biological Richness
Designing Surveys – Review of assignment 1
Why Study Biological Diversity?
Types & Aspects of Diversity
Evenness
Species Richness Indices
Rarefaction
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Diversity is Interesting
Stimulated many poets, artists, naturalists, etc.
Ecotourism is prompted by biological diversity
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Or at least biological, geological, climatological diversity
Continual novelty is a key feature
Increasing probability of novelty, because of high
biodiversity, leads to increasing visitation rates
E.g., most ecotourism is to tropics
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Diversity as an Indicator
Diversity = health of the ecosystem
Diversity and stability relationship
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Example of Shahid Naeem’s work on trophic
redundancy and stability
Diversity and recovery from perturbations, erosion,
etc.
Diversity as a detective tool of the past
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Use to determine how long ago land was altered by
human or natural activity
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Diversity is controversial
Define diversity
Simple definitions work well
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Richness
Abundance
BUT these are not really “Diversity”
More complicated ones are less clear
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What does it mean?
More we try to define it, the less definable it is
Some have argued that it is meaningless (Hurlbert 1971)
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Today: Introduction to
Biological Richness
Designing Surveys – Review of assignment 1
Why Study Biological Diversity?
Types & Aspects of Diversity
Evenness
Species Richness Indices
Rarefaction
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Types of Biological Diversity
Point: diversity at a single point or
microenvironment
Alpha: within habitat diversity
Beta: species diversity along transects & gradients
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High Beta indicates number of spp increases rapidly
with additional sampling sites along the gradient
Gamma: diversity of a larger geographical unit
(island)
Epsilon: regional diversity
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Aspects of Biodiversity
What can we measure?
Possibilities
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Species (richness)
Abundance
Diversity
• relationship between richness & abundance
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Guild
Trophic structure
Evolutionary diversity
Within species diversity (genetic, morphological)
Others?
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Diversity of Diversities
Difference between the diversities is usually one of
relative emphasis of two main envir. aspects
Two key features
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Richness
Abundance
Each index differs in the mathematical method of
relating these features
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One is often given greater prominence than the other
Formulae significantly differ between indices
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Today: Introduction to
Biological Richness
Designing Surveys – Review of assignment 1
Why Study Biological Diversity?
Types & Aspects of Diversity
Evenness
Species Richness Indices
Rarefaction
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Evenness
Definition of Evenness
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How equally abundant are each of the species?
A simple way to combine abundance and richness
Rarely are all species equally abundant
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Some are better competitors, more fecund, more
abundant in general than others
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Evenness increases diversity
Increasing evenness greater diversity
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True for all indices
S=4
N=8
S=4
N=8
Higher
Evenness,
Diversity
Site 1
Lecture 2 – Introduction to Biological Richness
Site 2
© 2003 Dr. James A. Danoff-Burg, [email protected]
Evenness as an Indicator
For many ecosystems, high evenness is a sign of
ecosystem health
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Don’t have a single species dominating the ecosystem
Often invasives dominate
Paradox of enrichment
• E.g., polluted / enriched Lake Okeechobee, Florida
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Disturbed areas are mostly edge species
• Simple biodiversity
• Dominance of a few species ecologically, numerically
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Evenness Across Locations
Between ecosystem comparability is usually not
possible
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Some areas have lower biodiversity naturally than
others
• Tiaga is naturally much less even than the deciduous forest
• Tiaga is often dominated by a single species (e.g., Blue Spruce)
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Seasonality may confound the comparison as well
• Earlier in temperate growing season, less even than later
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This is a general principle for most all indices this term
When would you want to compare across
locations?
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Trying to prioritize areas for conservation
Based largely on biodiversity (not ecol. uniqueness)
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Today: Introduction to
Biological Richness
Designing Surveys – Review of assignment 1
Why Study Biological Diversity?
Types & Aspects of Diversity
Evenness
Species Richness Indices
Rarefaction
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Species Richness Indices
Richness has largely been the variable of interest
for many conservationists
There are many ways to treat species richness
Two main ones
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Raw Richness
Species Density
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Numerical species richness =
Raw Richness
Works best with complete surveys (everything
taken)
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These can be destructive
Need equal sampling effort
Popular in aquatic studies
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species seen per 1000 individuals
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Species Density
Useful in botanical surveys, sometimes in aquatic
surveys
Species / m2 if on a 2D plane
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Mostly botanical surveys, some arthropod surveys
Species / m3 if in a 3D space
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Aquatic or botanical canopy surveys
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Today: Introduction to
Biological Richness
Designing Surveys – Review of assignment 1
Why Study Biological Diversity?
Types & Aspects of Diversity
Evenness
Species Richness Indices
Rarefaction
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Rarefaction
Method to post-hoc treat data to correct for lack of
standardization of sampling effort
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Not always possible to collect in a standardized manner
Particularly true with “Natural Experiments”
May have some treatment areas larger than others
Able to collect in some areas for more time than others
Outcome
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To calculate the # of spp expected in each sample
If hypothetically, all samples were of a standard size
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Rarefaction
Designed by Sanders (1968), modified by Hurlbert
(1971)
Drawbacks
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Loss of information through data loss
• Expected number of abundance / species is all that is left
• Loss of abundance, richness data
See Worked example #1 in Magurran for more
information on how to do the calculation
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We will work through this next week
Read the example before hand
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
After Standardizing Efforts
Can now conduct simple richness comparisons
between sites
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Need to be comparable
Can do Margalef, Menhinick, Shannon, Simpson
analyses
We’ll begin these in two weeks
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Our Data This Term I
Relationship between plant biodiversity, pest
insect biodiversity, and beneficial insect
biodiversity
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Read website at
http://www.columbia.edu/itc/cerc/danoff-burg/webpages/gardens_main.htm
Has a pretty good amount of background on the topic
Field sites were in Manhattan and Brooklyn community
gardens
Data collected during summer 2001
I will also email you the data matrix
• Please begin looking it over so that you are comfortable with it
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Our Data This Term II
Influence of Hemlock Woolly Adelgid on carrion
beetle biodiversity
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Separated by many (at least 3) trophic levels
Adelgid is a phloem-feeding insect
Carrion beetles are detritivores or predators on fly
larvae on carrion
Field sites at Black Rock Brook, Black Rock Forest
Data collected during summer 2001
I will also email you these data
• Please begin looking over the data set
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]
Next week:
Abundance, An Introduction
Read
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Magurran Ch 2
Magurran Worked Examples 1-6
Southwood & Henderson 2.1, 2.2, 13.1
We will conduct a few evenness and species
abundance models next week
Decide which of the two projects on which you are
interested in working collaboratively
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3 people per group
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]