Measuring Biological Diversity
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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:
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
Using regular intervals along a 2-dimensional design
Transect
Sampling with reference to a straight line
Random
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
Probably best to use a transect
Ensures comparability
Relatively uniform sampling area
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
Time, area, quantity sampled
Appropriately represent area studied
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
Need to be sited at a level appropriate to the question
Examples:
Point-Quarter
• Proximity to a central point within a cross
Quadrat
• Sampling within a small area
Pitfall traps
Beating Sheets
Mist netting
Seining
Etc…
Lecture 2 – Introduction to Biological Richness
© 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
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
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
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
Richness
Abundance
BUT these are not really “Diversity”
More complicated ones are less clear
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
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
Species (richness)
Abundance
Diversity
• relationship between richness & abundance
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
Richness
Abundance
Each index differs in the mathematical method of
relating these features
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
How equally abundant are each of the species?
A simple way to combine abundance and richness
Rarely are all species equally abundant
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
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
Don’t have a single species dominating the ecosystem
Often invasives dominate
Paradox of enrichment
• E.g., polluted / enriched Lake Okeechobee, Florida
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
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)
Seasonality may confound the comparison as well
• Earlier in temperate growing season, less even than later
This is a general principle for most all indices this term
When would you want to compare across
locations?
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
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)
These can be destructive
Need equal sampling effort
Popular in aquatic studies
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
Mostly botanical surveys, some arthropod surveys
Species / m3 if in a 3D space
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
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
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
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
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
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
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
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
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
3 people per group
Lecture 2 – Introduction to Biological Richness
© 2003 Dr. James A. Danoff-Burg, [email protected]