Measuring Biological Diversity EEEB G6185 James A. Danoff-Burg Dept. Ecol., Evol., & Envir. Biol. Columbia University

© 2003 Dr. James A. Danoff-Burg, Today: Course Introduction  Introduction to the course  Tools to acquire  Course format  Course requirements  Required materials  Content: Basics of measuring biological diversity

© 2003 Dr. James A. Danoff-Burg, Goals of the Course  Provide skills in censusing & measuring biological diversity  Choosing appropriate indices for your question  Comparing biodiversity between samples  Design your thesis / dissertation?  Publish a paper or two together?

© 2003 Dr. James A. Danoff-Burg, Course Format  Weekly meetings, W 4:10 - 6:00  252 Engineering Terrace computer center  Preparatory readings  Southwood & Henderson 2000  Magurran 1988  Primary literature & Web resources  Lecture introduction  In-class exploration of techniques  Write-ups of the techniques  Produce a publishable paper?

© 2003 Dr. James A. Danoff-Burg, Tools to Acquire  Survey techniques  How to design your survey  Specific to question, taxon, location  Diversity indices – understanding & use  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 (if time)  Applying biodiversity to conservation decisions

© 2003 Dr. James A. Danoff-Burg, Course Schedule  Week 1; 22 Jan - Intro to community diversity & biotic inventories,  Week 2; 29 Jan - Richness, abundance, & generation of biodiversity  Week 3; 5 Feb - Evenness & broken stick diagrams  Week 4; 12 Feb - Simple community diversity indices I  Week 5; 19 Feb - Simple community diversity indices II  Week 6; 26 Feb - Simple community diversity indices II  Week 7; 5 Mar - Choosing between & improving indices (JDB away?)  Week 8; 12 Mar - Beta diversity indices  Week 9; 19 Mar - Spring Break  Week 10; 26 Mar - Community ordination techniques  Week 11; 2 Apr - Gamma diversity indices I  Week 12; 9 Apr - Gamma diversity indices II  Week 13; 16 Apr - Prioritizing areas for conservation  Week 14; 23 Apr - Implementing conservation decisions  Week 15; 30 Apr - Deadline for submission of term paper

© 2003 Dr. James A. Danoff-Burg, Course Requirements  Several short write-ups through term – 20%  Approximately 4-8  Ex: describe an appropriate sampling protocol for your research question  In-Class participation – 30%  Final paper – 50%  Due at end of term  Written collaboratively

© 2003 Dr. James A. Danoff-Burg, Course Materials  Required:  Magurran 1988 (Labyrinth)  EstimateS (from Rob Colwell at  Excel and SPSS software programs  Others  Recommended:  Southwood & Henderson 2000 (Labyrinth)

© 2003 Dr. James A. Danoff-Burg, Content Introduction  Will begin biodiversity & indices next week  Today – Basics of Measuring Biological Diversity  Introduce some terms  Talk about experimental design to collect biodiversity data  Discuss how to implement designs

© 2003 Dr. James A. Danoff-Burg, Basics of Measuring Biological Diversity  What is a community?  What is biodiversity & how to survey it?  Censusing  Pseudoreplication  Applying these techniques  Assignment for next time

© 2003 Dr. James A. Danoff-Burg, Community  Define community?  Some possibilities  Group of populations in a single place (Krebs 85)  Assemblage of species populations which occur together in space & time (Begon et al. 86)  Distillation & modification:  Group of interacting populations, single time, single defined place

© 2003 Dr. James A. Danoff-Burg, Implications of Definition  Species in a community interact with each other  Can include all species  Can be limited to a single guild More common, more tractable  Defined by a consistent spatial boundary How we design our studies (sampling & indices) depends on our question

© 2003 Dr. James A. Danoff-Burg, Basics of Measuring Biological Diversity  What is a community?  What is biodiversity & how to survey it?  Pseudoreplication  Applying these techniques  Assignment for next time

© 2003 Dr. James A. Danoff-Burg, 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?

© 2003 Dr. James A. Danoff-Burg, How to Summarize & Describe Nature?  Near-infinite number of things to record  How to simplify?  Dictated by: experimental question, location, taxon  Sample (really subsample) from nature Choose an aspect of biodiversity Location Life stage Etc.

© 2003 Dr. James A. Danoff-Burg, 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

© 2003 Dr. James A. Danoff-Burg, 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

© 2003 Dr. James A. Danoff-Burg, 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)?

© 2003 Dr. James A. Danoff-Burg, 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…

© 2003 Dr. James A. Danoff-Burg, Basics of Measuring Biological Diversity  What is a community?  What is biodiversity & how to survey it?  Pseudoreplication  Applying these techniques  Assignment for next time

© 2003 Dr. James A. Danoff-Burg, Purposes of Replication  Why replicate?  Controls for random or stochastic error  E.g., untested independent factors may otherwise determine the outcome of the experiment  Increases the precision of the test  Increases the generalizability of the test  If you test across many sites – you can safely generalize to many others

© 2003 Dr. James A. Danoff-Burg, Some Definitions  Replicate = Sample  Maximize these in your experimental design  Greatest number possible, given logistical limitations  If you are a professional, use a power analysis  Subsample = Pseudoreplicate  Only true if the subsamples are incorrectly treated as true replicates for statistical analysis  Subsamples: useful to increase the accuracy of the data estimate for that replicate  A special type of statistical analysis are therefore possible

© 2003 Dr. James A. Danoff-Burg, Pseudoreplication - Defined  Incorrect “replication”  Replicating samples, not treatments  Replicates are not independent  Problem is that it violates a key assumption of statistical analysis:  Independence of replicates Increasing precision of studies if independent Approximates “truth” better if independent Accounts for normal random error Allows us to set α and keep it constant  All of these are violated if pseudoreplicated

© 2003 Dr. James A. Danoff-Burg, Prevalence of Pseudoreplication  48% of all studies had pseudoreplication (Hurlbert, S.H., Pseudoreplication and the design of ecological field experiments. Ecological Monographs 54: )  71% of studies using ANOVA (a common statistical test) had design errors (Underwood Techniques of analysis of variance in experimental marine biology and ecology. Ann. Rev. Oceanogr. Mar. Biol.19: )  Particularly acute in studies with logistical problems  Rare animals  Transportation or financial limitations  Many that are in print!

© 2003 Dr. James A. Danoff-Burg, Examples  Many samples from a single site  These are actually subsamples  Only a single sample for each treatment condition  These are actually replicates, but cannot do statistics on a sample size of one  Single samples from a single site, but replicated in time  Would be true samples if the experimental question is time-dependent  If not, it is pseudoreplication

© 2003 Dr. James A. Danoff-Burg, Pseudoreplication Example  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 Treatment ATreatment B Site 1 Site 2 Site 3 Site 4

© 2003 Dr. James A. Danoff-Burg, Controlling Pseudoreplication I  Know your question  Question determines whether design includes pseudoreplication Taxonomic level Ecological hierarchy level  Clearly define your independent and dependent variables

© 2003 Dr. James A. Danoff-Burg, Controlling Pseudoreplication II  What constitutes a unit of data?  Plant branch? Individual? Population? Etc.?  Identify what is the unit of replication  Individual? Population? Community? Site?  Replicate accordingly – sites are often the level of replication for our projects  Randomize your sampling design  Helps to decrease sampling errors  Increases accuracy of estimation

© 2003 Dr. James A. Danoff-Burg, Basics of Measuring Biological Diversity  What is a community?  What is biodiversity & how to survey it?  Pseudoreplication  Applying these techniques  Assignment for next time

© 2003 Dr. James A. Danoff-Burg, Application of Techniques – An Exercise  Group up  Design a study, avoiding pseudoreplication  Include visual representations of sampling method  Include:  Experimental question  Manipulations  Hypotheses (null, alternatives)  Target organisms  Censusing design  Censusing method

© 2003 Dr. James A. Danoff-Burg, Basics of Measuring Biological Diversity  What is a community?  What is biodiversity & how to survey it?  Pseudoreplication  Applying these techniques  Assignment for next time

© 2003 Dr. James A. Danoff-Burg, 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  to before the start of class next