Measuring Biological Diversity
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Measuring Biological Diversity EEEB G6185 James A. Danoff-Burg Dept. Ecol., Evol., & Envir. Biol. Columbia University 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu Course Materials Required: Magurran 1988 (Labyrinth) EstimateS • (from Rob Colwell at http://viceroy.eeb.uconn.edu/EstimateS) Excel and SPSS software programs Others Recommended: Southwood & Henderson 2000 (Labyrinth) © 2003 Dr. James A. Danoff-Burg, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu Prevalence of Pseudoreplication 48% of all studies had pseudoreplication (Hurlbert, S.H., 1984. Pseudoreplication and the design of ecological field experiments. Ecological Monographs 54:187-211) 71% of studies using ANOVA (a common statistical test) had design errors (Underwood. 1981. Techniques of analysis of variance in experimental marine biology and ecology. Ann. Rev. Oceanogr. Mar. Biol.19: 513-605) Particularly acute in studies with logistical problems Rare animals Transportation or financial limitations Many that are in print! © 2003 Dr. James A. Danoff-Burg, jd363@columbia.edu 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, jd363@columbia.edu Pseudoreplication Example Treatment A Treatment B Site 1 Site 3 Site 2 Site 4 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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, jd363@columbia.edu 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 jd363@columbia.edu before the start of class next week © 2003 Dr. James A. Danoff-Burg, jd363@columbia.edu
