Transcript MBD 2.ppt
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]