Transcript Slide 1
BIOL 3240 Plant and Animal Ecology Communities: Biodiversity © Getty Images/Taxis • What is biodiversity? • By definition it is the various forms of life • How many species are there anyway? • Estimated 1.4 million already described… perhaps up to 100 million waiting • How can we measure it? • An example from La Selva Field Station (OTS) • Studied ant species in leaf litter http://www.esf.edu/resorg/rooseveltwildlife/Research/soilbiodivers/soilbiodivers.htm • How can we measure it? • Species accumulation curves provide estimates of what remains as well as directs decision about sample size. • Is species richness even across the globe? • If not… where would you expect the greatest diversity (i.e. what are the two most diverse ecosystems on the planet)? •Primary productivity likely influences richness (rate of biomass accumulation per unit area as a result of photosynthesis). • Regional stability likely influences richness (what areas have been subjected to glaciation events?) • Climatic stability may influence richness (what areas are the most stable across months, years and longer?) • Is species richness even across taxonomic groups? • Name your favorite organism… • Why are some taxa richer? • Size limitations… • Adaptive radiation can occur when a novel form is introduced to an established environment (or vice versa). • Why should we be concerned about biodiversity? • Habitat loss is the major cause of extinctions/declines • Other anthropogenic causes • Examples for amphibian extinctions • Consequently, we need to know what exists where so that we can best be prepared to protect/save as many species as possible!!! •Hotspots… http://www.biodiversityhotspots.org/xp/Hotspots/ • Why should we be concerned about biodiversity? • Habitat loss is the major cause of extinctions/declines • Other anthropogenic causes • How can we measure it? • # of species (Richness) Campus A • Relative distribution of species abundance (Evenness) Type of Bird Campus A Campus B Pigeon 96 20 Starline Robin Grackle Sparrow Pigeon Campus B Robin 1 20 Starling 1 20 Purple grackle 1 20 Sparrow Pigeon Grackle House Sparrow 1 20 Robin Starline • How can we measure it? • Indexes measure both # of species and evenness (alpha and gamma) • Simpson’s index D= (n / N)2 • Between 0 and 1… 0 infinite div. and 1 no diversity • Simpson's Index of diversity 1 – D Flower Individuals # 1 Individuals # 2 Daisy 300 20 Dandelion 335 49 Buttercup 365 931 Total 1000 1000 • Simpson's n = the total number of organisms of a particular species Reciprocal Index 1 / D N = the total number of organisms of all species • Use the following data to calculate A) Simpson’s Index B) Simpson’s Index of Diversity C) Simpson’s Reciprocal Index Species Sample One Sample 2 Woodrush 2 2 Holly (seedlings) 8 56 Bramble 1 0 Yorkshire Fog 1 0 Sedge 3 6 Total (N) 15 64 D= (n / N)2 • How can we measure it? • Another popular Index is the Shannon – (Weaver/Wiener) index s • H = iΣ= 1– (Pi * lnPi) H = Shannon Index Pi = Fraction of entire population made up of species i S = Number of species encountered Σ = Indicates the sum from species 1 to species S • Calculate the Shannon Index for the data below... s H = iΣ= 1 – (Pi * lnPi) H = Shannon Index Pi = Fraction of entire population made up of species i S = Number of species encountered Σ = Indicates the sum from species 1 to species S Type of Bird Campus A Campus B Pigeon 96 20 Robin 1 20 Starling 1 20 Purple grackle 1 20 House Sparrow 1 20 • Calculate the Shannon Index for the data below... s H = iΣ= 1 – (Pi * lnPi) H = Shannon Index Pi = Fraction of entire population made up of species i S = Number of species encountered Σ = Indicates the sum from species 1 to species S Type of Bird Campus A Pigeon 96 96 Robin 1 1 Starling 1 1 Grackle 1 1 House Sparrow 1 1 Ni Pi lnPi -(Pi*lnPi)