Introduction to Biodiversity

Dr. Mark A. McGinley Texas Tech University BIOL 5311 Summer 2011 Biodiversity

Diversity Before we tackle “biodiversity” let’s think about the concept of diversity In the simplest terms, diversity is influenced by variation within and among groups As will hopefully make sense in just a little while, diversity is influenced by The type and amount of variation How that variation is distributed

Below is a group of letters. What “variation” do you see here? A A aa Bb bb b b bb c c D Dd dd Ee ee f

Variation Within a Group Different letters (variation in type of letter) Variation within a type of letter Capital vs. lower case Different sizes Different colors Different letters are represented different number of times

Variation Within a Group Thus, within a group Different types (letters) Variation of characteristics within a particular type.

What about variation between groups?

Which Group Contains More Variation? Group 1 A B C D E Group 2 A A A A A

Group 1 is more variable No variation in Group 2 -all of the letters are exactly the same More different types of letters in Group 1.

Variation Between Groups Groups can differ in the number of types they contain Therefore we think of a group containing more types of things as being more variable than a group that contains fewer types. In this case we would consider groups with more variation to be more diverse.

Which Group Contains More Variation? Group 1 B B B B B Group 2 B B B B B

Variation Between Groups The two groups share the same number of types and number of representatives within a type However, Group 2 has more variation among representatives within a type In this case we would consider the group with more variation with a type to be more diverse.

Which group has more variation? Group 1 A A A A A A Group 2 A A

Variation Between Groups There is variation between groups in the number of letters. Group 1 has more letters in it than Group 2 However, they are all the same letter all are the same format within a letter. Thus, variation in numbers of things doesn’t appear to affect diversity.

Which group has more variation? Group 1 AAA BBB CCC Group 2 AAAAAAA B C

Group 1 is more variable Group 1 and Group 2 have - the same total number of letters - the same number of different types of letter Therefore the variation among the two groups might be considered to be the same. But almost all of the letters in Group 2 are A. - therefore we might consider that Group 1 is more diverse than group 2.

Variation Between Groups So differences in the number of individuals within a type can influence diversity in some cases. New Term Diversity can be influenced by the “evenness” of the distribution of individuals among different types

Which Group is Most Even? Group 1 AAA BBB CCC DDD Group 2 AAAA BB CCC D

Factors That Influence Diversity Number of different types of things Variation of characteristics within a type Evenness of number of individuals across different types of things

Which Group is More Diverse? Group 1 AA BB CC DD EE Group 2 A BB CCC D EE F

This is a Tricky Question!!!!! Group 2 has more types of letters so we might consider it to be more diverse Group 1 contains a more even distribution of letters within a type so we might consider it to be more diverse Which group we consider to be the most diverse depends on how we rate the relative influence of number of types vs. evenness. The World is Complicated!!!!! (but luckily we can use math to help us solve this problem)

Which Sample is More Diverse? 1. AaBbCcDd 2. AAAAAAAA 3. AABBCCDD 4. AAaaBBbb 5. AaBbCcDd

Rank according to number of types of letters 1. AaBbCcDd - 4 letters 2. AAAAAAAA- 1 letter 3. AAAAABCD- 4 letters 4. AAaaBBbb- 2 letters 5. AaBbCcDd- 4 letters 1 = 3 = 5 > 4 > 2

Compare samples 1, 3, 5 1. AaBbCcDd 3. AAAAABCD Same richness but which is 5. AABBCCDD more diverse? Sample 1. Both capital and lower case letters More even (two copies of each letter) Sample 3 Only capital letters less even Sample 5 Only capital letters More even

Can you come up with an equation that we can use to calculate “diversity” that we can use to compare samples?

What is “Biodiversity”? Biodiversity is a contraction of the two words “biological diversity”. Because biodiversity is such a broad, all encompassing concept there is not one well agreed on definition. However, most definitions are similar.

Biodiversity A measure of the variety of organisms within a local area or region, often including genetic variation, taxonomic uniqueness, and endemism. Ricklefs, The Economy of Nature

Biodiversity The variety of organisms considered at all levels from genetic variants belonging to the same species through arrays of species to arrays of genera, families, and still higher taxonomic levels; includes the variety of ecosystems, which comprise both the communities of organisms within a particular habitat and the physical conditions under which they live. E.O Wilson- The Diversity of Life

Biodiversity The variability among living organisms from all sources including, inter alia , terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species, and of ecosystems." Convention on Biological Diversity

Genetic Diversity Members of the same population or species can vary in which particular alleles they possess at a particular gene locus. Population geneticists have a variety of techniques and metrics they use to measure the amount of genetic variation within and among populations. To learn more about this take an Evolution, Population Genetics, or Conservation Biology course.

Species Species are usually the focus of diversity studies in ecology Species- actually many definitions/species concepts Biological Species Concept - group of potentially interbreeding individuals that are reproductively isolated from other such groups

Biological Species Concept Two individuals are considered to be members of the same biological species if they can potentially exchange genes. Often difficult to apply this concept Asexual species Species that are geographically isolated How do we know whether a bird found in Europe can interbreed with a bird in North America Ring species But this is a conceptually pleasing definition of a species

Biological Species Species are basic unit of biodiversity Species may be subdivided into sub-species

Phenotypic Variation Within Species Variation at the genetic, molecular, physiological, morphological, or behavioral levels. Conservation biologists can be especially concerned about genetic variation Genetic variation influences the potential for natural selection

Species Diversity Species diversity is a characteristic of a community Two components of species diversity The number of species in a community Species richness evenness

Diversity Indices Ecologists have developed several metrics to quantify species diversity These indices differ in how they weight the two critical components of species diversity Species richness Evenness

Species Richness Species richness simply counts the number of species found in a community

Diversity Example Species number of individuals 1 10 2 20 3 15

Species Richness Because there are three species found in this community Species Richness = 3

Species Richness Strengths We are often interested in knowing about the numbers of species in a community Easy number to calculate All we have to do is count the number of species This is an easily understandable metric Weakness Ignores the evenness component of diversity

Which is more diverse? Try to make up a formula that will calculate a number to use to measure diversity? Remember- diversity increases as richness and evenness increases

Shannon Diversity Index s H = - ∑ (p i * ln p i ) i=1 where: H = the Shannon diversity index Pi = proportion of the population made up of species i S = numbers of species in sample

Let’s Try an Example Species # individuals 1 10 2 20 3 30

Shannon Index Example First calculate the p i for each of the S species in the sample (S = 3 species) 1. determine the total number of individuals sampled in the community # sp.1 = 10 # sp.2 = 20 # sp.3 = 30 Total # = 60 ind

Shannon Index Example 2. For each of the S species p i = # ind species i/total # ind p i sp 1- 10/60 = 0.17 sp 2- 20/60 = 0.33 sp 3- 30/60 = 0.50

Shannon Index Example Next calculate H s H = - ∑ (p i * ln p i ) i=1

Shannon Index Example H =- ((0.17*ln0.17 + 0.33*ln0.33 + 0.50*ln0.50)) H = - (0.17*-1.77 + 0.33*-1.11 + 0.50*-0.69) H = - (-0.30 – 0.37 – 0.35) H = - (-1.01) H = 1.01

Shannon Index The Shannon Index was designed such that H gets larger when there are more species Not surprising because H should get larger when there are more species in the sample (larger S)

Shannon Index The Shannon Index was designed such that H gets larger when evenness is greater

Shannon Index Pi 0.1 ln pi -2.30259 Pi * ln pi -0.23026 0.2 -1.60944 -0.32189 0.3 -1.20397 -0.36119 0.4 -0.91629 -0.36652 0.5 -0.69315 -0.34657 0.6 -0.51083 -0.3065 0.7 -0.35667 -0.24967 0.8 -0.22314 -0.17851 0.9 -0.10536 -0.09482 1 0 0

Shannon Index The value of H gets larger whe There are more species There is greater evenness Thus, diversity of a community increases as the value of H increases

Shannon Index Advantages The value of H changes in a way that is consistent with our view of how changing species richness and evenness should affect species diversity It is relatively easy to calculate Disadvantage The value of H doesn’t have a direct biological meaning What do you know if someone tells you that H = 2.3? Useful only for comparison

Pielou’s Evenness Index - based on Shannon Index E = H/H max H is the value of the Shannon Diversity Index for a particular population H max is the maximum value for the Shannon Diversity Index in a population with the same number of species and total number of individuals sampled

H max For a particular community the maximum value of H would occur if all species were equally abundant. After doing the algebra, H max can be calculated as follow- H max = lnS

Evenness Index Example E = H/H max E = 1.01/ln3 E = 1.01/1.098 E = 0.919

Simpson’s Index D = ∑ p i 2 D measures the probability that two randomly selected individuals in a population belong to the same species D ranges from 0 – 1 D will be largest when all individuals in a population are members of the same population Thus, as D gets larger diversity decreases

Example D = ∑ p i 2 D = (0.17 2 + 0.33 2 + 0.50 2 ) D = (0.0289 + 0.109 + 0.25) D = 0.388

Simpson’s Index of Diversity Simpson's index of diversity = 1 - D The probability that two randomly selected individuals in a community belong to different species. Thus, as the Simpson’s Index of Diversity increases the species diversity of the population increases.

Diversity Indices Shannon Index is more sensitive to changes in species richness Simpson’s Index is more sensitive to changes in evenness

Diversity Indices Which diversity index should you choose to use? It might depend on whether you were more concerned about rare species E.g., changes in the number of rare species has a much greater effect on Shannon’s Index than it does on the Simpson Index Many researchers choose to use a number of different diversity indices because they provide different information.

Introduction to Biodiversity

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Introduction to Biodiversity