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Introduction to Biodiversity


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Introduction to Biodiversity

  1. 1. Dr. Mark A. McGinley Texas Tech University BIOL 5311 Summer 2011 Biodiversity
  2. 2. Diversity <ul><li>Before we tackle “biodiversity” let’s think about the concept of diversity </li></ul><ul><li>In the simplest terms, diversity is influenced by variation within and among groups </li></ul><ul><li>As will hopefully make sense in just a little while, diversity is influenced by </li></ul><ul><ul><li>The type and amount of variation </li></ul></ul><ul><ul><li>How that variation is distributed </li></ul></ul>
  3. 3. Below is a group of letters. What “variation” do you see here? <ul><li>A A aa </li></ul><ul><li>Bb bb b b bb </li></ul><ul><li>c c </li></ul><ul><li>D Dd dd </li></ul><ul><li>Ee ee </li></ul><ul><li>f </li></ul>
  4. 4. Variation Within a Group <ul><li>Different letters (variation in type of letter) </li></ul><ul><li>Variation within a type of letter </li></ul><ul><ul><li>Capital vs. lower case </li></ul></ul><ul><ul><li>Different sizes </li></ul></ul><ul><ul><li>Different colors </li></ul></ul><ul><li>Different letters are represented different number of times </li></ul>
  5. 5. Variation Within a Group <ul><li>Thus, within a group </li></ul><ul><ul><li>Different types (letters) </li></ul></ul><ul><ul><li>Variation of characteristics within a particular type. </li></ul></ul>
  6. 6. What about variation between groups?
  7. 7. Which Group Contains More Variation? <ul><li>Group 1 </li></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>B </li></ul></ul><ul><ul><li>C </li></ul></ul><ul><ul><li>D </li></ul></ul><ul><ul><li>E </li></ul></ul><ul><li>Group 2 </li></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>A </li></ul></ul>
  8. 8. Group 1 is more variable <ul><li>No variation in Group 2 </li></ul><ul><li>-all of the letters are exactly the same </li></ul><ul><li>More different types of letters in Group 1. </li></ul>
  9. 9. Variation Between Groups <ul><li>Groups can differ in the number of types they contain </li></ul><ul><li>Therefore we think of a group containing more types of things as being more variable than a group that contains fewer types. </li></ul><ul><ul><li>In this case we would consider groups with more variation to be more diverse. </li></ul></ul>
  10. 10. Which Group Contains More Variation? <ul><li>Group 1 </li></ul><ul><ul><li>B </li></ul></ul><ul><ul><li>B </li></ul></ul><ul><ul><li>B </li></ul></ul><ul><ul><li>B </li></ul></ul><ul><ul><li>B </li></ul></ul><ul><li>Group 2 </li></ul><ul><ul><li>B </li></ul></ul><ul><ul><li>B </li></ul></ul><ul><ul><li>B </li></ul></ul><ul><ul><li>B </li></ul></ul><ul><ul><li>B </li></ul></ul>
  11. 11. Variation Between Groups <ul><li>The two groups share the same number of types and number of representatives within a type </li></ul><ul><li>However, Group 2 has more variation among representatives within a type </li></ul><ul><li>In this case we would consider the group with more variation with a type to be more diverse. </li></ul>
  12. 12. Which group has more variation? <ul><li>Group 1 </li></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>A </li></ul></ul><ul><li>Group 2 </li></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>A </li></ul></ul>
  13. 13. Variation Between Groups <ul><li>There is variation between groups in the number of letters. </li></ul><ul><ul><li>Group 1 has more letters in it than Group 2 </li></ul></ul><ul><li>However, </li></ul><ul><ul><li>they are all the same letter </li></ul></ul><ul><ul><li>all are the same format within a letter. </li></ul></ul><ul><li>Thus, variation in numbers of things doesn’t appear to affect diversity. </li></ul>
  14. 14. Which group has more variation? <ul><li>Group 1 </li></ul><ul><ul><li>AAA </li></ul></ul><ul><ul><li>BBB </li></ul></ul><ul><ul><li>CCC </li></ul></ul><ul><li>Group 2 </li></ul><ul><ul><li>AAAAAAA </li></ul></ul><ul><ul><li>B </li></ul></ul><ul><ul><li>C </li></ul></ul>
  15. 15. Group 1 is more variable <ul><li>Group 1 and Group 2 have </li></ul><ul><li>- the same total number of letters </li></ul><ul><li>- the same number of different types of letter </li></ul><ul><li>Therefore the variation among the two groups might be considered to be the same. </li></ul><ul><li>But almost all of the letters in Group 2 are A. </li></ul><ul><li>- therefore we might consider that Group 1 is more diverse than group 2. </li></ul>
  16. 16. Variation Between Groups <ul><li>So differences in the number of individuals within a type can influence diversity in some cases. </li></ul><ul><li>New Term </li></ul><ul><ul><li>Diversity can be influenced by the “evenness” of the distribution of individuals among different types </li></ul></ul>
  17. 17. Which Group is Most Even? <ul><li>Group 1 </li></ul><ul><ul><li>AAA </li></ul></ul><ul><ul><li>BBB </li></ul></ul><ul><ul><li>CCC </li></ul></ul><ul><ul><li>DDD </li></ul></ul><ul><li>Group 2 </li></ul><ul><ul><li>AAAA </li></ul></ul><ul><ul><li>BB </li></ul></ul><ul><ul><li>CCC </li></ul></ul><ul><ul><li>D </li></ul></ul>
  18. 18. Factors That Influence Diversity <ul><li>Number of different types of things </li></ul><ul><li>Variation of characteristics within a type </li></ul><ul><li>Evenness of number of individuals across different types of things </li></ul>
  19. 19. Which Group is More Diverse? <ul><li>Group 1 </li></ul><ul><ul><li>AA </li></ul></ul><ul><ul><li>BB </li></ul></ul><ul><ul><li>CC </li></ul></ul><ul><ul><li>DD </li></ul></ul><ul><ul><li>EE </li></ul></ul><ul><li>Group 2 </li></ul><ul><ul><li>A </li></ul></ul><ul><ul><li>BB </li></ul></ul><ul><ul><li>CCC </li></ul></ul><ul><ul><li>D </li></ul></ul><ul><ul><li>EE </li></ul></ul><ul><ul><li>F </li></ul></ul>
  20. 20. This is a Tricky Question!!!!! <ul><li>Group 2 has more types of letters so we might consider it to be more diverse </li></ul><ul><li>Group 1 contains a more even distribution of letters within a type so we might consider it to be more diverse </li></ul><ul><li>Which group we consider to be the most diverse depends on how we rate the relative influence of number of types vs. evenness. </li></ul><ul><ul><li>The World is Complicated!!!!! (but luckily we can use math to help us solve this problem) </li></ul></ul>
  21. 21. Which Sample is More Diverse? <ul><li>1. AaBbCcDd </li></ul><ul><li>2. AAAAAAAA </li></ul><ul><li>3. AABBCCDD </li></ul><ul><li>4. AAaaBBbb </li></ul><ul><li>5. AaBbCcDd </li></ul>
  22. 22. Rank according to number of types of letters <ul><li>1. AaBbCcDd - 4 letters </li></ul><ul><li>2. AAAAAAAA- 1 letter </li></ul><ul><li>3. AAAAABCD- 4 letters </li></ul><ul><li>4. AAaaBBbb- 2 letters </li></ul><ul><li>5. AaBbCcDd- 4 letters </li></ul><ul><li>1 = 3 = 5 > 4 > 2 </li></ul>
  23. 23. Compare samples 1, 3, 5 <ul><li>1. AaBbCcDd </li></ul><ul><li>3. AAAAABCD Same richness but which is </li></ul><ul><li>5. AABBCCDD more diverse? </li></ul><ul><li>Sample 1. </li></ul><ul><ul><li>Both capital and lower case letters </li></ul></ul><ul><ul><li>More even (two copies of each letter) </li></ul></ul><ul><li>Sample 3 </li></ul><ul><ul><li>Only capital letters </li></ul></ul><ul><ul><li>less even </li></ul></ul><ul><li>Sample 5 </li></ul><ul><ul><li>Only capital letters </li></ul></ul><ul><ul><li>More even </li></ul></ul>
  24. 24. Can you come up with an equation that we can use to calculate “diversity” that we can use to compare samples?
  25. 25. What is “Biodiversity”? <ul><li>Biodiversity is a contraction of the two words “biological diversity”. </li></ul><ul><li>Because biodiversity is such a broad, all encompassing concept there is not one well agreed on definition. </li></ul><ul><li>However, most definitions are similar. </li></ul>
  26. 26. Biodiversity <ul><li>A measure of the variety of organisms within a local area or region, often including genetic variation, taxonomic uniqueness, and endemism. </li></ul><ul><ul><ul><li>Ricklefs, The Economy of Nature </li></ul></ul></ul>
  27. 27. Biodiversity <ul><li>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. </li></ul><ul><ul><li>E.O Wilson- The Diversity of Life </li></ul></ul>
  28. 28. Biodiversity <ul><li>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.&quot; </li></ul><ul><ul><li>Convention on Biological Diversity </li></ul></ul>
  29. 29. Genetic Diversity <ul><li>Members of the same population or species can vary in which particular alleles they possess at a particular gene locus. </li></ul><ul><li>Population geneticists have a variety of techniques and metrics they use to measure the amount of genetic variation within and among populations. </li></ul><ul><ul><li>To learn more about this take an Evolution, Population Genetics, or Conservation Biology course. </li></ul></ul>
  30. 30. Species <ul><li>Species are usually the focus of diversity studies in ecology </li></ul><ul><li>Species- actually many definitions/species concepts </li></ul><ul><li>Biological Species Concept </li></ul><ul><ul><li>- group of potentially interbreeding individuals that are reproductively isolated from other such groups </li></ul></ul>
  31. 31. Biological Species Concept <ul><li>Two individuals are considered to be members of the same biological species if they can potentially exchange genes. </li></ul><ul><li>Often difficult to apply this concept </li></ul><ul><ul><li>Asexual species </li></ul></ul><ul><ul><li>Species that are geographically isolated </li></ul></ul><ul><ul><ul><li>How do we know whether a bird found in Europe can interbreed with a bird in North America </li></ul></ul></ul><ul><ul><li>Ring species </li></ul></ul><ul><li>But this is a conceptually pleasing definition of a species </li></ul>
  32. 32. Biological Species <ul><li>Species are basic unit of biodiversity </li></ul><ul><ul><li>Species may be subdivided into sub-species </li></ul></ul>
  33. 33. Phenotypic Variation Within Species <ul><li>Variation at the genetic, molecular, physiological, morphological, or behavioral levels. </li></ul><ul><ul><li>Conservation biologists can be especially concerned about genetic variation </li></ul></ul><ul><ul><li>Genetic variation influences the potential for natural selection </li></ul></ul>
  34. 34. Species Diversity <ul><li>Species diversity is a characteristic of a community </li></ul><ul><li>Two components of species diversity </li></ul><ul><ul><li>The number of species in a community </li></ul></ul><ul><ul><ul><li>Species richness </li></ul></ul></ul><ul><ul><li>evenness </li></ul></ul>
  35. 35. Diversity Indices <ul><li>Ecologists have developed several metrics to quantify species diversity </li></ul><ul><li>These indices differ in how they weight the two critical components of species diversity </li></ul><ul><ul><li>Species richness </li></ul></ul><ul><ul><li>Evenness </li></ul></ul>
  36. 36. Species Richness <ul><li>Species richness simply counts the number of species found in a community </li></ul>
  37. 37. Diversity Example <ul><li>Species number of individuals </li></ul><ul><li>1 10 </li></ul><ul><li>2 20 </li></ul><ul><li>3 15 </li></ul>
  38. 38. Species Richness <ul><li>Because there are three species found in this community </li></ul><ul><li>Species Richness = 3 </li></ul>
  39. 39. Species Richness <ul><li>Strengths </li></ul><ul><ul><li>We are often interested in knowing about the numbers of species in a community </li></ul></ul><ul><ul><li>Easy number to calculate </li></ul></ul><ul><ul><ul><li>All we have to do is count the number of species </li></ul></ul></ul><ul><ul><li>This is an easily understandable metric </li></ul></ul><ul><li>Weakness </li></ul><ul><ul><li>Ignores the evenness component of diversity </li></ul></ul>
  40. 40. Which is more diverse? <ul><li>Try to make up a formula that will calculate a number to use to measure diversity? </li></ul><ul><li>Remember- diversity increases as richness and evenness increases </li></ul>
  41. 41. Shannon Diversity Index <ul><li>s </li></ul><ul><li>H = - ∑ (p i * ln p i ) </li></ul><ul><li>i=1 </li></ul><ul><li>where: </li></ul><ul><li>H = the Shannon diversity index </li></ul><ul><li>Pi = proportion of the population made up of species i </li></ul><ul><li>S = numbers of species in sample </li></ul>
  42. 42. Let’s Try an Example <ul><li>Species # individuals </li></ul><ul><li>1 10 </li></ul><ul><li>2 20 </li></ul><ul><li>3 30 </li></ul>
  43. 43. Shannon Index Example <ul><li>First calculate the p i for each of the S species in the sample (S = 3 species) </li></ul><ul><li>1. determine the total number of individuals sampled in the community </li></ul><ul><li># sp.1 = 10 </li></ul><ul><li># sp.2 = 20 </li></ul><ul><li># sp.3 = 30 </li></ul><ul><li>Total # = 60 ind </li></ul>
  44. 44. Shannon Index Example <ul><li>2. For each of the S species </li></ul><ul><li>p i = # ind species i/total # ind </li></ul><ul><li>p i </li></ul><ul><li>sp 1- 10/60 = 0.17 </li></ul><ul><li>sp 2- 20/60 = 0.33 </li></ul><ul><li>sp 3- 30/60 = 0.50 </li></ul>
  45. 45. Shannon Index Example <ul><li>Next calculate H </li></ul><ul><li> s </li></ul><ul><li>H = - ∑ (p i * ln p i ) </li></ul><ul><li>i=1 </li></ul>
  46. 46. Shannon Index Example <ul><li>H =- ((0.17*ln0.17 + 0.33*ln0.33 + 0.50*ln0.50)) </li></ul><ul><li>H = - (0.17*-1.77 + 0.33*-1.11 + 0.50*-0.69) </li></ul><ul><li>H = - (-0.30 – 0.37 – 0.35) </li></ul><ul><li>H = - (-1.01) </li></ul><ul><li>H = 1.01 </li></ul>
  47. 47. Shannon Index <ul><li>The Shannon Index was designed such that </li></ul><ul><ul><li>H gets larger when there are more species </li></ul></ul><ul><ul><ul><li>Not surprising because H should get larger when there are more species in the sample (larger S) </li></ul></ul></ul>
  48. 48. Shannon Index <ul><li>The Shannon Index was designed such that </li></ul><ul><ul><li>H gets larger when evenness is greater </li></ul></ul>
  49. 49. 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
  50. 50. Shannon Index <ul><li>The value of H gets larger whe </li></ul><ul><ul><li>There are more species </li></ul></ul><ul><ul><li>There is greater evenness </li></ul></ul><ul><li>Thus, diversity of a community increases as the value of H increases </li></ul>
  51. 51. Shannon Index <ul><li>Advantages </li></ul><ul><ul><li>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 </li></ul></ul><ul><ul><li>It is relatively easy to calculate </li></ul></ul><ul><li>Disadvantage </li></ul><ul><ul><li>The value of H doesn’t have a direct biological meaning </li></ul></ul><ul><ul><ul><li>What do you know if someone tells you that H = 2.3? </li></ul></ul></ul><ul><ul><ul><li>Useful only for comparison </li></ul></ul></ul>
  52. 52. Pielou’s Evenness Index - based on Shannon Index <ul><ul><li>E = H/H max </li></ul></ul><ul><ul><li>H is the value of the Shannon Diversity Index for a particular population </li></ul></ul><ul><ul><li>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 </li></ul></ul>
  53. 53. H max <ul><li>For a particular community the maximum value of H would occur if all species were equally abundant. </li></ul><ul><li>After doing the algebra, H max can be calculated as follow- </li></ul><ul><ul><li>H max = lnS </li></ul></ul>
  54. 54. Evenness Index Example <ul><li>E = H/H max </li></ul><ul><li>E = 1.01/ln3 </li></ul><ul><li>E = 1.01/1.098 </li></ul><ul><li>E = 0.919 </li></ul>
  55. 55. Simpson’s Index <ul><ul><li>D = ∑ p i 2 </li></ul></ul><ul><ul><li>D measures the probability that two randomly selected individuals in a population belong to the same species </li></ul></ul><ul><ul><li>D ranges from 0 – 1 </li></ul></ul><ul><ul><li>D will be largest when all individuals in a population are members of the same population </li></ul></ul><ul><ul><li>Thus, as D gets larger diversity decreases </li></ul></ul>
  56. 56. Example <ul><li>D = ∑ p i 2 </li></ul><ul><li>D = (0.17 2 + 0.33 2 + 0.50 2 ) </li></ul><ul><li>D = (0.0289 + 0.109 + 0.25) </li></ul><ul><li>D = 0.388 </li></ul>
  57. 57. Simpson’s Index of Diversity <ul><ul><li>Simpson's index of diversity = 1 - D </li></ul></ul><ul><ul><li>The probability that two randomly selected individuals in a community belong to different species. </li></ul></ul><ul><ul><li>Thus, as the Simpson’s Index of Diversity increases the species diversity of the population increases. </li></ul></ul>
  58. 58. Simpson’s Index of Diversity <ul><ul><li>Simpson's index of diversity = 1 - D </li></ul></ul><ul><ul><li>The probability that two randomly selected individuals in a community belong to different species. </li></ul></ul><ul><ul><li>Thus, as the Simpson’s Index of Diversity increases the species diversity of the population increases. </li></ul></ul>
  59. 59. Diversity Indices <ul><li>Shannon Index is more sensitive to changes in species richness </li></ul><ul><li>Simpson’s Index is more sensitive to changes in evenness </li></ul>
  60. 60. Diversity Indices <ul><li>Which diversity index should you choose to use? </li></ul><ul><ul><li>It might depend on whether you were more concerned about rare species </li></ul></ul><ul><ul><ul><li>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 </li></ul></ul></ul><ul><ul><li>Many researchers choose to use a number of different diversity indices because they provide different information. </li></ul></ul>