1. Population Distribution and Abundance

2. region biosphere landscape ecosystem community interaction population individual Evolutionary change driven by ecological processes occurs at the population level

3. Population a group of individual organisms of the same species living in a specific area

4. Population Scale of area inhabited by a population varies depending on the organisms in question – could be a single mountain top or an entire continent Population may represent only a fraction of a species, or a single population may include all the individuals comprising a species.

5. Populations all share defining features: Distribution – physical location of individual organisms in area that the population inhabits Abundance – number and density of individual organisms within an area

6. Distribution Limits Physical environment imposes limits on the distribution of populations the range of environments in which a particular species can exist is limited at some point, the energy expended by an organism for survival in an extreme environment exceeds the maximum energy intake that is possible for the organism

7. Distribution Limits

8. Physical environment is not always directly responsible for limiting species distribution climate may act indirectly through its influence on other factors such as food production, habitat, and incidence of predators and parasites.

9. Distribution Limits Distribution of different species may overlap geographically, yet may be divided on a microclimatic scale

10. Distribution Limits

13. Distribution of species can also be limited by competitive interactions with other species

14. Distribution Limits – Interspecific competition

15. Large – and small – scale distribution of individuals within a population distinction between “large” and “small” scale depends on the size of the organisms being studied small-scale = small distances over which there is little environmental change significant to the organism under study large-scale = areas over which there is considerable environmental change from the perspective of the study organisms

16. Small – scale distribution of individuals in a population Random Regular Clumped

17. Small – scale distribution of individuals in a population Random, regular or clumped distributions are caused by the nature of interactions between individual organisms in a population and / or the structure of the physical environment

18. Small – scale distribution of individuals in a population Random distribution – occurs when individuals are indifferent to the presence of other individuals and neutral with respect to environmental conditions / resources

19. Small – scale distribution of individuals in a population Regular distribution – occurs when individual interactions are antagonistic and / or local resources are depleted

20. Small – scale distribution of individuals in a population Clumped distribution – occurs when individual organisms attract each other and/or individuals are attracted to a common resource

21. Dynamic small – scale distribution of individuals in a population: creosote

22. Assessing small – scale distribution of individuals in a population Count number of individuals of a species in a randomized series of spatial plots transect quadrats

23. Assessing small – scale distribution of individuals in a population for each plot, calculate the mean (x) number of individuals of a species and determine the variance (s 2 ) around the mean

24. Assessing small – scale distribution of individuals in a population if s 2 is less than x, the distribution is regular if s 2 is greater than x, the distribution is clumped if s 2 is equal to x, the distribution is random

25. Large – scale patterns of population distribution From a large-scale perspective, population distributions always appear clumped individuals are concentrated around environmentally suitable, resource-rich areas

26. Abundance smaller organisms tend to live at higher densities (numbers of individuals per unit area) than larger organisms Population density decreases as the size of organisms increases

27. Abundance

28. Population density decreases as the size of organisms increases – but…how much? Is the relationship the same for all types of organisms? aquatic invertebrates tend to live at higher densities than terrestrial invertebrates of similar size mammals tend to live at higher densities than birds of similar size

29. Abundance Plant population density also decreases with plant size, but population density is more dynamic, changes as plants mature and grow larger

30. Abundance Population density / organism size relationship is important to quantify, as this generalization can be used to calculate expected population densities for a species of a given size and taxonomic group. can determine whether a particular population is unusually abundant or sparse

31. Extinction Patterns of population distribution and abundance are a key factor determining a species’ persistence or extinction rare species are more prone to extinction than common species – but how are rarity and commonness determined?

32. Rarity Classification of commonness and rarity based on three factors: 1) geographic range (extensive vs. restricted) 2) habitat tolerance (broad vs. narrow) 3) local population size (large vs. small)

33. extensive geographic range broad habitat tolerance small local population size Tiger

34. restricted geographic range broad habitat tolerance small local population size Tasmanian Devil

35. restricted geographic range narrow habitat tolerance large local population size Andean Flamingo

36. Pritchardia monroei restricted geographic range narrow habitat tolerance small local population size

37. Artemesia californica (sagebrush)

38. Artemesia douglasiana (mugwort)

39. Encelia californica

40. Epilobium canum (CA fuchsia)

41. Eriodictyon crassifolium (yerba santa)

42. Hereromeles arbutifolia (Toyon or Hollywood)

43. Marah macrocarpus (wild cucumber or Manroot)

44. Opuntia littoralis (coastal prickly pear)

45. Penstemon spectablilis

46. Salvia apiana (white sage)

47. Salvia mellifera (black sage)

48. Umbellularia californica (CA bay laurel)

49. Population Dynamics and Growth Population distribution and abundance changes through time – not a static feature, but one that is in constant flux

50. Population Dynamics and Growth Patterns of population distribution and abundance arise through the dynamic balance of two types of processes: processes that ADD individuals to populations and those that REMOVE individuals from populations

51. Population Dynamics and Growth Immigration & births – add individuals to populations Emigration & deaths – remove individuals from populations

52. Dispersal movement of individuals to establish populations in new areas (range expansion) movement of individuals within the bounds of an established population range movement of individuals between spatially isolated populations