How do we get Biodiversity?

1. How do we get Biodiversity?

3. Biodiversity • Biodiversity • increases with speciation • decreases with extinction • Give-and-take between speciation and extinction  changes in biodiversity • Extinction creates evolutionary opportunities for adaptive radiation of surviving species

4. Interpretations of Speciation Two theories: 1. Gradualist Model (Neo-Darwinian): Slow changes in species overtime 2. Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change

6. Adaptive Radiation Emergence of numerous species from a common ancestor introduced to new and diverse environments Example: Hawaiian Honeycreepers

7. Convergent Evolution Species from different evolutionary branches may come to resemble one another if they live in very similar environments Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert)

9. Coevolution • Evolutionary change • One species acts as a selective force on a second species • Inducing adaptations • that act as selective force on the first species Example: • Wolf and Moose • Acacia ants and Acacia trees • Yucca Plants and Yucca moths • Lichen

11. Equilibrium Theory of Biodiversity • Diversity is a balance of factors that increase diversity and factors that decrease diversity • Production of new species (speciation), and influx can increase diversity • Competitive exclusion, efficient predators, catastrophic events (extinction) can decrease diversity • Physical conditions • variety of resources • Predators • environmental variability

12. Species Diversity Def: the variety of species in an area Two subcomponents: species richness species evenness

13. Species Richness vs. Evenness Species Richness: measurement of the number of species in a given area Species Evenness: measurement of how evenly distributed organisms are among species Community A Community B species 1 25 1 species 2 0 1 species 3 25 1 species 4 25 1 species 5 25 96

14. Determining Species Diversity Scientists may want to: * get an estimate of # of species in an area * compare species diversity of two communities To be accurate, need to: * take both species evenness and species richness into account

15. Species Diversity Indices Shannon-Weiner (Shannon-Weaver) Index Diversity = (p spp 1 - ln(p spp 1)) + (p spp 2 - ln(p spp. 2) + … (p spp N - ln(p spp. N) Simpson Index Diversity = 1 (pspp1)2 + (pspp2)2 + … (psppN)2

16. Why should we care about measuring biodiversity (species diversity)?

17. Biodiversity Factoids ~ 2,000,000 spp. have been described ~ 10-30,000,000 species actually exist (est.) ~ 8,000,000 – 22,000,000 spp. unidentified ~ 40 – 60% of all spp. occur in two areas: * tropical rainforests * coral reefs

18. Comparison of Two Communities • Richness (number of species) • Relative abundance • How do we describe these differences?

19. Biogeographical Changes • Richness declines from equator to pole • Due to: • Evolutionary history • Climate Fig 53.23 Bird species numbers

20. Geographic (Sample) Size • Species-area curve • The larger the geographic area, the greaterthe numberof species Fig. 23.25 North American Birds

21. Species Richness on Islands • Depends on: • Rate of immigration to island • Rate of extinction on island • These in turn depend on: • Island size • Distance from mainland

22. How do species move? • Humans (accidental and intended) • Animals (sticky seeds and scat) • Wind and ocean currents (+ or -) • Land bridges • Stepping stone islands • affected by climactic changes (glaciation) • ocean levels • short-term weather patterns

23. What allowed colonization? • Niche opening • No competition • Endemics not utilizing resources • Accessibility to colonists

24. Theory of Island Biogeography • Immigration rate decreases as island diversity increases • Extinction increases as island diversity increases • Species equilibrium on islands is a balance of immigration and local extinction

26. Theory of Island Biogeography • Smaller islands have lower total populations • Probability of extinction increases with lower population • Smaller islands have lower species diversity

28. Theory of Island Biogeography • Islands further from mainland have lower immigration rates • More distant islands have lower species diversity

30. Community Relationships

31. Niche is the species’ occupation and its Habitat location of species (its address)

32. Niche A species’ functional role in its ecosystem; includes anything affecting species survival and reproduction • Range of tolerance for various physical and chemical conditions • Types of resources used • Interactions with living and nonliving components of ecosystems • Role played in flow of energy and matter cycling

33. Fundamental niche: set of conditions under which a species might exist in the absence of interactions with other species Realized niche: more restricted set of conditions under which the species actually exists due to interactions with other species Niche

34. Types of Species • Generalist • large niches • tolerate wide range of environmental variations • do better during changing environmental conditions • Specialist • narrow niches • more likely to become endangered • do better under consistent environmental conditions

35. Types of Species • Native species normally live and thrive in a particular ecosystem • Nonnative species are introduced - can be called exotic or alien • Indicator species serve as early warnings of danger to ecosystem- birds & amphibians • Keystone species are considered of most importance in maintaining their ecosystem

36. Nonnative Species • Nonnative plant species are invading the nation's parks at an alarming rate, displacing native vegetation and threatening the wildlife that depend on them • At some, such as Sleeping Bear Dunes National Lakeshore in Michigan, as much as 23 percent of the ground is covered with alien species, and the rate of expansion is increasing dramatically.

37. Indicator Species • a species whose status provides information on the overall condition of the ecosystem and of other species in that ecosystem • reflect the quality and changes in environmental conditions as well as aspects of community composition

38. Keystone Species • A keystone is the stone at the top of an arch that supports the other stones and keeps the whole arch from falling • a species on which the persistence of a large number of other species in the ecosystem depends. • If a keystone species is removed from a system • the species it supported will also disappear • other dependent species will also disappear • Examples • top carnivores that keep prey in check • large herbivores that shape the habitat in which other species live • important plants that support particular insect species that are prey for birds • bats that disperse the seeds of plants

39. Species Interaction

40. Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species • Resource competition

41. Competition

42. Resource Competition

43. Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species • Resource competition • Preemptive competition

45. Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species • Resource competition • Preemptive competition • Competitive exclusion

46. Competitive Exclusion

47. Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species • Resource competition • Preemptive competition • Competition exclusion • Interference competition

48. Competition

49. Resource Partitioning • Division of resources in an ecosystem so that species with similar needs (overlapping ecological niches) use the same scarce resources at different times, in different ways, or in different places.

50. PREDATION