1. Evolution, Biodiversity, and Community Processes
Chapter 8

2. Biodiversity

4. How do we get Biodiversity?

5. 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

6. 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

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

9. 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)

11. Coevolution Evolutionary change Example: Wolf and Moose
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

13. Extinction
Extinction of a species occurs when it ceases to exist; may follow environmental change - if the species does not evolve
Evolution and extinction are affected by:
large scale movements of continents
gradual climate changes due to continental drift or orbit changes
rapid climate changes due to catastrophic events

15. Extinction
Background extinction - species disappear at a low rate as local conditions change
Mass extinction - catastrophic, wide-spread events --> abrupt increase in extinction rate
Five mass extinctions in past 500 million years
Adaptive radiation - new species evolve during recovery period following mass extinction

16. Date of the Extinction Event Marine vertebrates and invertebrates
Mass Extinctions
Date of the Extinction Event
Percent Species Lost
Species Affected
65 mya
(million
years ago) 85
Dinosaurs, plants (except ferns and seed bearing plants), marine vertebrates and invertebrates. Most mammals, birds, turtles, crocodiles, lizards, snakes, and amphibians were unaffected.
213 mya 44
Marine vertebrates and invertebrates
248 mya
75-95
380 mya 70
Marine invertebrates
450 mya 50

17. 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

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
Generally tropical communities are older than temperate than polar communities
Organisms have a richer evolutionary history in an area where they are adapted to the climate.
Energy input (solar) and water availability factor into this phenomenon.
Fig Bird species numbers

20. Geographic (Sample) Size
Species-area curve
The larger the geographic area, the greater the number of species
Note that both scales are logarithmic
Fig 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
Because of their size and isolation, islands provide great opportunities for studying some of the biogeographic factors that affect the species diversity of communities.
Imagine a newly formed island some distance from the mainland.
Robert MacArthur and E. O. Wilson developed a hypothesis of island biogeography to identify the determinants of species diversity on an island.

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
Aerial dispersal cause by wind, birds, flying insects. Dependent on long-term viableility of seeds, spores, etc.
Decreasing ocean levels may allow flow of organisms between land masses normally isolated. This allows for genetic mixing.
Coconuts are a good example of well adapted marine dispersed organism.
Long-lasting climactic changes such as glaciation may allow for the expansion and subsequent reduction of range, but during that expansion, gene-flow will occur.

23. What allowed colonization?
Niche opening
No competition
Endemics not utilizing resources
Accessibility to colonists
Colonization of young islands is especially rapid compared to older islands and especially the mainland
4 - Of course, if there is no access to colonists, there will be no colonization.

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. the species’ occupation and its
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. Niche
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

34. Types of Species Generalist Specialist 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. r and k strategists
Depending upon the characteristics of the organism, organisms will follow a biotic potential or carrying capacity type reproductive strategy
The r-strategists
High biotic potential – reproduce very fast
Are adapted to live in a variable climate
Produce many small, quickly maturing offspring = early reproductive maturity
“Opportunistic” organisms
The K-strategists
Adaptations allow them to maintain population values around the carrying capacity
They live long lives
Reproduce late
Produce few, large, offspring

36. 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

37. 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.

38. 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

39. 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

40. Species Interaction

41. 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 exploitation
Interference competition

42. Resource Competition

43. Competitive Exclusion

44. PREDATION

45. Predator Adaptations Prey detection and recognition Prey capture
sensory adaptations
distinguish prey from non-prey
Prey capture
passive vs. active
individuals vs. cooperative
Eating prey
teeth, claws etc.

46. Prey Adaptations Avoid detection Avoid capture
camouflage, mimics,
diurnal/nocturnal
Avoid capture
flee
resist
escape
Disrupt handling (prevent being eaten)
struggle?
protection, toxins

47. Herbivory Herbivore needs to find most nutritious
circumvent plant defenses
Herbivory strong selective pressure on plants
structural adaptations for defense
chemical adaptations for defense

48. Symbiosis: Mutualists, Commensalists and Parasites

49. Symbiosis and symbiotic relationship are two commonly misused terms
Translation of symbiosis from the Greek literally means “living together”
Both positive and negative interactions

50. Mutualism DEFINITION:
An interaction between two individuals of different species that benefits both partners in this interaction

51. Raise the carrying capacity
Mutualism
Increase birth rates
Decrease death rates
Increase equilibrium population densities,
Raise the carrying capacity

52. Pollination
Animals visit flowers to collect nectar and incidentally carry pollen from one flower to another
Animals get food and the plant get a pollination service

53. Yucca and Yucca Moth
Yucca’s only pollinator is the yucca moth. Hence entirely dependent on it for dispersal.
Yucca moth caterpillar’s only food is yucca seeds.
Yucca moth lives in yucca and receives shelter from plant.

54. Lichen (Fungi-Algae)
Symbiotic relationship of algae and fungae…results in very different growth formas with and without symbiont.
What are the benefits to the fungus?

55. Nitrogen Fixation
Darkest areas are nuclei, the mid-tone areas are millions of bacteria Gram -, ciliate

56. Obligatory Mutualism
Obligatory: An organism can't live without the mutualism--either cannot survive or cannot reproduce.
the common pollinator systems like bees and flowering plants
protozoans in the guts of termites
the alga in the lichen partnership

57. Facultative Mutualism
Facultative: This is "take it or leave it" for one or both partners
While the organism benefits when the mutualism is present, it can still survive and reproduce without it
ant mutualisms, such as ants protecting plants from predation
ants tending aphids

58. Commensalists Benefit from the host at almost no cost to the host
Eyelash mite and humans
Us and starlings or house sparrows
Sharks and remora

59. Parasites and Parasitoids
Parasites: draw resources from host without killing the host (at least in the short term).
Parasitoids: draw resources from the host and kill them swiftly (though not necessarily consuming them).

60. Parasitic wasps Important parasites of larvae.
In terms of biological control, how would this differ from predation?
ovipositor

61. Ecological Processes

62. Ecological Succession
Primary and Secondary Succession
gradual & fairly predictable change in species composition with time
some species colonize & become more abundant;
other species decline or even disappear.

63. Ecological Succession
Gradual changing environment in favor of new / different species / communities

64. Primary Succession
Gradual establishment of biotic communities in an area where no life existed before
No preexisting seed bank
newly formed islands (i.e. volcanic origin)
retreat of a glacier

66. Primary Succession Glacier Retreat

67. Secondary Succession
Gradual reestablishment of biotic communities in an area where one was previously present.
Preexisting seed bank
treefall gaps
"old field succession"
forest fire

70. Disturbance Event that disrupts an ecosystem or community;
Natural disturbance
tree falls, fires, hurricanes, tornadoes, droughts, & floods
Human–caused disturbance
deforestation, erosion, overgrazing, plowing, pollution,mining
Disturbance can initiate primary and/or secondary succession

71. Ecological Stability
Carrying Capacity – maximum number of individuals the environment can support

72. Ecological Stability - Stress
Drop in Primary Productivity
Increased Nutrient Losses
Decline or extinction of indicator species
Increased populations of insect pests or disease organisms
Decline in Species diversity
Presence of Contaminants