Chapter 19: Species Diversity in Communities

Question 1

Zoonotic Diseases

Answer 1

hosted by wildlife and are infectious to humans

Question 2

Factors that affect emergence of zoonotic diseases

Answer 2

climate change, species invasions, pollution, and land use conversion

Question 3

How does species diversity affect the emergence and transmission of zoonotic diseases?

Answer 3

declining species diversity facilitates emergence and transmission

Question 4

Landscapes

Answer 4

made up of a patchwork of communities of different types

Question 5

What does membership in a community depend on?

Answer 5

-regional species pools and dispersal ability
-environmental conditions
-species interactions

Question 6

Regional Species Pool

Answer 6

provides an upper limit on the number and types of species that can be present in a community

Question 7

Dispersal

Answer 7

supplies species to communities. The importance of dispersal can be seen in cases of non-native species invasions

Question 8

How have humans expanded regional species pools?

Answer 8

by serving as vectors of dispersal

Question 9

How do environmental conditions affect community membership?

Answer 9

a species may be able to get to a community but be unable to tolerate the environmental or abiotic conditions

Question 10

How do species interactions affect community membership?

Answer 10

-coexistence with other species is also required for community membership
-other species may be required for growth, reproduction, or survival
-species may be excluded by competition, predation, parasitism, or disease

Question 11

Biotic Resistance

Answer 11

occurs when interactions with the native species exclude the invader
-not a lot is known about biotic resistance

Question 12

Climate change may facilitate species invasion by

Answer 12

1. Altering pathways of transport and introduction
2. Alteration of environmental constraints
3. Alteration of the distributions of existing invasive species
4. Impacts of non-native species may be altered
5. Effects of management of non-native species

Question 13

Resource partitioning

Answer 13

competing species are more likely to coexist if they use resources in different ways

Question 14

Resource Spectrum

Answer 14

-each type of resource varies among a resource spectrum
-the resource use of each species falls somewhere along this spectrum and overlaps with the resource uses of other species to varying degrees

Question 15

Read Slides 35-36

Question 16

MacArthur (1958)

Answer 16

studied resource partitioning in a community of warblers in New England forests
-birds used different parts of the habitat different ways

Question 17

MacArthur and MacArthur (1961)

Answer 17

looked at bird communities in 13 different habitats
-species diversity increased with foliage height diversity
-tree species identity was less important than structural complexity

Question 18

Resource Ratio Hypothesis

Answer 18

species coexist by using resources in different proportions

Question 19

Robertson et al. (1988)

Answer 19

mapped soil moisture and nitrogen concentration and found variation over small spatial scales
-this suggested resource partitioning In plants

Question 20

What can modify species interactions and allow for species coexistence?

Answer 20

disturbance, stress, and predation

Question 21

If the dominant competitor is prevented from reaching carrying capacity…

Answer 21

competitive exclusion cannot occur and coexistence will be maintained

Question 22

Who was the first to consider disturbance as a mechanism to maintain species diversity?

Answer 22

Darwin

Question 23

How did Darwin discover disturbance as a mechanism to maintain species diversity?

Answer 23

-in a meadow that he stopped mowing, he observes that the species number went from 20 down to 11
-without disturbance, the dominant species was able to exclude several others

Question 24

Slides 49-51

Question 25

Paine (1966)

Answer 25

studied competitive exclusion in the rocky intertidal zone
-When Pisaster was present, diversity was higher. Without it Mytilus outcompeted everything else

Question 26

Intermediate disturbance hypothesis

Answer 26

-species diversity will be greatest at intermediate levels of disturbance
-at low levels of disturbance, competition regulates diversity. At high disturbance levels, many species cannot survive

Question 27

Sousa (How does disturbance affect amount of species?)

Answer 27

studied communities on intertidal boulders that were overturned by waves
-small boulders (most overturned) had one species due to frequent disturbance
-most large boulders had two species (rare disturbance)
-intermediate sized boulders had four to seven species

Question 28

Competitive Displacement

Answer 28

the best competition uses the limiting resources, reducing the weaker competitor’s population growth to the point of extinction

Question 29

Dynamic Equilibrium Model

Answer 29

combines disturbance frequency and rate of competitive displacement to predict max species diversity at low, intermediate or equal levels

Question 30

Slides 61-64

Question 31

Menge and Sutherland Model (1987)

Answer 31

predation is a biological interaction and should be considered separately from disturbance
-predation is most important in low environmental stress
-as stress increases, predation importance decreases, and importance of competition increases
-at high stress levels, neither are important

Question 32

Recruitment

Answer 32

influx of young individuals to a population
-if low, competition may not be important because resources are not limited

Question 33

What do lottery models and neutral models emphasize?

Answer 33

the role of chance in maintaining species diversity
-all species have equal chances of obtaining resources made available by disturbances, and this allows coexistence
-species must have similar interaction strength and growth rates and be able to respond quickly to disturbances

Question 34

Where is the lottery model most relevant?

Answer 34

very diverse communities where many species overlap in their resource requirements

Question 35

What controls community functions such as disease suppression, plant productivity, water quality, etc.

Answer 35

species diversity

Question 36

What valuable services do humans receive from community functions?

Answer 36

food and fuel production, water purification, oxygen and carbon monoxide exchange, flood protection

Question 37

Diversity-Stability Theory

Answer 37

species richness is positively related to community stability
-tendancy of a community to remain the same in structure and function, or to return after a disturbance

Question 38

Complementary Hypothesis

Answer 38

as species richness increases, community function will increase linearly
-each species has a unique and equally incremental effect

Question 39

Redundancy Hypothesis

Answer 39

Functional contribution of additional species reaches a threshold
-as more species are added, there is overlap in their function, or redundancy among species

Question 40

Idiosyncratic hypothesis

Answer 40

strength of ecological function varies greatly
-some species have a large effect, some have a minimal effect
-addition of dominant species will have a large effect on community function, producing a cure with a idiosyncratic shape

Question 41

Case Study at end of powerpoint Slides 82-84