Lecture 14: Communities: Asymmetry & context of competition

Question 1

resource

Answer 1

Any substance, structure, or environmental space that is consumed by an organism, and supports increased growth as its availability increases

Question 2

Intraspecific competition

Answer 2

• Competition among individuals of the
  same species
• key in density-dependent population dynamics

Question 3

Interspecific competition

Answer 3

• Competition among individuals of
  different species
• key in species coexistence in communities
• drives species adaptations to better exploit resources
• can depress the population growth of both species

Question 4

what does the outcome of competition depend on

Answer 4

efficiency of resource exploitation.

Question 5

Competitive exclusion principle

Answer 5

Two species cannot coexist indefinitely when they share a limiting resource

Question 6

how is competitive exclusion avoided?

Answer 6

Context-dependent outcomes

Question 7

define Context-dependent outcomes

Answer 7

The outcome of the ecological interaction depends on the conditions under which the interaction takes place

Question 8

Context-dependent outcomes - Coexistence on multiple resources

Answer 8

• Two species sharing two resources can shift the outcome of competition from competitive exclusion to coexistence
• Outcome of competitive interaction shifts with the availability of two shared resources

Question 9

Context-dependent outcomes - Asymmetry in competition from abiotic conditions

Answer 9

• asymmetrical competition
• Local coexistence can result from competitive advantage of different species in different microhabitats.

Question 10

define Asymmetrical competition

Answer 10

Competition in which one species has an inherent advantage in the acquisition of a contested resource under a certain set of environmental conditions.

Question 11

Asymmetrical competition - how can the outcome of interactions vary with microhabitats

Answer 11

resource availability doesn’t change, but competition takes place in a different environment.

Question 12

Context-dependent outcomes - common direct/Interference competition mechanisms in plants

Answer 12

• Allelopathy: Chemical competition
• Direct mechanical contact and constraint

Question 13

Context-dependent outcomes - Common direct/Interference competition mechanisms in animals

Answer 13

• Threat displays.
• Direct combat.
• Barriers to resource acquisition

Question 14

Context-dependent outcomes - Consumer impact on the outcome of competition

Answer 14

Consumer environment of competitive interactions can dramatically change the competitive context

Question 15

Apparent competition

Answer 15

• The numbers of one species impact its competitor indirectly through a shared predator
• not real competition, but the appearance of competition without more detailed information.

Question 16

define specialization

Answer 16

• allows an organism to “escape” its competition
• the escaping organism become really good at one thing and reduce resource overlap
• a common evolutionary response to competition

Question 17

what can specialization result from

Answer 17

a race for efficiency and extinction of some species, or it can result from reciprocal divergence of species (character displacement)

Question 18

evolution of specialization in individual species results in _____

Answer 18

community level pattern of “niche partitioning”

Question 19

Niche partitioning

Answer 19

• the use of different patterns of resource use, or different “niches”, as a result of natural selection
• evolved reduction in resource overlap and intensity of competition.

Question 20

Character displacement

Answer 20

Divergence in the traits of two otherwise similar species where the species’ ranges overlap, caused by the selective effects of competition between them.

Question 21

character displacement - Allopatric

Answer 21

Describes the situation where the geographic ranges of two or more species do not overlap

Question 22

character displacement - Sympatric

Answer 22

Describes the situation where the geographic ranges of two or more species do overlap

Question 23

Character displacement ___________ of species distributions is predicted when competition acts as a selective force

Answer 23

within the sympatric region

Question 24

character displacement - Species can have____________, relative to some other species.

Answer 24

allopatric regions and sympatric regions to their distribution