Download Species Interactions

SpeciesInteractions
Effect on Species 1
Effect on Species 2
–
0
+
–
Competition
Amensalism
Antagonism:
Predation
Herbivory
Parasitism
0
Amensalism
Neutralism?
Commensalism
+
Antagonism:
Predation
Herbivory
Parasitism
Commensalism
Mutualism
+ = Positive Effect
– = Negative Effect
0 = No Effect
KeyPoints:SpeciesInteractions
1) Species interactions can limit species
distributions and abundances.
2) Species are also important agents of selection
through their interactions.
3) Species compete when shared use of a resource limits a
species’ growth, survival or reproduction. Competing
species are more likely to coexist when they use resources
in different ways.
Competition
Occurs when shared use of a resource limits growth, survival,
and/or reproduction of two species (or individuals).
Interspecific:
Between individuals
of different species
Intraspecific:
Between individuals
of the same species
HowDoSpeciesCompete?
Exploitative:
Indirect competitions through
the reduction of a shared
resource pool.
Interference:
Direct antagonistic interactions
are used by one competitor to
interfere with use of limiting
resources by another.
CompetitionCriteria
1) Resource is shared between species
2) Resource is in short supply (limiting)
3) Removal of one species increases the fitness of the other
(or addition of one species reduces the fitness of the other)
Dipodomys spp.
Pogonomyrmex spp.
CompetitiveExclusionvsCoexistence
Competitive Exclusion!
Eat
Bacteria
Coexistence!
Eat Bacteria
Eat Yeast
Consumption(+/-)
A species interaction involving one species
eating another species.
Includes predation, herbivory, parasitism
Parasitism(Consumption)
Parasites are ubiquitous and probably represents
the most common lifestyle on Earth.
(~50% of insect species are parasites)
An interaction involving mutual benefits between two species
through the exchange of resources or services.
TheGhostofCompetitionPast
PRESENT
Resource Use
PAST
Resource Trait
(e.g., seed size)
Resource Trait
(e.g., seed size)
Competing species are more likely to coexist when they
use available resources in different ways.
CharacterDisplacement
Character Displacement:
Competition causes the phenotype of competing
species to evolve to become more different over time.
CharacterDisplacementinGalapagosFinches
These species are sympatric:
occupy the same or overlapping
geographic areas without
interbreeding.
These species are allopatric:
occupy different geographic
areas without interbreeding.
CharacterDisplacementè NichePartitioning
Niche Partitioning:
An evolutionary change in resource use and
partitioning between two or more species.
NicheDifferentiation
Tree Warblers in North America
MacArthur (1958)
Resource (Niche) Partitioning
Use of a limiting resource by
different species in different ways,
reducing interspecific competition
and allowing for coexistence.
PredatorsCanAffectPreyEvolution
Physical:
pangolin
Chemical:
poison dart frog
Crypsis:
gecko
Mimicry:
syrphid fly
Behavioral:
meerkats
Coevolution
Reciprocal evolutionary change in two species.
1) Reciprocity
2) Evolution occurs in response to another species
3) Specific sequence of events
An arms race is one possible consequence of coevolution.
SpeciesInteractions
What factors can influence the outcome and strengths
of species interactions?
1)
2)
3)
4)
AbioticContext:environmentalconditions(e.g.,temporrainfall)
BioticContext:othertypesofspeciesinteractions
Disturbance
Evolution
“Context-Dependent”
Example #1: Influence of Abiotic Context on Competition
(Cattle versus Wild Ungulates)
Cattle Weight Gain (kg/animal/day)
TheResults
Dry Season:
Competition (-/-)
Wet Season:
Commensalism (+/0)
Herbivory Treatments
Conclusion: For cattle, the outcome of the interaction with wild
ungulates was competitive only in dry seasons (abiotic context).
TheResults
Lots of Spiders:
Mutualism (+/+)
Spiders Rare:
Commensalism (+/0)
Conclusion: For treehoppers, the outcome of interaction with ants
was positive only when spiders were abundant.