Species Interactions - University of Vermont · 2019. 7. 8. · Species Interactions •...
Transcript of Species Interactions - University of Vermont · 2019. 7. 8. · Species Interactions •...
1
9 July 2019
Species Interactions • Interactions can be + or -
– Mutualism – Competition
• Resource Partitioning
– Predators and Prey • food webs
• Species diversity • Richness and Evenness
• Global patterns • Equilibrium of colonization and
extinction
• Succession • Primary and secondary
Species Interactions
Competition -/- both spp. suffer
Mutualism +/+ both spp.benefit
Predation, Parasitism +/- one sp. benefits at the expense of the other
Commensalism +/0 one sp. benefits with no effect on the other
Leafcutter ants are fungus farmers
https://www.youtube.com/watch?v=RH3KYBMpxOU
Many kinds of interactions can happen at the same time
Growth with limited resources
What type of population growth is shown? Why does the population size stabilize?
What is happening to the two populations of Paramecium (P. aurelia and P. caudatum) when housed together at
• Day 4
• Day 8
• Day 16
What do you predict will happen at Day 20? Why?
Questions to ponder or discuss with your neighbor:
2
Competitive Exclusion Principle
When two species compete for the same resources, the species that is more efficient at using the resources will outcompete the other.
Paramecium Competition
Why can these coexist?
Removal experiments can test the role of species interactions
Chthamalus
Balanus
High tide
Chthamalus
Balanus
Ocean Low tide
High tide
Chthamalus
Ocean Low tide
When Balanus was removed, Chthamalus expanded its range
Ocean
Chthamalus
Balanus
EXPERIMENT
RESULTS
High tide
Low tide
Chthamalus realized niche
Balanus realized niche
High tide
Chthamalus fundamental niche
Low tide Ocean
Realized niche: The actual species� use of resources (as constrained by interactions with other species)
Fundamental niche: Its potential resource space.
A. ricordii
A. insolitus usually perches on shady branches.
A. distichus perches on fence posts and other sunny surfaces.
A. aliniger A. distichus
A. insolitus
A. christophei
A. cybotes A. etheridgei
Niche partitioning
Competition among lizards causes species to forage in different microhabitats.
3
Resource Partitioning Can Cause Intraspecific Competition to Be Greater Than Interspecific Competition Niche evolution in lizards
Green Anole Brown Anole
Green anoles perch higher in trees and evolved larger toepads on islands where Brown anoles were introduced.
Los Hermanos
G. fuliginosa G. fortis
Beak depth
Daphne
G. fuliginosa, allopatric
G. fortis, allopatric
Sympatric populations
Santa María, San Cristóbal
Beak depth (mm)
Perc
enta
ges
of in
divi
dual
s in
eac
h si
ze c
lass
60 40 20 0
60 40 20 0
60 40 20 0
8 10 12 14 16
Sizes of Galapagos finch beaks are more different on islands where two species compete.
Fig. 53-20
Snowshoe hare
Lynx
Num
ber o
f lyn
x (th
ousa
nds)
Num
ber o
f har
es
(thou
sand
s)
160
120
80
40
0 1850 1875 1900 1925
Year
9
6
3
0
Predators and Prey
Fig. 53-19
Wolves Moose 2,500
2,000
1,500
1,000
500
Num
ber o
f moo
se
0
Num
ber o
f wol
ves
50
40
30
20
10
0 1955 1965 1975 1985 1995 2005
Year
Predator/Prey interactions Fig. 54-11
Carnivore
Carnivore
Carnivore
Herbivore
Plant
A terrestrial food chain
Quaternary consumers
Tertiary consumers
Secondary consumers
Primary consumers
Primary producers
A marine food chain Phytoplankton
Zooplankton
Carnivore
Carnivore
Carnivore
4
Fig. 54-12
Humans
Smaller toothed whales
Baleen whales
Sperm whales
Elephant seals Leopard
seals Crab-eater
seals
Birds Fishes Squids
Carnivorous plankton
Copepods Euphausids (krill)
Phyto- plankton
Fig. 54-13
Sea nettle
Fish larvae
Juvenile striped bass
Fish eggs Zooplankton
A Food Web in the Grasslands of Yellowstone National Park
Removing Wolves Initiated a Trophic Cascade
With sea otters Without sea otters Another Trophic Cascade Another Trophic Cascade
Largemouth Bass removed
Source: Estes et al. 2011
Bass Planktivorous fish Zooplankton Phytoplankton
5
Defense Mechanisms and Evolutionary Arms Races
Some places have high diversity
Boreal forest
Desert
Other habitats have low species diversity
“Diversity” depends on species richness and evenness
A B C D
Community 1 A: 25% B: 25% C: 25% D: 25%
Community 2 A: 80% B: 5% C: 5% D: 10%
Which of these communities is more diverse?
Tropical habitats support much larger numbers of species than do temperate and polar regions.
6
Mammals and Plants show the same pattern
Plant Species Richness
Mammals
Imagine a newly formed island some distance from the mainland…
What will determine the rate of arrival of new species?
Species richness will be a balance between immigration and extinction
Number of species on island
Rat
e of
imm
igra
tion
or e
xtin
ctio
n
Extinc
tion
Imm
igration How would these curves change for a larger island? How will that affect the equilibrium number of species?
Area and Isolation Influence Species Richness on Islands
Number of plant species on the Galápagos Islands in relation to island area.
Endemic Galapagos prickly pear cactus tree
Species increase with area even at continental scales.
Area (hectares)
Num
ber o
f spe
cies
1,000
100
10
1 0.1 1 10 100 103 104 105 106 107 108 109 1010
7
The Theory of Island Biogeography Can Be Tested
Experimentally remove insects from small mangrove islands. Will the species number come back to equilibrium?
The Theory of Island Biogeography Can Be Tested (Part 2)
How well does that experiment fit predictions of island biogeography theory?
Habitat Fragmentation in Tropical Forests
1950
1985
A Large-Scale Study of Habitat Fragmentation in Brazil
Which species are at most risk from fragmentation?
Other Habitat Fragmentation Experiments
8
Results from Habitat fragmentation experiments Sometimes the declines in species don’t show up for several years
Species composition changes over time
Disturbance can alter the species composition of communities
(a) Soon after fire
(b) One year after fire
Primary succession starts with empty sites
1941 1907
1860 Glacier
Bay
Alaska
1760
0
Pioneer stage Dryas stage
Kilometers Spruce stage Alder stage
5 10 15
1 2
4 3
Dung Beetle Species Composition Changes over Time
9
Intermediate levels of Disturbance can increase species richness
35
Num
ber o
f tax
a 30
25
20
15
10 0.9
Index of disturbance intensity (log scale) 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0