Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects. Vandermeer 1969 Dynamics in 4-species protist communities of Blepharisma, P caudatum, P.aurelia, and P. bursaria were consistent with predictions from 2- species L-V interactions.

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects B. Non-Additive Competitive Effects

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects B. Non-Additive Competitive Effects so, the addition of a third species changes the effect of one species on another.... which is defined as α 12 N 2.

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects B. Non-Additive Competitive Effects so, the addition of a third species changes the effect of one species on another.... which is defined as α 12 N 2. Well, that means the third species can influence the competitive effect by changing either component ( α 12 ) or (N 2 ).

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects B. Non-Additive Competitive Effects 1. Indirect Effects - mediated through changes in abundance

Worthen and Moore (1991) Indirect, non-additive competitive effects. D. falleni and D. tripunctata each exert negative competitive effects on D. putrida in pairwise contests, but D. putrida does better with BOTH competitors present than with either alone ADDITIVE NON-ADDITIVE

Worthen and Moore (1991) Indirect, non-additive competitive effects. D. falleni and D. tripunctata each exert negative competitive effects on D. putrida in pairwise contests, but D. putrida does better with BOTH competitors present than with either alone D. putrida D. tripunctata D. falleni

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects B. Non-Additive Competitive Effects 1. Indirect Effects - mediated through changes in abundance 2. Higher Order Interactions - mediated through changes in the competitive interaction (coefficient), itself; not abundance consider 2 species, and the effect of N2 on N1 as aN2. N2N1

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects B. Non-Additive Competitive Effects 1. Indirect Effects - mediated through changes in abundance 2. Higher Order Interactions - mediated through changes in the competitive interaction (coefficient), itself; not abundance Now, suppose we add species 3 HERE, as shown... N2N1N3

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects B. Non-Additive Competitive Effects 1. Indirect Effects - mediated through changes in abundance 2. Higher Order Interactions - mediated through changes in the competitive interaction (coefficient), itself; not abundance So NOW, N2 may shift AWAY from N1, reducing its competitive effect. N2N1N3

2. Higher Order Interactions - Wilbur 1972 Ambystoma laterale Ambystoma maculatum Ambystoma tremblay

2. Higher Order Interactions - Wilbur 1972 Mean mass of 32 A. laterale w/ 32 A. tremblayw/ 32 A. maculatumw/both g g g 32 A. laterale alone = g Abundances are constant, so the non-additive effect must be by changing the nature of the interaction

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects B. Non-Additive Competitive Effects 1. Indirect Effects - mediated through changes in abundance 2. Higher Order Interactions - mediated through changes in the competitive interaction (coefficient), itself; not abundance 3. Mechanisms: Change size of organisms and affect their competitive pressure Change activity level and affect their resource use Change behavior... and resource use

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects B. Non-Additive Competitive Effects C. Results

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects B. Non-Additive Competitive Effects C. Results 1. Niche Partitioning at the Community Level: Species Packing There should be a non-random ordering of species along some resource axis or associated morphological axis. This can be tested through nearest neighbor analyses. What would you see if they were ordered randomly? Then compare.

Worthen and Jones (2006, 2007)

AmberwingPondhawkBlue DasherGoldenwingSlatySaddlebags Williams (1994) V-test, v = 0.007, p < 0.05 Worthen (2009) Mean Perch Height (cm)

1. Niche Partitioning at the Community Level: Species Packing Dayan et al., Species packing in weasels in Israel.

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level A. Additive Competitive Effects B. Non-Additive Competitive Effects C. Results 1. Niche Partitioning in Communities: Species Packing 2. Optimal Size

For most groups of animals there is a 'right skew' to the frequency distribution of species ordered by size (log scale) SIZE % of Species

2. Optimal Size For most groups of animals there is a 'right skew' to the frequency distribution of species ordered by size (log scale) Why? Trade offs in reproductive work (Brown) - Large animals: lots of energy absorbed, but metabolic conversion to offspring is slow SIZE metabolic conversion to offspring

2. Optimal Size For most groups of animals, there is a 'right skew' to the frequency distribution of species ordered by size (log scale) Why? Trade offs in reproductive work (Brown) - Large animals: lots of energy absorbed, but metabolic conversion to offspring is slow - Small animals: good efficiency, but limited by energy they can collect SIZE

2. Optimal Size For most groups of animals, there is a 'right skew' to the frequency distribution of species ordered by size (log scale) Why? Trade offs in reproductive work (Brown) - result: there is a MOST EFFICIENT SIZE for a type of animal SIZE

2. Optimal Size For most groups of animals, there is a 'right skew' to the frequency distribution of species ordered by size (log scale) Why? Trade offs in reproductive work (Brown, 1993) - result: there is a MOST EFFICIENT SIZE for a type of animal

2. Optimal Size For most groups of animals, there is a 'right skew' to the frequency distribution of species ordered by size (log scale) Why? Trade offs in reproductive work (Brown) - result: there is a MOST EFFICIENT SIZE for a type of animal NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size

2. Optimal Size For most groups of animals, there is a 'right skew' to the frequency distribution of species ordered by size (log scale) Why? Trade offs in reproductive work (Brown) - result: there is a MOST EFFICIENT SIZE for a type of animal NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....this is not as great a size class, so species will move to new size class to avoid competition more rapidly...

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....this is not as great a size class, so species will move to new size class to avoid competition more rapidly...

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....this is not as great a size class, so species will move to new size class to avoid competition more rapidly...small size is constrained... but large is not.....

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....this is not as great a size class, so species will move to new size class to avoid competition more rapidly...small size is constrained... but large is not.....RESULT: RIGHT SKEW

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....this is not as great a size class, so species will move to new size class to avoid competition more rapidly...small size is constrained... but large is not.....RESULT: RIGHT SKEW Think about the Fretwell-Lucas model of habitat selection... the optimum is used first, and when this "size niche" is full, less optimal niches are colonized.

NOW: Consider multiple species filling up the environment... - each species will be selected to attain the optimum size - but since size is an important correlate to resource use, at some point a species will do better "off the optimum", rather than competing with lots of species on the optimum....this is not as great a size class, so species will move to new size class to avoid competition more rapidly...small size is constrained... but large is not.....RESULT: RIGHT SKEW Think about the Fretwell-Lucas model of habitat selection... the optimum is used first, and when this "size niche" is full, less optimal niches are colonized. Size correlates with so many patterns of resource use that it is a good generic proxy for niche use.

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels A. Keystone Predators

1. Paine (1966) - the rocky intertidal Arrows show energy flow; point to consumer.

A. Keystone Predators 1. Paine (1966) - the rocky intertidal - Pisaster prefers mussels

A. Keystone Predators 1. Paine (1966) - the rocky intertidal - Pisaster prefers mussels - When predators are excluded, mussels outcompete other species and the diversity of the system crashes to a single species - a mussel bed

A. Keystone Predators 1. Paine (1966) - the rocky intertidal - Pisaster prefers mussels - When predators are excluded, mussels outcompete other species and the diversity of the system crashed to a single species - a mussel bed - When predators are present, the abundance of mussels is reduced, space is opened up, and other species can colonize and persist.

A. Keystone Predators 1. Paine (1966) - the rocky intertidal - Pisaster prefers mussels - When predators are excluded, mussels outcompete other species and the diversity of the system crashed to a single species - a mussel bed - When predator is present, the abundance of mussels is reduced, space is opened up, and other species can colonize and persist. So, although Pisaster does eat the other species (negative effect) it exerts a bigger indirect positive effect by removing the dominant competitor

A. Keystone Predators 2. Lubchenco (1978) Littorina littorea feeding on algae

A. Keystone Predators 2. Lubchenco (1978) - Snails prefer Enteromorpha to Chondrus - E is dominant in tide pools, - C is dominant on exposed rock

A. Keystone Predators 2. Lubchenco (1978) - Snails prefer Enteromorpha to Chondrus - E is dominant in tide pools, - C is dominant on exposed rock In pools, snails are feeding on the dominant and you get a keystone effect from low to intermediate snail densities; then they are so abundant they eat everything.

A. Keystone Predators 2. Lubchenco (1978) - Snails prefer Enteromorpha to Chondrus - E is dominant in tide pools, - C is dominant on exposed rock In pools, snails are feeding on the dominant and you get a keystone effect from low to intermediate snail densities; then they are so abundant they eat everything. On rock, snails feed on competitive subordinate and Enteromorpha is whacked by competition AND predation, and diversity declines with increase snail abundance.

A. Keystone Predators 2. Lubchenco (1978) - Snails prefer Enteromorpha to Chondrus - E is dominant in tide pools, - C is dominant on exposed rock In pools, snails are feeding on the dominant and you get a keystone effect from low to intermediate snail densities; then they are so abundant they eat everything. On rock, snails feed on competitive subordinate and Enteromorpha is whacked by competition AND predation, and diversity declines with increase snail abundance. Effects depend on competitive dynamics, feeding preferences, and densities

A. Keystone Predators 3. Morin Dr. Peter Morin Community Ecology number of predatory salamanders

A. Keystone Predators 4. Worthen

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels A. Keystone Predators B. Apparent Competition

- consider 2 prey species consumed by the same predator PREDATOR PREY 1PREY 2

B. Apparent Competition - consider 2 prey species consumed by the same predator - suppose prey 2 increases PREDATOR PREY 1 PREY 2

B. Apparent Competition - consider 2 prey species consumed by the same predator - suppose prey 2 increases - this provides more food for the predator, which increases.... PREDATOR PREY 1 PREY 2

B. Apparent Competition - consider 2 prey species consumed by the same predator - suppose prey 2 increases - this provides more food for the predator, which increases and the other species experiences greater predation and declines… PREDATOR PREY 1 PREY 2

B. Apparent Competition - consider 2 prey species consumed by the same predator - suppose prey 2 increases - this provides more food for the predator, which increases and the other species experiences greater predation... - so an increase in one prey causes a decrease in the other... but this is an indirect effect mediated through a predator. PREDATOR PREY 1 PREY 2

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels A. Keystone Predators B. Apparent Competition C. Apparent Mutualism

- consider two prey, each eaten by specialized predators Predator 1Predator 2 Prey 1Prey 2

C. Apparent Mutualism - consider two prey, each eaten by specialized predators - Predator 1 increases and reduces Prey 1. Predator 1 Predator 2 Prey 1 Prey 2

C. Apparent Mutualism - consider two prey, each eaten by specialized predators - Predator 1 increases and reduces Prey 1. - Competition between prey is reduced and Prey 2 increases Predator 1 Predator 2 Prey 1 Prey 2

C. Apparent Mutualism - consider two prey, each eaten by specialized predators - Predator 1 increases and reduces Prey 1. - Competition between prey is reduced and Prey 2 increases - This provides more food for predator 2, which then increases Predator 1 Predator 2 Prey 1 Prey 2

C. Apparent Mutualism - consider two prey, each eaten by specialized predators - Predator 1 increases and reduces Prey 1. - Competition between prey is reduced and Prey 2 increases - This provides more food for predator 2, which then increases - So, an increase in one predator has had an indirect positive effect on another predator. Predator 1 Predator 2 Prey 1 Prey 2

Community Ecology I. Introduction II. Multispecies Interactions with a Trophic Level III. Multispecies Interactions across Trophic Levels A. Keystone Predators B. Apparent Competition C. Apparent Mutualism D. Intraguild Predation

- eat your competitor! - get a meal and reduce competition! Wissinger, et al Intraguild predation in larval dragonflies Damselflies - prey Erythemis simplicicollis Tramea lacerata

D. Intraguild Predation - eat your competitor! - get a meal and reduce competition! Wissinger, et al Intraguild predation in larval dragonflies significant non-additive effect

What effect will an introduced species have on a community? What effect will the loss of a species have on a community? “The first rule of the tinkerer is to save all the pieces” – Aldo Leopold