marine eco

exam 2 tamug

Reduces extinction
competition or Predation

Predation

High latitudes in terms of species richness (S)
source or sink

sink

Energy transferred to next trophic level
10% or 90%

10%

Greater number of trophic levels
Caribbean Sea or Bering Sea

Caribbean Sea

Under "kinetic energy hypothesis" higher temperatures lead to
Lower S or Higher S

Higher S

Food webs with MORE biomass at higher trophic levels
Marine or Terrestrial

Marine

Keystone species concept
Connell or Paine

Paine

Peak S of invertebrate megafauna at this depth 2000 m 4000 m

2000 m

Higher diversity at mid elevations explained
by this hypothesis
Kinetic Energy or Mid Domain

Mid Domain

Upwelling and primary productivity higher
Stable water mass or No thermocline

Stable water mass

Competition between two species
Intraspecific or Interspecific

Interspecific

Strong density-dependent predation
Smaller school size advantageous or Larger school size advantageous

Smaller school size advantageous

Decline in killer whale numbers
More kelp or Less kelp

More kelp

Lower population densities (for animals of comparable size)
Aquatic invertebrates or Terrestrial invertebrates

Terrestrial invertebrates

primary productivity in the center of subtropical gyres
low or high

low

describe mid-domain hypothesis

diversity peaks in mid latitude regions.
The center of the region
accumulates different species from all directions.
The effect will also apply to mid elevation regions

High disturbance or predation leads to
Higher biodiversity or Lower biodiversity

Lower biodiversity

Increases in cownose rays and declines in bay scallops due to shifts in the abundance of great sharks is an example of
A. Resource partitioning
B. Trophic cascade
C. Niche expansion
D. Competitive exclusion

B. Trophic cascade

If K1 (carrying capacity) is completely inside K2, what is the outcome of competitive interactions between the two species?
A. Species 1 wins
B. Species 2 wins
C. Species 1 and 2 coexist
D. Species 1 and 2 both go extinct

B. Species 2 wins

Term that describes competition for space by a second species (N2) on the population growth of N1 from the Lotka-Volterra competition model
A. K2
B. a12N2
C. pN1N2
D. [K1-N2]/K2

B. a12N2

Global patterns of biodiversity for Coastal species (seagrass, mangroves, corals) peak here
A. Polar regions
B. Mid latitudes (~20-40° latitude)
C. Equator
D. Western Pacific Ocean

D. Western Pacific Ocean

Expected signature for Bull Shark that feeds exclusively on green sea turtles which feeds exclusively on
sea grass (bull Shark sea turtle seagrass). Starting values for sea grass: 13 C \= -10.2, 15 N \= 2.0
A. 13 C \= -8.2, 15 N \= 5.0
B. 13 C \= -12.2, 15 N \= 8.0
C. 13 C \= -11.2, 15 N \= 5.0
D. 13 C \= -8.2, 15 N \= 8.0

D. 13 C \= -8.2, 15 N \= 8.0

Main primary producers supporting white grunts in backreef habitat in Puerto Rico (Rooker et al.
paper)
A. Phytoplankton, benthic microalgae, mangrove
B. Seagrass, benthic microalgae, and phytoplankton
C. Mangroves, seagrass, benthic microalgae
D. Phytoplankton, green macroalgae, POM

C. Mangroves, seagrass, benthic microalgae

'Center of Origin' hypothesis explaining higher S in Western Pacific Ocean is due to geographic
isolation through
A. Vicariance
B. Competition
C. Dispersal
D. Predation

C. Dispersal

Order from LOWEST to HIGHEST in terms of rate of primary productivity (note: assume maximum rate for each producer)
A. Phytoplankton (open ocean), phytoplankton (coastal upwelling), tundra
B. Phytoplankton (equatorial upwelling), phytoplankton (coastal upwelling), coral reef
C. Coral reef, seagrass, phytoplankton (open ocean)
D. Seagrass, tropical rain forest, phytoplankton (coastal upwelling)

B. Phytoplankton (equatorial upwelling), phytoplankton (coastal upwelling), coral reef

Most useful dietary tracers for determining the trophic position of consumers
A. S 15 N
B. S 13 C
C. S 12 C
D. S 18 O

A. S 15 N

Dominant (Foundation) species
A. Total impact on community structure low, biomass low
B. Total impact on community structure low, biomass high
C. Total impact on community structure high, biomass low
D. Total impact on community structure high, biomass high

D. Total impact on community structure high, biomass high

Energy produced by phytoplankton is eventually converted into shark biomass in the open ocean.
Based on the following food chain (phytoplankton krill jack mako shark), how much
energy (organic matter) produced by phytoplankton is converted to mako shark biomass?
A. 10%
B. 1%
C. 0.1%
D. 0.01%

C. 0.1%

8. Why does species richness (S) peak in the tropics? Describe three factors that may play a role
(6 pts).

9. Give three plausible explanations to explain the lower diversity of corals and reef fishes at
the Flower Garden Banks compared to coral reefs at the center of diversity (e.g. Jamaica) in the
Caribbean Sea. Please describe how each factor influences diversity (6 pts)

Competition: is

Sp 1 & Sp 2 use same resource in limited supply

Predation: is

Sp 1 à consumes all or part of Sp 2

Interference Competition:

species physically excludes another species from using a particular resource

Interference competition can involve

Space/habitat
-Food/Prey
-Mates

Interference Competition: characterized as

Direct antagonistic interactions between individuals
have profound effect on growth and survival and pop. dynamics

Resource competition defention

occurs between individuals associated with a shared limited resource but does not include direct antagonistic interactions

Resource competition also called

exploitative or scramble competition

Resource competition indirect interactions are

-Light/nutrients
-Space/habitat
-Food/Prey

Resource competition Superior competitor

exploits resources more efficiently than other competing species

Types of Competition

intraspecific and interspecific

intraspecific competition

competition between members of the same species

interspecific competition

competition between members of different species

in logistic growth model The carrying capacity (K) could be any

resource or combination of resources that limits population growth

competition assumption (2)

1.resources decrease as N increases due to intraspecific competition
2.resources decrease due to interspecific competition

All the notation in these equations is the same as the logistic growth equation. The only change is that we have notation added to the equation to denote the fact that \----- \----- and \-------- \----- are likely different between the two species.

population sizes
carrying capacities

We multiply \-- with N2 in order to get the \----- \------ that the population of species 2 has on species 1

a
cumulative effect

How can we model population growth in 2 competing species?? assumptions

1.resources decreases as N increases due to intraspecific competition
2.resources decreases due to interspecific competition

--Environment holds K1 individuals of Sp 1
--Some of resource used by Sp 2
--Resource use: Sp 1 does not equal Sp 2
--Convert Sp 2 individuals to
equivalents of Sp 1

If a \> 1 \= competition effect of Sp.2 on population growth of Sp.1 is \----- than that of an individual of Sp.1
interspecific competition __intraspecific

greater
interspecific competition \> intraspecific

If a \= 1 then

intraspecific effect \____ interspecific effect

intraspecific effect \= interspecific effect

If a

less
interspecific < intraspecific

*Predicts coexistence when interspecific competition is \----- than intraspecific competition!

weaker

We need to know, when pop sizes are not changing....
N1\= K1-aN2 (spps1)
N2\=K2-aN1 (spps2)
Isoclines of Zero Population Growth

aN2 (spps1)
K2 (spps2)
In the bottom two equations, the populations for each species are equal to the species' carrying capacity minus the competitive effect of the other species

Under logistic growth model, a population growing in isolation would eventually reach\------. At that point, \----- would be stable

K (N1 \= K1)
pop

With competitors present, the stable population size for species 1 would\---- \---- the carrying capacity, it would \---- \--- \----

not equal
fall below it

What if the combination of population sizes for species 1 and species 2 doesn't fall on the 0-population growth isocline for species 1 the point is below the isocline of species 1. Will it increase or decrease?

Because the point is below the isocline of species 1, the population size of species 1 will increase

If a species' population size is below its own isocline, the population size will always .....

increase.

If a species' population size is above its own isocline, the pop size will

decrease

Gause's "Competitive Exclusion Principle"

One population drives another to extinction
"Complete competitors cannot coexist"

Gause's "Competitive Exclusion Principle"
-Priority effect

Species establishing itself first
Usually wins out in competition
"Complete competitors cannot coexist"

Competitive Exclusion
Ecological Space:

\-- Inoculation
\-- Exponential growth (Pops A&B)
\-- Rates decrease
\-- Pops differ in r, competitive abilities, K
\-- Pop A (r\=0)--Pop B (still +)
\-- Pop B increase & competitive inhibition intensified
\-- Pop A: r negative--\> lead to extinction

resource partitioning

Potential competitors can avoid competition
by ecological segregation in time, space, food
When species divide a niche to avoid competition for resources

resource partitioning example

Terns on Christmas Island
Sooty feeds \> 100 km from land
Brown noddy : 0-100 km from land
Same size; same food;

Paradox of the plankton

Paradox --\>limited range of resources (light, nutrients) but high diversity of planktonic species
(No partitioning but high diversity)

Paradox of the plankton Exception

the competitive exclusion principle

Environment constantly changing (turbulence, vertical gradients of light, differential predation, etc.)--\> planktonic habitat never reaches an equilibrium where one species is favored (G.E. Hutchinson)
this is

Paradox of the plankton

Interspecific competition \----- the fitness of competing individuals

reduces

Long term competition among similar species
leads to \-------- of size & resource exploitation

separation

"Character displacement"

Ecologically similar species differ in
-resource
-exploitation
-associated morphology
Character mean (beak size) differs
for sympatric pops; more similar for
allopatric pops

'Ghost of Competition Past

Interspecific competition, acting as an evolutionary force in the past, has often left its mark on the behavior, distribution or morphology of species even when there is no present-day competition between them (Connell)

indirect effects of predation

via exploitation; 2 predators share common prey & interact indirectly through exploitative competition

this is direct or indirect effects of predation
effect without competition from predators; competition between the 2 prey species can affect one or both predators

inderct

Consequences of Predation
(list the 4 )

1) reduce abundance (àpop size, niche)
2) Influence organization of communities (Keystone Species)
3) Influence primary production (Trophic Cascade) & energy flow (transfer) through ecosystem(s)
4) Evolutionary force affecting adaptations

A species can exert a strong effect on community structure through predation
(enhance species diversity)
This is a

Keystone species hypothesis

Keystone species hypothesis example

-Pisaster feed heavily on a variety of barnacles, limpets, bivalves, and chitons.

-When Pisaster are removed, barnacles and bivalves are free to expand their populations

-Two years after Pisaster removal, barnacles and mussels have outcompeted most other species for space in the tide pool causing a drop in species diversity

what is a keystone species

A species that, despite low abundance exerts strong effects on the structure of ecological communities. The ecosystem would look different without them

Foundation species:

A habitat forming species that has strong influence over community structure due to their high abundance. The habitat wouldn't exist with out them!

Foundation spps vs keystone spps

foundation - habitat forming, high abundance
keystone spps- low abundance

Foundation species:
A. Total impact on community structure low, biomass low
B. Total impact on community structure low, biomass high
C. Total impact on community structure high, biomass low
D. Total impact on community structure high, biomass high

D. Total impact on community structure high, biomass high

Keystone species:
A. Total impact on community structure low, biomass low
B. Total impact on community structure low, biomass high
C. Total impact on community structure high, biomass low
D. Total impact on community structure high, biomass high

C. Total impact on community structure high, biomass low

Trophic cascade hypothesis

A multi-trophic level interaction, where a predator indirectly influences primary production through direct influence on an herbivore.

Results in changes in abundance at multiple trophic levels

Trophic cascade hypothesis example

Example: trophic cascade due to
feeding shifts of transient killer whales
When sea otter abundance is high, sea urchin biomass is low, which allows kelp biomass to be high (pink portion of graphs)
When sea otter abundance is low, sea urchin biomass increases, which causes kelp biomass to be decrease (gray portion of graphs)

Trophic cascades and the Earth is Green Hypothesis

The hypothesis: Globally, predators indirectly maintain plant biomass at high levels by limiting the densities of herbivores (Hairston et al., 1960)

Trophic cascades and the Earth is Green Hypothesis
argument

-Obvious depletion of plants by herbivores is rarely observed (plants are not limited by herbivores)
-Limitation of plants must be caused by their own depletion of available resources (nutrients, light)
-If herbivores are protected, they have the ability to limit or wipe out plants
-What keeps herbivores in check in natural systems?
-Predators keep herbivore populations down which, in turn, boosts plant populations

Trophic cascades and the Earth is Green Hypothesis -Conclusion

A simple predator - mediated trophic cascade helps structure plant communities

authors suggested that decreases in populations of large sharks caused an

an increase in the populations of meso-predators (skates and rays) that the sharks eat
•The increases in meso-predator populations were then blamed on population decreases in shellfish

Many trophic cascades are based on the idea of "predator release" where a

decrease in predators "releases" prey from the threat of predation and allows their populations to rise

Grubbs et al., showed cownose rays have \---- population growth rates relative to \-----

lower
large sharks
Cownose have ~1 offspring/year resulting in lifetime fecundity of

According to Hairston, Smith, and Slobodkin (1960) the earth is green because
a. plants are low in nutrients.
b. predators are limited by the abundance of prey.
c. herbivores are limited by predators.
d. plants are limited by herbivores.

c

Increases in sea urchins and declines in kep due to shifts in the abundance of sea otters is an example of

A.Resource partitioning
B.Trophic cascade
C.Niche expansion
D.Competitive exclusion

b

The equation below depicts what type of interaction?

A.Exponential growth
B.Intraspecific competition
C.Predator-prey dynamics
D.Interspecific competition
E.None of the above

r1n1(k1-n1-an2/K1)

d

Lotka-Volterra predator-
prey models produces reciprocal
Oscillations of Pred + Prey

The model produces oscillations of predator and prey populations through time

-An increase in hare causes an increase in lynx, which leads to a decrease in hare and eventually a decrease in lynx

W/O Time axis --\>
Reveals elliptical oscillations

Important to note that predator pop changes always lag behind changes in prey populations

-difference in cycles related to the time it takes for prey to be converted into new predators

Lotka-Volterra Predator-Prey model assumptiopns

-Prey populations can grow exponentially (no carrying capacity)

-Predator population will starve in absence of prey (will not switch to different prey species)

-Predators can consume infinite quantities of prey

-There is no environmental complexity

The importance of refuges in predator-prey dynamics
Gregory Gause (1935)

-Gregory Gause (1935) manipulated the populations of Paramecium (prey) and a protozoan (Didinium) to

-With no refuge Paramecium is driven to extinction by the predator

-By adding sediment at the bottom of the tank, Paramecium survive by hiding but Didinium (predator) dies off

-coexistence between the two species achieved with refuge for the prey and periodic introductions of new members of each species (immigration)

These findings emphasize the importance that refuge (protection) from predators has on allowing prey species to survive through time!

The importance of refuges in predator-prey dynamics -Huffaker

Huffaker used two different types of mites to examine how habitat complexity and dispersal affect coexistence between predator and prey

-His experiments consisted of differing numbers of oranges (habitat) that varied in the amount of surface exposed

-To slow the dispersal of predators, areas between oranges were covered in petroleum jelly and wooden posts were erected to allow prey mites to "parachute" to new oranges (habitat)

In all experiments where habitat complexity was low (fewer oranges, more orange exposed, less petroleum jelly, etc.) predators drove prey to extinction

Factors affecting feeding response of predators
4 things

1.Search Time- looking (requires energy - Want short time)
2.Handling Time- from the time it touches to eating (grouper vs cheetah)
3.Hunger level- high metabolism /active vs sedentary animals
4.Prey defenses-good prey doesn't make it easy

Factors affecting feeding response of predators
1.Search Time:

a)Mobility- to be very fast (trade of incrs energy but can eat anything )
b)Prey detection capability of the predator
c)Capture Success
- Many adaptations in predators to reduce search time in order to find prey quickly and efficiently

1.Search Time:
Mobility-Trade offs for differing strategies

a)Highly mobile species: ↑ energy cost but ↑ encounter rate with prey
b)Sit and wait species: ↓ energy cost but ↓ encounter rate with prey

- Many adaptations in predators to reduce search time in order to find prey quickly and efficiently

1.Search Time: (the dec search time reduce energy better getting pray
b.) Prey detection capability of the predator -

Predators have evolved ways to detect prey using multiple senses (sight, smell, touch, etc.)

1.Search Time:
c.) Capture success

Adaptations that allow predator to make the most out of every encounter with their prey (usually morphological)