Lecture 17: Synergistic Interactions

Question 1

What environmental stressors did we examine?

Answer 1

1. Climate Change
2. Land use
3. Overfishing
4. Pollution

Question 2

What’s been going on with atmospheric CO2?

Answer 2

• increased nearly 25% in 50 years

* ex of alterations of biogeochemical cycles

Question 3

How does increased CO2 effect invasive plants?

- Ex with desert ecosystem and cheat grass

Answer 3

• responses of a desert ecosystem to elevated CO2
• some respond positively to it
• If CO2 is limiting to certain plants, the ones that take advantage in changing conditions are usually invasive
  ex: Cheat grass, density biomass and seed production ALL go up for this sp in the presence of increased CO2

Question 4

List examples of evidence for changing species distributions in response to climate change (increases in temp, shifting isotherms of 300-400km in latitude)

Answer 4

1. Plants
2. Flying insects
3. Marine organisms
4. Terrestrial vertebrates

Question 5

Evidence for changing species distributions in response to climate change (increases in temp, shifting isotherms of 300-400km in latitude):
1. Plants

Answer 5

• antarctic vascular plants have increased in abundance due to greater seed germination and survival in warmer temp
  ex: with hair grass
• ex2: many species in the swiss alps are moving upward at a rate of 4m/decade

Question 6

Evidence for changing species distributions in response to climate change (increases in temp, shifting isotherms of 300-400km in latitude):
2. Flying Insects

Answer 6

Ex: European butterflies

• 60% + have shifted their range northward while 3% have shifted southward
• populations of checkerspot butterfly have moved 2 degrees North

** the cold adapted ones are shifting south

Question 7

Evidence for changing species distributions in response to climate change (increases in temp, shifting isotherms of 300-400km in latitude):
3. Marine Organisms

Answer 7

Ex1:
- Intertidal habitats in Cali
L> rocky invertebrates have been increasingly dominated by southern species (warmer)
** cosmopolitan sp are those without a defined N/S distribution
- Southern species are all increasing and northern species are decreasing

Ex2: Recruitment of exotic marine sessile inverts in New England

• move as larvae
• adults settle
• common in marine sub tidal systems
• mean winter temps tend to be warmer but with greater variation
• day of onset of recruitment: larvae = settlement = recruitment of adult pop
• recruitment is pretty well timed each year but it varies depending on mean winter temp
• once they reach a threshold they begin recruiting
• ***starts earlier with warmer winter temps

***annual recruitment of non native species is positively correlated with mean water temp in late winter, while native species recruitment is negatively correlated with water temp.

Question 8

Explain further about the Codium facilitation by a bryozoan

Answer 8

• Codium is a dense algal
• bryozoan cannot attach to it like it can with kelp
• calcareous colonies form on kelp making them brittle and less resilient to storms etc causing defoliation and therefore freeing up space for Codium
• acidified water also promotes the bryozoan
• *OCEAN ACIDIFICATION

Question 9

Evidence for changing species distributions in response to climate change (increases in temp, shifting isotherms of 300-400km in latitude):
4. Terrestrial Vertebrates

Answer 9

• northern range of bird species is going more north

-

Question 10

What is synergy ?

Answer 10

• an interactive effect greater than the sum of individual effects

Question 11

Land use:

- Explain how the alteration of fire regimes by land clearing and grass invasion interact.

Answer 11

• > woody vegetation is subject of ires every so many years, converting back to grass land which eventually community succession moves back to woody veg if given enough time
• freq of fires has increased for various reasons and some grasses sprout faster etc in the presence of fire

**Occurs with cheat grass

L> niche construction by creating a microclimate via making the area drier promoting further fires

Question 12

What makes a grass land more vulnerable to fires?

Answer 12

• lots of leaf litter
• open to sunlight
• open to wind

Question 13

How does overfishing impact an area?

Answer 13

• frees up niche for invasions to occur?
  ex: removing a herbivore via overfishing which is a constraint on algal growth = boom in algal
• this overgrowth kills coral
• *pollution from domestic sewage and agriculture ru off can also add to this

Question 14

What nutrient is commonly limiting in marine systems? Freshwater?

Answer 14

• marine: Nitrogen
  L> nitrogen pollution is increasing
• FW: phosphorus

Question 15

Talk about biological invasion and organic pollution in the black sea

Answer 15

• caused an increase in frequency of toxic algal blooms
• Mnemiopsis (jelly fish) feeds on zooplankton nd anchovy, releasing phytoplankton of predation
  L> further promoted by increase in organic pollution

Question 16

Cholera in Peru??

Answer 16

• 1 million people infected
• economic cost from Aquaculture was high
• vector = ballast water -> estimated 1 billion bacteria and 7 billion virus particles in 1 L
• *bacteria resides in copepods

** domestic sewage causes phytoplankton to bloom which causes zooplankton to bloom. Around the same time cholera was released in the water.. driving at the same time when it’s host population is large i.e. zooplankton

Question 17

What leads to coral reef die off?

Answer 17

• N pollution
• Biological Invasion
• Global warming
• *all together

-> Introduction of an exotic pathogen + increased temperatures and excessive nutrients stimulating microbial growth = bleached coral

Question 18

What can increase outbreaks of resistant pests?

Answer 18

Chemical pollution + biological invasions

** number of pesticide resistant species has been increasing since the early 1950s

Question 19

Avian botulism?

Answer 19

• in great lakes
• many birds killed (fish eating waterfowl)
• also effects benthic fishes
• Cause: Type E botulism from zebra mussels and quagga mussels

** enhanced light conditions via zebra = plants, weeds, etc take advantage, when plants die off after summer they need to be decomposed. Strip water of oxygen to get rid of it, can get hypoxic or anoxic conditions. Anerobic conditions trigger the gemreinaiton of the spores of Clostridium (avian botulism)

• Round goby eats zebra mussel which is infected with the bacteria = sluggish now, which is then eaten by Waterfowl

Question 20

What is the predicted consequence of an uncontrolled invasion rate?

Answer 20

• as the number of invaders increase, you’re increasing the number of synergies

Question 21

Summary of synergies.

Answer 21

1. climate change accelerates range expansion
2. synergies result from overlapping stresses from the connectedness of environmental systems
3. Synergies will become more frequent as the stresses intensify over time and space
4. even a partial reduction of any stress may yield major benefits

Question 22

What are the models linking invaders to impacts on native species

Answer 22

1. Passenger model = external stresses acting negatively on native species and positively on invader
2. Driver model : external stresses acts on both native and invaders BUT the invader interacts negatively with the native
3. Additive interaction model - External stressor acts negatively on the native sp, nothing on the invader BUT the invader interacts negatively with the native
4. Synergy model : there is a positive feedback with he invader and an external stresses (which acts negatively on the native sp) and the invader interacts negatively with the native.

Question 23

With freshwater fish in Iberian streams, what is the best predictor of natives decline? What is going on with habitat alteration?

Answer 23

• best predictor = invader abundance
• ## habitat alteraction ahd no influence on the per capita effect of invaders

Question 24

With freshwater fish in California what are the primary drivers of extinction

Answer 24

• invasions