Lecture 17: Synergistic Interactions Flashcards
What environmental stressors did we examine?
- Climate Change
- Land use
- Overfishing
- Pollution
What’s been going on with atmospheric CO2?
- increased nearly 25% in 50 years
* ex of alterations of biogeochemical cycles
How does increased CO2 effect invasive plants?
- Ex with desert ecosystem and cheat grass
- 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
List examples of evidence for changing species distributions in response to climate change (increases in temp, shifting isotherms of 300-400km in latitude)
- Plants
- Flying insects
- Marine organisms
- Terrestrial vertebrates
Evidence for changing species distributions in response to climate change (increases in temp, shifting isotherms of 300-400km in latitude):
1. Plants
- 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
Evidence for changing species distributions in response to climate change (increases in temp, shifting isotherms of 300-400km in latitude):
2. Flying Insects
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
Evidence for changing species distributions in response to climate change (increases in temp, shifting isotherms of 300-400km in latitude):
3. Marine Organisms
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.
Explain further about the Codium facilitation by a bryozoan
- 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
Evidence for changing species distributions in response to climate change (increases in temp, shifting isotherms of 300-400km in latitude):
4. Terrestrial Vertebrates
- northern range of bird species is going more north
-
What is synergy ?
- an interactive effect greater than the sum of individual effects
Land use:
- Explain how the alteration of fire regimes by land clearing and grass invasion interact.
- > 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
What makes a grass land more vulnerable to fires?
- lots of leaf litter
- open to sunlight
- open to wind
How does overfishing impact an area?
- 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
What nutrient is commonly limiting in marine systems? Freshwater?
- marine: Nitrogen
L> nitrogen pollution is increasing - FW: phosphorus
Talk about biological invasion and organic pollution in the black sea
- 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
Cholera in Peru??
- 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
What leads to coral reef die off?
- N pollution
- Biological Invasion
- Global warming
- *all together
-> Introduction of an exotic pathogen + increased temperatures and excessive nutrients stimulating microbial growth = bleached coral
What can increase outbreaks of resistant pests?
Chemical pollution + biological invasions
** number of pesticide resistant species has been increasing since the early 1950s
Avian botulism?
- 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
What is the predicted consequence of an uncontrolled invasion rate?
- as the number of invaders increase, you’re increasing the number of synergies
Summary of synergies.
- climate change accelerates range expansion
- synergies result from overlapping stresses from the connectedness of environmental systems
- Synergies will become more frequent as the stresses intensify over time and space
- even a partial reduction of any stress may yield major benefits
What are the models linking invaders to impacts on native species
- Passenger model = external stresses acting negatively on native species and positively on invader
- Driver model : external stresses acts on both native and invaders BUT the invader interacts negatively with the native
- Additive interaction model - External stressor acts negatively on the native sp, nothing on the invader BUT the invader interacts negatively with the native
- 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.
With freshwater fish in Iberian streams, what is the best predictor of natives decline? What is going on with habitat alteration?
- best predictor = invader abundance
- ## habitat alteraction ahd no influence on the per capita effect of invaders
With freshwater fish in California what are the primary drivers of extinction
- invasions
