Quiz 3 Flashcards
What was the early to mid-20th century perspective the role of disturbance in species communities?
Species communities were viewed as returning to equilibrium after a disturbance
Which of the following has been proposed about the relationship between disturbance and species invasion? (select best answer)
Disturbance facilitates invasion and invasion causes disturbance
Which of the following is true about crazy ant invasion on Christmas Island? (select all that are correct)
Removed red land crabs
Is an example of invasion resistance
Caused the loss of ground vegetation
Is an example of invasion meltdown
Removed red land crabs
Is an example of invasion meltdown
Flashcard 1: Q: What is the broad definition of disturbance according to White & Pickett (1985)?
“Any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment.”
Flashcard 2: Q: What are the types of disturbances?
A: Natural, Biotic, Human-caused, Abiotic, and Originate externally or internally.
Q: What are the key factors used to characterize a disturbance?
A: Intensity (Magnitude & Severity), Frequency (Number per unit time), Duration (Temporal extent), and Predictability (Regularity of occurrence).
Q: How does disturbance affect species adaptation and invasibility?
A: Disturbance provides open opportunities in a community, affecting native species’ adaptation and increasing the potential for invasibility.
Q: What disturbance characteristics can influence invasibility?
A: Severe intensity, High frequency, and High predictability. These can either favor native species or increase invasibility depending on the context.
Q: What is the ecological equilibrium theory?
A: Communities are considered equilibrium systems where disturbance is a temporary diversion, and communities return to equilibrium through regulating interactions.
Q: What is ecological succession?
A: The predictable changes in a habitat following a disturbance. Primary succession involves early community development, and secondary succession follows initial colonization.
Q: How does the equilibrium theory compare to the nonequilibrium theory of communities?
A: The nonequilibrium theory, which emerged in the 1980s, proposes that natural disturbances prevent populations from reaching equilibrium, with some communities never at equilibrium.
Q: How does an invasive species act as a disturbance?
A: An invasive species can act as a disturbance by being a keystone species that alters community dynamics or as an ecosystem engineer that changes ecosystem properties.
Q: What are the effects of invasive species like house cats and cane toads?
A: House cats reduce native faunal communities through predation, while cane toads disrupt native predator-prey dynamics.
How do invasive species act as ecosystem engineers?
A: Species like earthworms can fundamentally alter ecosystems by changing soil properties, affecting plant growth, and disrupting native vegetation.
Q: What is “Invasion Meltdown”?
A: A self-perpetuating cycle where invasive species facilitate further invasions or greater impacts, creating positive feedback loops.
Q: What is the Fluctuating Resource Hypothesis?
A: It suggests that communities are more susceptible to invasion when there is an increase in unused resources, as disturbance provides a pulse in resource availability.
Q: What factors make disturbance a facilitator of invasion?
A: Disturbance creates open opportunities, increases resource supply, and provides space and light, all of which can facilitate invasion.
What does Davis’s conceptual model of habitat invasibility explain?
A: It explains that habitat invasibility is determined by the gross resource supply and resource uptake, where an increase in resources and a decrease in resource uptake can facilitate invasion.
How does clearing vegetation affect invasibility in Davis’s model?
A: In plot 1, clearing all vegetation reduces resource uptake, which may increase invasibility, shifting the plot down along the y-axis of the model.
Q: What is the potential for native species adaptation in tropical rainforests and pine forests?
A: Tropical rainforests may have native species with high dispersal ability and long seed dormancy periods to adapt to disturbances, while pine forests have high potential for adaptation due to the frequency and predictability of fire.
Q: How does disturbance influence the equilibrium vs. non-equilibrium theory in tropical rainforests and pine forests?
A: Rainforests operate near equilibrium with low-frequency tree falls, while pine forests exist at a non-equilibrium state due to frequent fire disturbances.
What are the two factors used in Davis’s model of invasibility?
- Gross resource supply
- Resource uptake
Davis’s model of habitat invasibility is based on what ecological hypothesis?
Fluctuating Resource Hypothesis
A landscaper is hired to work on two plots that are overgrown with a mixture of native and non-native
species. In plot 1, the landscaper clears all of the existing vegetation and carries it to a landfill. In plot 2,
the landscaper shreds the overgrown vegetation and mixes it into the soil. The landscaper plants smaller
well-spaced native species in an aesthetically pleasing way in both plots. Compare and contrast these
two plots in terms of Davis’s conceptual model of invasibility
Plot 1. The removal of all of the cut vegetation does not affect the gross resource supply. However, the
planting of fewer plants reduces the resource uptake, thus, may result in greater invasibility of the plot.
On the Davis conceptual model this would be exemplified by moving down along the y-axis.
Plot 2. The shredding of the cut vegetation and leaving in in the plot increases the gross resource supply
by creating a nutrient influx. Also, and reduces the resource uptake of resources by the plants. On the
Davis conceptual model this would be exemplified by moving down along the y-axis AND up along the x-
axis.
What is an ‘invasion meltdown’?
When an invasive species have impacts that lead to invasion by other species and/or has impacts that cascade through a community
Which of the following was NOT ultimately caused by invasion of crazy ants on Christmas Island?
Canopy dieback
Vegetation grown on the forest floor
increase in sooty mold
Reduction in red crabs
Decline in ground vegetation
Increase in scale insects
Decline in ground vegetation
How did the authors demonstrate effects of crazy ants on the biotic communities on Christmas Island?
Set up replicated plots in area of the island that were ‘invaded’ and ‘not invaded’ by the crazy ant
Ran transects through the forest
All of these methods were used in this study.
Collected data from published studies using a meta-analysis
Set up replicated plots in area of the island that were ‘invaded’ and ‘not invaded’ by the crazy ant
Odowd: Specifically, what do the authors mean by ‘displacement of a native ‘keystone’ species?
A keystone species is a species that has a disproportionately large effect on an ecosystem
and/or biotic community. Displacement of a native ‘keystone’ species means that the keystone
species is effectively removed (or greatly reduced ) from the environment and, thus, this has
large effects on the biotic community and/or ecosystem.
Odowd: Describe the time scale and process (not impacts) by which the crazy ant invaded Christmas
Island.
After crazy ants were introduced to Christmas Island, they remained at a relatively low density
for several decades before they seemed to evolve the ability to form super colonies, which are
multi-queen colonies. These super colonies allowed the crazy ant to increase greatly in density
and become invasive on the island.
