Exam 3 Flashcards
How can communities be compared, composition-wise?
You can look at:
Species number (Richness)
Species Abundance (pi)
Species Evenness
Species-Area relationship
(Explanation and equations)
Larger areas tend to contain more species, while smaller areas tend to contain smaller species.
Best represented graphically on a log(richness) vs log(area) where the slope is linear and positive.
S=cAz
log S = log c + z log A
How do the species-area relationships differ for mainland vs islands?
Islands start lower but have a steeper slope.
Species Richness
The total number of species in a given sample/area
Species Abundance
The precent cover or number of individuals of each species in the sample
Relative Abundance
pi
The abundance of a given species divided by the total abundance of all species in the community
Species Evenness
How equally represented species abundances are in a sampe.
Low evenness is when one spp is very abundant but others are not.
Simpson’s Reciprocal Diversity Index
1/D=1/Σ(pi2)
More affected by spp ABUNDANCE/EVENNESS than spp richness.
Simpson’s Index
D
=Σ(pi2)
Primary Succession
Occurs on newly-exposed geologic substrates
Ex: Volcanos create substrate, Receding glaciers reveal substrate
Secondary Succession
Occurs after disturbances that kill community members but leave the soil intact.
Ex: Hurricanes, fires, human impacts
What three mechanisms affect the path of succession?
TOLERANCE
FACILITATION
INHIBITION
Tolerance
Ability to withstand harsh conditions
Facilitation
When a species or group of species makes an environment easier for other species to live in.
Ex: Legumes add Nitrogen to soil and facilitate the survival of other species
Inhibition
When one or a group of species change the envrionment to make it harder for other species to survive. AKA opposite of facilitation
Ex: Allelopathy
Priority Effects
Whichever species gets to a disturbed area first will dictate who can colonize later in the succession
Ex: Light seeds have higher mortality in shade than heavy seeds
What are some life history traits of early-successional species?
Small seeds
Tolerant of stress and disturbance
High fecundity
Quick growth
Poor competitors
Good dispersers
What are some life history traits of late-successional species?
Large seeds
Lower fecundity
Slow-growing
Good competitors
Poor dispersers
Intolerant of harsh conditions
What is old-field succession and how has it affected the successional pathway of SE Upland forests?
Old-field succession is the succession on abandoned farm fields.
Annual Plants -> Perennial Plants/Grasses -> Shrubs -> Softwood trees/Pines -> Hardwood Trees
Sere
An event that removes all or part of a community
Climax Community
The end-point or steady-state reached at the end of a successional pathway
Catherine Keever
Studied Old-Field Succession in SE Upland Forests
What can we measure to assess diversity?
Species
Genes
Ecosystems
How many species are estimated to exist on earth?
10-30 million
What kinds of factors determine community assembly?
LOCAL: abiotic and biotic interactions
REGIONAL: Climate, regional spp pool, and landscape processes
Local-Regional Richness Relationship
Tells you whether interspecies interactions (Lowest line) or dispersal (middle line) is more important in determining local diversity.
Assembly Rules
The idea that ECOLOGICAL FILTERS (abiotic and biotic) dictate what species exist in a community.
What are three theories that attempt to explain biodiversity?
Equilibrium Theory of ISLAND BIOGEOGRAPHY
INTERMEDIATE DISTURBANCE Hypothesis
Niche vs. NEUTRAL THEORY
Equilibrium Theory of Island Biogeography
Equilibrium number of species is higher on islands that are larger and closer to the mainland than for islands that are smaller and farther away.
Robert MacArthur and E.O. Wilson
Intermediate Disturbance Hypothesis
Describe it and say when it does not hold
Species richness/diversity is highest when disturbance is intermediate in amount.
*Doesn’t necessarily hold when there are multiple forms of disturbance acting on an ecosystem
Joseph Connell
Neutral Theory
Biodiversity is driven by random chance, and is not influenced by the idea of niches.
Stephen Hubbell
Alpha vs Beta vs Gamma Diversity
Alpha: Local Diversity (e.g. in Marsh)
Gamma: Large-scale diversity (Marsh+Dune+Thicket)
Beta: Spp turnover (change betw 2 localities)
Trophic Guilds
Divisions of species based on their method or location of foraging within a trophic level (Seed- vs insect-eating birds/mice)
What are three types of food webs and how do they differ?
Connectedness Web - All feeding relationships
Energy Flow web - Must have a transfer of energy
Functional Web - Must also affect “r” of other species
How have changes to top trophic levels affect communities and ecosystem processes?
It alters the abundances of species further down the cascade in alternating +/- ways.
These are often caused by human activities.
Food Chain vs Food Web
Food CHAIN: Linear relationship of what eats what
Food WEB: Shows interconnectedness and multiple prey/predator relationships.
Keystone Species
Species that have low biomass in the ecosystem but have large effects on community structure.
Ex: Beavers, Starfish
Dominant Species
A species that has a high biomass in the ecosystem AND a high influence on community structure by virtue of their biomass
How can you distinguish between a Bottom-Up food chain versus a Top-Down food chain?
Bottom-Up: Increase in producers -> Increase in ALL other levels
Top-Down: Increase in top level -> decrease in next -> alternating
Trophic Cascade
An effect of changing one trophic level which ends up affecting all of the other ones.
Can be done by adding a level to the top -> alternates +/- effects going down
What are some examples of human activity-induced effects on trophic structure?
Introducing wolves to grasslands increases primary production and decreases diversity, changing the structure of the ecosystem because they eat herbivores.
Basically, we add or remove top predators, which change the structure of the community by trophic cascades. If we remove secondary predators, it ends up decreasing PP/herbs.
Community Stability
The ability of a community to defy or rebound from change
Robert T. Paine
Defined KEYSTONE SPECIES using starfish and mussels
Steve Carpenter
(UW) TROPHIC CASCADES in aquatic systems
What are Earth’s natural climate cycles like?
~100,000 years long
~90K gradual cooling
~10K rapid warming
Sara Hotchkiss
Used pollen and diatoms to reconstruct climate 18,000 years ago -> tells us about disturbance and changes in plant communities
What influences global biodiversity over long periods of time?
Continental Drift
Catastrophes/extinctions
Climate Change
Phylogenetic effects
Species-Energy Hypothesis
More productive areas can support more diversity because:
1) More energy -> faster speciation
2) Large Populations -> Low Extinction
What geologic period are we in and where does this fall within earth’s natural climate cycles?
We are in the Holocene/Anthropocene epoch of the Quaternary Period within the Cenozoic Era, which is in the Phanerozoic Eon.
The Holocene is part of a warming period, but should start to cool soon.
Jack Williams
(UW Geog) How past climate change relates to today; climate forecasting.
Why is diversity greatest in the tropics?
1) Time
2) Species-energy hypothesis
3) Higher variability in resources
4) Tropical spp have lower enviro. toleranced
5) Area - more land in tropics over time
6) Mid-domain hypothesis (easier to have diversity bc its not an extreme on the earth)
Phylogenetic Effect
The existence of patterns of diversity that are due to evolutionary intertia
At what scale is landscape ecology conducted?
Whatever scale you choose, as long as you can observe heterogeneity.
What measures can be used to characterize and quantify a landscape in terms of its COMPOSITION and SPATIAL CONFIGURATION?
COMPOSITION: Proportion occupied
Relative richness
Diversity
Dominance
SPATIAL CONFIGURATION: contagion
Patch Size
Edge/Area
Proximity Index
What two concepts lie at the core of landscape ecology?
PATTERN
PROCESS
How can organisms influence landscape patterns?
Adaptive plant traits (serotinous cones)
Life history strategies (post-fire resprouting)
What metrics are used to characterize disturbance regimes?
Frequency
Size
Intensity/Severity
Duration
Monica Turner
(UW) Disturbance and Landscape Ecology of the YELLOWSTONE FIRE
Why are fish populations and demographics experiencing negative impacts?
Technological advances
What are the four conceptual phases in which a fishery can exist?
UNDEVELOPED
DEVELOPING
MATURE
SENESCENT (Heading to collapse)
Marine Protected Areas
Like nature preservations but for the ocean.
Have been very successful in conserving marine ecosystem health
Improve spp abundance, size, productivity, and diversity, and these can spill over to outside the boundaries
Catch Shares
Everyone gets an even amount of the fish that were caught in a particular area, so as to encourage law compliance and prevent overfishing.
Boris Worm
Ransom Myers
Study Overexpoitation of fisheries
Found that we are severely overfishing the oceans
~10% of fish left from the 1950s
Daniel Pauly
Online fish database
Big player in understanding overexploitation
Coined “Fishing Down Food Webs”
Tragedy of the Commons
Everyone shares a resource, and continue to deplete it despite knowing that it will run out because of their activity.
How do you determine Maximum Sustainable Yield (MSY) of a fishery?
Harvest when their population is at K/2 because that is when they are increasing the quickest in the LOGISTIC growth model
Individual Transferable Quotas
A transferable fishing quota given to an individual that is based on a rigid Total Allowable Catch for an area.
It is a type of catch-share that allows fishermen to sell and trade quotas according to how much they can catch.
Garrett Hardin
TRAGEDY OF THE COMMONS
Jim Estes
Trophic cascades of removing killer whales
Effectively increased kelp in the ecosystems where whales occurred
Why don’t fisheries always work well using the MSY calculations?
- Population not necessarily controlled by logistic equation
- K is difficult to pinpoint
- Time lags can occur
- Age/Stage structure not considered
- Immigration/Emigration not accounted for
- Trophic interactions ignored (bycatch feedback)
- Other ecosystem impacts (bycatch, habitat damage)
Why do population projections sometimes differ so much?
We don’t know our K on earth
What are two of the most important factors in determining the impact of human population on the environment?
1) Total population size
2) Per capita consumption of resources
Demographic Transition
1->2: Advances in Agruculture and Pop Health
2->3: Contraceptives, Advancement of Women
3->4: Population has reached stable levels
Heinz von Foerster
Showed that humans had HYPERBOLIC growth and would reach “infinity” on 11/13/2026
Was true until 70’s or 80’s
Paul Ehrlich
John Holdren
Ehrlich -> Stanford
Holdren -> Obama Admin.
Together came up with the equation for Human Enviro Impact
C=PAT
C=HEI, P=pop size, A=affluence (GDP/person), T=technology (energy const/GDP)
What are the primary ways that humans cause extinction?
Habitat Loss/Degradation
Non-native species
Overexploitation
Pollution
Disease
Climate Change
What kinds of populations are especially vulnerable to extinction and why?
SMALL populations
Due to stochasticity
HOWEVER, populations that are at once large can also go extinct due to interactions with humans
What are some values of biodiversity?
Ecosystem persistence
Efficiency of energy use
Ecosystem services (pollination, water filtration)
Aesthetic value
Recreational Value
Indicators of Enviro. Quality
etc.
What is the average “life span” of a species until it goes extinct?
~ 1-10 million years
What is the background extinction rate?
What is the current extinction rate?
1 species/yr
1 species/20 min
(~27,000 spp./yr)
What are some pathways to extinction?
Being a specialist
“Slow” life history traits
Small populations
Low dispersal ability
High value to humans/feared by humans
Loss of habitat
Low genetic diversity
etc.
Extinction Vortex
Population Viability Analysis (PVA)
A statistical analysis used to find out how long a species is likely to survive if no conservation practices are enacted.
Minimum Viable Population
The smallest population that can sustain itself in the face of environmental variation
Rule of 10s
10% of the species pass from one stage to the next in the process of introduction and invasion, suggesting the likelihood of invasion is very low
What are some characteristics of invasive species?
Generalists
Allelopathic
High reproduction rate
Escape natural controls
Good dispersers
Short generation time
Fast population growth rate
Good competitors
etc.
What are some characteristics of vulnerable ecosystems to invasion?
Human-altered
Disturbance areas
Fewer dispersal barriers
Productive systems
Absence of predators/pathogens
Simple communities -> low diversity
What is the best way to manage invasive species?
Depends, but usually involves integrating multiple methods as opposed to utilizing a single method.
What are the steps to a species becoming an established invasive species?
What are some ecological and economic impacts of invasive species?
Ecological: alter food webs, endanger other species, change hydrology, disturbance frequency
Economic: Clog pipes, ?
Biotic resistance hypothesis
species-rich communities are more resistant to invasion because they use resources more efficiently than communities with low species-richness.
Enemy release hypothesis
Invasives do so well because they do not encounter their traditional predators/pathogens that limit them in their native environments
Evolution of Increased Competitive Ability (EICA)
Stems off of the enemy release hypothesis, so that they are able to use the energy saved from escaping predators and use it to increase viability/evolution.
Pre-adaptation
When a species uses a previously-adapted trait for a use that it was not intended for, but nonetheless helps it.
Ex: feathers for show on dinosaurs –> use to fly
Sweat glands —> Mammary glands
Early Detection Rapid Response (EDRR)
The best way to deal with invasives and have a chance of preventing them.
Detect them early, and respond quickly.
Banu Subramaniam
Critiques use of the term “invasive species”
we should take a more holistic approach
We should be proactive in improving environmental quality and sustainability rather than individual species
What is the general pattern in the relationship between species richness and productivity?
Hump-shaped.
Species richness initially goes up with productivity, then goes down.
What are the multiple definitions of stability?
Variability
Resistance to change
Recovery after disturbance (resilience)
What is the general response of productivity to increased diversity?
Increased productivity with increased diversity, but productivity levels off at a certain point.
Why does productivity increase with increasing diversity?
1: Niche partitioning
2: Facilitation
3: Sampling effect
What did the Millennium Ecosystem Assessment do?
It categorized ecosystem services at a global scale into:
Provisioning resources
Regulating resources
Supporting resources
Cultural resources
Philip Grime
Found the hump-shaped relationship of the response of richness to increasing productivity
Gretchen Daily
BIG supporter of the valuation of ECOSYSTEM SERVICES
wrote software to help estimate it
What topics in ecological theory play a role in reserve design?
Metapopulations (Metacommunities)
Island Biogeography
What are some ecological processes promoted by habitat corridors?
Seed dispersal
Pollination
Seed predation
Plant Diversity
No-analogue Communities
Communities that will exist due to climate change that have never occurred before, due to differential abiotic tolerances for species overlapping
Robert Whittaker
Took lots of data on the Klamath-Siskyou Mountains across lots of enviro gradients.
Wet <—> Dry
North Slope <—> South Slope
Soil Types
Forest types
Temperatures
Biogeographic Affinity
Northerly vs Southerly species occurring on different slopes of a mountain.
Southerly will do better with climate change because they are adapted to warmer and drier.
How does ecological niche modeling work?
Take data from plots where spp occur
Make a niche cloud on the map
Extend niche map to areas that will develop similar conditions due to climate change
Ecological contingency
The idea that climate change will be noticeable in different amounts in different areas
Why are reference states for ecological restoration difficult to identify?
Difficult to define
May change over time
Can be influenced by other global changes (Climate change)
What impacts does land use history have on ecosystems?
- Agriculture
- Forestry
- Modification of natural disturbance regimes
- Manipulation of animal populations
