Post Midterm #2 Flashcards
Define Biodiversity
A measure of variety of organisms within a local area le region including genetic variation, taxonomic uniqueness, and endemism
Number of taxa in a local area or region
Species richness
Measure of the variety of taxa in a community that takes into account the relative abundance of each one
Dominance Index
3 Measures of Local Biodiversity and Descriptions
- Alpha Diversity: number of species in habitat and combined with info in evenness of abundance
- Gamma Diversity: number of species over larger region
- Beta Diversity: the turnover in number of species in habitat v region estimated
Define Species
Groups of interbreeding natural populations that are reproductively isolated from other groups
Morphological Species
Differing species in characters/traits
Phylogenetic Species
Differing species from lineages that maintain integrity
Genetic Species
Differing species from DNA
Ecological Species
Species defined from niche space
Due to geographic barrier of populations where there are dissimilar selective pressures or genetic drift
Allopatric speciation
Due to the isolated niche from isolation of a small population with unique traits
Peripatric speciation
From niche specialization with a population to reduce competition
Parapatric Speciation
From genetic divergence within a population, but not due to new niches
Sympatric Speciation
Founder Effect
When an isolated population is founded by a small number of pioneering individuals, the new population may turn out to be different from OG
Endemism
An endemic species is one whose geographic range is small (aka isolated)
3 Factors of Facilitating Endemism
- Time Stability
- Topographic barriers
- Low Productivity
3 factors to Species Rarity
- Range size
- Population size
- Habitat specificity
Division of area by ten, divides the fauna by two
- Darlington’s Rule
Ratio Extapolation
- Erwin used insecticidal forcing of trees to study diversity in Panama
- Used ratio method to predict number of total nettle species based on unique beetles per tree
Global Patterns of Biodiversity
- Notable negative latitudinal relationship
- Richness decreases with latitude
Biodiversity Hypothesis: Solar Energy, Precip., & PET
More energy = more niches (and more water needed for life)
Biodiversity Hypothesis: NPP and Structure
More biomass or structure = more niches
Biodiversity Hypothesis: Seasonality
High seasonality = low diversity (greater climatic tolerances)
Biodiversity Hypothesis: stability-time
Diversity increases with community age
Biodiversity Hypothesis: Area
Tropics have larger surface area of similar climate because it borders the equator
Biodiversity Hypothesis: Pathogens
Increase pathogen = increase diversity
Tropics have more pathogen pressure than temperate ecosystems, so individuals must spread out to avoid diseases
Mechanisms that Prevent Competitive Exclusion
- Mortality of dominant competitor via predation, herbivore, or abiotic disturbance
- Environmental fluctuations (ex: droughts)
- Local extinction and rescue effect (ex: re-invasion of species)
Theory:
Consider spatial patterns in populations (source-sink dynamics) relative to patches of habitat with immigration (dispersal) “rescuing” Populations lost or declining, thus maintaining more diversity in a region
Rescue Effects
Abiotic Disturbances at Non-Equilibrium
- Density-independent mortalities
- Selective mortalities
Species richness-productivity Relationship
- More productive ecosystems are often assumed to contain higher species diversity
- Global scale NOT LOCAL SCALE
Natural Processes Promoting Extinction
- Demographic stochasticity
- Environmental variability
- Catastrophes
- Theory that there is a need to keep evolving to “keep up” or potentially go extinct
Red Queen Hypothesis
Mass extinction definition and numbers
- Mass extinction if when over 75% of species disappear within a geologically short interval less than 5 million years
- Loss of Animals whose weight was greater than 44 kg (100 lbs) by 72% in North America at the end of the Pleistocene
Megafauna
- Controversial hypothesis about overkill causing extinctions of species
Overkill Hypothesis
Theory:
- Extinction events amplified by the interaction of both biotic and abiotic drivers. Coupling of marked climate change with direct human impacts is especially pernicious
Multiplicative Effects of Megafauna Loss
Theory:
Loss of key megafauna resulted in loss of dispersal for large-fruited species
Megafauna Dispersal Syndrome
Environmental Impacts of Invasive Species
○ Negatively impact biodiversity
○ Cause extirpation and extinction
○ Cause soul degradation and erosion
○ Alter ecosystem processes like fire cycles
Societal Impacts of Invasive Species
○ Can cause disease/suffering for humans and pets
○ Reduce recreational opportunities
Economic Impacts of Invasive Species
○ Control and management costs can be significant
○ Reduce productivity in resources
○ Cause export/import trade restrictions
○ Reduce property values
Traits of Invasive Species
- Fast growth and rapid reproduction
- Excellent dispersal ability
- Generalist species (thrive in different environments/climates)
- Few or no predators
- Often associated with humans and surface disturbances
Positive association between absolute average individual fitness and population size over some finite interval
As populations move back from critical point, the growth rate decreases
- Recovery impossible
- allee effect
Known Invasive Species Effects
- Economic losses of $138 B per year
- Forage losses on pastures alone cost $1B per year
How do you deal with invasive species?
- Eradicate it early
- Difficult to eradication once established
ecosystems with higher species richness were less subject to invasive species because of fewer available niches (competition)
Native-Exotic richness (Elton)
Paradox: Natively rich ecosystems are likely to be hotspots for exotics. “The rich keep getting richer”
Invasion Paradox
Land Sparing v. Sharing
Debate whether conservation should occur within each farm lowering yield (sharing) or triaging and separating high yield with no habitat from areas of habitat (sparing)
Land Sharing Traits
- Conservation within agricultural areas
- Production benefits from ecosystem
- More land allocated to agriculture
- Less inputs (more self-sustainable ag)
- Diverse or associated crops
Land Sparing Traits
- Conservation in separate areas
- Production intensification
- Less land allocated to agriculture
- More inputs to agricultural production
- Mono-cropping
Species richness on islands is due to a dynamic equilibrium between colonization of new species and extinction of established species affected by area and isolation
Island Biogeography (IBG) Theory
IBG Theory Two Main Processes
- Colonization (immigration) rate decreases with distance
- Extinction rates decrease with island area
Managing uncertainty theory: low uncertainty and high controllability like in forest harvesting and fisheries
Maximum Sustained Yield
Managing uncertainty theory: low uncertainty, but also low control. This would represent a form of insurance where foresters may leave extra volume due to the risk of catastrophic fire
Hedging
Systematic approach to improving resource management by learning from management outcomes with high uncertainty but controllable
Adaptive Management
Used when there is high uncertainty and low controllability. EXAMPLE: climate change. Models used to understand implications of different actions before actions
Scenario Planning
Triage Principle and 3 Levels
- Triage threatened species by dividing species bas on likelihood of survival with and without help.
- Levels
1. Low danger: ignore (probably fine)
2. Lost: ignore (can’t be saved anyways)
3. Acute Danger: salvageable. Concentrate limited conservation money here.
- Levels
