WFC110 Final

Biogeography

study of distribution

Biogeography influenced by

plate tectonics, geological patterns, climate, anthropogenic impacts

Vicariance Model of Speciation

1 area breaks into 2 areas, speciation occurs because of geographic split between areas

Dispersal Model of Speciation

area starts off with geographic splits, and individuals disperse across separate areas, leading to speciation

Which model of speciation occurred in the split of Pangea?

vicariance model because species evolved in one area (Pangea) and then Pangea split apart leading to different species emerging

Great American Biotic Exchange

3.5 MYA, crossing of animals across filter through American continent; many more mammals migrated N → S vs. S → N because of human and environmental pressures

Factors influencing the colonization rate of islands

1. Size of island (larger = more species)

2. Distance (closer to mainland = more species)

Latitudinal species diversity gradient trend

increased latitude = decreased species diversity

Elevation species diversity gradient trend

very high or low elevations = low species diversity; moderate elevation = medium species diversity

Native species

species that historically lived in a specific location (Example = Western harvest mouse)

Endemic species

species that live exclusively in one location (Example = Salt marsh harvest mouse in SF Bay Delta)

Non-native or exotic species

species that live now in a location they historically did not

Introduced species

type of non-native species moved by human activities

Invasive specie

type of non-native species whose population grows and spreads rapidly without sufficient control in the environment (Example = house mouse)

Range

geographic limits where a species is found

Historic range

range historically occupied by species

Current range

range within historic range that is currently occupied by the species

Non-native range

range occupied by species outside historic range

Range shifts occur when

environment and ecology change

Three types of range shifts

1. Range contraction

2. Range expansion

3. Change of density or distribution within range

Five types of human impacts leading to range shifts

1. habitat loss

2. habitat fragmentation

3. persecution or exploitation

4. invasive species

5. climate change

Range contraction

species disappears from part of its historic range

Risk factors for range contraction

1. specialist

2. poor disperser or colonizer

3. heavily harvested

4. narrow climate envelope

5. sensitive to humans

6. invasive predators or competitors

Range expansion

species establishes outside of historic range

Range expansion can be due to

1. animals follow humans and habitat changes

2. climate shifts

3. natural dispersal

Benefits of a home range

knowledge of foraging, hunting, nesting, denning sites, conspecifics

Site fidelity

repeated use of a small area to perform behaviors including; applies to corridors, den/forage/hunt sites, social interaction

Strong site fidelity required for home range behavior?

No

Determinants of home range shift

1. body mass (larger body = larger home range)

2. environment

3. diet

Human sensitivity score relative to body mass

inc body mass = inc sensitivity score

Human sensitivity score relative to home range size

inc home range size = inc sensitivity score

Territory

sub-area of home range that animal defends from conspecifics; actively defended and contains resource that an animal controls or restricts others' access to

Territory defense - two strategies

1. direct conflict

2. communication

Benefit of communication as territory defense strategy

saves energy before resorting to conflict

Who defends a territory?

individual, mating pair, or family/communal group

Is territoriality beneficial or costly at large spatial scales?

cost of territoriality outweighs benefits over large spatial scales

Territory/Habitat Example (list territory, defender, strategy, limiting resource) — Mountain lion

- T/H = home range stable, related to food + den sites

- Who = individual M vs. other individual M

- How = scent marking, direct conflict

- Limiting resource = mating opportunities

Territory/Habitat Example (list territory, defender, strategy, limiting resource) — American beaver

- T/H = lodge site availability related to stream, pond, meadow conditions

- Who = mating pair

- How = scent marking, direct conflict

- Limiting resource = food + lodge sites

Territory/Habitat Example (list territory, defender, strategy, limiting resource) — Chimpanzee

- T/H = fruitng trees, other food resources related to habitat type

- Who = group defense vs. other groups

- How = boundary patrols

- Limiting resource = food, mates

Four ways home ranges are important in wildlife ecology

1. selection for resources — preferential habitat use and home range location relative to landscape

2. area requirement — how much space req. and how much overlap?

3. energetics/behavior — movement amount, reasons, energy costs

4. resilience to environment — animal anchored to location or access to diverse habitat types?

Benefits of dispersal

avoid inbreeding, avoid local competition

Two types of dispersal

1. natal dispersal — movement from birth range to first reproductive site

2. breeding dispersal — movement from new range between reproductive events

Why is dispersal difficult to study?

involves movement of individuals and tracking

Sex bias in dispersal

most species have male dispersal bias (M disperse more often or further)

Three stages of dispersal

1. emigration = elave curent range

2. transfer = movement through new territory

3. immigration = settle into new range

Dispersal stage 1 (emigration) influences

- leave current stage

- genetically hardwired or condition dependent

- sex ratio, body or habitat condition

Dispersal stage 2 (transfer) influences

- failed dispersal attemps vs. test-drives

- movement through new territory

Dispersal stage 3 (immigration) influences

- new range settlement

- habitat selection + social integration

- dispersers may accept low quality habitat

Migration

extreme strategy to manage resource availability variability; repeated movement between distinct, non-overlapping ranges

Benefits of migration

- migrants can persist and increase density

- migrants can access differential resources required seasonally

Types of migration - Descriptive

1. Resident = high repeatability, low displacement

2. Nomadic = high displacement, low repeatability

3. Dispersal = high displacement, low repeatability

4. Migration = high displacement, high repeatability

5. Facultative = only some years, dependent on internal state or environment

6. Partial = only some individuals, related to competition within population

7. Mixed = different summer vs. winter ranges, different migratory distances

Migration types - Space

1. Latitudinal (ex = whale, wildebeest)

2. Altitudinal (ex = guanacos, bighorn sheep, elk)

3. Unrelated to altitude or latitude (ex = elephant seal)

Migration types - Scale

1. Spatial

- Regional

- Local

2. Temporal

- Seasonal

- Diel

Migration types - Drivers

1. Alimental movement/feeding/tracking = to increase access to water or food

2. Climatic movement/wintering/refuge = avoid poor conditions, predation, avoid disease and parasites

3. Gametic movement/spawning/breeding = to access mates, inc. offspring recruitment

Migrator groups

1. ruminants/foregut fermenters/artiodactyls = less tolerate to low-quality food, migrate for food

2. hindgut fermenters/perissodactyls = limited by water, migrate for surface water

Large vs. small body size in migration

1. large and small travel least, medium size travel furthest

2. too small = migration is inefficient

Migration for mammals in high vs. low productivity environments

- less needed in high productivity environments

- more needed in low productivity environments because limited food and water

Four stages of migration

1. Preparation = fuel load via increased forage, metabolic changs

2. Movement = occurs over land or water, aerial or marine travel further than land mammals

3. Stopovers = settle in habitat to rest or feed

4. Arrival = re-establish territory, choose mate, store energy for reproduction

Connectivity

measure of ability of organisms to move between separate patches of suitable habitat

Island biogeography

high diversity of sp when close to mainland, large fragment; low diversity of sp when far from mainland, small fragment

Metapopulation source vs. sink

source = positive pop growth; sink = negative pop growth leading to migration

Corridor

space identifiable by the species using it that facilitates animals and plants movements over time between disjunct habitat fragments

Considerations for corridor establishment

1. focal species or taxa

2. scale of interest

3. habitat requirements

4. generalist vs specialist

5. human tolerance

- all determine type and dimensions of corridor

Corridor scales

1. small scale = reactive, for hard barrier or pinch point (ex = highway crossing)

2. intermediate scale = proactive, for preventing connectivity loss (ex = land purchase or easement)

3. large scale = integrative, for linking cores across species ranges (ex = collaborative landscape conservation plans)

Benefits of corridors - three categories

1. individual animals

2. animal populations

3. human wellbeing

Benefits of corridors for individual animals

1. increase survival

2. increase movement and dispersal

3. increase access to resources

Benefits of corridors for animal populations

1. increase genetic variation

2. maintain metapopulation dynamics

3. increase population growth rate

Benefits of corridors for human wellbeing

1. reduced risk from vehicle collisions

2. ecosystem services

Example of benefits of corridors

1. mountain lion corridor → prevents inbreeding and extinction by maintaining genetic variability and also mountain lions eat deer so prevents human/deer collisions (benefits to animals, population, and humans)

Provisions of Wildlife Corridors and Habitat Connectivity Conservation Act (2024)

1. Fed agencies can designate national wildlife corridors

2. Fund to manage NWC on federal lands

3. Grants to fund state/tribal groups for initiatives promoting wildlife connectivity

4. Committee to develop national plan

5. Database to inform connectivity decisions

Population change equation

🔼N = B + I - D - E

Population

collection of individuals of a species in an area

Population growth over time

abundance or density trend, can be negative positive or zero

Lambda

geometric population growth rate, proportional change of abundance between times

$$lambda = e^r$$

r

exponential population growth rate, instantaneous per capital growth rate

$$r = ln(lambda)$$

Population growth trends - Three types

1. increasing population

2. stable population

3. decreasing population

Population trends - Increasing population

- R0 > 1

- r > 0

- lambda > 1

Population trends - Stable population

- R0 = 1

- r = 0

- lambda = 1

Population trends - Decreasing population

- R0 < 1

- r < 0

- lambda < 1

Survivorship curves

1. Type 1 = survival decreases with age, low death rate when young, many live to old age (ex = large mammals); convex down

2. Type 2 = mortality constant with age (ex = small and medium mammals), linear down

3. Type 3 = high mortality when young, few live to old age (rare in mammals, common in invertebrates), concave down

Factors structuring populations

1. Intraspecific competition

2. Predation

How does intraspecific competition structure populations

acts as a perfect density-dependent regulatory factor

1. Fence effect = unfenced population has less competition within species bceause they can disperse, fenced population has more intraspecfic competition because cannot disperse

2. Interspecific prey resource competition = affects both sexes range size and energetic burden of conspecifics

Example of interspecific prey resource competition in Allenby's gerbils

- M+F prefer semi stabilized sand dunes > stabilized

- M active earlier in the night than F

- F stay active later at night than M

- F use stabilized (less favored) sand dunes more than M because they are restricted by M-F intraspecific compeition

- M have more active time so they monopolize the favored sand dunes

How does predation structure populations?

- Two responses to changes in food availability

- Numerical response = affects reproduction, immigration, death, emigration (when prey availability inc, predator availability inc)

- Functional response = change in behavior

- Type 1 functional response = linear to satiation point, rare in nature

- Type 2 functional response = immediate response to resource change (specialist forager), then hit threshold due to satiation — quick response due to reliance on one type of prey

- Type 3 functional response = delayed response to allow for prey switching (generalist), slower response because don't rely on one type of prey

Foraging vs hunting trends in larger vs smaller predators

1. large predators = forage on more prey species, hunt more selectively

2. small predators = forage on fewer prey species, hunt more opportunistically

Exponential population growth equation

dN/dt = rN (Exponential, DI)

Two possible outcomes of exponential population growth

1. population overconsumes and crashes (Exponential)

2. population growth gradually limited by resources (Logistic)

Density dependent population growth equation

dN/dt = rN ((K-N)/(K)) (Logistic, DD)

Density dependent factors

- Do change with population density

- non-linear function of density

- change rate of mortality as density changes

- biotic (food, disease, etc)

Density independent factors

- do not change with population density

- linear functions of density

- no change in rate as density increases

- abiotic (weather, etc.)

Draw graphs of absolute vs. rate; births vs. deaths for DI and DD factors

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Population Cycles

- animals with strong DD have marked chnages in population numbers and demographic cycling

- ex - snowshoe hares boom/crash on 8-10yr cycle

Factor X causes population cycling (H0) is supported when

- C+, E+ (cause is present and effect is present)

- C-, E- (cause is absent and effect is absent)

- C is necessary and sufficient for E to occur

Factor X cases population cycling (H0) not supported when

- C-, E+ (cause is absent but effect/cycle still occurs) — cause is not necessary for effect

- C+, E- (hypothesized cause is present but effect/cycle does not occur) — cause is not sufficient for effect to occur

- C is either not necessary or not sufficient for E to occur

What does necessary mean in decision table

C required for E to be observed