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ESRM 350 mac

Terms in this set (106)

Wildlife Popultion
groups of animals, all of the same species that live together in a particular area and can interbreed
What delineates populations?
1. Geographic barriers eg. mountains, bodies of water
2. habitat borders eg. populations are bound by hospitable environments
3. Biotic interactions
a. intra-specific borders set by adjacent pops of the same species where interbreeding does not occur
b. inter-specific: competition, paratism, predation
Key Population Characteristics
1. Frequency of different genotypes, changes result in evolution
2.Age structures: proportions of indiv. in various age classes, influences population growth trajectory
3. Dispersion, density and spacing of indiv.
Dispersion
spacing of individuals in a pop with respect to one another
Types of Dispersion
1. Clumped: individuals in discrete groups
2. Uniform: indiv. maintain a minimum distance from other indiv. or evenly spaced
3. Random: indiv. spaced independently from each other
Clumped Dispersion Causes
Causes:
1. social predisposition to form groups eg. thermoregulation, foraging, safety from predators
2. clumped dist. of resources
3. tendency of offspring to remain near parents
Uniform Dispersion Causes
Causes:
1. Interactions among individuals eg avoiding fights over food or interference while foraging
2.territoriality or defense of a fixed area against other indiv. to protect mating opportunities or resources
Territoriality
1. Only viable if resources or reprod. opportunities can be defended otherwise energetic costs are too high
2. cost of terr. sometimes reduced if neighbors are familiar
a. "Dear enemy" effect lower levels of aggression towards familiar individuals compared to other unfamiliar ones, keeps energetic costs lower
b. territorial boundaries well established
Random Dispersion Causes
1. Overlapping home ranges (no territoriality)
2.randomly dispersed resources
Wildlife Demography involves....
1. description of population characteristics
2. exploration of determinants of population size
3. use of math. techniques to predict (model) growth
Drivers of Population Size
B.I.D.E
Births, immigration, deaths, emigration
Inputs: Births and immigration
Outputs: Deaths and emigration
Population grow in proportion with...
their size
ex: at 10% annual rate of increase:
- a pop of 100 adds 10 individuals in one year
- a pop of 1000 adds 100 individuals in one year
Exponential Growth Types
1. Continuous: individuals are added to pop growth without interruption
2. Discrete or Geometric growth: indivs. added to pop in pulses (non-overlapping generations) ie. species that have a breeding season
General Exponential Growth equation
N t+1 = N t +(B-D) + (I-E)

where,
N t = size of pop at some time t
t +1 = size of pop at some future time

In closed population:
N t+1 = N t + (B-D)
Continuous Pop. Growth
*Time step between t and t +1 infinitely small (no pause in growth) ie growth that occurs over a very small interval of time

dN/dt = B-D

Instantaneous rate where,
B = bN, b is the instantaneous (per capita) birth rate
D = dN, d is the instantaneous (per capita) death rate

Thus, dN/dt = bN- dN or dN/dt = (b-d)N

So, b - d = r, the instantaneous rate of increase

dN/dt = rN
Population growth rate (dN/dt) is proportional to...
r so,
1. If r or b-d > 0 , then the pop increases
2. If r = 0, then there is no increase
3. If r < 0, then the pop decreases
Population growth rate also proportional to...
N so,
the greater the population size, the faster the rate of change
To predict a population size at some point in future, we need to know...
r and N, then we can describe growth rate of population which is used with

N t = No e^rt

where,
N t = # of indivs. at time t units
No = initial pop size
e = base of ln
r = per capita rate of increase

This will exhibit a smooth upward curve
discrete exponential growth
When species don't have overlapping generations ie they have breeding seasons we use discrete pop growth

N t+1 = λ (N t)
where,
N t+1 = # of indivs. after time unit
N t = initial pop size
λ = finite (geometric) rate of increase (ratio of future to current pop)
Recursive Equation
Output for one time interval becomes input for next time interval

General equation after t time intervals is,

N t = λ ^t (No)
where,
original pop size (No) is multiplied by the finite rate of increase (λ) for the appropriate # of time intervals
Why are growth population models the cornerstone of population biology?
1. All pops have potential for exponential growth
a. recognize multiplicative nature of pop growth ( positive feedback yields accelerating growth)

2. Realistically describes growth of many populations in short term
a. often resources are temporarily unlimited
assumptions of exponential growth model
1. No size or age structure
a. no difference in B and D among individuals due to age or body size

2. Constant B and D over time
a. unlimited resources, space, food required
Age Structured Population Growth
1. Usually B and D values are dependent on age structures
eg. elephants take decades to reach sexual maturity
old indivs. suspetible to predation, disease etc.
What population characteristic affects population growth?
1. Age structure
a. can't assume the same r for populations with different age structures
b. pops dominated by juveniles will grow less rapidly than a pop dominated by reproductively mature adults
What is a life table?
age-specific schedules of the survival and reproduction that enable us to project a pop's size and age structure in the future
Stable Age Distribution
1. Proportion of each age class in pop doesn't change

2. occurs when a pop growth with a constant schedules of survival and reproduction
Under Stable Age Distribution....
1. all age classes grow or decline at the same rate, λ

2. all pop grows/declines at this constant rate, λ

3. Is at equilibrium
Components of a Life Table
Summarize demographic info:
1. age (x)
2. number alive
3. survivorship (I x ): multiply survivor probabilities
at each age = the probability of surviving from birth to age, x
4. mortality rate (mx): probability an indiv.dies before reaching age x +1
5. survival rate(s x): the probability of surviving from x to x +1
6.Fecundity (b x): number of female offspring per female
a. males have infinite reproductive potential
b. easier to document
Cohort Life Tables
are based on data collected from a group of indivs. born at the same time and followed throughout their lives
a. has to be a large population to be representative of whole pop.
b. may be hard to apply to mobile or long-lived species
Statistic Life Tables
considers survival of indivs. of known age during a single time interval

1. removes confounds of yearly variation in environment (but assume year is representative of life history)

2. Require some means of determining ages of indivs.

3. Survivorship determined through carcasses
Calculating r from Life Tables
Under assumption of stable age distribution, can approximate the intrinsic rate of increase (r)

1. have to compute the net reproductive rate, Ro, or the sum of IxDx
a. average # of female offspring produced per female per lifetime
Net Reproductive Rate (Ro)
the expected # of total offspring of an indiv. over the course of her life span

Ro = 1 represents the replacement rate
Ro < 1 represents the declining pop
RO > 1 represents the increasing pop
Generation Time (T)
the generation time (T) is the average age which females reproduce ie. how long does it take for females to be sexually mature

T = Σx Ixbx / Σ Ixbx

Divide values of the last two columns of the life table
Intrinsic Rate of Increase (r) computation is based on...
Ro (Net Reproductive rate) and T (generation time or how long it takes for females to reach reprod. maturity)

r =log e Ro /T

-Large Values of Ro (high per capita female reprod.) and small values of T (short time to reprod. readiness) lead to most rapid pop growth!
Growth Potential of Wildlife Pops is High yet....
In the case of the reintroduction of the ring-neck pheasant, they experienced exponential growth

but,
most pops remain stable, pop growth checked by increased death rates and/or decrease birth rates as population get large
What keeps pop. growth in check?
Crowding
Crowding
as populations grow, crowding:

1. reduces access to food (other resources) for indiv. and their offspring

2. aggravates social strife

3. spread disease

4. attracts attention of predators
What do the effects of crowding lead to?
Density Dependence
Density Dependence
decreasing growth with increasing population size
How can density dependence be modeled?
With the logistic growth model
Logistic growth model
1. includes carrying capacity (k)

1. k is the size at which no more indiv. can be supported by local resources over long time periods

dN/dt = rN (1-N/k)

As N approaches k, growth rate approaches zero
Logistic growth model shape is described as....
An s-shaped curve where k is the asymptote

1. pops below k increase
2. pops above k decrease
3. pops at k remain the same
Inflection point separates....
Accelerating and decelerating phases of growth

Inflection point at k/2
Mating Systems
sexual or asexual process by which organisms produce indiv. of same kind
From evolutionary perspective mating systems are
1. a means by which indivs. pass on genes
2.ultimate determinant of fitness
Two-Fold Cost of Reproduction
1. Sexual reprod. transfers only half of an indivs. genes to their offspring
a. asexual org. get double the fitness benefit per reprod. event

2. "two-fold costs of males", females in asexually reproducing species don't needs males
Why are there so many sexually reproducing animals?
Recombination of alleles/ genes leads to increased diversity, adaptability in populations
Sexual Selection
1.Natural selection where fitness differences manifest as variance in the number of mates
a. female choice
b. male-male competition

2.Can lead to sexual traits that are otherwise costly
a. energetically expensive
b. dangerous (makes you more seen to predators)

3. Contributes to diversity of mating tactics
Mating Systems Def
describes how males and females in wildlife pops pair when choosing a mate
Four Categories of mating systems:
1. monogamy

2.polygyny

3. polyandry

4. promiscuity
Monogamy
Pairing with a single member of the opposite sex
-lifetime
-serial

Benefits:
1.shared parental care
2.resource defense

Costs:
1. offspring not as diverse
solution: extra-pair copulations in which they mate with another indiv
Polygyny
Pairing where one male mates with several females
-Harem: dominant male lives with group of females, mates with each during breeding interval
-Serial: one male attracts passing females

Benefits:
1. females mate with "high-quality" males
2. males get access to numerous mates

Costs:
1. low operational sex ration (few males have mating)
2. reduces effective pop size
Special Case of Polygny is called...
Lek Mating is where males gather and display competitively for females, who do the choosing

1. males defend small territory solely for display
2.no resources involved
3.gathering may help males attract females

Sage Grouse!
Polyandry
Pairing where one female mates with several males
-simultaneous: females breeding territory encompasses that of many males
-sequential: female mates with several males

Same Benefits and Costs as polygyny but,

1. males invest in parental care
2.females often the larger (more colorful) sex (energetically costly)
Promiscuity
Males and females both mate with multiple partners

-Low Skew in mating success among individuals
-competition often take the form of sperm competition
a. increase sperm prod. -> higher chance of paternity
b. copulatory plugs
The two types of reproductive strategies
r-selected species:
-fast lane
-short lived
-produce lots of offspring
-little parental care
-high mortality rate


k-selected species:
-slow lane
-long lived
-produce few offspring
-provide parental care
-low mortality rate
Competition
defined as:
-active demand by two or more organisms for common vital resources

-any use or defense of a resource that reduces the availability of that resource to other indiv.
Competition can be....
1. Intra-specific (within species) contributes to density-dependence (worse with crowding)

2. Inter-specific (btwn species) depresses carrying capacity (k) for both competing pops
Types of Competition
1. exploitation
2.interference
3. IGP
4. Competitive Exclusion
Exploitation competition
Competition through reduced availability of a shared resource

1. no direct interaction
2. winner is the forager that turns resources into offspring the quickest (more efficiently)
Interference
competition with direct interactions between indivs.

1. may involve contests or fights over food
2.may involve physical obstruction
3.winner often an indiv. that gets resource first
4. resource doesn't have to be in short supply, but interference competition is more likely if shortages exist

hummingbirds exclude others from flowering plants
intraguild predation (IGP)
an extreme form of competition where predator and prey are also competitors
- cannibalism is when IGP occurs within a species

eg. Lions and hyenas
Competitive Exclusion
1. two species that are too similar in their ecological requirements cannot coexist for long
2. or two species cannot coexist forever on the same limiting resource
3.the lesser competitor will be excluded from an area or go extinct
Lotka-Volterra Model
is the model used for competing species

1. ai,j is the competition coefficient
- quantifies effect of species j on the pop growth of species i
-value of 1 signifies equivalence

a i,j (eg. 2)

aj,i (eq. 0.5)
Lotka-Volterra Model Assumes...
1. all indivs. are the same

2. competition coefficients are constant

3. linear effect of competition

4. density-dependence

Still, models allows us to solve for the growth trajectory of a pop subject to comp. from second pop
Zero-growth isocline
describes expected equilibrium pop size of one species if abundance of the second species is held constant, and vice versa
When does stable equilibrium occur?
Occurs when:
K1/a1,2 > K2

and

K2/a2,1 > K1
What allows for competitors to coexist?
1. competition coefficients are small (low dietary overlap)

2.Competitive refuge
area where superior competitor cannot exist

3. Temporal heterogeneity where two species may do better at differing temps, winner dependent on year's conditions

4. predation and other mortality agents if populations are kept low then there isn't any competition and many species coexist
eg. newts and anurans
Predation
the consumption of all or part of another animals, killing it in the process

1. most common form of death
2.a major driver of wildlife pop dynamics, can suppress pops
Modeling Pop growth with Predation
dN/dt = rN -cNP
where,

N= # of prey
P=# of predators
rN= number of prey added,
cNp= number of prey killed
c=constant expressing efficiency of predation
r= the prey's per capita exponential growth rate
"Doomed Surplus"
model assumes that all depredated animals would have otherwise survived but, they would have died anyway
-eg. sick, lame, starving
-sources of death increase with crowding
Additive Predation
predation that decreases survival in prey population, adds to existing sources of mortality

negative slope line on graph
Compensatory Predation
predation that does not
affect overall survival in a prey population
, replaces for existing sources of death

straight horizontal line on graph
Predators tend to be....
larger than their prey

larger prey= larger predator groups
Predatory Tactics
1. Stalking: try to get close to prey

2.ambush: let prey come to you

3.Roving (active hunting): does not require surprise, requires high activity rate to maximize prey encounter potential

4.Prey herding and manipulation: often requires teamwork, bubble netting by humpbacks

5.Prey debilitation
eg. fish whacking or venom

6.Batch feeding: consuming large number of prey items in a single feeding

7.tool use: when an object is taken from the enviro and modified from its original purpose
eq. chimps with weapons
Parasitism
1. Consumption of part of another animal, the host, without killing it
-host like habitat

2. every animal has parasites, most are host-specific
Kinds of Parasites
Endo-
-live inside the body of host
-eg. flukes, tapeworms, gungi, bacteria, viruses, protozoa

Ecto-
-live and feed on the body of the host
-eg. ticks and lice, protozoa, bacteria, fungi
Parasit Transmission
1. Direct transmission
-host to host contact required
-eg bacteria and virsuses

2. Indirect transmission
-host to 3rd party to host
-requires vectors: carry parasites in daily activities
eg. mistiquitos
-sometimes involves intermediate hosts (secondary hosts in which parasites must spend time to complete its life cycle)
Plasmodium Life Cycles
Primary Host (development, maturation, release of gametes)

Secondary Host- anopheles mosquito (fertilization and development of zygote)
Parasit-Host Interaction
1. parasite-host interaction reps a balance btwn parasite virulence and host defense

-immune system of host can recognize and disable parasites

-but parasites may multiply rapidly before an immune response can be deployed
Ecological Effect of Parasites
1. reduce survival and reproduction of hosts

-low-quality indiv, more susceptible to parasites, and therefore not selected as mates, leads to lower fitness
-parasites may want host killed to be transmitted, case of parasite in rats that make them fearless and attracted to cat urine

2. May reduce population growth

-intensity of parasitism increases with crowding (density-dependent)
-large populations tend to be heavily parasitized
Disease
1. a disturbance to the normal structure or functioning of an animal

2.many parasites do not cause disease, pathogens do

3. diseases caused by parasites are communicable
a. transmission increase with density
b. selective pressure against disease severity reduced with density so, you can cause disease that kill swiftly if new hosts are close by
Sylvatic Plague
-Bacterial disease
-primary host: wild rodents
-vectors: fleas
-symptoms: sever infection of the lymph nodes (bubonic), blood (septicemic), or lung (pneumonic)

Humans are a dead end host
Black-Footed Ferrets and Sylvatic Plague
-affects prairie dogs, has wiped out entire colonies (> 90% mortality rate)

Conservation Concern:
1. black-footed ferrets, one of the most endangered mammals and are prairie dog specialists
-for food and shelter
2.ferret recover requires protecting prairie dogs and ferrets from plague with vaccine
Brucellosis
-bacterial disease
-Host:
-animal-to-animal transmission, no vector
symptoms: commonly induces abortion during latter half of gestation can also cause chronic infections of the bones and joints

Conservation issue:
-bison are restricted to stay in Yellowstone bc of the concern that cattle will transfer the disease
-prevents them from populating their historical home ranges
West Nile Virus
-athropod-borne virsus
-primary host: irds (225 species)
a. impacts on bird pops unknown
-vector: mosquitoes
-causes encephalitis and meningitis (inflammation of the brain and surrounding tissue)
-humans are dead end
Ecological communities
sets of interacting or potentially interacting species living in the same area
Types of Interactions in Communities
0,0 Neutral
+,+ Mutualism
+,0 Commensalism
-,- Competition
-,0 Amensalism
+,- Predation, parasitism
Community structure
The mix of species in a community, including the number of species, relative abundances, and trophic interactions
Relative Abundance
percentage of individuals a species contributes to the total number of indivs. in a community
Trophic interactions
interactions involving the flow of biomass (energy) from one species to another
- via predation, herbivory, scavenging etc
Measuring Community Structure: Richness
-Species richness (s): # of spicies
a. relatively easy to measure for many wildlife species (present or not)
b. good for capturing broad regional differences in species representations

BUT,
-misses differences in relative abundance which is important for conservation bc many species may be present but scarce
Measuring Community Structure: Diversity
Species diversity: accounts for both the # of species and their relative abundance
a. diversity indices take into account the proportion of indivs. each species contributes to the total
b. rare species given less weight
c. for given s , diversity increases with evenness (good representation)
Trophic Interactions
-interactions involving flow of biomass (energy) between species
-often characterized by food chains
a. linear directions of energy flow
b. arrows show direction of flow
c. simple abstractions of complex relationships, links rep. trophic levels:broad feeding positions within communities (primary producers, herbivores ,predators)
Trophic Pyramid
-Rule of 10 - between 8-13% efficiency/lost between each level
a.ecological efficiency: energy of a trophic level divided by the energy supplied to that trophic level
-primary productivity
limited by light or chemical nutrients
Trophic levels Influenced by Predation and Production
Trophic Interactions: Webs
depicted as food webs

-systems of interlocking and interdependent food chains
-more realistic
-recognize omnivory (species J)
What determines mix of species?
species can persist in community if....

1.community falls within its range, and
2.local conditions and resources promote occupancy (idea of habitat)
3.it is not excluded by other spcies (biotic interactions)

-If species meets these standards, the community offers space for the species niche
Ecolgical niche
1. a species place and role in a community/ecosystem
-place: needs (conditions, resources)
-role: (nature of interaction with others)

2. Two Variants:
Fundamental and realized
Fundamental Niche
the full range of the enviro conditions and resources an organisms can possibly occupy and use, when limiting factors are absent
Realized Niche
The part of fundamental niche that an organism occupies as a result of limiting factors present in its habitat

-provides the organism with everything it needs
What does niche space mean?
means room for an organisms lifestyle
Determining Outcome of Competition: Coexistence or Exclusion? what are the trjectories?
Case 1:
Determining Outcome of Competition: Coexistence or Exclusion? what are the trjectories?
Case 2
Determining Outcome of Competition: Coexistence or Exclusion? what are the trjectories?
Case 3
Determining Outcome of Competition: Coexistence or Exclusion? what are the trjectories?
Case 4
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