-is made up of individuals of a species within a given area

-live within patches of suitable habitat

Subpopulations are subdivisions within a population having restricted exchane of individuals with remainder of population

** The distribution of a population is its geographic range***

-the dispersio of individals within a population describes their spacing with respect to one another (is different from dispersal (movement))

CLUMPED- individuals are foud in descrete groups

SPACED- individual maintains a maximum distance between itself and its neighbors

RANDOM-homogenous area without regard to presence of others

-views a population as a set of subpopulations occupying patches of a partcular habitat type, between which individuals move occasionally

-habitat matrix is viewed only as a barrier to th movement of individuals between subpopulations

-population model that assumes that there are differences in the quality of patches of the suitable habitat type.

-WHere resources are abundant, individuals produce more offspring that required to replace themselves, and the surplus offspring disperse to other patches. Such populations serve as source populations.

-a population model that goes a step beyond the metapopulation model by considering the effects of differences in habitat quality within the habitat matrix.

-habitat matrix also influences the movement of individuals from one subpopulation to another. Clearly, some travel routes are more attractive that others because of the habitat types encountered along the way

-also considers high/low quality habitat (as does source-sink model)

-the distribution of individuals across resource patches of different intrinsic quality that equalizes the net rate of gain of each indiviudal when competition is taken into account

**each individual in the population will be exploiting a patch of equal apparent quality, regardless of intrinsic patch quality

(ie. a good patch will simply have more individuals on it than a bad patch)

1)individuals do not have perfect knowledge of patch quality

2)territorial behavior by dominant individuals reduces free choicein subordinates

**Rreproductive success varies between havitats!**

**this establishes a net movement from source models to sink**

-the ultimate measure of a population is the number of individuals it contains

-total population size has two components, density and area.

DENSITY- defined as the number of individuals per unit of area

D=N/area .. therefore N=D*area

-used to determine population size

-uses the propotion of recaptured individuals

N= nM/x

N=population

M=released marked fish

n=future sample size

x=number of recaptures (tagged)

**must assume complete mixing of marked individuals into the population

-movements within populations

-movements between subpopulations (ie. b/w sources and sinks)

1)emigration - leaving

2)immigration - entering

3)migration - more general

-pertains when young individuals are added to the population continuously and a plot of the population increase as a function of time forms a smooth curve

N(t)= N(0)e^rt

N(t) = # of individuals in a population after t units of time

N(0) = the initial population size (t=0)

r=exponential growth rate

*the rate at which individuals are added to a population is the slope of the population growth curve, or the derivative of the exponential equation

*******THERFORE, rate of change in a population = the contribution of each individual to population growth X number of individuals in the population *****

-periodic increase or decrease in a population in which the increment is proportional tot he number of individuals at the beginning of the period, oftend the breeding season

N(t) = N(0)λ^t

N(t) = population at given time

N(0) = initial population

 λ^t = ratio of population size in one year to that in the preceeding year

=exponential growth rate of a population

exponential- r=b-d (birth rate - death rate)

geometric- λ=B-D (annual birth- annual death rate)

 ____________________________

λ = e^r

log_eλ = r

Constant Population

r=0

λ=1

Increasing Popuation

r>0

λ>1

Decreasing Population

r<0

λ<1

-two populations haing identical birth and death rates at corresponding ages, but different age structures (proportions of individuals in each age class), will grow at different rates

-provided that age-specific birth and survival rates remain unchanged, the population eventually assumes a STABLE AGE DISTRIBUTION ***(under such conditions, each age class in a population grows or declines at the same rate, and therefore so does the total size of the population)

-hypothetical table ofbirth and survival rates

-can be used to model the addition and removal of individuals in a local population (in absence of immigration/emigration)

-females usually used, as paternity is difficult to determine in many species

VARIABLES USED

fecundity

surival rate

mortality

survivorship

number alive

age

**survival rate is the probability of survival at a given age, while survivalship is how many are currently living based on probability of survival***

COHORT

-folllows the fate of a group of individuals born at the same time from birth to the death of the last individual. (can take a long time to collect the data, and is difficult to use on highly mobile animals)

STATIC

-sidesteps the time problem by considering the survival of individuals of known age duing a single time interval

*-the investigator estimates each age specific survival value independently for each age class of a population during the same time period 

-to employ this method, must know age of individuals

-r_m

-is the exponential rate of increase (r) assumed by a population with a stable age distribution

-in practice, populations rarely achieve stable age distributions

-shows how a population would grow if environmental conditions remained constant

**intrinsic rate of increase of a population depends heavily on both the net reproductive rate and the generation time

-a population grows when net reproductive rate (R₀) exceeds 1

R₀

-one may think of it as the expected total number of offspring of an individual over the course of his or her lifespan

T

- the average age at which an individual gives birth to its offspring

-the rat of population growth increases as yung are bortn to their mothers at younger ages, that is, as T (generation time) decreases

-is another way of expressing growth rate

t₂(doubling time) = log_e2/log_eλ

*According to Logistic Equation, the exponential rate of increase decreases as a linear function of the size of a population* (ie. population of USA)

dN/dT = r₀N(1 - N/K)

Population growth rate

=

intrinsic growth rate at N close to 0

X

population size

X

Xthe reduction in growth due to crowding

*when N exceeds K, the ratio N/K exceeds one, the population begins to decrease

K(carrying capacity) is teh eventual steady state or equilibrium size of a population growing according to the logistic equation

the point at which logistic or other sigmoid-shaped growth curve changes from accelerating to decelerating phase

-the point of maximum productivity

 DEPENDENT

-influence rates of population growth,

-whose effect increasees with crowding, can bring a population under control

-things such as supplies of food and places to live... also predators parasites and diseases are felt more in large populations

INDEPENDENT

-these may influence the growth rate of a population, but do not regulate its size

-the relationship between average plant weight and density

-such is the regularity of this relationship, that may have referred to it as the -3/2 POWER LAW

(slope of decreasing line is approximately -3/2)

1)magnitude of fluctuation in the environment

2)the inherent stability of the population

*populations of small, short-lived organisms may fluctuate wildly over many orders of magnitude within short periods

** large animals tend to have HIGH INTRINSIC STABILITY

-the period between successive highs or lows is remarkably regular in some populations

-variation in population dynamics tends to leave its ark on the age structure of a population... and changing age structure can affect the rate of population growth.

-can be caused by time delays

-delays in the response of birth and death rats to changes in the environment of populations

-can result in cycling of overshooting carrying capacities, and falling below again.

-time delays that cause populations to oscillate are inherent in models with descrete generations

 -When the per capita growth rate is small (r₀), the population will approach the carrying capacity directly, without oscillation

-When r exceeds 1 but is less that 2, a population will tend to overshoot its equilibrium, but will nonetheless end up closer to the equilibrium than it was before

-this behavior is called DAMPED OSCILLATION

-When r exceeds around 2, the population can end up farther from the equilibrium each generation, and oscillations tend to increase

-The population may nonetheless settle into stable oscillations called LIMIT CYCLES

**With increasing r, these oscillations can take on very complex, eventually unpredictable forms referred to as chaos

-water flea Daphnia magna exhibited marked oscillations when cultured at 25C but these oscillations disappeared at 18C

-caused by a time delay in warmer environments that doesn't exist when cooler

some outside influence.. either a 

1)change int he carrying cpaacity (K)

or

2)a catastrophic change in population size

-areas of habitat with the necessary resources and conditions for a population to persist

*the individuals of a species that live in a habitat patch constitute a subpopulation

-a set of subpopulations interconnected by occasional movements between them

-is one of ecology's most important tools for understanding teh dynamics of species living in fragmented habitats

Two Types of Processes Contribute to the Dynamics of Metapopulations:

1)includes the growth and regulation of subpopulations within patches

2)comprises colonization to form a new subpopulation by migration of individuals to an empty patch and extinction of established subpopulations

***when individuals move frequently between subpopulations in a metapopulation, fluctuations and chances for extinction are damped out

*THE MORE CONNECTED THE SUBPOPULATIONS, THE MORE THEY MIRROR THE CHARACTERISTICS OF THE METAPOPULATION**

ρ= 1 - e/c

 ρ = proportion of occupied patches @ equilibrium

e = probability that subpop will go extinct

c = rate of colonization

*when e=c, ρ=0, and the metapopulation heads toward extinction

*when the rate of colonization exceeds the rate of extinction, the fraction of occupied patches reaches equilibrium between 0 and 1.

*this model assumes that all patches are equal and that rates of extinction and colonization for each patch are the same

**in reality, patches vary in size, quality, and accessability from other patches

*larger patches can support larger subpopulation which have lower probabilities of extinction

-immigration from large, productive subpopulations can keep declining subpopulations from dwindling to small numbers and eventual extinction

-can be incorporated into metapopulation models by making the rate of extinction decrease as the fraction of occupied patches increases (that is, with more numerous sources of migrants/rescuers)

-population models that assume large population sizes and no variation in the average values of birth and death rates due to chance

-with these models, outcomes can be predicted with certainty

Ecologists recognize three types of randomness tha affect populations in the natural world:

1)Catastrophes - populations may be subjected to unpredictable catastrophes that strongly affect all individuals in the population, causing reproductive failure or a high proportion of deaths

2)consists of variations in physical conditions and other environmental factors that continually influence rates of population growth and the carrying capacity of the environin all years

3)stochastic processes - due to random sampling - can result in variation in populations even in a constant environment

-chance events like these exert their influence more forcefully in small populations than in large ones

p₀(t) = [bt/1+bt]^N

 p₀(t) = probability that the population will have 0 individuals

t = time

b = birth rate

-because the term in the brackets is always less than 1, the probability of extinciton decreases with increasingpopulation size and increases with larger b, indicating more rapid population turnover

*-also, prob of extinction also increases with time

-most stochastic extinction models do not include density dependent changes in birth and death rates

-in those that do, extinction becomes exceedingly rare except in the smallest populations because, as a population drops below its carrying cpaacity, birth rates typically increase and death rates decrease

HOWEVER

1)land use patterns and habitat fragmentation are such that many species now exist as collections of exceedingly small subpopulations, often so isolated that their eventual demise cannot be prevented by mmigration

2)changing environmental conditions are likely to reduce the fecundity of populations trapped in isolated habitat patches and bring them closer to extinction

3)When endangered species compete for resources with other species, the advantages that they would gain because of their low density may be usurped by they competitors

4)small populations sometimes exhibit positive density dependence owing to inbreeding effects and problems of locating mates, and so numbers decline all the more rapidly

-predators catch prey and consume them, thereby removing them from the prey population

PARASITE

-consumes parts of a living prey organism (host)

-not a predator, as it does not itself remove an individual from a resource population

PARASITOID

-species of wasps and flies whose larvae consume the tissues of living hosts

-inevitably leads to host's death, but not until larvae have pupatd

-resemble parasites and predators (reside within, eat, and kill)

HERBIVORES

-depending on what part or how much of plant they eat, herbivores can act as either predators or parasites

DETRITIVORES

-consume dead organic material

-have no direct efect on the populations that produce those resources

-consumption of a portion of a plant's tissues is referred to as grazing or browsing

-grazing generally applied to grasses and other herbaceous vegetation and algae

-browsing generally applied to woody vegetation

-Apredator's form and function are closely tied to tis diet

*as the size of prey increases in relation to that of the predator, prey become more difficult to capture, and predators become specialized for pursuing and subduing them

-specializations can be seen in digestive tract, teeth, claws, etc

CRYPSIS

-blending in with background by matching the color and pattern of bark, twigs, leaves, etc.

****the behavior of a cryptic organizm must correspond to its appearance (can't move around really fast, etc)

 -edible animals do this

APOSEMATISM

-produce noxious chemicals or accumulate them from food plants, and they advertise the fact with conspicuous color patterns in teh form of warning coloration (aposematism)

**chemical defences use a large portion of an individual's energy or nutrients that might otherwise be allocated to growth or reproduction

Batesian Mimicry

-palatable prey that evolve to resemble the noxious organisms

-mimicry confers an advantage on mimics

Mullerian Mimicry

-occurs among unpalatable species that come to resemble one another

-each participant is both model and mimic

-when single pattern is adopted by many species, avoidance is learned more efficiently by predators

-parasites either live on surfaces (ticks, lice, mites) or inside tthe body (viruses, bacteria protozoans, roundworms, flukes, tapeworms, arthropods)

-parasites that live inside enjoy a benign physical environment regulated by their host

-complex lifecycles can ensure dispersion

-the balance between parasite and host populations is influenced by the virulence of the parasite and by the immune response of the host

-some parasites produce chemical factors that suppress the immune systems of their hosts

-others have surface proteins that mimic the host's owm proteins and thus escape notice by the immune system

-antibodies can persist long after an infection has been controlled, thereby reducing the probability of subsequent infection

-Plants have structural and chemical adaptations for defence against herbivores

-conflict resembles that of host/parasite because both are waged on biochemical battlegrounds

DEFENCES

-inherently low nutritional value (tannins)

-toxic compounds produced (SECONDARY COMPOUNDS)

-structural (spines, haris, tough coats, sticky gums/resins)

-compounds not used for metabolism, but for other purposes, chiefly defence

3 Major Classes:

1)Nitrogen compounds - (lignin, alkaloids such as morpheine, atropine, nicotine, cyanide

 2)TERPENOIDS -include essential oils, latex, and plant resins

 3)PHENOLICS - many simple phenols have antimicrobial properties

CONSTITUTIVE DEFENCES - when degensive chemicals are maintained at high levels in plant tissues at all times

-other plant defenses may be INDUCED by herbivore damage (caused by wounding)

***some chemical defences are too costly to maintain under light grazing pressure, though responses to herbivory can substantially reduce subsequent herbivory.

-in grasslands, native herbivores typically consume 30-60 % of the above round vegetation, thus acting as parasites (when considering the biomass available as a whole)

-similar to maximum sustainable yield... animals are doing it, why don't we?

1)Do predators reduce the size of prey populations substantially below the carrying capacities set by resources for the prey?

2)Do the dynamics of predator-prey interactions csue populations to oscillate?

-most predator-prey interactions also have response lags because of the time required to produce offspring

-large herbivores tend cycles with periods of 9-10 years in canada, and small herbivores around 4 years

*population dynamic models predict that the period of a population cycle should be about four to five times the response lag* (ie. for 4 year cycle- 1 year, and 9-10year cycle - 2 years)

-with parasites, development of immunity causes the lag (ie. measles are 2 yera intervals)

-lag also caused by host population density

*in lab cultures, extremely efficient predatos often eat their prey populations to extinction and then become extinct themselves

-predicts oscillations in the abundance of predator and prey populations with predator numbers lagging behind those of their prey

P=#of prey individuals

R=# of resource individuals

c=rate of increase of the prey population

r=exponential growht rate

dR/dt = rR = cRP

(rate of change in prey population)=(intrinsic  growth rate of prey population without predator) - (removal of prey individuals by predators)

dP/dt = acRP - dP

(growth rate of predators) = (birth rate, which depends on # prey captured) - (death rate imposed by outside system)

a=coefficient for efficiency with which food is converted to population growth

cRP = # prey captured

d= death constant

When both predator an prey populations achieve equilibrium (dR/dT=0 and dP/dt = 0), rR=cRP and acRP=dP

-We can rearrange these to give:

P*=r/c and R*=d/ac

Where P*/R* are the equilibrium sizes of teh predator and prey populations.

*P* and R* are boeth constant values, each independent of the abundance of the other population

**When these values are graphed, the point at which the lines representing P* and R* cross is called the JOINT EQUILIBRIUM, and is the ONLY combination of populations sizes P and R that is stable

-according to the Lotka-Volterra model, when the populations stray from their joint equilibrium, rather than returning to the equilibrium point, they oscillate around it in a continuous cycle

-the period of the oscillation is approximately 2pi/SQRT(rd)

-hence, the higher the population growth potential of the prey or the death rate of the predator, that is, the higher the rate of population turnover, the shorter is T, and the faster the system oscillates.

-see figure 18.8

-The horizontal line P*=r/c represents the condition that dR/dT=0... this is the equilibrium isocline

-for any combination of predator and prey numbers that lies in the region below this line, the population of prey increases because there are relatively few predators. In the region above the equilibrium isocline, the prey population decreases because of overwhelming predator pressure

The population of predators can increase only when the abundance of prey exceeds a vertical line representing R*=d/ac, the quilibrium isocline of the predator

-The change in predator and prey populations together follows a closed cycle that combines the individual changes of the predator and prey populations

-this cycle, called a POPULATION TRAJECTORY, can be traced through the four sections of the graph (fig18.9)

-The equilibrium isocline of the predator (dP/dt=0) is the minimum level of prey (R*=d/ac) that can sustain the growth of the predator population

-The equilibrium isocline of the prey (dR/dt=0) is the greatest number of predators (P*=r/c) that the population of prey can sustain.

***If the reproductive rate of the prey (r) were to increase, or the capture efficiency of the predators (c) were to decrease, or both, the prey isocline (r/c) would increase. That is, the prey population would be able to bear the burden of a larger predator population, and the predator population would increase.

-like the Lotka-Volterr model, because no internal forces act to restore the populations to the joint equilibrium

-Therefore, random perturbations will eventually increase the oscillations to the point at which the trajectory reaches one of the axes of the predator-prey graph (RorP=0) and one or both populations will die out.

-basically, Lotka-Volterra model is unrealistic

The Functional Response

***FIG18.12***

-is the relationship of an individual predator's rate of food consumption to the density of its prey

TYPE I FUNCTIONAL RESPONSE
-prey are consumed in direct proportion to their abundance or density at rate "c" (cRP-predation term- divided by P = cR predation rate per predator)

-means that the fecundity of individual predators, which in the model is properotional to the number of prey consumed, increases without limit in direct proportion to prey availability. Thus, when there are few predators but many prey, the birth rate of the predators is very high, the predator population grows rapidly, and the prey population can be brought under control.

 -characteristic of Lotka-Volterra model

TYPE II FUNCTIONAL RESPONSE

-modification of type I, in which the number of prey consumed per predator initially rises quickly as the density of prey increases, but then levels off with further increases in prey density

 -predator satiation(fullness) and also processing time are the cause

TYPE III FUNCTIONAL RESPONSE

-resembles type II in having an upper limit to prey consumption, but it differs in that the response of predators to prey is depressed at low prey densities

-predator response is depressed at low prey density because of:

1)low hunting efficiency (prey hiding in the limited # of safe areas)

2)lack of reinforcement of learned searching behavior owing to a low rate of prey encounter may reduce capture efficiency at low prey densities

3)switching to alternative sources of food when prey are scarece may reduce pressure on the prey

-Individual predators can increase their consumption of pre only to the point of stiation. Continued predator response to increasing prey density above this level can be achieved only through an increase in the number of predators, either by immigration or by population growth, which together constitute a NUMERICAL RESPONSE

*The numerical response of the predator tends to lag behind that of the prey, whether the prey population is increasing or decreasing. Consequently, the relatioship between predation and prey population density differs between the increasing and declining phases of a population cycle. When prey are increasing, predators tend to be scarce, when they are decreasing, predators tend to be relatively abundant.

-Stability in predator-prey systems may be thought of as the tendency of populations of predators and prey to achieve non-varying equilibrium sizes

Five factors tend to reduce the amplitude of predator-prey cycles and thus promote stability of predator-prey populations:

1)predator inefficiency(or enhanced prey escape or defence strategies)

2)Density-dependent limitation of either the predator or the prey by factors external to their relationship

3)Alternative food sources for the prdator

4)Refuges from predation at low prey densities

5)Reduced time delays in predator response to changes in prey abundance

FIGURE 18.7 = VERY IMPORTANT

-under some circumstances, a population may have two or more stable equilibrium points, only one of which may be occupied at a given time

-Has to do with interaction between predation rate and recruitment rate. In a type III functional response, increasing predation rate may cross the recruitment rate, then cross again when it begins to deminish, then finally cross a third time as prey population hits carrying capacity.

-Populations tend to gravitate towards either one of these stable states. It has been evidenced that a population can be "bumped" past the middle interesection in order to increase towards the other stable state near carrying capacity, and vice versa.

***The middle point represents the changeover between strong predator control and strong resource control of a prey population.***

-any use or defence of a resource by one individual that reduces the availability of that resource to other individuals

-can be intraspecific or interspecific

-When one population can continue to grow at a resource level that curtails the growth of a second population, the first will eventually replace the second

-any substance or factor that is consumed by an organism and that supports increased population growth rates as its availability in the environment increases.

-resources can constitue space for sessile animals (barnacles on rocks), and safe hiding places for mobile animals

-can be classified as RENEWABLE (constantly being regenerated) or NON-RENEWABLE (not regenerated ie. space... once occupied, becomes unavailable... replenished only when consumer leaves)

1)includes resources that have a srouce external to the system, beyond the influence of consumers (ie. sunlight and rain will come regardless)

2)Generated within the ecosystem, and their abundances are directly depressed by their consumers (ie. prey of a predator)

3)regenerated within the ecosystem, but resource and consumer are linked indirectly, either through other resource-consumer steps, or through abiotic processes. (ie. different elements of Nitrogen cycle)

-while all resources are, by definition, reduced by their consumers, not all resources limit consumer populations.

-depends on a resource's availability relative to demand

Liebig's law of the minimum is the principle that populations are limited by the single resource that is most scarce

-this law applies strictly only to resources having an independent influence on the consumer. In many cases two or more resources interact to determine the growth rate of a consumer population

-states that two species cannot coexist indefinitely on the same limiting resource

-expresses itself only when consumption depresses resources to the degree that it limits population growth

dN/dt= r([K₁-N₁-a_1,2N₂]/K)

- r is the rate of increase of the given population

- K₁-N₁/K accounts for interspecific competition (as population size approaches carrying capacity, this term approaches 0, which indicates no growth)

-N₂ is the number of individuals of species 2

-a_1,2 is the coefficient of competition, that is, the effect of an individual of species 2 on the exponential growth rate of the population of species 1.

-If two species are to coexist, the populations of both must reach a stable size greater than zero

-interspecific competition reduces the effective carrying capacity of the environment for species 1 by the amount a_1,2N*₂, that is, in proportion to the population size and coefficient of competition of the second species

-Coexistence is most likely (N1* and N2* > 0) when coefficients of interspecific competition ( a_1,2and a_2,1) are relatively weak, in particular, less that 1.

-above ground and below ground competition

-in some cases, intensity of competition increases with resource available, in other cases, it is the other way around

EXPLOITATIVE

-individuals compete indirectly through their mutual effects on shared resources

INTERFERENCE
-less frequently, when consumers can profitably defend resources, competitors may interact directly through various antagonistic behaviors

-chemical competition

-most frequently used in terrestrial plants

-

-eucalyptus trees promote frewuent fires, which kill competitors

-Salvia use chemicals to inhibit growth of other vegetation

-Pisaster (sea star) is a predator of many things

-when removed from area, biodiversity decreased, as barnacles and mussels increased and crowded out many of the other species (no longer being eaten by Pisaster)

-when populations of two or more species interact, each may volve in response to those cahracteristics of the other that affect its own evolutionary fitness.

CONVERGENCE -in response to similar physical stresses in the environment, many kinds or organisms evolve similar adaptations.

 -ie. leaves of desert plants

-suggested that frequencies of virulence and resistance genes should tend to oscillate over time in much the same manner as predator-prey population cycle

-assumed that pathogen virulence and host resistance each were controlled by a single, and that borth virulence and resistance were, by themselves, costly to organism

-when host is susceptible (genotype rr), selection favors virulent pathogens (genotype VV or Vv). Virulent pathogens cause selection for host resistence (RR or Rr). When the host is resistant, selection favors avirulent pathogens (genotype vv), because virulence is so costly.

-reinforced the conclusion that populations evolve in response to each other

-used flies and parasitoid wasps

-in one, host not allowed to evolve (population fluctuated dramatically)

-in other, flies had been exposed to wasps for a long time, and stability was evident... (very resistant to wasps)

-contains teh essential element of coevolution envisioned by Mode: an interaction between the fitnesses of the genotypes of the host and teh genotypes of the pathogen. The system is kept in flux by the introduction of new virulence genes in the rust, and perhaps by new resistance genes in the wheat.

-also evidenced in the relationship between scale insects and certain pines.

-scale insects are so sedentary that they migrate from tree to tree very little and basically evolve on the same tree

 **the survival rate of scale insects transplanted between trees was much lower than that of controls transferred between branches. Reason exists to believe that this difference is genetic

*GENOTYPE-GENOTYPE INTERACTIONS!! - case of strict coevolution(which is difficult to define)

-a simple graphic model that relates the rates of evolution of a consumer and a resource population to the efficiency with which the consumer exploits the resource can depict the evolutionary responses of teh two populations

-selective pressure on resource populations increases as teh exploitation rate increases; adaptations by resource populations tend to decrease the rate of exploitation. Exploitation is brought into equilibrium when teh population consequences of consumer and resource adaptations balance.

-consumer adaptations tend to increase the rate of resource exploitation

-but as the exploitation rate increases, selective pressure to increase it further diminishes because resource populations are driven to lower and lower levels and become less suitable resources

-when exploitation is very high, consumers may be selected to switch to alternative resources, and the rate of change in exploitation levels resulting  from new adaptations may become negative.

**in this model, when predator adaptations are relatively effectiveand the prey are exploited at a high rate, selection on the prey population tends to improve its escape mechanisms faster than selection on the predator population improves its ability to exploit the prey.

**Conversely, when the exploitation rate is low, prey populations evolve more slowly than predator populations

-a balance in these two should result in a relatively stable state of exploitation, regardless of adaptations (RED QUEEN HYPOTHESIS)

* Competitive ability must exhibit genetic variation so that it may respond to selection and evolve*

**A rare competitor can evolve superior competitive abilities, due to the fact that interspecific competition is higher than intraspecific competition

-Blowflies remoed at 38 weeks were superior competitors when tested with wild blowflies. They had evolved sperior competitive ability even though on the verge of extermination

-When blowflies lived with houseflies, houseflies dominated for a long period of time, then blowflies eventually evolved superior competitive ability and took over.

-Where two species coexist within the same geographic area, they are said to be sympatric; where their distributions do not overlap, they are said to be allopatric.

Character Displacement - Divergence in the characteristics of two otherwise similar spcies whee their ranges overlap, caused by the selective effecs of competition between the species in the area of overlap.

-The beaks of the Galapagos ground finches illustrate character displacement.

-The beak size range of each ground finch species varies with the number of other species with which it coexists on an island.

 -On islands where more than one finch species occurs, the beak depths  do not overlap...(more competition, less generalized)

-However, on islands with only one species, their beaks are an intermediate depth (more generalized)

Mutualism - each party to a mutualism is specialized to perform a complementary function for the other

 -Fall into 3 categories:

1)Trophic - usually inolve partners specialized in complementary ways to obtain energy and nutrients, which pertains to feeding relationships

-Rhizobium bacteria and plant roots that form nitrogen fixing root nodules.

-also exists in lichens and mycorrhizae

-bacteria in rumens of cows can digest cellulose... bacteria receive a steady supply of food in warm, chemically regulated environments

2)Defensive

 -involve specis that receive food or shelter from their partners in return for defending those partners against herbivores, predators, or parasites.

-in some marine ecosystems, specialized fish and shrimp clean parasites from the skin and gills of other ish species

-fish come to cleaning stations to be groomed by fish of striking colors

3)Dispersive

 -generaly involve animals that transport pollen between flowers in return for rewards such as nectar, or that east nutritional fruits and disperse the seeds they contain to suitable habitats

-rarely involve close living arrangements

-not usually highly specialized for seeds... ie. a single bird species may eat many kinds of fruit, and vise versa.

-plant-pollinator relationships tend to be more restrictive because it is in a plant's interest that a flower visitor carry its pollen to another plant of the same species. 

Symbioses- intimate associations in which the members together form a distinctive entity "living together"

-Reciprocal evolutionary responses between pairs of populations are referred to as coevolution

-but the term has also been used more broadly to describe the close associations of certain species and groups of the species in biological communities

-**Do pairs of populations undergo reciprocal evolution, or do "coevolved" traits arise from the responses of populations to selective pressures exerted by a variety of species and physical factors, followed by an ecological sorting out of subsets of species with compatible features?

**Are species organized into interacting sets based on their evolved adaptations, whether "coevolved" or not?

-The difficulty we have in recognizing true cases of coevolution is illustrated by a mutualism in which ants protect aphids and leafhoppers from predators and, in return, harvest the nutritious honeydew that those insects excrete.

-one species of ant is more efficient at protecting aphids, while a different species is more efficient at prodecting leaf-eaters, yet both species will exhibit mutualism with both aphids and leaf eaters

**all the elements of co-evolution exist, yet how can we be sure that the adaptations of the ant and homopteran participants evolved in response to each other?

-honeydew production may simply reflect diet rather than having eolved to encourage protection by ants..

-ants may need no special adaptations to deter predators, as they are already aggressive

-BEST PROOF OF CO-EVOLUTION COMES FROM RECONSTRUCTIONS OF THE EVOLUTIONARY HISTORY OF TRAITS IN COEVOLVING GROUPS OF ORGANISMS!!

-the application of phylogenetic reconstruction to the problem of coevolution can be illustrated using the pollination relationship  b/w yucca plants and moths

-obligatory relationship, in which female yucca moths carry balls of pollen between yucca flowers by means of specialized mouthparts

-during pollination, she enters the floer, makes cuts in the ovary with her obipositor, and deposits one to fifteen eggs.

-after eggs are laid, moth deposits pollen on the stigma, guaranteeing that the flower is fertalized and the oth's offspring will have developing seeds to feed on.

-the moth may then take pollen from this plant before moving on.

*larvae can grow nowhere else, and yucca has no other pollinator*

-the yucca regulates the number of eggs laid per flower.... when too many eggs are laid in the ovary of a particular flower, the flower is aborted and the moth larvae die

-this mechanism used to "keep moth pollinators in line"

 PREADAPTATIONS- we can see from a phylogenetic tree that many of the adaptations that occur in the yucca-yucca mutualism appear to have been present in the moth lineage before the establishment of mutualism itself

*this phenomenon may be thought of as coevolution in a broad sense - sometimes called DIFFUSE COEVOLUTION

-pursuit of knowledge

-resource management (fisheries,trees,hunting)

-agro-ecosystems

-conservation biology

-ecological services

-

-cowbirds don't live in forested areas, forest birds close to edge are very heavily parasitized

-nest parasites come from cowbirds

-fragmentation increases amount of edge

-maximum sustainable yield

-approximately at inflection point

-so why are fisheries screwed?

-need accurate initial data

-politicians manipulate

EXAM QUESTION!

What is Ricklef's definition of population growth?

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When P>P*, R will be decreasing.

When R<R*, P will be decreasing.

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-enriching the environment will destabilize predator-prey interactions

-look for example in text??

-introduced to Australia... became big pest

-argentine cactus moth introduced in hopes that it would control

-the could eat through and eat it from inside

-complete eradication occurred due to caterpillars

*want LOW LEVEL EQUILIBRIUM so that caterpillars don't disappear... don't notice either, but still there... ideal situation

-******example that things of low abundance in nature cannot be assumed to not be important

-acute senses (vision/taste/smell) for detecting food

-right shape and size for access to plant needed

-strong jaws, durable teeth, bill, other mouthparts

-rumen or caecum to digest cellulose

-a good liver (process plant toxins)

-acute senses (vision, hearing, smell) for prey detection

-powerful/fast muscles for agility/strength/coordination

-claws and mouthparts for handling prey

-big stomach and short intestine

-humpback whale uses baleen for filter feeding

-detects host using chemical cues

-female parasitoids produce and inject substances that regulate the host's development and suppresses the host's immune system

-infecting hosts and getting from one host to another to complete life cycle

-feed in or on the host

-overcome immune response of host

-numerical increase

-keep host alive

-adapt to chance factor (huge # of eggs) (ie. tapeworm)

-locate hosts through a combination of chemical (C02) and thermal cues

-chance game... can't just randomly fall of a tree... has to respond to cues

-come at a cost.... would not evolve without strong selection pressure

-speed, aglity, vigilance, socal communication, size, dangerous weapons, aggregations, spines, sprays, etc.

*parameter that determines rate of attack of a predator is a combination of predator/prey adaptations

-plant that exhibits chemical defences

-uses constitutive defence

-kills by paralysis and asphyxiation

-inexperienced animals caneat it... 2kg of it can kill a calf

Methyllycaconatine
•grow in rangelands of western Canada and the US, extremely toxic to cattle, horses, sheep and wild herbivores. All parts of the plant are toxic and the toxin is constitutive.
•alkaloid inhibits acetylcholine receptors in muscles and kill by asphyxiation and paralysis—other symptoms salivation, bloat, constipation.

-interspecific competition can restrict range over which a species is found

-experiments on bedstraw

-grew seperately and then together on both alkaline and acid soils

-both can grow on both, but one specis dominates acid and one dominates alkaline when grown together

*competitive exclusion principle

-two types of paramecium .. do well seperately

-one species had a slightly higher K and slightly lower r (rate)

-when together, one with lower k and higher r gets early head start, but higher k and low r eventually catches up and outcompetes

-physical.. controlled by environment

-biological... coevolution

 *in similar physical environments, we tend to see convergence (long lets and long bills)

*divergence is typically seen in biological interactions (ie. shape of bill) (character displacement)

-may species of each in tropical rainforest

-larval herbivory

-closely related butterflies tend to feed on closely related flowers, and have evolved intricate relationships with them

-chemical defences and chemical tolerances... 

-only a select few kinds of butterfly can lay eggs on a certain vine

-virus artificially introduced to control rabbit populations

-transferred by mosquito bites, therefore in order to complete "lifecycle" must be transferred back to mosquito

-at first, virus too effective, killed too fast and could not be passed on

-virus selected to act more slowly..

-mortality rate of rabbits fell significantly (developped resistance)

DEFENSIVE

 -Ant/Acacia - not symbiotic... two completely separate organisms

-protection in exchange of food and/or shelter

-ants remove new shoots that develop around tree

-ants live inside thorny bits of tree

-tree produces nectar for ants

-Maray Eel and Prawn

-prawn is proted by eel in exchange for cleaning????

-Goby and Shrimp (Crayfish)

-shrimp digs burrow... both live there

-though shrimp has bad eyesight, Goby keeps a lookout while it feeds

TROPHIC

-mycorrhizae allow plants to pick up more nutrients/phosphorous

-in payback, plant supplies carbs

-corrals/lichens

-photosynthetic algae live within corals calls and provide 90% energy

-algae/lichen .. one provides photosynthesis other ??

-Herbivores/Rumen bacteria

-sheep/deer/cattle have mircroorganisms that digest cellulose... huge energy supply

-Leguminous plants/N-fixating bacteria

 -change atmospheric nitrogen into a biologically accessible form

dN/dt = r_mN

exponential

N(t) = N(0)e^rt

geometric

N(t) = N(0)λ^t

The Malthusian Parameter is "r_m", the intrinsic rate of increase of a population, which is assumed by a population with a stable age distribution.

-it is biologically unrealistic

1)density dependence does not exist

2)predator satiation (type II functional response)

3)prey refuges (type III functional response)

-experiment on predator/prey dynamics within a spatial framework 

-In each experimental tray, four oranges half-exposed are distributed at random, with the rest of the spaces occupied by rubber balls.

-Each orange has its exposed area numbered in sections for enumeration.

Result **** A spatial mosaic can allow predators and prey to coexist****

-Distributions shifted as prey colonize new areas and get wiped out of areas where the predator invades
-The spatial mosaic can allow the prey to stay a jump ahead of the predators.

**On a single orange, the predator mite always wipes out the prey mite***