Ecology Exam 3

Niche

Environmental factors that influence the growth, survival, and reproduction of a species.

Fundamental Niche

Physical conditions under which a spp. lives in absence of interactions with other spp.

Realized Niche

Actual niche of a spp. whose distribution is restricted by biotic interactions.

Factors limiting distributions of populations on geographic and local spatial scales

Abiotic factors & biotic factors. Climate, physical barriers, evolutionary factors.

Limited distribution can be indirectly determined by climate through

Food production, water supply, habitat, incidence of parasites, pathogens, competitors. Indirectly dictates spp. distribution. No one species can live in all climates.

Random Distributions

Individual has equal probability of occurring anywhere in an area. Neutral interactions.

Regular Distributions

Individuals are uniformly spaced through the environment. Antagonistic interactions.

Clumped Distributions

Individuals live in areas of high local abundance. Separated by areas of low abundance. Attraction interactions. Most common.

Distribution between tropical bee colonies

Stingless bees. Aggressive forage in groups. Feed on flowers in high-intensity clumps. Regular distribution of nests. Non-aggressive forage solitary and small groups. Feed on widely-distributed flowers. Random distribution of nests.

Large-scale distribution patterns

Populations show clumped distr. patterns. Due to env. variation—> individual. Aggregate in env. favorable areas.

More aspects of rarity leads to

More vulnerable to extinction.

Population density is _____corr with body size

Negatively

Body size tend _____conserved across species/ taxa.

Highly

Classification of commonness & rarity based on:

1) Geographic range (extensive v restricted)

2) Habitat tolerance (broad v narrow)

3) Local population (large v small)

Cohort method

Identify individuals born at same time & keep records from birth. Produces cohort life table. May not be value method for all study spp./ population.

Age at death method

Record age of death for a number of individuals. Produces static life table. Requires that age of death be determined. (Growth rings sheep, trees, turtles, coral, fish, otoliths)

Age distribution method

Calculate differences in proportion of individuals in each age class. Produces static life table. Assumes differences from mortality. Reflects a population’s history & indicate periods of successful reproduction. Periods of high/ low survival potential for future population growth.

Type I survivorship curve

Survivorship in juvenile survival is high & high mortality occurs among older individuals. Produce few offspring. Provide parental care. Ex. Humans

Type II survivorship curve

Constant rate of survival throughout lifetime. Ex. Butterflies

Type III survivorship curve

High mortality among young, followed by high survivorship. Do Not produce parental care. Ex. Fish

Geometric Rate of Increase

Ratio of the population size at 2 points in time. NT +1 = population size at future time (T +1) NT= Populations size at earlier time (t). >1.0 —> Population growing. <1.0 —>population declining. = —> Population at equilibrium.

Net Reproductive Rate

Average number of offspring produced by an individual in a population during its lifetime. X= age interval. 1_x = number of surviving to each age (x)/ M_x = average number of offspring produced by each individual at age (x).

Per Capita Rate of Increase

Measurement of population growth in a spp. with continous/ overlapping reproduction . r>0 —> popgrowing. r<0 —> population declining. r=0 —> population stable.

Geometric Population Growth

Population growth in which generations do not overlap and successive generations differ in size by constant ratio. Species with pulsed or seasonal reproduction. Nt = number of individuals at any time (t). N₀ = inital number of individuals ħ= geometric rate of increase. t= number of time intervals or generations.

Exponential Population Growth

Population growth in which generations overlap & the per capita rate of increase is constant. NT= number of individuals at any time (t). N₀ =inital number of individuals. r= per capita rate of increase. T= number of time intervals or generations.

Exponential Growth in Nature

Natural pop. may grow exponentially for short periods of time when resources are abundant. Important in establishment of new environments. During favorable env. conditions recovery from exploitation (or other threats). Organic matter decay rates.

Logistic Population Growth

Population growth that occurs when resources are limited and produces a sigmodial (s-shaped) curve. Given environment can only support so many individuals of a spp. Carrying Capacity important.

Density Dependent Factors

Biotic factors that limit pop. growth and are influenced by pop. density. These factors tend to regulate a pop. at relatively consistent size near k. Influence pop. growth by increasing/ decreasing birth/death rates. Ex.: competition, predation, disease.

Density-independent factors.

Abiotic factors that limit population growth and are not influenced by population density. Affect in unpredictable ways. Ex. weather events, habitat destruction, etc..

Principal of Allocation

If an organism allocates energy to one expense, reduces amount of energy available for other expenses.

Energetic Trade offs: Individual offspring size v number of offspring

Darters. Larger spp. produce more eggs. If produce smaller eggs, produce fewer.

In plants, there is a negative relationship between seed size & seed number, Influenced by plant growth form and dispersal mode.

Before maturity

Effort allocated to growth & maintainece

After maturity

Effort allocated to growth, maintainece, and reproduction.

High mortality rate leads to

Earlier age of reproductive maturity.

R selection

A form of natural selection favoring higher pop. growth rate. Semelparity- single reproductive event in which many,smaller offspring are produced

K selection

Form of natural selection favoring more efficient use of resources. Iteroparity- related to reproduction to produce fewer, larger offspring.

J.P Grime

Proposed 2 env. variables that determine life history characteristics in plants: Intensity of disturbance & intensity of stress. Envinsioned 4 env extremes: 1) Low disturbance-low stress. 2) Low disturbance-high stress. 3) High disturbance-low stress. 4) High-disturbance-high stress.

Winemiller & Rose

Proposed a classification scheme for fish life histories based on: 1) Age of reproduction maturity. 2) Juvenile survivorship. 3) Fecundity.

Life history strategies: Opportunistic: Low juvenile survival, low fecundity, early maturity

Equilibrium: High investment in offspring, high juvenile survival

Periodic: low juvenile survival, high fecundity, late maturity

Intraspecific Competition

Competition between individuals of the same species

Intraspecific competition in Plants

Plant biomass found to be higher in low density populations. Competition increases with density. Leads to mortality among competing plants—> self thinning- reduction in pop. density as stand of plants increases in biomass. Competition for resources is more intense at higher densities (3/2 rule)

Intraspecific competition in Terrestrial Isopods

Can occur in absence of limited food. Lower survival at high densities due to canibalsm.

Interspecific Competition

Competition between individuals of different species. Can lead to extenction and drive speciation.

Competitive exclusion principal

Two species with identical niches cannot coexist indefitely. More effective competition excludes other species leading to extenction.

Interspecific competition in Caterpillars

Interspecific competition can lead to specialization. Flies & wasps show size preference for caterpillars. Competition reduces via resource partitioning.

Competiton & Niches

Competition can restrict species to their realized niches. Physical factors limit Balanus (crustateion) to lower/ middle intertidal zone. Competition excludes Chtamalos from middle intertidal zone.

Lotka -Volera model

Mathmatical model that predicts coexistance of 2 species when interpsecific competition is weaker than intraspecific competition.

Exploitative interactions

Interactions in which 1 organism increases its fitness at the expense of another organism

Herbivory

Caddisfly larve graze on bacteria & alge. Lambertiy and Resh studied influence.

Predation

Influence of birds/bats on tropical forest arthropods. Treatments: Controls, daytime bird exclusion, nighttime bat exclusion.

Pathogens

Chytrid fungus decimates amphiban pops.. Causes chytriodiomycosis —> skin sloughiing, leasions, lethargy. Can persist in env. w/o host. Compromises respiration & osmoregulation. At least 501 amphibian spp. in decline, approx 90 presumed extenctions.

Snowshoe Hare & predator population cycles

Snowshoe Hare and Lynx have same population cycle patterns seen in other northern pops.

Elton: Sunspot hypothesis. Keith: Overpopulation hypothesis & Predator hypothesis.

Role of food supply

Exhibit fast reproduction, exhibit high feeding rate (approx 300-1,500 per day per hare) —> reduces quantity of food. Overbrowsing increases levels of plant chemical defenses—> reduces quality of food.

Role of Predators

Accounts for 60-90% of mortality during peak hare densities. Numerical response—> cyote & lynx pop. increase 6-to-7-fold as hare population increases. Functional response—> lynx kill more hares when hares decrease cyotes kill more hares when hares increase.

How parasites can sometimes alter host behavior

Spihyheaded worms can change behavior of isopods —> more likely to be eaten by verterbrate host.

Rust fungus manipulates growth of host mustard plants. Puccing alters plant growth to promote fungus reproduction. Forms yellow pseudoflower—> visited by pollinators—> completes fungus life cycle.

Refuge

Protection of exploited populations from predators and parasites.

Types: Physical (large size), Flight, Spatial (burrows, trees, env.), Numbers/growing.

Opportunistic

Low juvenile survival, low fecundity, early maturity

Periodic

Low juvenile survival, high fecundity, late maturity

Equilibrium

High investment in offspring, high juvenile survival