Experiments 2

Lack

Lack

pattern reflected an underlying evolutionary mechanism

longer days enable parents to hunt more which will support larger clutches

environmental variability was the driving force

maximizes fitness in its local environment

LIDET experiment

• 27 locations, each major biome, 6 leaf litter bags and 3 root litter bags

• Aboveground and belowground litter decompose at different rates

• Composite index works because it accounts for water stress and temperature variation

winemiller and rose

classified fish based on juvenile survivorship, fecundity, and age at maturity

opportunistic, equilibrium, periodic

Oxygen container experiment

High oxygen container decomposed better and produced more Co2

Low oxygen container produced more methane

Woolly adelgid

central Appalachia

attacks hemlocks, the needle stalk that connects to the branch, drinks fluid from it

David Lack

• Hypothesized that the optimal clutch size reflects the maximum number of young the parents can rear, limited by the amount of food they can collect

• Birds nesting in higher latitudes lay more eggs because longer summer days allow parents to spend more time foraging, can feed larger clutches

Cor Dijkstra - common kestrel

• Investigating the evolution of clutch size in common kestrels

• Clutch-size manipulation test to study the prediction that the clutch size maximizes their reproductive output

• Found that kestrels law fewer eggs than they can successfully fledge

• Parental cost hypothesis

• Verified that parents deliver more food to enlarged clutches

• Female parents of enlarged clutches lose more weight than those of reduced clutches

• The survival of parents with enlarged clutches is lower than that of parents with naturally or experimentally reduced clutches.

Parental cost hypothesis - kestrels

A smaller clutch increases the likelihood parents will survive to reproduce in the future, thus increasing their total fitness

Predation risk hypothesis - tropical songbirds

A smaller clutch reduces both parental foraging effort and noise created by hungry nestlings, which lowers the risk that predators discover the nest

barnacles and dolphins

similar growth rates but different age structure classification

barnacle population was younger individuals

more barnacles die young, more dolphins survive to old age

Colombian ground squirrels

rough life

most die in their first year

Variable food supply hypothesis - bald eagles

A smaller clutch increases the likelihood that parents successfully rear chicks in years when food in scarce

Red colobus monkeys - Fourrier

• Examined the demographics of the monkey inside and out of the chimps’ hunting range

• Young monkeys are the most susceptible to chimp attacks

• Does the predation pattern threaten the long-term viability of hunted monkeys

  • yes

• Will elevated fecundity enable hunted populations to persist even when predation rates are high

  • Nope

• Immigration of surrounding monkeys may be able to stabilize the population IF there are wildlife corridors implemented

SimSturegon

A heritable life-history trait will evolve by natural selection when some variants confer greater fitness than others

Sturgeon

• Fecundity of real sturgeon is related to body mass

• Sturgeon spawn at 18-27

• Habitats lack large predators, immune to predation as adults

• More fecund when they reach sexual maturity but also less likely to be killed

Schaffer x2

• Understand iteroparity and semelparity differences between yucca and agave

• Hypothesis: reproductive strategies reflect differences in how these plants are pollinated

Agave - iteroparity

• Agave are pollinated by a wide variety of pollinators

• Agave with taller stalkers were more successful and had higher fitness

• Little benefit for them to conserve resources for future reproductive efforts

• Shallow roots

Yucca - semelparity

• Yucca are pollinated by the yucca moth

• Attracting too many moths decreases fitness

• Make smaller stalks during repeated bouts of reproduction 

• Long taproots

Grime’s Plant classification system

arrayed species according to how they responded to stress and sitrubance

ruderal, stress-tolerant, and competitive

Stress looks different depending on the habitat

Three archetypal plant life-history strategies

Common waterhemp

geometric

• Taking over soybean fields

• Reduces the amount of soybeans for harvest

Soybean aphid

exopnential

• Native to china

• Well established in the pacific

• Feed on sap, cause loss of up to 50% of crop

• Parthenogenetic reproduction

Paramecium yeast experiment

Replaced yeast at a constant rate but the paramecium eventually stopped growing because they were eating as fast as it was being replaced

Tiger salamanders

• In danger of going extinct

• Higher death rate than birth rate

• The population is not decreasing because there are multiple populations near each other

• Salmandars frequently disperse to breed

Livins realized that metapopulation dynamics

amongst subpopulations are analogous to logistic growth for individuals within a single population