Reproduction and NichesReproduction and Niches

ES 100ES 100August 20, 2007August 20, 2007

OpportunistsOpportunists vs.vs. CompetitorsCompetitors

• Do well in variable climate or with disturbance

• Population boom and bust cycles

• Rapid development• Early reproduction• Small body size• Single reproductive

effort

• Do well in stable climate

• Population carrying capacity

• Slow development• Late reproduction• Large body size• Repeated

reproduction

Practical Aspects of r vs. KPractical Aspects of r vs. K

Robin Eagle

Why different life strategies?Why different life strategies?

• More ways to live in an environment and More ways to live in an environment and use its resources.use its resources.

• Another way to say this: filling Another way to say this: filling nichesniches• Fundamental vs. Realized nicheFundamental vs. Realized niche• Principle of competitive exclusionPrinciple of competitive exclusion

What is a What is a nicheniche??

• A A nicheniche is the total of all biotic and abiotic is the total of all biotic and abiotic factors that determine how an organism factors that determine how an organism fits into its environment.fits into its environment.

• Where and how does an organism live and Where and how does an organism live and function?function?• habitathabitat• role in communityrole in community

Fundamental vs. Realized nicheFundamental vs. Realized niche

All possible environmental (biotic and abiotic) conditions in which an organism can live.

Fundamental niche:

The actual environmental conditions in which an organism lives.Realized niche:

Environmental variable (Temperature, for example)

Succ

ess

optimum

potential survival,

but stressed

potential survival,

but stressed

intolerant intolerant

Niche in n-variable hyperspaceNiche in n-variable hyperspace

Fundamental vs. Realized NicheFundamental vs. Realized Niche

Fundamental niche: where a Fundamental niche: where a species species couldcould live live

Realized niche: with competition Realized niche: with competition from other species, where a from other species, where a species species doesdoes live live

Principle of Competitive Principle of Competitive ExclusionExclusion

Two species can’t occupy the same niche… one would out-compete other and drive it to extinction

Niche Partitioning in AnimalsNiche Partitioning in AnimalsSpecies divide up an apparent nicheSpecies divide up an apparent niche

Selection minimizes Selection minimizes competitioncompetition

Two species living Two species living separately.separately.

In a guild, natural In a guild, natural selection minimizes selection minimizes competitioncompetition

Disease prevention via C.E.Disease prevention via C.E.

Convergent EvolutionConvergent Evolution•Organisms adapt to fill open niches

•Niches that are separated by geographic barriers may be filled by different species (1 species, 1 niche, 1 location)

•Unrelated species who fill a similar niche and display similar form or function exemplify convergent evolution

Summary of TodaySummary of Today Life History: Reproductive StrategiesLife History: Reproductive Strategies

opportunists vs. competitorsopportunists vs. competitors Insight into ecosystem managementInsight into ecosystem management

Life tablesLife tables Insights into population dynamicsInsights into population dynamics

Vulnerable age stagesVulnerable age stages FitnessFitness Generation timeGeneration time Population trajectoriesPopulation trajectories

NichesNiches Fundamental vs. realized nicheFundamental vs. realized niche Competitive exclusion principleCompetitive exclusion principle Convergent evolutionConvergent evolution