EcologyEcology

Lecture 8Lecture 8

Ralph KirbyRalph Kirby

Life History PatternsLife History Patterns

GrowthGrowthDevelopmentDevelopmentReproductionReproduction

Their interaction with other organisms Their interaction with other organisms gives rise to the organisms fitnessgives rise to the organisms fitnessOne of the most important aspects of One of the most important aspects of fitness revolves around the type of fitness revolves around the type of reproduction stragegyreproduction stragegy

Sexual or Asexual ReproductionSexual or Asexual Reproduction

Asexual reproductionAsexual reproduction– RapidRapid– If fitness is high, matches organism to environmentIf fitness is high, matches organism to environment– If fitness is low, possible extinctionIf fitness is low, possible extinction– Stress can result in use of sexual cycle to give new gene Stress can result in use of sexual cycle to give new gene

combinationscombinations

Sexual ReproductionSexual Reproduction– Greater energy commitmentGreater energy commitment

Specific organellesSpecific organellesMating ritualsMating ritualsFeeding offspringFeeding offspring

– Cost not equal between sexesCost not equal between sexes– Can produce new gene combinations able to cope with a Can produce new gene combinations able to cope with a

changing environmentchanging environment– Greater loss due to selection against divergent genotypes in a Greater loss due to selection against divergent genotypes in a

static environmentstatic environment

Types of sexual Types of sexual reproductionreproduction

DioeciousDioecious– Most familiarMost familiar

Sexes are separate individualsSexes are separate individuals– Greatest diversity of offspringGreatest diversity of offspring

HermaphroditicHermaphroditic– PerfectPerfect

Male and females organs in Male and females organs in same flowersame flower

– Can result in significant Can result in significant inbreedinginbreeding

– MonoeciousMonoeciousSeparate male and female Separate male and female flowersflowers

– Reduces but does not Reduces but does not eliminate inbreedingeliminate inbreeding

– Simultaneous hermaphroditicSimultaneous hermaphroditicBoth sets of organs at same Both sets of organs at same timetime

– EarthwormsEarthworms– Outbreeding, but maximizes Outbreeding, but maximizes

offspringoffspring

– Sequential hermaphroditicSequential hermaphroditicFirst one sex then the other First one sex then the other sexsex

– Mollusks, echinoderms and Mollusks, echinoderms and some plants. Sometimes some plants. Sometimes animalsanimals

– Allows all individual to Allows all individual to participate in both sides of participate in both sides of sexual cyclesexual cycle

Mating StrategiesMating StrategiesDifferent mating stategies have different advantages Different mating stategies have different advantages and disadvantagesand disadvantages– MonogamyMonogamy

Seasonal or permanentSeasonal or permanent– Allows sharing of cost of raising offspringAllows sharing of cost of raising offspring– Increases survival chances of offspringIncreases survival chances of offspring– Many bird species and some mammalian speciesMany bird species and some mammalian species– Cheating does occur and has specific advantages to fitnessCheating does occur and has specific advantages to fitness

– PolygamyPolygamyMore than one mate of one sex for a single individual of the other sexMore than one mate of one sex for a single individual of the other sex

– Free individual to compete for resources and protect territoryFree individual to compete for resources and protect territory– Better food etc for matesBetter food etc for mates– Some protection of offspring from competitionSome protection of offspring from competition

– PromiscuityPromiscuityGreatest number of offspringGreatest number of offspringLarge amount of competitionLarge amount of competitionFemale only responsible for offspring in terms of resourcesFemale only responsible for offspring in terms of resources

– Poorer survival change for offspringPoorer survival change for offspring

Sexual SelectionSexual SelectionFor Monogamy, Polygamy and For Monogamy, Polygamy and PromiscuityPromiscuity– All involves the selection of a mate and All involves the selection of a mate and

therefore sexual based selectiontherefore sexual based selection– Results in sexual dimorphismResults in sexual dimorphism– Selection for secondary sexual characteristicsSelection for secondary sexual characteristics

Peacock versus PeahenPeacock versus Peahen– Large tail feathers, more matingLarge tail feathers, more mating– Smaller tail feathers, less matingSmaller tail feathers, less mating

DeerDeer– Characters that aid competition such as hornsCharacters that aid competition such as horns

HumansHumans– Faster sports car such as a FerrariFaster sports car such as a Ferrari

What is the mate really looking for What is the mate really looking for in sexual selectionin sexual selection

Sports carSports car– Is this just a displayIs this just a display

Big red car that makes a lot of noiseBig red car that makes a lot of noise

– Or does it measure resourcesOr does it measure resourcesFerraris are expensiveFerraris are expensive

In most cases the sexually selected In most cases the sexually selected characteristic is an indirect measure of characteristic is an indirect measure of resources or fitnessresources or fitness– Bigger males have captured more resoucesBigger males have captured more resouces

InbreedingInbreedingIf a population is small then inbreeding occursIf a population is small then inbreeding occurs– Self-fertilizationSelf-fertilization

Reassortment of genes but no new genesReassortment of genes but no new genes

– A population in terms of genetics always has some A population in terms of genetics always has some degree of inbreedingdegree of inbreeding

Proportional to size of populationProportional to size of populationSmall population – Large inbreeding indexSmall population – Large inbreeding indexInbreeding depressionInbreeding depression

– Rare recessive alleles become homozygous and are deleteriousRare recessive alleles become homozygous and are deleterious

– Only when outbreeding between populations occurs Only when outbreeding between populations occurs is this avoidedis this avoided

More new gene combinationsMore new gene combinationsOutbreeding depressionOutbreeding depression

– Maladaption to environment such as by colourMaladaption to environment such as by colour

Reproductive EffortReproductive Effort

Reproductive females invest less energy in Reproductive females invest less energy in growth, etcgrowth, etcIteroparousityIteroparousity– Multiple cycles of reproduction means the organism Multiple cycles of reproduction means the organism

must balance growth, maintenance, escaping must balance growth, maintenance, escaping predators, defending territory, etc against predators, defending territory, etc against reproductionreproduction

When – early or lateWhen – early or lateHow many offspringHow many offspring

SemelaritySemelarity– One reproductive effort with all resources, then deathOne reproductive effort with all resources, then death– No balance necessaryNo balance necessary– Environmental effect can be disastrousEnvironmental effect can be disastrous

Number of Number of offspringoffspring

Produce helpless offspringProduce helpless offspring– AltricialAltricial– MiceMice

Longer period sucklingLonger period suckling– RobinRobin

Other bird feedsOther bird feeds

Produce more mature offspringProduce more mature offspring– BeesBees

Colonial careColonial care– FoxesFoxes

Mating pair careMating pair care– HumansHumans

Family careFamily careGrandmothers, Grandfathers, Aunts, Grandmothers, Grandfathers, Aunts, Uncles, Brothers and SistersUncles, Brothers and Sisters

Large NumberLarge Number– Less resources per individualLess resources per individual– More chances of successMore chances of success

Extreme with released eggs and sperm in Extreme with released eggs and sperm in fish, etcfish, etc

Few NumberFew Number– More resources per individualMore resources per individual– More chance of accidental lossMore chance of accidental loss

Extreme with single offspring over long Extreme with single offspring over long period like humans and elephantsperiod like humans and elephants

RuderalSmall and rapid lifecycle to invade

new sites. Large dispersal areaCompetitive

Stable environment, slower lifecycleWith more resources to growthStress-tolerant

Limited resources. Ability to adapt

Food supply is important to Food supply is important to reproductive successreproductive success

Birds in temperate Birds in temperate regions have a regions have a larger clutch size larger clutch size than tropical birdsthan tropical birdsAnimals in Animals in temperate regions temperate regions have a larger litter have a larger litter size than those in size than those in tropicstropics– Food supply with Food supply with

longer day length?longer day length?– Adaption to large Adaption to large

climate variation to climate variation to allow rapid allow rapid regrowth after a regrowth after a poor seasonpoor season

– Greater mortality in Greater mortality in winter results in winter results in more food next more food next springspring

Habitat SelectionHabitat Selection

Filling the available niches Filling the available niches and keeping out and keeping out competitorscompetitors

Exception humansException humans– All habitatsAll habitats– Left Africa and adapted the Left Africa and adapted the

environment rather than environment rather than adapted to the environmentadapted to the environment

Communities, Guilds and Communities, Guilds and CompetitionCompetition

Organisms in a given Organisms in a given area make up a area make up a communitycommunity– SpatialSpatial– May be subset of whole May be subset of whole

community with some community with some linking characteristicslinking characteristics

Organisms competing Organisms competing for the same resource for the same resource make up a guildmake up a guildIn both cases, the effects In both cases, the effects can be positive, negative can be positive, negative or neutralor neutral

Species numbers in Species numbers in a community can a community can vary from very vary from very abundant and abundant and dominant to rare by dominant to rare by essential to the essential to the communitycommunitySpecies diversitySpecies diversity– Species richnessSpecies richness

How many speciesHow many species– Species evennessSpecies evenness

How many How many individualsindividuals

DominantsDominants– Big trees in a forestBig trees in a forest– Removal changes Removal changes

the character of the the character of the systemsystem

KeystoneKeystone– PredatorsPredators– Removal changes Removal changes

limits of the systemlimits of the system

– Food WebFood WebHow How resources resources move about move about in terms of in terms of predation, predation, competition, competition, parasitism, parasitism, mutualism, mutualism, etcetc

Really much Really much more more complexcomplex

Communities have a defined physical Communities have a defined physical structure than is relatively stablestructure than is relatively stable

Vertical as well as hroizontal Vertical as well as hroizontal structurestructure

One community can have more One community can have more than one zonethan one zone

Defining the edges Defining the edges of communities can of communities can be both complex be both complex and difficultand difficultStatisticalStatisticalScale dependentScale dependentChanges with time Changes with time over the yearover the yearChanges with time Changes with time over longer periodsover longer periods– PrimaryPrimary

New environmentNew environment– Volcanic islandVolcanic island

– SecondarySecondaryAfter disturbanceAfter disturbance

– HumanHuman– None humanNone human

YearYear

Longer periodLonger period

Succession works for the whole Succession works for the whole systemsystem

Over even Over even longer periods longer periods with climate with climate changeschanges

Ice AgesIce Ages– Expansion Expansion

and and contraction of contraction of species in species in communitiescommunities

How environment How environment can affect can affect communitiescommunities

Does clustering Does clustering exist?exist?– Sub-groupingsSub-groupings

AssociationsAssociations

EcotonesEcotones

Or is there a Or is there a continuum?continuum?– No sub-groupingsNo sub-groupings

Probably bothProbably both