1Predictor variable(s): e.g., PARResponse variableooooooooN hot spot?Grazing hot spot?Prediction*ObservationpresentabsentpresentabsentSufficient resourceTolerable conditionsDispersallimitation?Enemies?SubsidiesSinksRelicts?InsufficientresourcesIntolerableconditions2Definitions:Relict population: Residual populationleft over from time when environmentcould support its survival andreproduction, which can no longerreplace itself locallySink habitat: Habitat where deathrates exceed birth rates, and organismsare present only because of immigrationfrom Source Habitats (where birthsexceed deaths)Resource subsidy: Resources producedin one habitat that support consumers ina second habitat.Beach wrack (seaweed detritus)Spotted owl(Barred owl)Sequoiaredwoods3Autecology, behavior, andlife history traits•Size matters•Life history tradeoffs•Life history bottlenecks4Ecological Significance ofBody SizeEnvironmental heterogeneity--refuges, hazards,stresses, opportunities for organisms depend on its bodysizeLife in moving fluids (Steve Vogel)--small, slow organismssubject to viscous, adhesive forces, large, fastorganisms subject to gravity and turbulenceHomeostasis: maintaining an internal state with anarrower (and physiologically more favorable) range ofconditions than the external environment5Larger organisms have more metabolicreserves so can maintain homeostasislonger through periods of stress orresource deprivationSurface:Volume ratios decrease with size,so less heat or water loss,thermoregulation, osmoregulation(maintaining salinity balance) easier6Sheet flow across a stream boulderInsect larvae need food flux, oxygensupply (fundamental niche) and coverfrom predators (realized niche)7Velocity (cm s-1)Depth(cm)Boundary layerFree-StreamvelocitySurface dragsurface01.02.0050 100Body size determines how organisms experience environment8Time dependencies• Acclimatization (“acclimation in the lab): shifts in theresponse of an organism to a condition caused by theregime it has experienced in the past.– E.g. trees can tolerate lower temperatures inOctober than they can if surprised in mid-summer,because they’ve induced new types of proteins andrestructured cell membrane phospholipids.• Are organisms limited by the maximum level of acondition, or by whether it lasts a certain period oftime?– Crayfish or starfish displaced by short bursts offast flow, but if current increases gradually, mayhunker down and hold on– Saguaro cacti can tolerate freezing if there is adaily thaw, but can’t take it if freezingtemperatures last more than 30 hours.9Western fence lizardsSceloporus occidentalisBehavioral fevers: lizards (ectotherms) choose warmermicrohabitats when they have an infectionfemalemale*Ectotherms rely on external sources of heat to regulatetemperature; endotherms use their own metabolic heatproduction to regulate their body temperature.10020406080100120Lizard Density (spring 1997)Cobble Bar Upland MeadowJohn Sabo, Arizona State Univ.11Females select large rocks with highheat capacity, to keep themselves atoptimal temperatures overnight.(Energy savings may go into eggproduction.)Males warm up faster inthe morning on sand.The early lizard mayfather the clutch (ofeggs)! John Sabo,Arizona State Univ.12Find the hottest and coolestplaces in this habitat…13Temperature-Time “Degree Days”• Temperature governs rates ofdevelopment and growth inectotherms (microbes,invertebrates, plants, amphibians,reptiles, fish)– E.g. insects emerge from eggs inground, trees flower earlier duringwarm springs…• Temperature may serve as a cuefor seasonal life cycle events (e.g.emergence of aquatic insects).14Life history definitions• Life history: organism’s lifetime pattern ofgrowth, differentiation, storage,reproduction• Life cycle: sequence of stages through whichorganism passes to develop from zygote to areproductive adult producing more zygotes15reproductive polypAsexual buddingmale medusaspermzygoteovumpolypformingbranchingBenthicfeedingpolypJellyfish life cycle and ontogenetic nichesFigure 23.10a frompage 363 of yourtextPlanktonic medusaeBenthic planula larva16Life historydefinitions, cont.Propagule: individual,group, or bioticfragment that canpotentially begin anew population.17Unitary vs Modular organisms• Unitary organismsdevelop from zygote toadult with determinantform• Modular organisms growby repeated interationsof its parts (modules)into an adult ofindeterminate form(coral, poison oak)– Genet: genetic individual,all the biomass thatderived from single embryo– Ramet: subunit of genetthat is physiologicallyviable as an autonomousfragment18Apical (tree, shrub) vs basal(grass) meristems (sites ofactively growing tissue)19Currencies: energy, nutrients, timegrowth maintenanceactivityReproduction:offspring qualityoffspring quantityAllocation?unitarymodularLife history Tradeoffs20Life history trade offs of plants oranimals• Starting growth early in theseason entails risk of freezing• If reproductive resourcesallocated to larger seeds, plantmakes fewer, so incurs morepredation risk, and risk of badluck (unfavorable microsites)• Dispersal: reduces competitionwith parent, but increases risk oflanding in unsuitable habitat.Bet hedging by sea rocket—half theseed pod floats, half sinks21Life history tradeoffs, cont.• Allocation to reproductioncomes at expense ofindividual’s own growth,and possibly survival (andvice versa)• If resources are storedrather than spent onoffspring, parents morelikely to survive overperiods of starvation (e.g.winter)Kestrel survivaldecreases withbrood size22Life history bottlenecks24Bullfrogs threaten nativefoothills yellow leggedfrogs, whose tadpolesemerge as froglets aftertheir first summer.Exotic invaders--bullfrogs--2 yeartadpole stage2nd year bullfrog tadpole25Sarah Kupferberg foothills yellow legged frogRana boylii26Immobile / Susceptible Mobile / ResistantQApril-MayMay-JulyMediterranean hydrograph: River discharge (Q) versus time27“North Fork of the Feather flows through a beautiful granite canyon … with aseries of dams and powerhouses plugging the river. In the past all of the waterwas diverted from one powerhouse to the next leaving dry rocks in between thedams and reservoirs. American Whitewater worked hard to secure dam releasesto irrigate these rocks. Now on select weekends during the summer and fall, thedams release enough water for rafters and kayakers to float the river.”Immobile /
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