Prediction Observation present Dispersal limitation Enemies o Response variable Insufficient resources Sink habitat Habitat where death rates exceed birth rates and organisms are present only because of immigration from Source Habitats where births exceed deaths Intolerable conditions N hot spot o o Relict population Residual population left over from time when environment Sequoia could support its survival and redwoods reproduction which can no longer replace itself locally Subsidies Sinks Relicts Sufficient resource Tolerable conditions absent Definitions absent present o o o o o Grazing hot spot Predictor variable s e g PAR Resource subsidy Resources produced in one habitat that support consumers in a second habitat 1 Autecology behavior and life history traits Spotted owl Barred owl 2 Beach wrack seaweed detritus Ecological Significance of Body Size Environmental heterogeneity refuges hazards stresses opportunities for organisms depend on its body size Size matters Life history tradeoffs Life history bottlenecks Life in moving fluids Steve Vogel small slow organisms subject to viscous adhesive forces large fast organisms subject to gravity and turbulence 3 Homeostasis maintaining an internal state with a narrower and physiologically more favorable range of conditions than the external environment 4 Sheet flow across a stream boulder Insect larvae need food flux oxygen supply fundamental niche and cover from predators realized niche Larger organisms have more metabolic reserves so can maintain homeostasis longer through periods of stress or resource deprivation Surface Volume ratios decrease with size so less heat or water loss thermoregulation osmoregulation maintaining salinity balance easier 5 6 surface 2 0 FreeStream velocity Depth cm 1 0 Boundary layer 0 0 Time dependencies Surface drag 50 100 Velocity cm s 1 7 Body size determines how organisms experience environment Acclimatization acclimation in the lab shifts in the response of an organism to a condition caused by the regime it has experienced in the past E g trees can tolerate lower temperatures in October than they can if surprised in mid summer because they ve induced new types of proteins and restructured cell membrane phospholipids Are organisms limited by the maximum level of a condition or by whether it lasts a certain period of time Crayfish or starfish displaced by short bursts of fast flow but if current increases gradually may hunker down and hold on Saguaro cacti can tolerate freezing if there is a daily thaw but can t take it if freezing temperatures last more than 30 hours 8 Ectotherms rely on external sources of heat to regulate temperature endotherms use their own metabolic heat production to regulate their body temperature male female 120 Lizard Density spring 1997 100 80 Western fence lizards Sceloporus occidentalis 60 40 John Sabo Arizona State Univ 20 Behavioral fevers lizards ectotherms choose warmer microhabitats when they have an infection 9 0 Cobble Bar Upland Meadow 10 Females select large rocks with high heat capacity to keep themselves at optimal temperatures overnight Energy savings may go into egg production Males warm up faster in the morning on sand The early lizard may father the clutch of eggs John Sabo Arizona State Univ 11 Find the hottest and coolest places in this habitat 12 Temperature Time Degree Days Life history definitions Temperature governs rates of development and growth in ectotherms microbes invertebrates plants amphibians reptiles fish Life history organism s lifetime pattern of growth differentiation storage reproduction E g insects emerge from eggs in ground trees flower earlier during warm springs Life cycle sequence of stages through which organism passes to develop from zygote to a reproductive adult producing more zygotes Temperature may serve as a cue for seasonal life cycle events e g emergence of aquatic insects 13 Jellyfish life cycle and ontogenetic niches reproductive polyp Asexual budding Planktonic male medusae medusa ovum Life history definitions cont Propagule individual group or biotic fragment that can potentially begin a new population sperm zygote Benthic feeding polyp branchi ngpolyp forming 14 Benthic planula larva Figure 23 10a 15 from 16 page 363 of your text Unitary vs Modular organisms Unitary organisms develop from zygote to adult with determinant form Modular organisms grow by repeated interations of its parts modules into an adult of indeterminate form coral poison oak Genet genetic individual all the biomass that derived from single embryo Ramet subunit of genet that is physiologically viable as an autonomous fragment 17 Apical tree shrub vs basal grass meristems sites of actively growing tissue 18 unitary Life history Tradeoffs modular Life history trade offs of plants or animals Starting growth early in the season entails risk of freezing If reproductive resources allocated to larger seeds plant makes fewer so incurs more predation risk and risk of bad luck unfavorable microsites Currencies energy nutrients time Allocation growth activity maintenance Reproduction offspring quality offspring quantity Dispersal reduces competition with parent but increases risk of landing in unsuitable habitat Bet hedging by sea rocket half 20 the seed pod floats half sinks 19 Life history tradeoffs cont Allocation to reproduction comes at expense of individual s own growth and possibly survival and vice versa Life history bottlenecks Kestrel survival decreases with brood size If resources are stored rather than spent on offspring parents more likely to survive over periods of starvation e g winter 21 22 Exotic invaders bullfrogs 2 year tadpole stage Bullfrogs threaten native foothills yellow legged frogs whose tadpoles emerge as froglets after their first summer 2nd year bullfrog tadpole 24 Sarah Kupferberg foothills yellow legged frog Mediterranean hydrograph River discharge Q versus time Q May July April May Immobile Susceptible Rana boylii Mobile Resistant 25 North Fork of the Feather flows through a beautiful granite canyon with a series of dams and powerhouses plugging the river In the past all of the water was diverted from one powerhouse to the next leaving dry rocks in between the dams and reservoirs American Whitewater worked hard to secure dam releases to irrigate these rocks Now on select weekends during the summer and fall the dams release enough water for rafters and kayakers to float the river discharge 26 Adult frogs breed in the female s
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