tolerance curves principle of allocation ray huey
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Tolerance Curves
Principle of Allocation
Ray Huey
Tolerance Curves
Principle of Allocation
Ray Huey
Tolerance Curves
Principle of Allocation
Ray Huey
Performance plotted against temperature
Hypothetical response curves showing interactions
Resource Budgets
Principle of Allocation
Time, Matter, and Energy Budgets
Rock Pipits Anthus spinoletta
Mild Winter versus Harsh Winter
Feeding: 6.5 hours vs. 8.25 hours
Resting: 1.75 hours vs. 0.6 hours
Fighting: 0.75 hours vs. 0.1 hour
Leaf Tactics• Light
• Water availability
• Prevailing winds
• Herbivores• Costs and Profits of Leaf Size, Shape, and Placement
Leaf TacticsSimilar types of leaves have evolved independently in different plant
lineages subjected to comparable climatic conditions
Compound leaves conserve woody tissue
Small leaflets in hot dry regions, but larger under warm moist conditions
Shade tolerant understory species usually have larger and less lobed leaves than canopy species
Lobed leaves do not cast as dense and solid a shadow as do leaves with continuous margins
In lowland wet tropical rainforest,trees tend to have large evergreen leaves
In chaparral, plants tend to have small sclerophyllous evergreen leaves
Arid regions tend to support leafless stem succulents such as cacti or plants with entire leaf margins
Cold wet climates tend to support plants with notched or lobed leaf margins
Adaptive Geometry
Evergreen vs. Deciduous
Monolayered vs Multilayered plants
Shade Tolerance
Plant Life Forms
Evergreen vs. Deciduous
Monolayered vs Multilayered plants
Shade Tolerance
Xerophytic vs. Mesophytic leaves
Also Hydrophytes (water lilies)
Gordon Orians Otto Solbrig
Plant Life Forms
Evergreen vs. Deciduous
Monolayered vs Multilayered plants
Shade Tolerance
Xerophytic vs. Mesophytic leaves
Also Hydrophytes (water lilies)
Creosote Bush Larrea divaricata--
Mesquite Prosopis -------
Foraging Tactics and Feeding Efficiency
Costs and Profits of Foraging
An optimal foraging tactic maximizes the difference betweenforaging profits and their costs
Food = matter and energy for maintenance and reproductionHazards: exposure to predators, loss of time for other activities
Sit-and-Wait ambush predators (e.g. spiders at webs)Widely foraging active hunters (go out and find prey)
Search Time (per item eaten) versus Pursuit Time (per item eaten)Search for all possible prey items, but pursue them one at a time
Prey items can be ranked from most preferred to least desirable
Foraging Tactics and Feeding Efficiency
Costs and Profits of Foraging
An optimal foraging tactic maximizes the difference betweenforaging profits and their costs = net benefit
Food = matter and energy for maintenance and reproductionHazards: exposure to predators, loss of time for other activities
Sit-and-Wait ambush predators (e.g. spiders at webs)Widely foraging active hunters (go out and find prey)
Search Time (per item eaten) versus Pursuit Time (per item eaten)Search for all possible prey items, but pursue them one at a time
Prey items can be ranked from most preferred to least desirable
“Economics of Consumer Choice”
Assumptions:
a) Environmental structure is repeatable, with statistical expectation of finding a given resource (habitat, microhabitat, or prey item)
b) Food items can be arranged along a continuous spectrum, such as by size or energy reward
c) Similar phenotypes are closely equivalent in harvesting abilities
d) Principle of Allocation applies: no one phenotype can be maximally efficient on all prey types
e) An individual’s economic “goal” is to maximize its total intake of food resources
Robert MacArthur
“Economics of Consumer Choice”
Four Phases of Foraging:
1) deciding where to search
2) searching for palatable food items
3) upon locating a potential food item, deciding whether or not to pursue it
4) pursuit itself, with possible capture and eating
Search and pursuit efficiencies for each food type in each habitat are entirely determined by preceding assumptions about morphology and environmental repeatability. These efficiencies dictate probabilities associated with search and pursuit (phases 2 and 4) . Thus, need to consider only the two decisions: where to forage and which prey items to pursue (phases 1 and 3 above)
Robert MacArthur
“Economics of Consumer Choice” (R. H. MacArthur)
Clearly, an optimal consumer should forage where its expectationof yield is greatest — an easy decision to make, given knowledge of efficiency probabilities and the structure of the environment (of course, in reality, animals are not omniscient and must make decisions based on incomplete information).
The decision as to which prey items to pursue is also simple. Upon finding a potential prey item, a consumer has just two options: either pursue it or go on searching for a better item and pursue that one instead. Both decisions end in the forager beginning a new search, so the best choice is clearly the one that returns the greatest yield per unit time.
An optimal consumer should opt to pursue an item only when it cannot expect to locate, catch and eat a better item during the time required to capture and ingest the first prey item.
From Huey and Pianka (1981)
C. S. Holling
400 Frames per second (3/100ths of a second)
Thomas FrazzettaTom Frazzetta
Physiological Ecology
Homeostasis: maintenance of a relatively stable internal state under a much wider range of external environmental conditions
Temperature regulation (thermoregulation)
Physiological Optima and Tolerance Curves
Acclimation
Physiological Ecology
Homeostasis: maintenance of a relatively stable internal state under a much wider range of external environmental conditions
Temperature regulation (thermoregulation)
Physiological Optima and Tolerance Curves
Acclimation
Energetics of Metabolism and Movement
Ingestion = Assimilation + Egestion
Assimilation = Productivity + Respiration
Productivity = Growth + Reproduction
Ingestion = Egestion + {Respiration + Growth + Reproduction}
{Assimilation}
------------------------------------------------Homeotherm versus Poikilotherm
Ectotherm versus Endotherm
Body Mass, grams
