chap. 6 population ecology (ii)

Chap. 6 Population Ecology (II)

鄭先祐 (Ayo)國立台南大學環境與生態學院

2008 年 2 月至 6 月

chap.6 population ecology (II) 2

Population ecology

1. Properties of the population2. Basic concepts of rate3. Intrinsic rate of natural increase4. Concept of carrying capacity5. Population fluctuations and cyclic oscillations6. Density-independent and density-dependent

mechanisms of population regulation


7. Patterns of dispersion8. The Allee principle of aggregation and refuging9. Home range and territoriality10.Metapopulation dynamics11.Energy partitioning and optimization: r- and K-

selection12.Population genetics13.Life history traits and tactics


7 Patterns of DispersionPatterns of dispersion

RandomRegular (uniform)ClumpedRegular clumped

Fig 6-22. four basic patterns of the dispersion of individuals within a population.


Table 6-2

In all but 3 of 11 quadrates, spiders were randomly distributed.


8 The Allee Principle of Aggregation and Refuging

AggregationLocal habitat or landscape differencesDaily and seasonal weather changesReproductive processesSocial attraction

Allee principle of aggregation undercrowding or overcrowding may be

limiting


Fig. 6-23. Illustration of the Allee principle.

(A)Growth and survival is greatest when the population size is small.

(B)In an intermediate-sized population being the most favorable.

In the latter instance, undercrowding is as detrimental as overcrowding.


Refuges a very successful aggregation strategy has bee

n termed refuging.Refuges are site or situations where members of

an exploited population have some favorable central place or core – for example, a starling roost or a large breeding colony of sea birds.

Lek (mating arena) ( 求偶競技場 ) A lek is a gathering of males, of certain animal specie

s, for the purposes of competitive mating display.


Relevant to human

The Allee principle is relevant to the human condition.

Aggregation into cities and urban districts (a refuging strategy) is obviously beneficial

But only up to a point, in connection with the law of diminishing returns.


9 Home Range and Territoriality

Isolation usually is the result of 1. Competition between individuals for resourc

es in short supply2. Direct anagonism, involving behavioral resp

onses in higher animals and chemical isolation mechanisms (antibiotics and allelopathics) in plants, microorganisms, and lower animals.

Home range vs. territory


Fig. 6-25. (A) home ranges of meadow voles (Microtus pennsylvanicus) in fragmented and nonfragmented habitat patches.


Fig. 6-25 (B) Territories of song thrushes (Turdus philomelos) in two consecutive years.

Note that individuals 1,6, and 7 maintained the same territories both years.


Fig. 6-26. Fitness in terms of body weight gained or lost daily of territory-holding spiders compared with individuals unable to establish and hold territories (floaters).


10 Metapopulation Dynamics

Fig. 6-27. Hypothetical metapopulation distribution. Species may periodically disappear from low-quality patches.


11 Energy Partitioning and Optimization: r- and K-Selection

Partitioning or allocation of energy Maintenance, Growth, Reproduction net energy r-selection K-selection


Fig. 6-28. Hypothetical allocation of energy to three major activities necessary for survival in four contrasting situation (A-D) where the relative importance of each activity varies.


Fig. 6-29 Optimization cost-benefit models (A) Balancing use of food sources.

∆S = energy expended in searching for a preferred food item;

∆P = energy expended in pursuing a particular food item

不分好壞食物

找較難找的食物


Fig. 6-29 (B) Balancing use of foraging areas.

∆T = energy expended on traveling between catches;

∆H = energy expended on hunting


Fig. 6-29. Balancing time spent on reproduction and feeding.


Table 6-3


Table 6-4


Fig. 6-31. Reproductive effort plotted against nonreproductive biomass in six populations of four species of goldenrods (Solidago).


12 Population Genetics

Population geneticsNatural selectionEvolution Adaptation

refers to traits of an organism that increase its fitness to survive and reproduce.

Hardy-Weinberg equilibrium law


Hardy-Weinberg equilibrium law

1. Mating is random2. New mutations do not occur3. No gene flow4. No natural selection5. The population size is large


12 Population Genetics

Neutral mutationGenetic driftEffective populationInbreeding

Altruistic behaviorsEusocialityKin selectionInclusive fitness


Fig. 6-35. The Florida scrub jay (Apelocoma coerulescens)


13 Life History Traits and Tactics

four life history traits that are key to survival tactics

1. Brood size2. Size of young (at birth, hatching, or germinat

ion)3. Age distribution of reproductive effort4. Interaction of reproductive effort with adult m

ortality (especially the ratio of juvenile to adult mortality)


Life history theories1. Where adult mortality exceeds juvenile mortalit

y, the species should reproduce only once in a lifetime, where juvenile mortality is higher, the organism should reproduce several times.

2. Brood size should maximize the number of young surviving to maturity averaged over the lifetime of the parent. Ground-nesting birds, clutch size 最大 Nesting in a cavity or other protected place will have

a much smaller clutch size.


3. In expanding populations, selection should minimize age at maturity (r-selected organisms); in stable populations, maturation should be delayed.

4. When there is risk of predation, scarcity of resources, or both, size at birth should be large; conversely, size of young should decrease with increasing availability of resources and decreasing predation or competition pressure.


5. For growing or expanding populations in general, not only is the age of maturity minimized and reproduction concentrated early in life, but also brood size should be increased and a large portion of energy flow partitioned to reproduction – a combination of traits recognizable as an re-selection tactic. For stable populations, K-selection.

6. When resources are not strongly limiting, breeding begins at an early age.

7. Complex life histories enable a species to exploit more than one habitat and niche.


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chap. 6 population ecology (ii)

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