Competing for resource

Ch

1

2

Evolutionaryily Stable Strategy(ESS) 演化穩定策略

A strategy that was adopted by all members of a population,

cannot be bettered by alternative strategy.

(Smith & Price, 1973)

ESS

3

The Hawk-Dove game

Each strategy does best when it is relatively rare.

4

The stable mixture

h = the proportion of Hawks in population

H average= -25h + 50 (1-h)

D average= 0 h + 25 (1-h)

h = 1/2

V<C

In V<C V/C (the stable proportion of Hawks)

If V>C, then Hawk is an ESS!

Competition by exploitation : the ideal free distribution

The ideal free model 理想自由模型 (Fretwell, 1972)

當資源豐富的棲地在有a個競

爭者的情況下，個體報酬會趨

近於競爭者較少的低資源棲地。

Fig. 5.1 The ideal free distribution. 5

Which line will you choose?

6

Competing for food: sticklebacks and ducks

Competition by exploitation : the ideal free distribution

7

Competing for food: sticklebacks (Milinski, 1979)

8

(Milinski, 1979)

9

B=2A A=2B

理想值

實驗平均值

Competing for food: Ducks (Harper, 1982)

10

N=33

Numerical prediction 數值預測

Equal intake prediction 等量攝取預測

Prey risk prediction 獵物風險預測

Fish and Ducks settle in a stable distribution between feeding patches.

11

Competing for mates: dung flies

What is the optimum time to spend waiting for females at each cowpat?

12

(Parker, 1970)Males adopt evolutionarily stable waiting times.13

Fig. 5.3

牛糞上的雄糞蠅數量會

隨著時間的增加而減少

在不同的等待時間，

雄糞蠅的交配成功率皆一致

Competition by resource defence : the despotic distribution 專橫的分佈

14

Fig. 5.4

(Brown, 1969)

The ideal free distribution with unequal competitors

The Competitive unit model

Hypothesis:

the number of competitive units ,

rather than the number of

individual, is equalized across

patches.

15

(Parker & Sutherland, 1986)

2:1

8:4

8:4

Fig. 5.5

Habitat Selection

in Gill aphid (Whitham, 1978)

16

窄葉楊

每片葉子上的雌蚜蟲數

每隻

雌蚜

蟲的

子代

數

葉片面積

繁殖成功率在不同數量

的競爭者皆無顯著差異

Fig. 5.6

Average success is equal on leaves of different quality,

but individuals near the leaf base do better.

Leaf is not a

homogeneous habitat.

17

The economics of resource defence

Economic defendability 經濟的可防禦性 (Brown, 1964)

18Fig. 5.7

The Economics of territory defence in the

Golden-Winged sunbird

Box 5.1

(Gill & Wolf, 1975)

Forage time

Net energy saving

of defending

Extra cost of defence

19

Metabolic costs

The economics of resource defence

Shared resource defence 資源的共同防禦

With satellite20

With satellite

NO satellite

Fig. 5.8

Producers and scroungers 生產者與投機者

21

Fig. 5.9

Make the best of a bad job.

22

The variable foraging techniques

of ruddy turnstone

Routingexpose prey

Stone

turning

Digging

Probing

Surface

pecking

Hammering

barnacles

(Whitfield, 1990)

23

Dominant Subordinate

Routingexpose prey

Steal

Routing

24

Variation could also be maintained in a

population even if there was no difference in

competitive ability between individuals.

25

(Mottley & Giraldeau, 2000)The stable equilibrium frequency

of producers and scroungers

Covered Uncovered

pridected

stable

equilibrium

26

Alternative mating strategies and tactics 替代的交配策略與戰術

Strategy

Tactic

A genetically based decision rule, so differences between

strategies are due to differences in gene.

A behaviour pattern played as part of a strategy.

27

Natterjack toads:

callers & satellites

Conditional strategies with alternative tactics

(Arak, 1983)

兩倍

callers

satellites

Fig. 5.11

28

Satellite males make adaptive choice concerning

which callers to parasitize.

Fig. 5.12

29

Morphological switches with body size:

dung beetles and earwigs

Fig. 13

30

Fig. 5.14

31

The threshold morphological switch between alternative within a

conditional strategy. (Gross, 1996)

(Hunt & Smon, 2001)

閾值

Fig. 5.15

32

(Emlen, 1996)

Use selection experiment shows : Threshold has a genetic basis

Fig. 5.16

33

(Tomkins & Brown, 2004)

How selection has shifted a threshold switch in morphology

forceps

Knoxes Reef

Bass Rock

K

B

B

K

(北海上22個島上的結果)

Forcept變長能保護越多雌性

34

Alternative strategies: equilibria and cycles 平衡與循環

參考fig.5.9 (b)

Proportion of scroungers

Fitn

ess

35

Ruffs:

fighters, satellites and female mimics

36

A marine isopod with three male morphs

alpha beta gamma

Each male morph gains equal success.

37

Side-blotched lizards:

cycles of orange, blue and yellow

38

Thanks for your Listening