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Competing for Resources

Competing for Resources. Speaker: Yu-ju Chen 2009/10/2. Contents. The ideal free distribution Resource defence: 1.The despotic distribution 2.Unequal competitors 3.The economics of resource defence 4.Shared resource defence 5.Interspecific territoriality Discussion.

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Competing for Resources

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  1. Competing for Resources Speaker: Yu-ju Chen 2009/10/2

  2. Contents • The ideal freedistribution • Resource defence: 1.The despotic distribution 2.Unequal competitors 3.The economics of resource defence 4.Shared resource defence 5.Interspecific territoriality • Discussion

  3. The ideal freedistribution

  4. Rich habitat Poor habitat The ideal freedistribution(Fretwell,1972) Fig. 5.1 At point “a”， the poor habitat will be equally attractive. e.g “Supermarket” Rewards per individual a Number of competitors

  5. Example of the sticklebacks(Milinski,1979) Fig. 5.2 The point x to the point y End B of the tank had twice the amount of as end A.

  6. Example of the sticklebacks Competitor numbers adjusting All individuals visiting both habitats

  7. Resource defence

  8. 1.The despotic distribution

  9. Number gaining access to resource Rich habitat Poor habitat a b Number of competitors The despotic distribution(Brown,1969) Fig. 5.3 The point a and the point b habitat become full

  10. 2.Unequal competitors

  11. Competitive unit With unequal competitor If one individual can consume resources twice as rapidly as another it score twice the number of competitive unit.

  12. 90 225 20 The difficulty Fig. 5.4 (c) has the same numerical pattern as (e).

  13. Example of the aphids(Whitham,1980) Fig. 5.5 Number of stem mother per leaf

  14. Example of the aphids Larger leaves correspond to better habitats Three conclusions: 1.The average reproductive success increases with habitat quality. 2.Within a habitat of certain quality, reproductive success decreases as the number of competitors increases. 3.”Alone on a leaf” or “share”?

  15. 3.The economics of resource defence

  16. Economic defendability(Brown,1964) The defence of a resource has costs as well as the benefits of priority.

  17. The golden-winged sunbird(Gill & Wolf,1964) The nectar level from 2μl to 3μl: 1.(1000x1.3)froaging – (400x1.3)resting =780cal(save) 2.(3000x0.28) defence – (400x0.28) no resting=728cal(cost) 780cal-728cal=52cal>0

  18. Optimal territory size(Carpenter et al,1983) Fig. 5.7 A rufous hummingbird’s weight change

  19. Graphical models(Schoener,1983)

  20. 4.Shared resource defence

  21. Example of the wagtails(Davies & Houston,1981) Fig. 5.9 Solid dots shared territories; open dots not shared Asymptotic level of food Renewal rate of food http://commons.wikimedia.org/wiki/File:Motacilla_alba_alba_cropped.JPG

  22. 5.Interspecific territoriality

  23. Chaffinches v.s great tits(Reed,1981) • Playback experiment • Removal experiment Chaffinch Great tit http://www.advrider.com/forums/showthread.php?t=496004 http://www.pbase.com/u14/tirc/upload/41790348.IMG_0016.jpg

  24. Discussion • Do animal ever defend more resources than they need? • How can the effects of predation differences between patches be incorporate into the ideal free distribution? • How would you apply the idea of economic defendability to resources other than food?

  25. The End Pictures from: http://books.google.com.tw/books?id=CA31asx7zq4C&printsec=frontcover&source=gbs_navlinks_s#v=onepage&q=&f=false

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