Competition. Interspecific Competition. Competition. Intraspecific. Interspecific Between individuals of different species. Which one is stronger?

Transcription

1 Intraspecific etween individuals of the same species Interspecific etween individuals of different species Which one is stronger? Interspecific dn 1 rn α N = dt K1 dn 2 rn α21 N = dt K2 Lotka-Voltera Interspecific competiton onvert individuals of species 1 into species 2 equivalents. -α 12 mount of spp.1 s niche overlapped by spp 2 s niche - α 21 mount of spp.2 s niche overlapped by spp 1 s niche 1

2 What happens to species 1 in the presence of species 2? d /dt =0 What happens to species 1 in the presence of species 2? d /dt =0 What happens to species 2 in the presence of species 1? d /dt =0 /α 21 2

3 What happens to species 2 in the presence of species 1? d /dt =0 /α 21 d /dt =0 d /dt =0 /α 21 Species 2 wins /α 21 3

4 K2 Species 2 wins /α 21 /α 21 Species 1 wins /α 21 Unknown who wins ut somebody loses /α 21 Unknown who wins ut somebody loses oth species win oexistence /α 21 4

5 What are the requirements for coexistence? > > α 12 > /α 21 > α 21 Translation? /α 21 What are the requirements K PH /α PH,MD for coexistence? > > α 12 > /α 21 K MD > α 21 N MD Translation? Species coexistence occurs when each species limits its own population growth more than its growth is limited by the other species Interspecific > Intraspecific? Interspecific < Intraspecific? K PH K MD /α MD,PH Example Yellowstone ungulates K PH > α PH,MD K MD K MD > α MD,PH K PH N Pronghorn ntelope Mule Deer Time 5

6 Example Yellowstone ungulates K PH > α PH,MD K MD K MD > α MD,PH K PH N Pronghorn ntelope Mule Deer K PH = 2000 K MD = 1200 Time Example Pronghorn ntelope Yellowstone ungulates 2000 K PH > α PH,MD K MD N Mule Deer K MD > α MD,PH K PH 1000 K PH = 2000 K MD = 1200 Time Resource Use / day g Grass g Forbs g Shrubs PH MD Example Pronghorn ntelope Yellowstone ungulates 2000 K PH > α PH,MD K MD N Mule Deer K MD > α MD,PH K PH 1000 K PH = 2000 onvert pronghorn into mule deer α MD,PH : niche overlap = 35/220 =16% onvert mule deer into pronghorn α PH,MD : niche overlap = 35/95 =37% Time K MD = 1200 Resource Use / day g Grass g Forbs g Shrubs PH MD

7 Example Yellowstone ungulates K PH > α PH,MD K MD 2000 > 0.37* > 444 K MD > α MD,PH K PH 1200 > 0.16* > 320 onvert pronghorn into mule deer α MD,PH : niche overlap = 35/220 =16% onvert mule deer into pronghorn α PH,MD : niche overlap = 35/95 =37% N Time Pronghorn ntelope Mule Deer K PH = 2000 K MD = 1200 Resource Use / day g Grass g Forbs g Shrubs PH MD Tillman competition Resource based Graph of the amount of resources a species needs in order to survive mt. of Sp.1 survives but R 0 =1 ZNGI 1 Sp.1 survives and reproduces Sp.1 does not survive mount of resource X Tillman competition Resource based Graph of the amount of resources a species needs in order to survive for both species an both species survive? ZNGI 1 mt. of Sp.2 survives but R 0 =1 ZNGI 2 Sp.2 survives and reproduces mount of resource X 7

8 Tillman competition Resource based Graph of the amount of resources a species needs in order to survive for both species If resources fall anywhere in area Neither species survives ZNGI 1 mt. of ZNGI 2 mount of resource X Tillman competition Resource based Graph of the amount of resources a species needs in order to survive for both species If resources fall anywhere in area Neither species survives If resources fall anywhere in area Only species 1 survives ZNGI 1 mt. of ZNGI 2 mount of resource X Tillman competition Resource based Graph of the amount of resources a species needs in order to survive for both species If resources fall anywhere in area Neither species survives If resources fall anywhere in area Only species 1 survives If resources fall anywhere in area Only species 1 survives ZNGI 1 mt. of ZNGI 2 mount of resource X 8

9 ZNGI 1 mt. of ZNGI ut what if the ZNGIs overlap? Need to determine relative consumption rates of the resources for each species. mount of resource X ZNGI PH ZNGI MD Shrub density D MD E F Grass density PH ut what if the ZNGIs overlap? It depends on the relative consumption rate of the resources for each competitor Grass density is more limiting for pronghorns. Shrub density is more limiting for mule deer. - Neither spp. survives - Mule deer win F - Pronghorn win ZNGI PH ZNGI MD Shrub density MD D E F PH ut what if the ZNGIs overlap? Grass density is more limiting for pronghorns. Shrub density is more limiting for mule deer. - Mule deer win More shrubs available then grass D - oexistence Each species consumes relatively more of its limiting resource The relative availability of the two resources must be between the two consumption vectors. E - Pronghorn win More grass available than shrubs Grass density 9

10 ZNGI PH ZNGI MD Shrub density MD D E F PH ut what if the ZNGIs overlap? Grass density is more limiting for pronghorns. Shrub density is more limiting for mule deer. - Mule deer win More shrubs available then grass D - Unknown who will win but only one species will survive E - Pronghorn win More grass available than shrubs Grass density Lotka-Voltera Implicitly concerned with resources Explicitly concerned with population sizes Provides estimate of equilbrium size of both species llows determination of winning competitor or coexistence Tilman Explicitly concerned with resources Implicitly concerned with population sizes Doesn t provides estimate of equilbrium size of both species llows determination of winning competitor or coexistence 10