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COMPETITION – COLONIZATION TRADE-OFF AND COEXISTENCE Ants and Acacia trees in Eastern Africa Angelica Cuevas Francesca Palmeira Irina Barros Mauricio Montellano Paulo Oliveira Raul Barriga

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Acacia drepanolobium

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Herbivory

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Mutualism Acacia - Ants

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Mutualism Acacia - Ants Shelter

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Mutualism Acacia - Ants Shelter Food

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Mutualism Acacia - Ants Shelter Food

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THE SYSTEM Competition –Colonization trade-off

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THE SYSTEM Competition –Colonization trade-off > Dispersion and Colonization >> Crematogaster sjostedtiC. mimosaeC. nigricepsTetraponera penzigi

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THE SYSTEM Competition –Colonization trade-off > < Dispersion and Colonization Competition > < > < Crematogaster sjostedtiC. mimosaeC. nigricepsTetraponera penzigi

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THE QUESTION How can the tree dynamics (growth, birth and death) affect the coexistence of the ants?

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THE MODEL Competition –Colonization trade-off and Coexistence Strong Competitor Good Colonizer

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THE MODEL Competition –Colonization trade-off and Coexistence Strong Competitor Good Colonizer Species 1

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THE MODEL Competition –Colonization trade-off and Coexistence Strong Competitor Good Colonizer Species 2 Species 1

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THE MODEL Competition –Colonization trade-off and Coexistence Young Mature

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α > β μ m < μ y D < β α m > α y G e < G i THE MODEL Competition –Colonization trade-off and Coexistence Colonization rates Mortality rates Conquer and colonization rates Colonization rates for all ants Growth rates

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dT ye /dt = rT m – G e T ye – α y T 1 T ye – β y T 2 T ye – μ y TT ye dT y1 /dt = α y T 1 T ye – G i T y1 – a y T 2 T y1 – μ y TT y1 dT y2 /dt = β y T 2 T ye + a y T 2 T y1 – G i T y2 – μ y TT y2 dT me /dt = G e T ye – α m T 1 T me – β m T 2 T me – μ m TT me dT m1 /dt = G i T y1 + α m T 1 T me – a m T 2 T m1 – μ m TT m1 dT m2 /dt = G i T y2 + β m T 2 T me + a m T 2 T m1 – μ m TT m2 THE MODEL Competition –Colonization trade-off and Coexistence Young empty trees Young – species1 Young – species 2 Mature empty trees Mature - species 1 Mature – species 2

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RESULTS Competition and Coexistence There is coexistence! - Predominance of the strongest - Strongest win on the mature trees, and loose at the young one

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RESULTS Evaluating change in Parameters - If the strongest species is fast enough, the Weakest disappears. - The growth of the trees is not essential to coexistence - Different death rates are important to the proportion of ants

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RESULTS Evaluating change in Parameters - The Strongest must be, indeed, stronger then the Sp 1 in order to continue to exist.

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THE MODEL 3 species Competition –Colonization trade-off and Coexistence Young Mature

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RESULTS Competition and Coexistence There is also coexistence! - The middle species can survive alongside the others depending on the parameters.

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RESULTS Evaluating change in Parameters At the start of the process, Sp1 increase. After the death of Sp2, Sp1 starts to decrease There is a “phase transition” on the number of coexisting ants species

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RESULTS Evaluating change in Parameters

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So this model predicts the existence of mature trees without ants. FIXED POINTS

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CONCLUSIONS - Increase of Predominance of the strongest species depends of its rate of dispersion - Coexistence is possible because of the colonization-competition trade- off - The rate of growth and rate of birth affects the ratio between the species, but not necessarily the coexistence itself. - The coexistence depends of the rates of dispersion and colonization.

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THANK YOU!

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