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COMPETITION – COLONIZATION TRADE-OFF AND
COEXISTENCE
Ants and Acacia trees in Eastern Africa
Angelica CuevasFrancesca PalmeiraIrina BarrosMauricio MontellanoPaulo OliveiraRaul Barriga
Acacia drepanolobium
Acacia drepanolobium
Acacia drepanolobium
Herbivory
Mutualism Acacia - Ants
Mutualism Acacia - Ants
Shelter
Mutualism Acacia - Ants
Shelter
Food
Mutualism Acacia - Ants
Shelter
Food
THE SYSTEM
Competition –Colonization trade-off
THE SYSTEM
Competition –Colonization trade-off
>Dispersion and
Colonization
> >
Crematogaster sjostedti C. mimosae C. nigriceps Tetraponera penzigi
THE SYSTEM
Competition –Colonization trade-off
>
<
Dispersion and
Colonization
Competition
>
<
>
<Crematogaster sjostedti C. mimosae C. nigriceps Tetraponera penzigi
THE QUESTION
How can the tree dynamics (growth, birth and death) affect the coexistence of the ants?
THE MODEL
Competition –Colonization trade-off and Coexistence
Strong Competitor
Good Colonizer
THE MODEL
Competition –Colonization trade-off and Coexistence
Strong Competitor
Good Colonizer
Species 1
THE MODEL
Competition –Colonization trade-off and Coexistence
Strong Competitor
Good Colonizer
Species 2Species 1
THE MODEL
Competition –Colonization trade-off and Coexistence
Young
Mature
α > β
μm < μy
D < β
αm > αy
Ge < Gi
THE MODEL
Competition –Colonization trade-off and Coexistence
Colonization rates
Mortality rates
Conquer and colonization rates
Colonization rates for all ants
Growth rates
• dTye/dt = rTm – GeTye – αyT1Tye – βyT2Tye – μyTTye
• dTy1/dt = αyT1Tye – GiTy1 – ayT2Ty1 – μyTTy1
• dTy2/dt = βyT2Tye + ayT2Ty1 – GiTy2 – μyTTy2
• dTme/dt = GeTye – αmT1Tme – βmT2Tme – μmTTme
• dTm1/dt = GiTy1 + αmT1Tme – amT2Tm1 – μmTTm1
• dTm2/dt = GiTy2 + βmT2Tme + amT2Tm1 – μmTTm2
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
RESULTS
Competition and Coexistence
There is coexistence!
- Predominance of the strongest
- Strongest win on the mature trees, and loose at the young one
RESULTSEvaluating 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
RESULTSEvaluating change in Parameters
- The Strongest must be, indeed, stronger then the Sp 1 in order to continue to exist.
THE MODEL 3 speciesCompetition –Colonization trade-off and
Coexistence
Young
Mature
RESULTSCompetition and Coexistence
There is also coexistence!
- The middle species can survive alongside the others depending on the parameters.
RESULTSEvaluating 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
RESULTSEvaluating change in Parameters
So this model predicts the existence of mature trees without ants.
FIXED POINTS
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.
THANK YOU!
Questions?!
