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

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?!