Comparison of the life strategy of two invasive speciesComparison of the life strategy of two invasive species((CentaureaCentaurea maculosamaculosa LamLam. . && SenecioSenecio inaequidensinaequidens DCDC..))

A. Thébault1, D. Pasche1, F. Gillet1, H. Müller-Schärer2 & A. Buttler1

IntroductionThe ability of a species to invade, i.e its invasiveness, is the consequence of ecological and evolutionary processes.

- Enemy release hypothesis- Novel weapon hypothesis- Propagule pressure

- Evolutionary increase of competitive ability- Evolution reduced competitive ability- Hybridization to increase genetic variations

We studied growth and some functional traits of two worldwide invasive species (Asteraceae), Centaurea maculosa Lam. and Senecio inaequidens DC., to compare their strategies regarding evolutionary and ecological processes.

Experimental design2 species: - C. maculosa (native from Europe, invasive in North-America) - S. inaequidens (native from South-Africa, invasive in Europe)3 pools : - Native diploid (Nat 2n)- Native tetraploid (Nat 4n)- Introduced tetraploid (Int 4n)

Growing conditions: - Individual growth, pots in greenhouse (controlled conditions), water supply

} Ecological processes

Evolutionary processes

Hypotheses• According to evolutionary processes, polyploid genotypes (4n) perform better thandiploid ones (2n)

1 Ecole Polytechnique Fédérale de Lausanne (EPFL), Ecological Systems Laboratory(ECOS), Station 2, CH-1015 Lausanne, Switzerland

2 University of Fribourg, Dept Biology, Unit Ecology & Evolution, Chemin du Musée 10, CH-1700 Fribourg, Switzerland

aurelie.thebault@epfl.ch

}

904545S. inaequidens

901872C. maculosa

Int. 4nNat. 4nNat. 2nReplicates

CentaureaCentaurea maculosamaculosa

Slow vegetative growth, lowSpecific Leaf Area (SLA) and high Leaf Dry MatterContent (LDMC) leading to unpalatable leaves. Resources preferentiallyallocated to roots

SenecioSenecio inaequidensinaequidens

Fast vegetative growth (not shown), low LDMC and highSLA. Resources allocated to shoots and reproductive effort (high flowering)

2 invasive species, 2 invasion strategies (Comparison of the pools)

Centaurea maculosa- Increase in root allocation supports the theory of novel weapon hypothesis (Evolutionary process)- Decrease in leaves palatability might be the consequence of the release from herbivores (Ecological process)

Senecio inaequidens- Fast vegetative growth and resource allocation to shoots seems to support the theory of an increase in competitiveability (Evolutionary process)- High and early flowering leads to an important propagule pressure involved in invasion process(Ecological process)

It seems that ecological and evolutionary processes are involved in species invasions. Nevertheless, except for flowering, we neither show significant differences between diploid and tetraploids genotypes, nor between native and introduced ones. Aknowledgements: University of Lausanne for providing greenhouse and material

Growth Traits

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Centaurea maculosa

Ti me si nce fi rst leaf (days)

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bero

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ves

Native 2nNative 4nIntroduced4n

Native 2nNative 4nIntroduced4n

Individual values

Fitted logistic growth

Comparison of the species

SLA (m2 /kg )

C. maculosa S. inaequidens

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2n 4n 4n 2n 4n 4nNat. Nat. Int. Nat. Nat. Int.

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Shoot/Root

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C. maculosa S. inaequidens

Flowering

Species: ****Pool: nsSpecies*Pool: ms

Species: ****Pool: nsSpecies*Pool: ns

Species: ****Pool: nsSpecies*Pool: ns

Species: ****Pool: ***Species*Pool: ****

P < .05*; P < .01**; P <. 001***; P < .0001****; ms: .05 < P < .1; ns:SLA: Specific Leaf AreaLDMC: Leaf Dry Matter Content

Comparison of some functional traits of diploid (2n) and tetraploid (4n)genotypes of native (Nat.) and non-native(Int.) seeds of Centaureamaculosa and Senecio inaequidens

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2n 4n 4n 2n 4n 4nNat. Nat. Int. Nat. Nat. Int.

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LD MC (mg/g)

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non significant result

• Following ecologicalprocesses, genotypesfrom introduced range (Int.) perform betterthan those from native one (Nat.)

Trait

2n 4n 4nNative Introduced