Late-acting self-incompatible system, preferential allogamy and delayed selfing in the 1 heterostylousheteromorphic invasive populations of Ludwigia grandiflora subsp. hexapetala

19 MatingBreeding system influences local population genetic structure, effective size, 20 offspring fitness and functional variation. Determining the respective importance of selfand 21 cross-fertilization in hermaphroditic flowering plants is thus important to understand their 22 Définition du style : Élevé Mis en forme : Police :Italique Mis en forme : Couleur de police : Noir, Anglais (États-Unis) Mis en forme : Couleur de police : Noir, Anglais (États-Unis) Mis en forme : Couleur de police : Noir, Anglais (États-Unis) Mis en forme : Couleur de police : Noir, Anglais (États-Unis) Mis en forme : Police :Times New Roman Mis en forme : Espagnol (Guatemala) Mis en forme : Anglais (États-Unis) ecology and evolution. The worldwide invasive species, Ludwigia grandiflora subsp. 23 hexapetala (Lgh) presents two floral morphs: one self-compatible short-styled morph (S24 morph) and one self-incompatible long-styled morph (L-morph). Most invasive populations 25 worldwide are only composed of self-incompatible L-morphs, which questions the importance 26 of sexual reproduction during the invasion. In this study, we identified the matingbreeding 27 systems of western European experimental and natural populations of Lgh by comparing 28 structural characteristics of pollen and style, by studying selfand cross-pollen tube elongations 29 and the viability of the resulting seeds and seedlings in both floral morphs. Our results showed 30 no differences in pollen shape and stigma surfaces among and between the two floral morphs. 31 In the self-incompatible L-morph flowers, self-pollen tubes were stopped tardily, in the ovarian 32 area, and were unable to fertilize the ovules. This first formal identification of a late-acting, 33 prezygotic self-incompatible system in Ludwigia genus questions on the distribution of this 34 matingbreeding system in the Myrtales order. In the self-compatible S-morph flowers, rarer in 35 worldwide invasive populations, self-pollen always succeeded to self-fertilize the ovules that 36 nearly all developed into viable seedlings. However, cross-pollen tubes always elongated faster 37 than self-pollen tubes. S-morph individuals may thus advantage preferential allogamy over 38 selfing when cross-pollen is available despite its self-compatibility. As expected in late-acting 39 self-incompatible systems, L-morph flowers authorised 0.2‰ of selfed seeds during the 40 uppermost flowering season, that increased to 1‰ at the end of the flowering season. Such 41 delayed selfing resultingresulted in a significant quantity of viable floating seeds. They may 42 contribute to the local regeneration, seed bank and propagation of the L-morph, which may 43 contribute to explain its invasion success worldwide. Management plans of Lgh would gain to 44 consider the mixed mating systembreeding systems we identified. 45

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