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When Is It Worth Being a Self-Compatible Hermaphrodite?

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When Is It Worth Being a Self-Compatible Hermaphrodite? When is it worth being a self-compatible hermaphrodite? Context-dependent effects of self-pollination on female advantage in gynodioecious Silene nutans Emna Lahiani, Pascal Touzet, Emmanuelle Billard, Mathilde Dufaÿ To cite this version: Emna Lahiani, Pascal Touzet, Emmanuelle Billard, Mathilde Dufaÿ. When is it worth being a self- compatible hermaphrodite? Context-dependent effects of self-pollination on female advantage in gyn- odioecious Silene nutans. Ecology and Evolution, Wiley Open Access, 2015, 5 (9), pp.1854-1862. 10.1002/ece3.1410. hal-01141623 HAL Id: hal-01141623 https://hal.archives-ouvertes.fr/hal-01141623 Submitted on 11 May 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. When is it worth being a self-compatible hermaphrodite? Context-dependent effects of self-pollination on female advantage in gynodioecious Silene nutans Emna Lahiani, Pascal Touzet, Emmanuelle Billard & Mathilde Dufay Unite Evolution Ecologie Paleontologie, UMR CNRS 8198, Universite de Lille 1 - Sciences et Technologies, Villeneuve d’Ascq, France Keywords Abstract Female advantage, gynodioecy, male sterility, pollen limitation, self-pollination, Silene In gynodioecious plant species with nuclear-cytoplasmic sex determination, nutans. females and hermaphrodites plants can coexist whenever female have higher seed fitness than hermaphrodites. Although the effect of self fertilization on Correspondence seed fitness in hermaphrodites has been considered theoretically, this effect is Mathilde Dufay, Unite Evolution Ecologie far from intuitive, because it can either increase the relative seed fitness of the Paleontologie, UMR CNRS 8198. Bat. SN2, females (if it leads hermaphrodites to produce inbred, low quality offspring) or Universite de Lille 1 - Sciences et decrease it (if it provides reproductive assurance to hermaphrodites). Hence, Technologies, F-59655 Villeneuve d’Ascq Cedex, France. empirical investigation is needed to document whether relative seed fitness var- Tel: +33 320 335 923; Fax: +33 320 436 ies with whether pollen is or is not limiting to seed production. In the current 979; E-mail: [email protected] study, we measured fruit set and seed production in both females and hermaphrodites and the selfing rate in hermaphrodites in two experimental Funding Information patches that differed in sex ratios in the gynodioecious plant Silene nutans.We – This work was funded by the Region Nord found an impact of plant gender, patch, and their interaction, with females suf- Pas-de-Calais, the Fondation pour la fering from stronger pollen limitation when locally frequent. In the most pol- Recherche en Biodiversite (GENEFRAG project) and the French Agence Nationale de len-limited situation, the selfing rate of hermaphrodites increased and provided la Recherche (ANR 11-BSV7-013-03). E.B. hermaphrodites with a type of reproductive assurance that is not available to benefitted from a contract from the females. By integrating both the beneficial (reproductive assurance) and costly University of Lille. E.L.’s PhD fellowship was effects (through inbreeding depression) of self-pollination, we showed that funded by the Centre National de la whether females did or did not exhibit higher seed fitness depended on the Recherche Scientifique and the Region Nord- degree of pollen limitation on seed production. Pas-de Calais. Received: 7 October 2014; Revised: 9 January 2015; Accepted: 9 January 2015 Ecology and Evolution 2015; 5(9): 1854–1862 doi: 10.1002/ece3.1410 Introduction tics of plant reproduction. Indeed, most of the well-docu- mented gynodioecious species are self-compatible, while The evolution from hermaphroditism towards separate gynodioecious species in which hermaphrodites are sexes is considered a major evolutionary transition in the unable to self-pollinate appear very rare (Dufay and history of flowering plants (Barrett 2010). One possible Billard 2012), suggesting that separate sexes may evolve evolutionary step within that transition is the evolution more easily in self-compatible lineages. Accordingly, both of gynodioecy, that is the co-occurrence of female and theoretical (e.g. Charlesworth and Charlesworth 1978) hermaphroditic individuals within the same population and empirical studies (reviewed in Dufay and Billard (Charlesworth and Charlesworth 1978). This evolutionary 2012) have shown that the maintenance of females within pathway does not seem to be independent from a plants’ a hermaphroditic population should be facilitated if ability to self-pollinate, which is another key characteris- hermaphrodites partly self-pollinate, because hermaphro- 1854 ª 2015 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. E. Lahiani et al. Effect of Selfing on Female Advantage ditic progeny may therefore suffer from inbreeding roditic individuals found in natural populations (Jurgens depression. Such inbreeding avoidance is one way for et al. 2002; Dufay et al. 2010). The determination of sex is females to benefit from a so-called “female advantage”, nuclear-cytoplasmic, with cytoplasmic sterility factors that and thus compensate for their fitness loss in terms of pol- can be counteracted by nuclear restorers (Garraud et al. len production. However, in case of pollen limitation, the 2011), although the determination of the gynomonoecious ability to self-pollinate may provide hermaphrodites with phenotype is not known yet. With such genetic determina- a reproductive assurance, therefore reducing the magni- tion, theory has shown that the maintenance of females tude of the female advantage. Although the positive effect only requires a slightly higher seed fitness in females com- of selfing on reproductive assurance for hermaphrodites pared to hermaphrodites (Lewis 1941; Gouyon et al. 1991). of gynodioecious species has been hypothesized by several Sex ratio varies among populations from 0 to 60% of theoretical studies (Charlesworth, 1981; Maurice and female plants and from 0 to 100% at the level of patches of Fleming 1995; Dornier and Dufay 2013), empirical inves- plants (Dufay M, unpubl. data). Population size is highly tigation of such an effect is lacking. Furthermore, because variable and can be extremely small (Hauser and Weidema self-pollination potentially can both increase the relative 2000; Van Rossum and Prentice 2004). Flowers are visited fitness of females versus hermaphrodites (in case of by a number of different insect species, including Noctui- inbreeding depression) and decrease it (in case of pollen dae, Sphingidae, Hymenoptera, and nectar robbing Hyme- limitation), whether or not gynodioecy is more likely to noptera (Jurgens et al. 1996). Hermaphrodites produce be maintained in a self-compatible lineage is clearly not larger flowers than females (Dufay et al. 2010) but the intuitive. number of ovules per flower does not vary between sexes The aim of this study is to empirically disentangle the (Dufay M, unpubl. data). Perfect flowers are protandrous, positive and the negative effects of self-pollination in which makes autonomous selfing unlikeley, but self-polli- hermaphrodites on the female advantage in a gynodioe- nation can occur by geitonogamy. cious species. In particular, we aimed at testing whether self-pollination provides hermaphrodites with a reproduc- Plant material tive assurance in pollen-limited situations. We thus mea- sured seed production in females and hermaphrodites as Individual plants used in the experiment were sampled in well as the selfing rate in hermaphrodites when pollen 2008 from natural populations. All plants were cloned limitation varies. We carried out the study in two patches from plantlets grown and over-wintered in the green- exhibiting different sex ratios, since a low proportion of house for 10 weeks during the winter of 2010. Plants were hermaphrodites in a local context is expected to enhance then potted in a soil mix (3/4 compost; 1/4 perlite) and pollen limitation in gynodioecious species (e.g. Graff placed in greenhouse at a temperature of 20°C for 1999; Alonso 2005; Zhang et al. 2008; De Cauwer et al. 7 weeks until the population reached the peak of flower- 2010). Our study was carried out in semi-controlled con- ing. All focal plants used in this study originated from a ditions, in order to control for other parameters that single wild population in Olloy-sur-Viroin in Belgium might affect seed fitness, such as habitat quality or polli- (Van Rossum et al. 1997), which contained ca 400 indi- nator availability, and to allow the two experimental pop- viduals and a female ratio of 0.16 during the survey in ulations to differ only in the magnitude of pollen 2008, with local female frequency varying from 0 to ca limitation. We then combine our empirical measurements 0.7 (Dufay M, unpubl. data). To properly establish our of seed production, self-pollination and a previous esti- experimental
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