Biology subjects

Harang, M.

Publications and source records attributed to Harang, M..

3 recordsLinked to original sources

bioRxiv2024

Reproductive modes of polyploid Ludwigia grandiflora subsp. hexapetala in western Europe: the effects of a late-acting self-incompatibility system and its absence on genetic diversity within populations

Reproductive mode, i.e., the proportion of individuals produced by clonality, selfing and outcrossing in populations, determines how hereditary material is transmitted through generations. It shapes genetic diversity and its structure over time and space, which can be used to infer reproductive modes. Ludwigia grandiflora subsp. hexapetala (Lgh) is a partially clonal, polyploid, hermaphroditic, and heteromorphic plant that recently colonized multiple countries worldwide. In western Europe, individuals are either self-incompatible caused by a late-acting self-incompatibility (LSI) system developing long-styled flowers, or self-compatible (SC), with short-styled flowers. In this study, we genotyped 53 long- and short-styled populations newly colonizing France and northern Spain using SNPs to estimate rates of clonality, selfing and outcrossing. We found that populations reproduced mainly clonally but with a high diversity of genotypes along with rates of sexuality ranging from 10% up to 40%. We also found evidence for local admixture between long- and short-styled populations in a background of genetic structure between floral morphs that was twice the level found within morphs. Long- and short-styled populations showed similar rates of clonality but short-styled populations presented significantly higher rates of selfing, as expected considering their breeding system, and despite the small rates of failure of the LSI system. Within the 53 studied populations, the 13 short-styled populations had fewer effective alleles, lower observed heterozygosity, and higher inbreeding coefficients, linkage disequilibrium and estimates of selfing than what was found in long-styled populations. These results emphasize the necessity to consider the variation of reproductive modes when managing invasive plant species. The overall maintenance of higher genetic diversity with the possibility of maintaining populations clonally in the absence of compatible partners may explain why long-styled individuals seem to be more prevalent in all newly expanding populations worldwide. Beyond Lgh, our methodological approach may inspire future studies to assess the reproductive modes in other autopolyploid populations.

evolutionary biology↗

bioRxiv2021

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

AO_SCPLOWBSTRACTC_SCPLOWBreeding system influences local population genetic structure, effective size, offspring fitness and functional variation. Determining the respective importance of self- and cross-fertilization in hermaphroditic flowering plants is thus important to understand their ecology and evolution. The worldwide invasive species, Ludwigia grandiflora subsp. hexapetala (Lgh) presents two floral morphs: one self-compatible short-styled morph (S-morph) and one self-incompatible long-styled morph (L-morph). In this study, we identified the breeding systems of western European experimental and natural populations of Lgh by comparing structural characteristics of pollen and style, by studying self- and cross-pollen tube elongations and the viability of the resulting seeds and seedlings in both floral morphs. Our results showed no differences in pollen shape and stigma surfaces no matter the floral morph. In the self-incompatible L-morph flowers, self-pollen tubes were stopped tardily, in the ovarian area, and were unable to fertilize the ovules. This first formal identification of a late-acting, prezygotic self-incompatible system (LSI) in Ludwigia genus contributes a case of LSI in an additional family within the Myrtales order. In the self-compatible S-morph flowers, self-pollen always succeeded to self-fertilize the ovules that nearly all developed into viable seedlings. However, cross-pollen tubes always elongated faster than self-pollen tubes in both morphs. S-morph individuals may thus advantage preferential allogamy over selfing when cross-pollen is available despite its self-compatibility. As expected in late-acting self-incompatible systems, L-morph flowers authorised 0.2{per thousand} of selfed seeds during the uppermost flowering season, that increased to 1{per thousand} at the end of the flowering season. Such delayed selfing resulted in a significant quantity of viable floating seeds. They may contribute to the local regeneration, seed bank and propagation of the L-morph, which may contribute to explain its invasion success worldwide. Management plans of Lgh would gain to consider the breeding systems we identified.

ecology↗

bioRxiv2020

Self-incompatibility limits sexual reproduction rather than environmental conditions in an invasive aquatic plant

SummaryFruitfulness and fertility are important components of sexual reproductive success in plants, and often depends on environmental conditions and reproductive systems. For invasive plants, fruitfulness and fertility control their ecological success and adaptation in invaded ecosystems. We studied which factors bring about fruitfulness and fertility in invasive populations of the aquatic plant Ludwigia grandiflora subsp. hexapetala.We analysed fruitfulness and fertility of 37 populations growing under variable climatic conditions in Western Europe, and sub-sampled fruitful and fruitless populations grown in common controlled conditions. We carried out self- and cross-pollinations and measured their floral biometrics.Environmental conditions, and temperature in particular, did not affect fruitfulness and fertility in-situ or in common controlled environments. Hand-pollinations resulted in fruit production by individuals sampled from fruitless populations when pollen came from fruitful populations, and by individuals sampled from fruitful populations whatever the origin of pollen. Floral biometrics evidenced the existence of two floral morphs that overlapped with fruitfulness, and individual incompatibility.Our results rebutted the hypothesis that environmental conditions control fruitfulness and fertility in these invasive populations. We instead found that fruit and seed production were controlled by a reproductive system involving a self-incompatible approach herkogamous morph and a self-compatible reverse herkogamous morph. We assessed the floral morphs distribution worldwide of fruitless and fruitful native and invasive populations that matched our results at larger scale. Our results may constitute the first evidence of a possible heteromorphic self-incompatible system in Ludwigia populations and in Onagraceae phylogeny. It calls for further investigations on reproductive systems in this plant family. Finally, the observation that the self-incompatible morph seemed to be the world most invasive morph in this species tackles our understanding of biological and ecological conditions for invasiveness.Synthesis. Our study showed that fruitfulness and fertility in the aquatic invasive plant, Ludwigia grandiflora subsp. hexapetala depend on a self-incompatibility system coinciding with two floral morphs, rather than environmental conditions and limitations. These new explanations on the sexual success of Ludwigia invasive populations will help defining new predictions about its worldwide spreads and ecological success, and will help reappraising future management plans.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗