Biology subjects

Joffard, N.

Publications and source records attributed to Joffard, N..

3 recordsLinked to original sources

bioRxiv2026

Local genetic neighbourhoods but resilient gene flow across anthropogenic landscapes in the red campion (Silene dioica)

Background and AimsIn the plant kingdom, gene flow occurs through pollen and seed dispersal, shaping both within-population spatial genetic structure and among-population genetic differentiation. Anthropogenic land-use change can affect levels of gene flow by reducing pollinator abundance and altering pollen and seed dispersal pathways. Yet, how environmental features shape gene flow events in common herbaceous plants - a fundamental building block of many ecosystems - remains poorly understood. We address this gap by investigating how environmental context influences population genetic structure at regional and local scales in the red campion (Silene dioica). MethodsBy sampling 1,005 individuals from 29 populations across habitats ranging from semi-natural to strongly human-altered, we assessed whether population size and landscape composition influenced within-population genetic diversity and population genetic differentiation. At the local scale, we examined whether landscape composition affected fine-scale spatial genetic structure and pollen dispersal distances in a subset of six populations representing the two extremes of an anthropogenic gradient. Key ResultsNo effect of either demographic or landscape factors was found on levels of genetic diversity. We detected moderate levels of genetic differentiation among populations that matched an isolation-by-distance pattern, with high levels of population admixture, while landscape composition did not explain variation in population genetic differentiation. At the local scale, five of the six studied populations exhibited significant spatial genetic structuring, indicating distinct neighbourhoods at spatial scales less than 10 m. Paternity analyses based on 4,800 offspring further revealed predominantly short-distance pollen dispersal together with substantial immigration from external sources. Neither fine-scale genetic structure nor pollen dispersal distances differed between habitat types. ConclusionsAltogether, our results demonstrate a multimodal pattern of gene flow and a remarkable resilience of this common herbaceous species to anthropogenic habitat change, as substantial genetic connectivity is maintained despite insect-mediated pollen dispersal and gravity-driven seed dispersal.

plant biology↗

bioRxiv2026

Male-biased sexual selection persists across contrasting habitats in a dioecious plant

In most angiosperms, pollinators mediate access to sexual partners, making attractive floral traits key targets of sexual selection. Theory predicts stronger selection through the male function, due to greater dependence of male reproductive success on mate acquisition. However, habitat degradation may alter plant-pollinator interactions and disrupt sex-specific selection. In particular, reduced pollinator density may increase the dependency of female reproductive success on mate acquisition and strengthen selection on floral traits in both sexes. We tested this hypothesis in the dioecious species Silene dioica by measuring pollinator visitation, pollination service, and phenotypic selection on floral traits in both sexes across six populations located in either forest or anthropogenic habitats. Despite lower visitation in anthropogenic sites, pollination service was comparable between habitats with consistent selection on fertility-related traits in females. In contrast, we found stronger selection on a male trait likely promoting efficient pollen transfer in anthropogenic habitats, indicating a sex-specific response to land use change. Finally, male--but not female--reproductive success increased with the number of sexual partners in both habitats, supporting stronger sexual selection in males. More broadly, our results emphasize the need for a sex-specific perspective on floral trait evolution and demonstrate the persistence of male-biased sexual selection under environmental change.

evolutionary biology↗

bioRxiv2025

Floral display size does not affect the distribution of paternal diversity in Silene dioica

Premise of the studyPaternal diversity and its distribution within maternal plants is governed by various factors, including frequency of pollinator visits, patterns of pollinator movement and pollen carryover. Floral display size may have opposite effects on fruit and plant-level paternal diversity, because plants with large displays should receive more pollinator visits but also more sequential probes per visit. MethodsTo investigate the effect of floral display size on the distribution of paternal diversity in Silene dioica, we genotyped and assigned paternity for 1320 seeds sampled in several fruits per plant in control and manipulated females, whose flower number was artificially increased. We estimated within-fruit paternal diversity and sire profile dissimilarity among fruits and compared these metrics between control and manipulated plants. We then studied pollen carryover using controlled pollinator visits and pollen counts. Key resultsMost fruits were multiply sired, but we found no effect of flower supplementation on within-fruit paternal diversity. Sire profiles were more similar between fruits located on the same than on different females, but sire profile similarity was not higher within manipulated than within control plants. The pollen deposition curve was steep, with an increasing carryover fraction throughout the visitation sequence. ConclusionsOur results suggest that the effect of floral display size on pollinator foraging behaviour is too weak to affect paternal diversity and its distribution in S. dioica, or that other processes, such as limited pollen carryover and spatially restricted pollen dispersal, blur the effect of pollinator visit frequency and movements on sire profiles.

plant biology↗