Biology subjects

De Cauwer, I.

Publications and source records attributed to De Cauwer, I..

5 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↗

bioRxiv2021

Effects of sexual dimorphism on pollinator behaviour in a dioecious species

Floral traits often display sexual dimorphism in insect-pollinated dioecious plant species, with male individuals typically being showier than females. While this strategy is theorized to be optimal when pollinators are abundant, it might represent a risk when they become scarce, because the disproportionately high number of visits on the most attractive sex, males, might preclude efficient pollen transfer from males to females. Here, the effect of sexual dimorphism on pollination efficiency was assessed in experimental arrays of dioecious Silene dioica that were exposed to one frequent visitor of the species, Bombus terrestris, and that differed in the magnitude of sexual dimorphism for either flower number or flower size. While flower size dimorphism did not impact pollination efficiency, we found that flower number dimorphism negatively affected the number of visits on female plants, on female flowers and on the number of female flowers visited after a male flower. However, flower number dimorphism had no effect on the number of pollen grains deposited per stigma, presumably because the decrease in the number of visits to female flowers was compensated by a higher number of pollen grains deposited per visit.

ecology↗

bioRxiv2020

Widespread coexistence of self-compatible and self-incompatible phenotypes in a diallelic self-incompatibility system in Ligustrum vulgare (Oleaceae)

The breakdown of self-incompatibility (SI) in angiosperms is one of the most commonly observed evolutionary transitions. While multiple examples of SI breakdown have been documented in natural populations, there is strikingly little evidence of stable within-population polymorphism with both inbreeding (self-compatible) and outcrossing (self-incompatible) individuals. This absence of mating system polymorphism corroborates theoretical expectations that predict that in/outbreeding polymorphism is possible only under very restricted conditions. However, theory also predicts that a diallelic sporophytic SI system facilitates the maintenance of such polymorphism. We tested this prediction by studying the mating system of Ligustrum vulgare L., an entomophilous hermaphroditic species of the Oleaceae family. Using stigma tests with controlled pollination and paternity assignment of open-pollinated progenies, we confirmed the existence of two self-incompatibility groups in this species. We also demonstrated the existence of self-compatible individuals in different populations of Western Europe arising from a mutation affecting the expression of the pollen component of SI. We then estimated the selfing rate in a garden experiment. Our results finally show that the observed low frequency of self-compatible individuals in natural populations is compatible with theoretical predictions only if inbreeding depression is very high.

evolutionary biology↗