De Frenne, P. | Search bioRxiv

bioRxiv2025

On the edge of extinction: Delayed plant genetic response to forest edge dynamics

Understanding genetic responses to forest dynamics is essential for predicting the long-term viability of understory plant populations and for developing effective conservation strategies. This study investigates genetic extinction debt and colonization credit in Circaea lutetiana, a clonal forest understory species, across its European range. Using pooled genotype-by-sequencing data from 40 forest edge and core populations, we examined to what extent population size, latitude and historical changes in forest configuration predict genetic diversity. Our findings reveal that the historical forest configuration profoundly shapes present-day genetic diversity. Long-established forest edge populations exhibit significantly reduced allelic richness (-9%) compared to core populations, indicating the partial pay-off of a genetic extinction debt. In contrast, populations from recently established forest edges maintain comparable allelic richness to core populations, suggesting delayed population genetic responses to land use changes. Finally, populations established in areas that were afforested during the past 250 years exhibit lower genetic diversity than historical forest core populations, indicating a delay in genetic recovery and thus a potential genetic colonization credit. Our results highlight that C. lutetiana populations are not at equilibrium with the current forest configuration, underscoring the role of lagged genetic responses across very long time scales. Connectivity and population size further moderate genetic diversity, with smaller, isolated populations particularly vulnerable to genetic erosion. Given the limited research on delayed evolution in forest understory species, our results improve the understanding of extinction risk dynamics and underscore the need for history-informed restoration efforts.

ecology↗

bioRxiv2024

Trade-offs between averages and intra-individual variation within vegetative, phenological, and floral traits

O_LIIntra-individual trait variation in plants represents an often ignored but important dimension of phenotypic variation that contributes to functional diversity and the dynamics of ecological communities. It can be expressed differently across plant traits, but the induction of intra-individual variation in different trait types under environmental stresses has not yet been explored. C_LIO_LIWe used the clonal forest herb, Galium odoratum, to investigate intra-individual variation within vegetative, phenological, and floral traits, and trade-offs between trait average and variation under a full-factorial experimental design using drought and shading treatments. C_LIO_LIIntra-individual variation (expressed as CV) differed in magnitude between trait types, with vegetative and floral traits showing the highest and lowest CV, respectively. CV occurring in the different traits responded to the drought and shade treatments. Trade-offs between CV and trait averages appeared across most of traits under the different treatment combinations, whereas trade-offs were less pronounced under control conditions. C_LIO_LIDrought and shading in forest environments induce trade-offs between intra-individual variation and the average trait expression, indicating the relevance of intra-individual variation for functional adaptations of forest plants to climatic changes. Our findings suggest that plastic responses in intra-individual variation may be an important component for mechanistic adjustments of plants to environmental stresses. C_LI

evolutionary biology↗