Biology subjects

Karrenberg, S.

Publications and source records attributed to Karrenberg, S..

6 recordsLinked to original sources

bioRxiv2026

Failure to invest below-ground may limit the Northern expansion of invasive knotweed: lessons from a two-phase transplant experiment

The ecological and evolutionary processes determining species range limits remain poorly understood. Ultimately, range limits depend on the species abilities to persist under heterogeneous conditions, by adaptive differentiation and phenotypic plasticity, including transgenerational effects. To investigate ecological differentiation and transgenerational effects in the clonal invasive knotweed, Reynoutria japonica, in Europe, we conducted a two-phase transplant experiment: plants sampled along the entire latitudinal gradient were planted in three sites located at the northern range margin, mid-range and near the southern range margin, and then re-transplanted among all three sites after two years. Biomass production and allocation were generally not associated with latitude of origin and previous growth at the same site did not promote performance. We therefore find no evidence that adaptive differentiation or transgenerational effects contribute to the wide distribution of R. japonica in Europe. However, at the northern site, with a 25% shorter season, knotweed plants invested much less biomass below-ground, and the pattern was further strengthened in plants that had grown in the northern site in the previous generation. Overwintering below-ground rhizomes are essential for survival and spread. We further explored limiting climate conditions in a species distribution model for the European range and found that mean annual temperature and temperature annual range are the main predictors of the European distribution of R. japonica. Taken together, our study suggests that low temperatures and associated short seasons may pose a limit to the broad environmental tolerance of R. japonica and restrict its northward spread by reducing below-ground biomass accumulation.

ecology↗

bioRxiv2025

Phenotypic plasticity of invasive knotweed across Europe: a distributed common garden experiment

O_LIBiological invasions expose populations of introduced species to strong selection forces in abiotic and biotic factors, which is expected to lead to adaptive differentiation of populations, particularly for large-scale invaders. C_LIO_LITo better understand population differentiation and phenotypic plasticity of invasive Japanese knotweed (Reynoutria japonica) in Europe, we compared the performance of 45 European knotweed populations, collected across a 2000 km latitudinal transect, in three common gardens with contrasting climatic conditions, one at the southern edge, one in the center, and one at the northern edge of the species European distribution. C_LIO_LIThe plants exhibited strong phenotypic plasticity across the three gardens, with a more acquisitive growth strategy in the southern garden, and a more conservative strategy and change of architecture in the climatically unfavorable north. Although we observed phenotypic selection on several leaf traits, and on the plasticity of leaf thickness, with some selection differences between the gardens, there was little evidence of population differentiation, and none for local adaptation. Only for plant architecture (shrubbiness), we detected heritable population variation in trait means and plasticity. However, variation in plasticity was unrelated to climatic variability of origin, and to plant fitness. C_LIO_LISynthesis. Our results suggest that evolutionary processes - local adaptation and evolution of plasticity - did not play a key role in the success of Japanese knotweed in Europe. Instead, its high baseline plasticity appears to be the key factor that makes it such a strong invader across a broad range of environments. C_LI

ecology↗

bioRxiv2023

Female-biased population sex ratios caused by genetic rather than ecological mechanisms

1. Biased sex ratios among reproductive individuals are common in plants, but the underlying mechanisms, as well as the evolutionary consequences, are not well understood. The classical theory of Dusing and Fisher predicts an equal primary sex ratio at seed production, based on the selective advantage of the rare sex. Biased sex ratios among reproductive plants can arise from sexual dimorphism in survival and flowering. Sex ratio biases can also be present from seed; in these cases, assumptions of Dusings and Fishers theory, for example, random mating or demographic equilibrium, were not met. 2. We investigated mechanisms leading to female-biased sex ratios in the arctic-alpine dwarf willow Salix herbacea L. We studied sex ratios in three natural populations over three years as well as in 29 crosses (full-sib families) under controlled conditions over four growth periods. We tested whether sex ratio was associated with germination, survival or flowering, and whether females and males differed in habitat, size or flowering. 3. We detected a strong and consistent female bias, both in natural populations (sex ratio [proportion of females]: 0.71-0.82) and in our controlled experiment (overall sex ratio: 0.70-0-72). Our data did not support habitat segregation of the sexes or sexual dimorphism in size or flowering. Family sex ratios varied largely (from 0.25 to 1), including many female-biased families, but also unbiased families and two male-biased families. Families with lower germination, seedling establishment, survival or flowering did not have stronger female bias, indicating that intrinsically higher survival or flowering in females does not explain overall female bias. 4. Synthesis. Our results suggest that sex ratio bias in S. herbacea is already present in seeds and does not arise through intrinsic differences between sexes. Candidate mechanisms that can lead to both overall female bias and variation in sex ratio among families are meiotic drive or cyto-nuclear interactions. The pioneer habit of Salix may lead to non-equilibrium population dynamics that allow for the long-term persistence of variable genetic sex ratio distortion systems that arise from genetic conflict.

evolutionary biology↗

bioRxiv2023

The Silene latifolia genome and its giant Y chromosome

In some species, the Y is a tiny chromosome but the dioecious plant Silene latifolia has a giant [~]550 Mb Y chromosome, which has remained unsequenced so far. Here we used a hybrid approach to obtain a high-quality male S. latifolia genome. Using mutants for sexual phenotype, we identified candidate sex-determining genes on the Y. Comparative analysis of the sex chromosomes with outgroups showed the Y is surprisingly rearranged and degenerated for a [~]11 MY-old system. Recombination suppression between X and Y extended in a stepwise process, and triggered a massive accumulation of repeats on the Y, as well as in the non-recombining pericentromeric region of the X, leading to giant sex chromosomes. One-Sentence SummaryThis work uncovers the structure, function, and evolution of one of the largest giant Y chromosomes, that of the model plant Silene latifolia, which is almost 10 times larger than the human Y, despite similar genome sizes.

genomics↗

bioRxiv2021

A polygenic architecture with conditionally neutral effects underlies ecological differentiation in Silene

O_LIEcological differentiation can drive speciation but it is unclear how the genetic architecture of habitat-dependent fitness contributes to lineage divergence. We investigated the genetic architecture of cumulative flowering, a fitness component, in second-generation hybrids between Silene dioica and S. latifolia transplanted into the natural habitat of each species. C_LIO_LIWe used reduced-representation sequencing and Bayesian Sparse Linear Mixed Models (BSLMMs) to analyze the genetic control of cumulative flowering in each habitat. C_LIO_LIOur results point to a polygenic architecture of cumulative flowering. Allelic effects were mostly beneficial or deleterious in one habitat and neutral in the other. The direction of allelic effects was associated with allele frequency differences between the species: positive-effect alleles were often derived from the native species, whereas negative-effect alleles, at other loci, tended to originate from the non-native species. C_LIO_LIWe conclude that ecological differentiation is governed and maintained by many loci with small, conditionally neutral effects. Conditional neutrality may result from differences in selection targets in the two habitats and provides hidden variation upon which selection can act. Polygenic architectures of adaptive differentiation are expected to be transient during lineage divergence and may therefore be unrelated to high genetic differentiation at the underlying loci. C_LI

evolutionary biology↗

bioRxiv2019

Evolution of barrier loci at an intermediate stage of speciation with gene flow

Understanding the origin of new species is a central goal in evolutionary biology. Diverging lineages often evolve highly heterogeneous patterns of differentiation; however, the underlying mechanisms are not well understood. We used an integrated approach to investigate evolutionary processes governing genetic differentiation between the hybridizing campions (Silene dioica (L.) Clairv. and S. latifolia Poiret). Demographic modeling indicated that the two species diverged with continuous gene flow. The best-supported scenario with heterogeneity in both migration rate and effective population size suggested that 5% of the loci evolved without gene flow. Differentiation (FST) and sequence divergence (dXY) were correlated and both tended to peak in the middle of most linkage groups, consistent with reduced gene flow at highly differentiated loci. Highly differentiated loci further exhibited signatures of selection and differentiation was significantly elevated around previously identified QTLs associated with assortative mating. In between-species population pairs, isolation by distance was stronger for genomic regions with low between-species differentiation than for highly differentiated regions that may contain barrier loci. Moreover, differentiation landscapes within and between species were only weakly correlated suggesting that the interplay of background selection and conserved genomic features is not the dominant determinant of genetic differentiation in these lineages. Instead, our results suggest that divergent selection drove the evolution of barrier loci played and the genomic landscape of differentiation between the two species, consistent with predictions for speciation in the face of gene flow.

evolutionary biology↗