Biology subjects

Parepa, M.

Publications and source records attributed to Parepa, M..

10 recordsLinked to original sources

bioRxiv2026

Long-term stomatal and leaf trait dynamics in invasive knotweeds in Europe - insights from 160 years of herbarium records

O_LIStomata and leaf traits are key regulators of plant water use efficiency and are expected to have changed in response to rising atmospheric CO2 concentrations and climate warming over the past centuries. However, long-term data documenting such changes are rare. C_LIO_LIWe leveraged herbarium collections to track changes in stomatal characteristics and leaf traits in 656 individuals of invasive Japanese knotweed and its hybrid Bohemian knotweed collected across their European range and spanning 160 years of invasive spread. C_LIO_LIWe found that several functional traits including stomatal density and maximum anatomical stomatal conductance did not show significant changes over time but that plants adjusted their stomatal size and shape over time, and that these changes were associated with increased atmospheric CO2 levels. Interestingly, Reynoutria japonica showed increases in stomatal size and stomatal elongation, while the hybrid R. x bohemica showed a reduction in stomatal size. Traits also varied systematically with climates of origin. Plants from warmer origins with higher evaporative demands during the growing season had thicker leaves, lower SLA, smaller stomata and higher stomatal density, indicating more conservative water-use strategies. Stomatal density and gas exchange capacity co-varied with leaf structural traits, and there was a trade-off between stomatal size and number. Overall, "fast" leaf economic traits were associated with "slow" physiological traits. C_LIO_LIOur results suggest that stomatal anatomical plasticity may enhance climate resilience by maintaining a stable maximum gas exchange capacity across environmental gradients. Herbarium collections provide a unique resource for reconstructing plant responses to historical environmental changes and understanding intraspecific trait variation. C_LI

ecology↗

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↗

bioRxiv2024

General purpose genotypes and evolution of higher plasticity in clonality underlie knotweed invasion

Many widespread invasive plant species express high phenotypic variation across novel environments, providing a unique opportunity to examine ecological and evolutionary dynamics under global change. However, biogeographical studies often lack information about the origin of introduced populations, limiting our understanding of post-introduction evolution of introduced species in the new range. Here, we assessed the responses of Reynoutria japonica from 128 populations spanning three latitudinal transects in the native ranges of China and Japan, and the introduced ranges of North America and Europe. When grown in two common gardens in the native range, plants from introduced populations in North America and Europe differed in almost all traits from those from native Chinese populations, but were similar to plants from native Japanese populations. Compared to Chinese populations, North American, European and Japanese populations expressed lower trait values and plasticity in most traits. However, plants from both introduced ranges and from Japanese populations expressed higher clonality and plasticity in clonality than plants from Chinese populations. In addition, introduced populations expressed higher plasticity in clonality but lower plasticity in basal diameter compared to Japanese populations. Our study showed heritable differences in phenotypes between plants from the native ranges of Japan and China, and those from the introduced ranges were similar to the putative source of origin in Japan. However, we found that introduced populations may have evolved higher plasticity in clonal growth. Our findings emphasize the critical role of clonality and plasticity in invasion success, demonstrating the importance of discriminating between source and non-source native populations to identify ecological and evolutionary responses of invasive plants to novel environments.

ecology↗

bioRxiv2024

Analysing bird population trends from monitoring data with highly structured sampling designs

Population trends derived from systematic monitoring programmes are essential to identify species of conservation concern and to evaluate conservation measures. However, monitoring data pose several challenges for statistical analysis, including spatial bias due to an unbalanced sampling of natural regions or habitats, variation in observer expertise, frequent observer changes, and overdispersion or zero-inflation in the raw data. An additional challenge arises from so-called rolling survey designs, where each site is only visited once within each multi-year rotation cycle. We developed a GAMM-based workflow that addresses these challenges and exemplify its application with the highly structured data from the Ecological Area Sampling (EAS) in the German federal state North Rhine-Westphalia (NRW). First, we derive a routine that allows informed decisions about the most appropriate combination of distribution family (Poisson or negative binomial), model covariates (e.g., habitat characteristics), and zero-inflation formulations to reflect species-specific data distributions. Second, we develop a correction factor that buffers population trend estimates for variation in observer expertise as reflected in variation in total bird abundance. Third, we integrate region-specific trends that adjust for between-year variation in the representation of habitat or natural regions within the yearly subset of sampled sites. In a consistency check, we found good match between our GAMM-based EAS trends and TRIM-based trends from the German Common Bird Monitoring scheme. The study provides a template script for R statistical software so the workflow can be adapted to other monitoring programmes with comparable survey designs and data structures.

ecology↗

bioRxiv2024

Global heterogeneity of latitudinal patterns in herbivory between native and exotic plants

Latitudinal gradient of herbivory that differs between native and exotic plants has been an open issue. It is expected that a latitudinal gradient of herbivory will be evident for native plants; this gradient in exotic plants may lag behind native plants in terms of co-evolution with local abiotic and biotic factors in introduced area. Our study aims to elucidate the difference in latitudinal gradient of herbivory between native and exotic plants globally, while exploring the underlying mechanisms driving the latitudinal gradient of herbivory with biotic and abiotic factors. To achieve this, we analyzed herbivory data from 94 studies and calculated 862 herbivory effect sizes (zr) to quantitatively characterize the intensity of latitudinal herbivory gradient. For each herbivory data, we matched the corresponding plant identity (native/exotic), herbivore feeding guilds and climate data to reveal the contribution of these factors to zr. Our findings demonstrate a significant decrease in the latitudinal gradients of with increasing latitude for native plants, a pattern not observed for exotic plants. The heterogeneity in latitudinal gradients of herbivory between native and exotic plants is mediated by herbivore feeding guilds. There is a significant influence of climatic factors on the latitudinal gradient of herbivory for native plants, but not for exotic plants. Overall, our results underscore a general heterogeneity in global macroecological herbivory patterns between native and exotic plants, and highlight the role of biotic and abiotic factors in explaining these global-scale differences.

ecology↗

bioRxiv2023

Divergence in herbivore resistance during the invasion of a global plant invader

O_LISuccessful plant invasions are often explained with adaptation to novel environments. However, invasive species often occupy broad niches within their native and introduced ranges, and a true understanding of microevolution during invasion therefore requires broad sampling of ranges, ideally with a knowledge of introduction history. C_LIO_LIWe tested for genetic differentiation in herbivore resistance among 128 introduced (Europe, North America) and native (China, Japan) populations of the invasive Japanese knotweed (Reynoutria japonica) in two common gardens in the native range. C_LIO_LIIn both common gardens we found that resistance traits of introduced populations differed from most Chinese native populations, but not from populations in Japan, the putative sources of introduction. Compared to Chinese populations, introduced European populations had thicker leaves with a lower C:N ratio but higher flavonoids contents. In the native range, variation in herbivore resistance was much more strongly associated with climate of origin than in introduced populations. C_LIO_LIOur results support the idea that founder effects played a key role in the invasion of knotweed into Europe and North America, with introduction of particular resistance phenotypes from Japan. Our study also demonstrates how knowledge of introduction history can avoid drawing wrong conclusions from observed biogeographic divergence. C_LI

ecology↗

bioRxiv2021

Parental environmental effects are common and strong, but unpredictable, in Arabidopsis thaliana

The phenotypes of plants can be influenced by the environmental conditions experienced by their parents. In some cases, such parental effects have been found to be adaptive, which has led to much speculation about their ecological and evolutionary significance. However, there is still much uncertainty about how common and how predictable parental environmental effects really are. We carried out a comprehensive test for parental effects of different environmental stresses in the model plant Arabidopsis thaliana. We subjected plants of three Arabidopsis genotypes to a broad range of biotic or abiotic stresses, or combinations thereof, and compared their offspring phenotypes in a common environment. The majority of environmental stresses (16 out of 24 stress treatments) caused significant parental effects, in particular on plant biomass and reproduction, with positive or negative effects ranging from -35% to +38% changes in offspring fitness. The expression of parental effects was strongly genotype-dependent, with some effects only present in some genotypes but absent, or even in the opposite direction, in others. Parental effects of multiple environmental stresses were often non-additive, and their effects can thus not be predicted from what we know about the effects of individual stresses. Intriguingly, the direction and magnitude of parental effects were unrelated to the direct effects on the parents: some stresses did not affect the parents but caused substantial effects on offspring, while for others the situation was reversed. In summary, parental environmental effects are common and often strong in A. thaliana, but they are genotype-dependent and difficult to predict. SignificanceStress experienced by plants can alter the phenotypes of their offspring. To understand the ecological and evolutionary significance of such parental effects, we must know how common and how predictable they are. In a large experiment with Arabidopsis thaliana, we show that the majority of 24 environmental stresses cause significant, and often strong, positive or negative parental effects. However, we also find that parental effects are genotype-specific and unrelated to the direct effect of individual stresses, and that multiple stresses often act in non-additive ways across generations. Thus, parental effects appear to be common and strong, but difficult to predict. Our findings have important implications for the study of plant responses to environmental change, and the design of stress experiments.

ecology↗

bioRxiv2021

Environmental stress determines the colonization and impact of an endophytic fungus on invasive knotweed

O_LIThere is increasing evidence that microbes play a key role in some plant invasions. A diverse and widespread but little understood group of plant-associated microbes are the fungal root endophytes of the order Sebacinales. They are associated with exotic populations of invasive knotweed (Reynoutria ssp.) in Europe, but their effects on the invaders are unknown. C_LIO_LIWe used the recently isolated Sebacinales root endophyte Serendipita herbamans to experimentally inoculate invasive knotweed and study root colonisation and effects on knotweed growth under different environmental conditions. We verified the inoculation success and fungal colonisation through immunofluorescence microscopy and qPCR. C_LIO_LIWe found that S. herbamans strongly colonized invasive knotweed in low-nutrient and shade environments, but much less under drought or benign conditions. At low nutrients, the endophyte had a positive effect on plant growth, whereas the opposite was true under shaded conditions. C_LIO_LISynthesis. Our study demonstrates that the root endophyte S. herbamans has the potential to colonize invasive knotweed fine roots and impact its growth, and it could thus also play a role in natural populations. Our results also show that effects of fungal endophytes on plants can be strongly environment-dependent, and may only be visible under stressful environmental conditions. C_LI

ecology↗

bioRxiv2020

Intraspecific variation in land use-related functional traits in Plantago lanceolata

Background and aimsIntraspecific variation in functional traits is essential for the evolutionary success of organisms. The co-variation between trait variation and environment, as well as between different traits, can help us to understand which ecological factors drive habitat adaptation, and to what extent adaptation may be constrained by trait correlations and trade-offs. In managed grasslands, plants experience a combination of competition, recurrent biomass removal and nutrient pulses. Each of these ecological challenges requires specific plant tolerances, and populations should locally adapt if intraspecific variation exists in these traits. MethodsWe studied variation in land use-related traits in the common grassland plant Plantago lanceolata. In a common environment, we quantified the competitive ability (R*), clipping tolerance and responses to a nitrogen pulse of plants from 54 populations with different land use intensities across Germany. Key resultsWe found significant population differentiation in competitive ability but there was little evidence that trait variation was related to land use intensity. There was a positive relationship between competitive ability and clipping tolerance at the population level, indicating a genetic, and possibly functional, link between these two traits. In contrast, clipping tolerance and nitrogen responses were negatively correlated at the levels of plant individuals, indicating a physiological trade-off between plant responses to these two land-use processes. ConclusionsOur results show that there is substantial intraspecific variation in some of the key functional traits for plant success in managed grasslands, and that rapid evolution and adaptation is therefore possible in these traits.

plant biology↗