Gentianella Campestris Research Articles

The decline of Gentianella campestris: three decades of population development of an endangered grassland plant in Sweden

Species‐rich semi‐natural grasslands are declining all over northern Europe, and many plant species confined to such grasslands are currently under threat. We studied the development of populations of one such species, the field gentian Gentianella campestris, during three decades in the County of Södermanland, south of Stockholm, Sweden. Gentianella campestris is Red Listed as Endangered in Sweden. It is a strict biennial, and as far as known with only a transient seed bank. Large population fluctuations are a characteristic of this species, and its life history makes the species inherently sensitive to factors causing population reductions. We found that the number of sites with G. campestris has declined with over 60% in the last three decades. The total number of flowering individuals also show a strong decreasing trend, although there was an increase the last year (2020) at a few remaining sites. Cessation of grazing management is a major cause of the decline, but populations also disappeared from managed sites. It is possible that the management has been inappropriate, and circumstantial evidence suggests that summer drought might be an additional cause of population decline. Data from 2018, a year with an exceptional summer drought, supports this explanation. A sowing experiment indicated that recruitment of new populations is unlikely in the present‐day landscape where most vegetation is unsuitable for G. campestris. Due to the poor prospects for long‐term maintenance of grazing management in still remaining semi‐natural grasslands, and the decline even at sites with current management, G. campestris faces a risk of becoming regionally extinct within the coming decades.

Genetic variation of Gentianella campestris ssp. campestris in the Northern Alps: how important are population size and isolation?

In this study, we analysed the impact of population size and isolation on the genetic variation of the short-lived alpine plant species Gentianella campestris ssp. campestris from two study regions (Allgau and Karwendel) in the Northern calcareous Alps in Germany. We determined the size and isolation of the study populations and analysed genetic variation using amplified fragment length polymorphisms. Genetic variation of G. campestris ssp. campestris differed significantly between the two study regions. Genetic variation did not depend on population size. However, the level of genetic variation within populations was about three times lower in the Karwendel, where the species is much more isolated than in the Allgau. Conversely, genetic variation among populations was much stronger in the Karwendel than in the Allgau. Our results support the observation that the level of genetic variation within populations of alpine plant species may not only be affected by population size, but also by population isolation. Depending on the distance among populations, gene flow by exchange of pollen and seeds triggers the influx of genetic variation, thereby sometimes superimposing the effects of population size. Our results suggest that for seed collections in conservation projects, not only population size, but also isolation should be considered.

Growing competitive or tolerant? Significance of apical dominance in the overcompensating herb Gentianella campestris.

As a compensatory response to herbivory, plants may branch vigorously when the growth of dormant meristems is triggered by shoot damage. Undamaged plants, on the other hand, often restrain branching, and this limitation on growth can be considered a cost of tolerance to herbivory. Restrained branching is caused by apical dominance and may, alternatively, be associated with fitness benefits in competitive environments that favor fast vertical growth. To test these hypotheses regarding selection for restrained branching, we compared the performance of two subspecies of the biennial grassland herb Gentianella campestris; the tall, apically dominant ssp. campestris and the short, multi-stemmed ssp. islandica, which shows reduced apical dominance. For both subspecies, we manipulated the height of surrounding vegetation (competition) and damage intensity in grasslands of differing productivity (high, medium, low), and examined population growth rates using matrix population models combined with life table response experiments. In the absence of damage, ssp. campestris exhibited a higher population growth rate than ssp. islandica in the tallest vegetation, however with the growth rate still being below one. In the medium and low productivity environments where the vegetation was shorter, the population growth rate of ssp. islandica was considerably higher than that of ssp. campestris as long as no more than about 50% of the plants were damaged. When plants were damaged, the apically dominant ssp. campestris showed a positive population growth rate (λ>1) and often overcompensatory seed production in all productivity levels, while ssp. islandica showed no compensation and therefore the population was predicted to decline (λ<1). We conclude that restrained branching in Gentianella cannot be selected for by competition alone, but that episodes of apical damage are required to maintain the trait. Furthermore, because of the costs of restrained branching, apical dominance should be selected against in grasslands where competition and disturbance are low.

Grazing is the key to the conservation ofGentianella campestris(L.) Börner (Gentianaceae): evidence from the north Merseyside sand-dunes

AbstractPopulations and habitat of the internationally-declining Gentianella campestris (L.) Borner were studied on a calcareous coastal sand-dune system at Ainsdale in north-western England. The total of 140,700 plants is thought to be the largest population in Britain and may be of European significance. In recent years, this species has greatly increased at Ainsdale, especially within a ‘Dune Restoration Area’ where pine trees and scrub were removed in the 1990s, followed by sheep-grazing. G. campestris was mainly found in dry-slacks where patches of short grassy vegetation are maintained by rabbits within areas largely dominated by Salix repens (UK National Vegetation Classification SD16d: Salix repens–Holcus lanatus dune-slack, Agrostis stolonifera sub-community). There was a close coincidence between G. campestris occurrence and compartments fenced for winter sheep-grazing, but plants were absent from older, more acidic, slacks in the eastern part of the study area. It is inferred that the recent po...

Grazing tolerance and mycorrhizal colonization: Effects of resource manipulation and plant size in biennial Gentianella campestris

As herbivory usually leads to loss of photosynthesizing biomass, its consequences for plants are often negative. However, in favorable conditions, effects of herbivory on plants may be neutral or even beneficial. According to the compensatory continuum hypothesis plants can tolerate herbivory best in resource-rich conditions. Besides herbivory, also primarily positive biotic interactions like mycorrhizal symbiosis, bear carbon costs. Tritrophic plant–fungus–herbivore interaction further complicates plant's cost-benefit balance, because herbivory of the host plant is expected to cause decline in mycorrhizal colonization under high availability of soil nutrients when benefits of symbiosis decline in relation to costs. To gain insight into above interactions we tested the effects of plant size and resource manipulation (simulated herbivory and fertilization) on both above-ground performance and on root fungal colonization of the biennial Gentianella campestris. Clipping caused allocation shift from height growth to branches in all groups except in large and fertilized plants. For large plants nutrient addition may have come too late, as the number of meristems was most likely determined already before the fertilization. Clipping decreased the amount of DSE (dark septate endophytic) fungi which generally are not considered to be mycorrhizal. The effect of clipping on total fungal colonization and colonization by arbuscular mycorrhizal (AM) fungal coils were found to depend on host size and resource level. Dissimilar mycorrhizal response to simulated herbivory in small vs. large plants could be due to more intensive light competition in case of small plants. Carbon limited small plants may not be able to maintain high mycorrhizal colonization, whereas large clipped plants allocate extra resources to roots and mycorrhizal fungi at the expense of above-ground parts. Our results suggest that herbivory may increase carbon limitation that leads re-growing shoots and fungal symbionts to function as competing sinks for the limited carbon reserves.

A case with blue gentian blues: roadside‐cutters creating neo grasslands as refugia for endangered Gentianella campestris

In this paper, we report how roadside cutting affect individuals of field gentian Gentianella campestris, a highly cutting tolerant grassland herb, and if roadsides could serve as refugia for this endangered species. Injured plants produced four times more branches located close to the ground and the plants were more than two times heavier compared to the uninjured ones. No differences in final reproductive parameters between the injured and uninjured plants were observed. Unsuccessful and slow allocation of belowground resources to reproductive organs to be the reason for the overcompensation injured plants, when measured in vegetative biomass, but not in reproductive output. However, because the injured plants either fully compensated, or even overcompensated, the damage in all parameters, our results suggest that substitutive habitats, such as the roadside in question, may provide temporary safe‐sites for some species, and from these refugia they may disperse back to their original, restored habitats in the future.

Xanthones fromGentiana campestrisas New Acetylcholinesterase Inhibitors

In order to discover new acetylcholinesterase (AChE) inhibitors, different plant extracts were screened by a previously established TLC bioautographic method. The methanol extract of Gentiana campestris leaves exhibited significant inhibition of AChE activity. A bioactivity-guided fractionation approach was undertaken to isolate the active components. Four xanthones, bellidin, bellidifolin, bellidin 8-O-beta-glucopyranoside (norswertianolin), and bellidifolin 8-O-beta-glucopyranoside (swertianolin), were found to be responsible for the anti-AChE activity effects. Bellidifolin showed similar activity to galanthamine in this enzyme assay.

Grazing tolerance of Gentianella amarella and other monocarpic herbs: why is tolerance highest at low damage levels?

Plants have adapted to compensate for the loss of vegetative biomass and reproductive potential caused by grazing. Shoot damage breaks down the correlative inhibition maintained by apical dominance. The consequent increased branching may lead to increased production of flowers and fruits in damaged plants, provided that enough resources, both in terms of meristems and nutrients, are available. In Gentianella amarella, the removal of the apex of the main stem (10% clipping) had no pronounced effect on branching and plant performance. In one of the two study populations, however, apically damaged plants produced more fruits than undamaged control plants. The plants also fully compensated for 50% removal of the main stem in terms of above-ground biomass, but their fruit production was reduced compared to control and apically damaged plants. After 75% clipping, fruit production was not significantly reduced compared to 50% clipping. Consequently, G. amarella showed highest tolerance in the presence of minor shoot damage. The pattern is qualitatively similar in some other monocarpic species (Gentianella campestris, Erysimum strictum and Rhinanthus minor). Multiple constraints as well as selective forces may shape these compensatory responses: (1) A lack of basal meristems may constrain tolerance of high damage levels. (2) Species with basal meristems may have a potential to tolerate major damage, but a shortage of resources or otherwise unfavourable growth conditions may constrain their compensatory ability. (3) It may be adaptive to have maximum tolerance of low and moderate damage levels if chemical defences reduce the risk of extensive shoot damage as well as the risk of repeated grazing. (4) The compensatory ability of monocarpic species may be affected by selective forces that favour fast vertical growth early in the season and unbranched architecture in undamaged conditions. Therefore, it is not the mere grazing history, but also other factors associated with growth conditions that are required to explain the variation in grazing tolerance.

EXTINCTION THRESHOLDS AND DISRUPTED PLANT–POLLINATOR INTERACTIONS IN FRAGMENTED PLANT POPULATIONS

In order to estimate how much population extinction risk may be affected by local fragmentation, population viability analyses were performed in six populations of the endangered grassland herb Gentianella campestris in Sweden. The populations had been experimentally reintroduced to grasslands that were locally fragmented by juniper shrubs. The sites represented three sizes of grassland and two levels of grassland abundance in the landscape. Five years' demographic data were evaluated in a stochastic matrix population model, and studies of seed set, pollinator abundance, and inbreeding depression were performed in order to examine possible links between population viability and pollination. In all six sites, plants with reduced capacity of self-pollination (due to herkogamy) showed strongly reduced population viability in locally fragmented grassland habit, with pronounced extinction thresholds at certain levels of local fragmentation. Population viability was reduced because of inbreeding depression and reduced seed production in combination, both caused by pollinator deficit in locally fragmented grasslands. Plants with high selfing capacity had low population viability over the entire local fragmentation gradients. Selfing yielded high seed set in the absence of pollinators and was advantageous in fragmented parts of the grasslands. However, selfing had negative effects in nonfragmented parts of the grasslands, because it decreased the chances of cross-pollination and because selfed progeny had reduced fitness compared to outcrossed offspring. A comparison among the six sites indicated that the negative effects of local fragmentation were amplified by reduced size of the grassland sites and by reduced abundance of grassland habitat in the landscape. To my knowledge, this is the first quantitative estimate of increased extinction risk in fragmented plant populations.

Mycorrhizal plants of traditionally managed boreal grasslands in Norway

This paper reports on the mycorrhizal status of 82 plant species growing in traditionally managed grasslands in three different locations in the boreal and boreo-nemoral vegetation zone in the eastern part of Norway. Seventy-four species were found to have arbuscular mycorrhiza (AM). To our knowledge, we report AM for the first time in Achillea ptarmica, Ajuga pyramidalis, Alchemilla glaucescens, Carex brunnescens, Carex pallescens, Crepis praemorsa, Hieracium lactucella, Rumex longifolius, Scorzonera humilis, Trifolium aureum and Trifolium spadiceum. The rare and threatened species Arnica montana, S. humilis, C. praemorsa, Gentianella campestris, Parnassia palustris, T. aureum and T. spadiceum, all confined to grasslands, were found to possess AM fungi.

Demographic variation and population viability in Gentianella campestris: effects of grassland management and environmental stochasticity

Summary Transition matrix models were used to evaluate the effects of environmental stochasticity and four different methods of grassland management on dynamics and viability of a population of the biennial Gentianella campestris (Gentianaceae) in species‐rich grassland. Data were collected between 1990 and 1995. Continuous summer grazing, the prevailing management strategy in Scandinavian grasslands, resulted in high recruitment of new plants, mainly because litter accumulation was prevented and gaps were created by trampling. Trampling and repeated grazing, however, caused damage which reduced seed production. Lambda for the average matrix was c. 0.77, and a stochastic matrix model yielded an extinction probability for the total population of c. 0.08 within 50 years. Mowing in mid‐July (used as a conservation tool) increased seed production, but litter accumulation following re‐growth of the vegetation prevented establishment. Lambda and extinction risk were similar to continuous grazing. Mowing in October (another conservation tool) promoted recruitment because of low litter accumulation, but the seed output decreased because plant growth was impaired by tall vegetation. Lambda was 0.64, while the extinction probability was very high (c. 0.98 within 50 years). Mid‐July mowing followed by autumn grazing (the historical management regime) yielded high values for both seed production and establishment of rosettes. Lambda was 0.94 and the probability of extinction within 50 years was below detection level. Log‐linear analysis showed that the matrices differed significantly both between treatments and between years. The latter indicates environmental stochasticity, here caused by summer drought that increased the extinction risk. Lambda may be slightly underestimated because drought occurred in one out of five summers during the study period, which is high compared with the natural frequency. We conclude that traditional grassland management is more favourable for G. campestris than the methods that prevail in Scandinavia today. This indicates a serious conservation problem, because grazing has replaced traditional management in many of the remaining semi‐natural grasslands throughout Europe.

Koeleria macrantha (Ledeb.) Schultes (K. alpigena Domin, K. cristata (L.) Pers. pro parte, K. gracilis Pers., K. albescens auct. non DC.)

<i>Koeleria macrantha</i> (Ledeb.) Schultes (<i>K. alpigena</i> Domin, <i>K. cristata</i> (L.) Pers. pro parte, <i>K. gracilis</i> Pers., <i>K. albescens</i> auct. non DC.)

The evolution of tolerance to damage in Gentianella campestris: natural selection and the quantitative genetics of tolerance

In the framework of phenotypic plasticity, tolerance to browsing can be operationally defined as a norm of reaction comparing plant performance in undamaged and damaged conditions. Genetic variation in tolerance is then indicated by heterogeneity in the slopes of norms of reaction from a population. We investigated field gentian (Gentianella campestris) tolerance to damage in the framework of phenotypic plasticity using a sample of maternal lines from natural populations grown under common garden conditions and randomly split into either a control or an artificial clipping treatment. We found a diversity of tolerance norms of reaction at both the population and family level: the impacts of clipping ranged from poor tolerance (negative slope) to overcompensation (positive slope). We detected heterogeneity in tolerance norms of reaction in four populations. Similarly, we found a variety of plastic architectural responses to clipping and genetic variation in these responses in several populations. Overall, we found that the most tolerant populations were late flowering and also exhibit the greatest plastic increases in node (meristem) production in response to damage. We studied damage-imposed natural selection on plasticity in plant architecture in 10 of the sampled populations. In general, there was strong positive direct selection on final number of nodes for both control and clipped plants. However, the total selection on nodes (direct + indirect selection) within each treatment category depended heavily on the frequency of damage and cross-treatment genetic correlations in node production. In some cases, strong correlated responses to selection across the damage treatment led to total selection against nodes in the more rare environment. This could ultimately lead to the evolution of maladaptive phenotypes in one or both of the treatment categories. These results suggest that tolerance and a variety of architectural responses to damage may evolve by both direct and indirect responses to natural selection. While the present study demonstrates the potential importance of cross-treatment genetic correlations in directing the evolution of tolerance traits, such as branch or node production, we did not find any strong evidence of genetic trade-offs in candidate tolerance traits between undamaged and damaged conditions.

Tolerance of Gentianella campestris in relation to damage intensity: an interplay between apical dominance and herbivory

Meristem allocation models suggest that the patterns of compensatory regrowth responses following grazing vary, depending on (i) the number of latent meristems that escape from being damaged, and (ii) the activation sensitivity of the meristems in relation to the degree of damage. We examined the shape of compensatory responses in two late-flowering populations (59°20′N and 65°45′N) of the field gentian. Plants of equal initial sizes were randomly assigned to four treatment groups with 0, 10, 50 and 75% removal of the main stalk. The plants were clipped before flowering, and their performance was studied at the end of the growing season. The northern population showed a linear decrease in shoot biomass and fecundity with increasing biomass removal, while the response in the southern population was quadratic with maximum performance at the damage level of 50% clipping. This nonlinear shape depended upon the activation sensitivity of dormant meristems in relation to their position along the main stem. The highest plant performance was achieved by inflicting intermediate damage which induced regrowth from basally located meristems. In contrast, the topmost branches took over the dominance role of the main stem after minor apical damage (10% clipping). Consequently, the breakage of apical dominance is a necessary precondition of vigorous regrowth in this species. However, compensation in the field gentian is unlikely to be a mere incidental by-product of apical dominance. The ability to regrow from basally located meristems that escape from being damaged by grazing may well be a sign of adaptation to moderate levels of shoot damage.

Ecological significance and heritability of floral reproductive traits in Gentianella campestris (Gentianaceae)

We investigated the occurrence of herkogamy and dichogamy in 43 populations of the grassland biennial Gentianella campestris in Sweden, and experimentally tested their significance for the reproductive system of the species. Furthermore, we performed a heritability test to evaluate the potential for selection on traits related to herkogamy. Dichogamy did not occur in the studied populations, and herkogamy was restricted to five populations. Two types of herkogamy were found, one with the stigma protruding above the anthers (hyper-stigmatic), and one with the stigma positioned below the anthers (hypo-stigmatic). In both types, the stamens elongated during anthesis. In the hyper-stigmatic plants, the anthers reached and pollinated the stigma after c. 34 days. This did not occur in hypo-stigmatic plants. Pollination experiments showed that the plants were self-compatible and that elongation of stamens provided a mechanism for reproductive assurance in hyper-stigmatic plants. The type of herkogamy did not differ between flowers of the same developmental stage within a plant. In two of the five herkogamous populations, the herkogamy differed between plants, but there was a normal distribution of the anther-stigma separation. Herkogamy was not related to population size. A comparison of the anther-stigma separation of self-pollinated mother plants and their offspring showed that herkogamy was a highly heritable trait (average h 2 = 0.85), that clearly has the potential to respond to selection

Regrowth following ungulate herbivory in Ipomopsis aggregata: geographic evidence for overcompensation.

Studies were conducted on eight populations of scarlet gilia, Ipomopsis aggregata, across Colorado and in northern Arizona, to assess the fitness consequences of natural and simulated herbivory. To date, geographic studies have failed to incorporate treatment groups that included naturally browsed plants along with clipping treatments. The results presented here clearly demonstrate the importance of assessing, a priori, whether or not clipping experiments accurately reflect natural patterns of herbivory. Although because of the timing of the clip no evidence of overcompensation was found in any of the Colorado populations when ungulate herbivory was simulated in experimental clipping treatments, evidence for overcompensation was found in more than half the populations when plants that were naturally browsed and matched for size using root diameters were included early in the season. Matching plants for size based on root diameter late in the season would be problematic because root diameters significantly increased in size in all eight populations following high levels of ungulate herbivory and/or experimental clipping. Results from this study, and other recent studies on another biennial herb, the field gentian, clearly demonstrate that overcompensation is not only a real phenomenon but also is more widespread, both taxonomically and geographically, than previously thought.

Plant Adaptations to Herbivory: Mutualistic versus Antagonistic Coevolution

The discovery of overcompensatory responses to damage in some plant species has inspired attempts to classify some plant-herbivore interactions as mutualism. Since the debates over plant-herbivore mutualism and overcompensation have been intense, we attempt to outline three conceptual models of plant-animal interactions and evaluate the status of interactions with help of three different fitness criteria: relative fitness, absolute fitness, and mean absolute fitness. Our three plant-animal interactions are assumed to represent plant-pollinator mutualism, plant-herbivore antagonism and the evolution of overcompensation, respectively. Each case describes how absolute fitness, and consequently also the other two fitness criteria, is assumed to change with animal encounters for plants with special adaptations to cope with those encounters and for plants with no such adaptations. As a result, all these types of interactions may be considered as mutualism when taken relative fitness only into account. Obviously, this criterion is too weak because any trait, evolving under natural selection, should improve fitness relative to other, alternative traits. Absolute fitness increases with animal encounters for the adapted phenotype in the first and in the last case and thus, in the context of absolute fitness, overcompensation in plants would indicate plant-herbivore mutualism. However, absolute fitness as such may not be sufficient when discussing the evolutionary history of plant-animal mutualism. In the light of mean fitness, overcompensation as presented in earlier studies does not represent mutualism between plants and herbivores. Mean absolute fitness in plant populations decrease with the risk of herbivore attack in our model of overcompensation, while the reverse trend characterises our plant-pollinator model. We, therefore, suggest that mean absolute fitness may well provide an appropriate criterion for distinguishing mutualistic and antagonistic plant-animal interactions in coevolutionary contexts. In order to evaluate our model-system, we compare the predicted patterns with empirical data on the grassland biennial Gentianella campestris.

Site occupancy, recruitment and extinction thresholds in grassland plants: an experimental study

There is a great need for simple but realistic methods for assessing status and management prescriptions for declining plants in fragmented landscapes. In this study we discuss a method for estimating extinction thresholds for metapopulations, based on analyses of site occupancy and recruitment of 18 species characteristic of semi-natural grasslands in Scandinavia. The extinction threshold refers to the fraction of remaining suitable habitat at which a species becomes extinct. Site suitability was estimated from sowing experiments and occupancy was estimated from site inventories. A comparison between the estimated extinction thresholds and remaining suitable habitats indicated that a decline in species diversity would accompany a further reduction of suitable habitat. An alternative `quasi-equilibrium' extinction threshold was also tested based on the assumption that there is a delay in population decline. With this approach, eight of the 18 selected species presently live `below' the extinction threshold. In order to estimate the accuracy of the methods, we made a tentative comparison of the results with knowledge of species status from other sources of information. We suggest that three species, Agrimonia eupatoria, Antennaria dioica, and Gentianella campestris may experience further decline in Scandinavia in the near future. Studies of occupancy, recruitment and extinction thresholds provide a useful framework for community-wide surveys of species in declining habitats.

Reduced community diversity in semi-natural meadows in southern Sweden, 1965–1990

Two data sets, one from the 1960s and one from 1990, from continuously managed semi-natural meadows (semi-natural grasslands used for hay-cutting) in Smaland, southern Sweden, were analysed to describe the vegetation and in an attempt to characterise changes that have occurred in the vegetation. Based on a classification of the data set, nine plant communities were recognised. The main vegetational differences, as revealed by an ordination, were due to variation in soil moisture, which ranged from wet to dry. During the investigation period, the amount of hay meadow area decreased, particularly the area of wet-moist meadows. In addition, the total variation in the vegetation diminished, and three plant communities more or less disappeared. The turnover index of species in the data set was 36%, and most of the species that were lost had initially been uncommon. Lost species included rare taxa, such as Gentianella campestris and Linum catharticum, while the new species tended to be common in the region. Annual and biennial species accounted for a greater proportion of the lost taxa than did perennial species. The mean cover of species per plot and the relative abundance of graminoids per plot increased. The recorded changes in the vegetation may be related to the increased loads of nitrogen pollutants as well as to a decrease in management intensity. The diminished area is related to changes in land-use. The meadow sites in Smaland have been part of a landscape rich in grasslands, but today they have a more or less relict status. They differ from grasslands found elsewhere in Sweden and Scandinavia. In Sweden, the majority (68%) of endangered vascular plants belong to the agricultural landscape. To ensure the survival of individual species it is important to preserve all types of meadows, not only a few selected ones, since no two meadows are alike.

Induction of Overcompensation in the Field Gentian, Gentianella campestris

Induction of Overcompensation in the Field Gentian, Gentianella campestris