Tomáš Dostálek

Genetic diversity and its effect on fitness in an endangered plant species, Dracocephalum austriacum L.

The aim of this study was to estimate genetic diversity and assess its importance for plant fitness in a species belonging to the most endangered species in Europe, Dracocephalum austriacum L., and to select the most valuable populations for conservation of genetic diversity within the species in the studied regions. We analyzed allozyme variation of 12 populations in three distinct regions (Czech Karst, Moravia and Slovak Karst) in Central Europe. The results showed high genetic diversity within populations (80.14%) and relatively low differentiation among populations within regions (9.42%) and between regions (10.45%). Seed production was significantly higher in larger, genetically more diverse and less inbred populations. The results suggest that genetic diversity has important effect on seed production in this species and thus can be expected to have strong direct consequences for plant fitness and vitality of the whole populations. They also show large variation in genetic diversity between populations and indicate which populations should get a priority in attempts to conserve all the genetic diversity within the region.

The Effect of AMF Suppression on Plant Species Composition in a Nutrient-Poor Dry Grassland

Arbuscular mycorrhizal fungi (AMF) are expected to be one of the key drivers determining the diversity of natural plant communities, especially in nutrient-poor and dry habitats. Several previous studies have explored the importance of AMF for the composition of plant communities in various types of habitats. Surprisingly, studies of the role of AMF in nutrient-poor dry grassland communities dominated by less mycotrophic plant species are still relatively rare. We present the results of a 3-year study in which a plant community in a species-rich dry grassland was subjected to the fungicide carbendazim to suppress AMF colonization. We tested the effect of the fungicide on the following parameters: the plant species composition; the number of plant species; the cover of the rare, highly mycorrhiza-dependent species Aster amellus; the cover of the dominant, less mycorrhiza-dependent species Brachypodium pinnatum; and the cover of graminoids and perennial forbs. In addition, we examined the mycorrhizal inoculation potential of the soil. We found that the suppression of AMF with fungicide resulted in substantial changes in plant species composition and significant decrease in species richness, the cover of A. amellus and the cover of perennial forbs. In contrast the species increasing their cover after fungicide application were graminoids—the C3 grasses B. pinnatum and Bromus erectus and the sedge Carex flacca. These species appear to be less mycorrhiza dependent. Moreover, due to their clonal growth and efficient nutrient usage, they are, most likely, better competitors than perennial forbs under fungicide application. Our results thus suggest that AMF are an essential part of the soil communities supporting a high diversity of plant species in species-rich dry grasslands in nutrient-poor habitats. The AMF are especially important for the maintenance of the populations of perennial forbs, many of which are rare and endangered in the area.

Comparative Population Biology of Critically Endangered Dracocephalum austriacum (Lamiaceae) in Two Distant Regions

Our study aims to compare the population dynamics of critically endangered species, Dracocephalum austriacum, in two distant regions (Czech and Slovak Karst) with similar habitat conditions, and to evaluate if conclusions concerning factors affecting population performance in one region could help in understanding species dynamics in the other region. Transition matrix models were used to examine population dynamics of the species. Results show that populations in the Slovak Karst are performing better than populations in the Czech Karst. The transitions contributing most to the population growth rates were those of stasis in the small and large adult plant stage. These transitions are, however, stable between populations and years, suggesting that they are not very sensitive to the ongoing changes. Transitions that contribute most to variations in population growth rate include seed and seedling production by large adult plants, seed germination and stasis and growth of small adult plants. These transitions seem to be affected by habitat conditions (soil depth and bare rock cover), genetic parameters of the populations, climate fluctuations (especially severe droughts), and shrub expansion. The transitions contributing most to the population growth rates are very similar between the regions except for contributions of seedling growth and stasis of large adults. These differences need to be considered before using information about the most important life cycle transitions in other regions. We suggest that similar results would be found for other species with narrow habitat requirements occupying very similar habitats, even in very distant regions.

Plant–soil feedback in native vs. invasive populations of a range expanding plant

Background and aimsAlthough plant–soil feedback has been suggested as a mechanism that drives the success of invasive plants, studies that investigate differences in the intensity of plant–soil feedback among native and invasive populations of the same species are still lacking. However, such knowledge is important because it can provide an understanding of the mechanisms responsible for the spread of a species. Rorippa austriaca is a potentially invasive species - a successful range expander in Europe.MethodsWe compared the plant–soil feedback of R. austriaca in populations from its native and invasive range. We explored both intraspecific feedback as well as feedback on a co-occurring grass species.ResultsOur results revealed a strong negative feedback effect as a consequence of soil conditioning by R. austriaca from the native range. On the contrary, a negative feedback effect was not observed for invasive R. austriaca. Interestingly, R. austriaca from the invasive range had a higher biomass than native R. austriaca.ConclusionOur results might be explained by pathogen accumulation and soil modification by native R. austriaca, which had strong intra- and interspecific effects that seemed to be lost in the invasive R. austriaca. The loss of negative intraspecific plant–soil feedback and the increased growth of the invasive population may contribute to its successful range expansion. In spite of its increased growth, the co-occurring grass species is expected to successfully coexist with the invasive R. austriaca.

Trade-off among different anti-herbivore defence strategies along an altitudinal gradient

We found that Salvia nubicola distributed along a broad altitudinal gradient developed a range of defence strategies against insect herbivores. The strategies, however, do not seem to be used simultaneously in all populations even though most of them are correlated with the altitudinal gradient along which herbivore pressure is decreasing. Our study thus shows the importance of simultaneous study of different defence strategies since understanding trade-offs among them could be necessary for detecting the mechanisms by which plants are able to cope with changes in plant-herbivore interactions as a consequence of future climate change.

Does pollen limitation affect population growth of the endangered Dracocephalum austriacum L.

Reproductive strategies can have significant consequences for the viability of plant populations. Still, the effects of lower fruit set due to pollen limitation on plant demography and population persistence have rarely been explored. The objectives of this study were to assess the ecological factors determining female reproductive success and to study the impact of pollen limitation on population growth of Dracocephalum austriacum L. (Lamiaceae), a critically endangered species with a discontinuous distribution across Europe. Despite the significant background information gathered on the population dynamics and genetic diversity of D. austriacum, little is known about its reproductive strategy and the effect it has on population growth. Thus, the reproductive system, pollinator assemblage and pollen limitation were studied in natural populations and the impact of pollen-limited seed production on population growth was assessed using existing transition matrix models. The results revealed that D. austriacum is protandrous self-compatible species that produces very few seeds in the absence of pollinators. The flowers are visited by several insects, including legitimate pollinators (e.g., Bombus hortorum, Osmia spp.) and nectar robbers (other Bombus spp., O. aurulenta). Fruit and seed production was significantly pollen-limited in all populations studied. However, despite the positive effect of pollen supplementation on seed production, the resulting increase in seed number did not significantly increase population growth rates in any of the studied populations. Hence, we conclude that populations are demographically stable and current natural seed production is sufficient for the species’ persistence.

Evolutionary responses to climate change in a range expanding plant

To understand the biological effects of climate change, it is essential to take into account species’ evolutionary responses to their changing environments. Ongoing climate change is resulting in species shifting their geographical distribution ranges poleward. We tested whether a successful range expanding plant has rapidly adapted to the regional conditions in its novel range, and whether adaptation could be driven by herbivores. Furthermore, we investigated if enemy release occurred in the newly colonized areas and whether plant origins differed in herbivore resistance. Plants were cloned and reciprocally transplanted between three experimental sites across the range. Effects of herbivores on plant performance were tested by individually caging plants with either open or closed cages. There was no indication of (regional) adaptation to abiotic conditions. Plants originating from the novel range were always larger than plants from the core distribution at all experimental sites, with or without herbivory. Herbivore damage was highest and not lowest at the experimental sites in the novel range, suggesting no release from enemy impact. Genotypes from the core were more damaged compared to genotypes from newly colonized areas at the most northern site in the novel range, which was dominated by generalist slug herbivory. We also detected subtle shifts in chemical defenses between the plant origins. Genotypes from the novel range had more inducible defenses. Our results suggest that plants that are expanding their range with climate change may evolve increased vigor and altered herbivore resistance in their new range, analogous to invasive plants.

Sustainable harvesting strategy of medicinal plant species in Nepal – results of a six-year study

Although many studies have demonstrated great variation in the life histories of various perennial plants between years and habitats, current studies on sustainable harvesting of medicinal plants have only lasted two to four years. We explored the effects of harvesting on the survival of populations of highly used perennial medicinal plants (Rheum acuminatum and R. australe) that are endemic to the Himalayan region. We collected data on recruitment, growth and survival in populations of R. acuminatum in open and forest habitats as well as R. australe in open habitats over six years in central Nepal. We used a matrix modelling approach to compare population growth and the effect of different harvesting regimes on population survival. Although the population dynamics among the studied Rheum species in the two habitat types and among various years of the study were relatively similar and stable, there were significant differences in sensitivity to harvesting. The results of our study suggest that harvesting of both species can be considered sustainable under certain conditions. Either selective (only vegetative or only flowering individuals) or rotational (once every five or more years) harvesting strategies should be adopted. Optimal management, however, partly differs between species and strongly depends on habitat conditions. The conclusions of this study could also be applied to other commonly harvested alpine and perennial medicinal plants in the Himalayan region.

Arbuscular mycorrhizal fungi and associated microbial communities from dry grassland do not improve plant growth on abandoned field soil

After abandonment of agricultural fields, some grassland plant species colonize these sites with a frequency equivalent to dry grasslands (generalists) while others are missing or underrepresented in abandoned fields (specialists). We aimed to understand the inability of specialists to spread on abandoned fields by exploring whether performance of generalists and specialists depended on soil abiotic and/or biotic legacy. We performed a greenhouse experiment with 12 species, six specialists and six generalists. The plants were grown in sterile soil from dry grassland or abandoned field inoculated with microbial communities from one or the other site. Plant growth, abundance of mycorrhizal structures and plant response to inoculation were evaluated. We focused on arbuscular mycorrhizal fungi (AMF), one of the most important parts of soil communities affecting plant performance. The abandoned field soil negatively affected plant growth, but positively affected plant response to inoculation. The AMF community from both sites differed in infectivity and taxa frequencies. The lower AMF taxa frequency in the dry grassland soil suggested a lack of functional complementarity. Despite the fact that dry grassland AMF produced more arbuscules, the dry grassland inoculum did not improve phosphorus nutrition of specialists contrary to the abandoned field inoculum. Inoculum origin did not affect phosphorus nutrition of generalists. The lower effectiveness of the dry grassland microbial community toward plant performance excludes its inoculation in the abandoned field soil as a solution to allow settlement of specialists. Still, the distinct response of specialists and generalists to inoculation suggested that they differ in AMF responsiveness.

Slow recovery of arbuscular mycorrhizal fungi and plant community after fungicide application: An eight-year experiment

Dry grasslands represent one of the most speciesrich communities in Europe (de Vries et al., 2012). These grasslands, however, are also among the most endangered habitats due to the abandonment of traditional extensive land use such as mowing and grazing (Cousins, Lindborg, & Mattsson, 2009; Eriksson, Cousins, & Bruun, 2002). Some of the grasslands were also changed to agricultural fields with intensive application of fertilizers or pesticides. After abandonment, the former fields may be recolonized by dry grassland species. However, the recovery is a slow process, and many rare plant species, typical for dry grassland habitats, are absent in the former abandoned fields even after several decades (Hemrová & Münzbergová, 2015; Knappová, Hemrová, & Münzbergová, 2012; Knappová & Münzbergová, 2015). One of the reasons for the slow recovery may be negative changes in soil biotic and abiotic properties after intensive agriculture due to fertilizer and fungicide application (Howell, Hilton, Received: 24 February 2016 | Revised: 9 March 2018 | Accepted: 25 April 2018 DOI: 10.1111/jvs.12656