2016. január 21., csütörtök

Sonkoly et al. (2016) Journal of Ecology

Sonkoly J., E. Vojtkó A., Tökölyi J., Török P., Sramkó G., Illyés Z., Molnár V. A. (2016): Higher seed number compensates for lower fruit-set in deceptive orchids. – Journal of Ecology DOI 10.1111/1365-2745.12511

1. Floral deception is widespread in orchids, with more than one-third of the species being pollinated this way. The evolutionary success of deceptive orchids is puzzling, as species employing this strategy are thought to have low reproductive success (less flowers yielding fruits) because of low pollination rates. However, direct measurements of total seed production in orchids – which is a better measure of reproductive success – are scarce due to the extremely small size of their seeds.
2. Here, we quantified seed numbers in 1015 fruits belonging to 48 orchid species from the Pannonian ecoregion (central Europe) and obtained fruit set and thousand-seed weight data for these species from the literature. We used phylogenetic comparative methods to test the hypothesis that deceptive species should compensate for their lower fruit set by having either more flowers, larger seeds or more seeds in a fruit.
3. Similarly to previous studies, we found that deceptive orchids have substantially lower fruits-set than nectar-rewarding ones. Also, we found that deceptive species have more seeds in a fruit but not more flowers or larger seeds compared to nectar-rewarding ones. Based on our results, deceptive species compensate for their lower fruit set by having higher seed numbers per fruit. As a consequence, their seed numbers per shoot do not differ from that of nectar-rewarding ones.

4. Together with other benefits of deceptive pollination (e.g. lower energy expenditure due to the lack of nectar production and higher genetic variability due to decreased probability of geitonogamous pollination), our results can explain why deceptive strategies are so widespread in the orchid family.

5. Synthesis. Our results indicate that deceptive orchids can compensate for their lower fruit set by having more (but not larger) seeds in a fruit than rewarding species. These findings highlight possible ways in which plants can increase their reproductive success in face of pollinator limitation. We emphasize that fruit set in itself is an inappropriate measure of the reproductive success of orchids – the total number of seeds per shoot is a much better approximation.

deception, nectar reward, Orchidaceae, phylogenetic comparative methods, pollination, reproductive ecology, reproductive success, seed mass, seed number, thousand-seed weight

Molnár V. et al. (2015) PeerJ

Molnár V. A, Tóth J. P., Sramkó G., Horváth O., Popiela A., Mesterházy A., Lukács B. A. (2015): Flood induced phenotypic plasticity in amphibious genus Elatine (Elatinaceae). – PeerJ 3:e1473; DOI 10.7717/peerj.1473

Vegetative characters are widely used in the taxonomy of the amphibious genus Elatine L. However, these usually show great variation not just between species but between their aquatic and terrestrial forms. In the present study we examine the variation of seed and vegetative characters in nine Elatine species (E. brachysperma, E. californica, E. gussonei, E. hexandra, E. hungarica, E. hydropiper, E. macropoda, E. orthosperma and E. triandra) to reveal the extension of plasticity induced by the amphibious environment, and to test character reliability for species identification. Cultivated plant clones were kept under controlled conditions exposed to either aquatic or terrestrial environmental conditions. Six vegetative characters (length of stem, length of internodium, length of lamina, width of lamina, length of petioles, length of pedicel) and four seed characters (curvature, number of pits / lateral row, 1st and 2nd dimension) were measured on 50 fruiting stems of the aquatic and on 50 stems of the terrestrial form of the same clone. MDA, NPMANOVA Random Forest classification and cluster analysis were used to unravel the morphological differences between aquatic and terrestrial forms. The results ofMDA cross-validated and Random Forest classification clearly indicated that only seed traits are stable within species (i.e., different forms of the same species keep similar morphology). Consequently, only seed morphology is valuable for taxonomic purposes since vegetative traits are highly influenced by environmental factors.

Adaptation, Macrophyte, Seed-morphology, Cultivation experiments, Seed characters, Vegetative characteristics,Water depth,Wetland ephemerophytes, Morphological variability

Miglécz et al. (2015) Scientia Horticulturae

Developing sustainable farming practices to support ecosystem functions and services are key issues of agro-ecology and conservation biology. In organic wine production, preserving soil fertility and weed control are essentialtasks, because the use of synthetically processed herbicides, pesticides and fertilizers is strongly limited. Thus, itis vitalto propose and test alternative techniques to link issues of weed control, preservation of soil fertility and the improvement and conservation of agro-biodiversity. To fulfil these issues, the use of species-rich cover crops became increasingly integrated into organic wine production. We evaluated the establishment of three vineyard cover crop seed mixtures sown in the vineyards of the Tokaj region, East-Hungary to answer the following questions: (i) which sown species were successfully established during the first year after sowing? (ii) Which sown species established successfully even during the second year? (iii) How effective were the sown cover crop seed mixtures in weed control? We evaluated three types of species-rich seed mixtures: Biocont-ECOWIN, Grass-medical forb and Legume seed mixtures. Percentage cover of vascular plant species was recorded in the inter-rows in five 1 × 1 m permanent plots in late June, 2012 and 2013. All sown species established within the study period. During the first year mostly short-lived species established successfully from the sown seed mixtures. During the second year Lotus corniculatus, Medicago lupulina, Plantago lanceolata, Trifolium repens and Trifolium pratense established the most successfully, and had high cover scores at most sites out of the sown species. A significant weed suppression was detected for all sown mixtures (Biocont-ECOWIN seed mixture: at two sites; Grass-medical forb seed mixture: at every site; Legume seed mixture: at two sites). The magnitude of weed suppression varied with the sown seed mixture. During the first year BiocontECOWIN seed mixture was the most successful in weed suppression. During the second year the cover of weeds was suppressed most effectively by Grass-medical forb and Legume seed mixtures. Our findings suggest that high diversity seed mixtures are suitable to establish permanent cover crops, which enables to use them successfully at sites with different abiotic conditions.

Agro-biodiversity, Biodiversity, Ecosystem services, Grapevine, Soil protection, Weed management

Lukács et al. (2015) Tuexenia

Lukács, B. A., Török, P., Kelemen, A., Várbíró, G., Radócz, Sz., Takács, S., Miglécz, T., Tóthmérész B., Valkó O. (2015): Rainfall fluctuations and vegetation patterns in alkali grasslands – Self-organizing maps in vegetation analysis. Tuexenia, 35: 381-397

Knowledge about the drivers of vegetation dynamics in grasslands is fundamental to select appropriate management for conservation purposes. In this study, we provide a detailed analysis of vegetation dynamics in alkali grasslands, a priority habitat of the Natura 2000 network. We studied vegetation dynamics in five stands of four alkali grassland types in the Hortobágy National Park (eastern Hungary), between 2009 and 2011. We analysed the effect of fluctuations in precipitation on both the overall vegetation composition and on the cover of each species using Self Organizing Map neural networks (SOM). We found that SOM is a promising tool to reveal plant community dynamics. As we analysed species cover and overall vegetation composition separately, we were able to identify the species responsible for particular vegetation changes. Fluctuations in precipitation (a dry season, followed by a wet and an average season) caused quick shifts in plant species composition because of an increasing cover of halophyte forbs, probably because of salinisation. We observed a similar effect of stress from waterlogging in all studied grassland types. The species composition of Puccinellia grasslands was the most stable over the three years with varying precipitation. This was important as this grassland type contained many threatened halophyte species. Self-organising maps revealed small-scale vegetation changes and provided a detailed visualisation of short-term vegetation dynamics, thus we suggest that the application of this method is also promising to reveal community dynamics in more species-rich habitat types or landscapes.

halophytes, neural network, precipitation changes, salt stress, SOM, water stress

Kelemen et al. (2015) Preslia

Kelemen, A., Lazzaro, L., Besnyői, V., Albert, Á-J., Konečná, M., Dobay, G., Memelink, I., Adamec, V., Götzenberger, L., de Bello, F., Le Bagousse-Pinguet, Y., Lepš J. (2015): Net outcome of competition and facilitation in a wet meadow changes with plant’s life stage and community productivity. Preslia 87: 347–361.

Positive and negative plant-plant interactions generally co-occur in communities but their relative importance should depend on site productivity; the importance of facilitation is expected to increase and that of competition to decrease with the adversity of the environment. Moreover the effect of surrounding vegetation on an individual’s performance can vary depending on the individual’s life stage and on the variables used to characterize an individual’s performance. To test these theories, we established a transplant experiment in a wet meadow in order to assess the effects of surrounding vegetation on individual plants under varying environmental conditions and changes in these effects during an individual’s development within one growing season. We asked whether (i) the net effects of plant interactions differ with differences in productivity and disturbance, and (ii) the net effects of interactions differ according to life stage, species and the performance measure used. We utilized a long-term experiment with three treatments (application of fertilizer, mowing and removal of the dominant species) in a full factorial design, yielding eight combinations, with three replicate plots per combination. In each plot four individuals of three species (Lysimachia vulgaris, Prunella vulgaris and Plantago lanceolata) were transplanted, two into gaps and two into intact vegetation. Survival (alive/dead) of each individual was recorded twice during the season. The presence of flowers and above- and below-ground biomass were recorded at the end of the transplant experiment. The survival of transplants early in the season was higher when growing among vegetation, indicating that at an early stage in its life the net effect of the surrounding vegetation was positive. At later stages, competition became more important and had a negative effect on biomass production and plant reproduction. This negative effect was more pronounced in fertilized plots while the effect of mowing and removal of dominant species on plant interactions was generally negligible. Our results indicate, particularly under more productive conditions, the importance of changes in the net outcome of plant interactions during different life stages, highlighting the dynamic nature of positive and negative interactions within a community.

above-ground biomass, disturbance, fertilization, Molinia removal, mowing, neighbour-effect, ontogenetic shift, plant-plant interactions, root-shoot ratio, survival

Kelemen et al. (2016) Applied Vegetation Science

Kelemen, A., Valkó, O., Kröel-Dulay, Gy., Deák, B., Török, P., Tóth, K., Miglécz, T., Tóthmérész, B. (2016): The invasion of common milkweed (Asclepias syriaca L.) in sandy old-fields – Is it a threat to the native flora? Applied Vegetation Science, doi: 10.1111/avsc.12225

Common milkweed (Asclepias syriaca L.) is an invasive ‘super species’ that has invaded extensive areas in Europe, forming novel ecosystems. One study has reported neutral effects of common milkweed on the native flora of sand dune grasslands in Hungary after the removal of invasive pine plantation. However, the effects of common milkweed on native flora more generally are unknown. Focusing on the potential effect of milkweed, we tested the following hypotheses: (1) the cover of native grassland species decreases with increasing cover of common milkweed; and (2) native species with low specific leaf area (SLA), height, seed mass and clonal spreading ability (i.e. low competitive ability) are more likely suppressed by milkweed compared with natives with high competitive ability.

Late successional sandy old-fields invaded by milkweed in the Great Hungarian Plain (Kiskunság, central Hungary).

We recorded the cover of vascular plants in seven old-fields; in each old-field we sampled 12 plots including plots with different milkweed cover and control plots without milkweed. We used linear mixed effect models for exploring the effects of milkweed on the species richness and cover of native grassland species. To identify the common traits of the most affected native species, we used trait-based analyses; we studied leaf–height–seed traits and clonal spreading ability.

We detected no effect of common milkweed on total species richness, but it had a negative effect on the cover of grassland species. The negative effect of common milkweed was most pronounced on the cover of species with low SLA, low seed mass and low clonal spreading ability.

Our results suggest that native, late successional sandy grasslands invaded by common milkweed form undesirable novel ecosystems because of significant negative impacts on the cover of native grassland species, especially those species with low competitive ability. For these species, management of milkweed might be needed to ensure their persistence in sandy grasslands in this landscape.

Clonal spreading, Competition, Functional traits, Novel ecosystem, Old-field, Plant invasion, Sandy vegetation, Seed mass, Specific leaf area

2015. november 11., szerda

Popiela et al. (2015) Acta Botanica Gallica

Elatine trianda Schkuhr is the most widespread species within the genus Elatine L.; it can be found in all continents, except Antarctica, but the majority of the locations have been recorded in Europe. The study is based on an extensive dataset of literature, herbaria and web data, which spans the period 1828–2012. The range of the species in Europe is disjunctive; it covers the southern and western parts of the Central European Plain and the northern shores of the Baltic Sea, it can also be found along some river valleys. In Central Europe many localities especially isolated ones in northern part of the range are historical now. According to the dataset we determined that E. triandra can be observed between May and October. We also found a remarkable historical decrease of observation time. We found that species observation has a near significant shift since 1828 that correlates to changes in environmental variables. Depending on the environmental conditions individuals of the taxon could develop in two forms: terrestrial and aquatic. The aquatic form is characterized by twice longer stems and internodes, and also almost twice longer lamina and petiola. E. triandra seeds show consistent characteristics both in terms of forms and populations. Our studies show that the best diagnostic feature, in addition to the construction of flowers, are size, shape and surface structure of seeds. In Central Europe E. triandra occurs exlusively in communities classified to the Isoëto-Nano-Juncetea, however the number of species characteristic for the class and lower syntax in patches decreases from north to south of the continent.

chorology, ephemerophyte, Isoëto-Nano-Juncetea, phytogeography, vegetation, morphology, maps, phenology