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-Dulay and S. Bartha. 2000. Organization of grasslands along ecological gradients: US-Hungarian LTER Grassland cooperation. In: K. Lajtha and K. Vanderbilt (eds.), Cooperation in Long-term Ecological research in Central and Eastern Europe . Proceedings
To detect neuroactive factors in biological fluids, we have previously elaborated a moveable biosensor, the preparation of isolated neuron penetrated with recording microelectrode [1]. Here, we report that, in the pond snail, signals emanated from a central pattern generator (CPG) for feeding and detected by such biosensor correspond to long-term changes in motor output of the CPG as recorded from buccal nerves. The results suggest that combined recording from motor nerves, neurons in situ and the neuron-based biosensors may be a useful tool in studies of the mechanisms underlying network organisation.
The identification of the drivers of diversity in understorey plant assemblages is a major challenge in forest ecology. However, it is not yet fully understood whether the same factors consistently affect different facets of species organization, such as species richness, composition and turnover. Here, we compare the influence of fine-scale environmental variables and spatial organization on the herb-layer flora of two unmanaged and ecologically different forest stands in the Muniellos Biosphere Reserve, Northern Spain. The aims of our study are to identify the most important factors influencing different facets of herb-layer plant organization, and to test whether the effect of such drivers is consistent across facets and forest types. We used Generalized Linear Models, Redundancy Analysis and Multiple Regression on Distance Matrices to model, respectively, the response of species richness, species composition and species turnover to spatial distances as well as to several environmental factors, including forest structure, light conditions, soil and topographical features. We observed a substantial consistency among variables affecting the different facets of ground-layer species organization within stands, with a subset of topographical variables with a transversal effect across facets. Although potential solar radiation was the main variable influencing species richness in the two stands, the factors shaping species composition and turnover varied across forest types: in the beech stand, slope and canopy openness were the main determinants of herb-layer species diversity and turnover; in the oak stand, the main drivers of species composition were related to topography and spatial structure, while spatial distance was the main driver of species turnover. Our study shows that the ecological processes driving fine-scale variation of ground-layer plant richness and composition are similar to those driving species turnover. Although the ecological factors shaping different facets may be the same, we highlight that, at least in temperate forests, these factors are system-specific and vary according to forest types.
Ecological transition zones are believed to be unique in their ability to shed light on the organization of populations and communities. In this paper, we study vegetation dynamics in the Great Plains short-grass steppe and Chihuahuan desert grassland ecotone in New Mexico, USA, using long-term, high resolution transect studies of the Sevilleta Long-Term Ecological Research Program. We focus on spatial pattern and examine this in several ways: patch size distribution, spatial autocorrelation analysis, and fractal scaling. These methods are used to examine patch size distributions in two sites representing distributional limits of the dominant species and for detection of an emergent scaling property. We found no characteristic spatial resolution (quadrat size), but rather a fractal structure of spatial variation in abundance and a trend towards consistency of the pattern in time when species were closer to their distributional limit. In this, we were able to detect a robust power law behaviour (the emergent property), indicating strong spatial organization via anti-persistence. Our investigation was exploratory in nature; we feel the results are highly suggestive of intrinsic organization in ecological dynamics and may also be useful in generating testable hypotheses regarding the behaviour of species along ecotones.
Belowground soil characteristics are recognised as possible key factors in affecting plant species coexistence and community organisation. In this study, soil heterogeneity was generated by the growth of different herbaceous plants under controlled conditions, and thus related to growth and competitive ability of three naturally co-occurring species (Holcus lanatus, Inula viscosa and Pulicaria dysenterica). Soil changes induced by all species caused significant specific effects on the performance of these species and on their competitive hierarchies. Holcus lanatus was the strongest competitor on disturbed soil, but showed a dramatic negative feedback in monoculture. The experimental results are relevant for understanding community ecology and suggest that the investigation of species coexistence should take into account the possible role of plant-soil feedback processes.to the agricultural.
Organization of the innervation of the buccal region by 5-HT-immunoreactive (IR) elements was investigated in the pond snail, Lymnaea stagnalis , with special attention to developmental aspects. A gradual maturation is characteristic for the 5-HT-IR muscle innervation, appearing first by late (E80–90%) embryogenesis. It runs parallel with the muscle development and the maturation of the 5-HTergic innervation in the buccal ganglia, peaking by the mid-postembryogenesis (P3) with the presence of a 5-HTIR network in the buccal mass and rich innervation in the buccal ganglia, including axo-somatic contacts. The whole process seems to match with the appearance of the adult-like feeding (radula protrusion).
Lymnaea are capable of learning an association between light and rotation. The conditioning paradigm to produce this association and the unconditioned escape response are the same for both Lymnaea and Hermissenda , but the underlying neural mechanisms appear to differ between the two species due to differences in the organization and function of their visuo-and vestibular-sensory systems. The RPeD11 interneuron in Lymnaea controls withdrawal behavior. We analyzed the electrophysiologic characteristics of the RPeD11 and observed an increase in cell excitability; that is, spontaneous activity of the postsynaptic potential in the RpeD11 was increased in conditioned animals after learning acquisition.
The forest, which is exposed to fewer anthropogenic impacts, has a rich and complex community. In Hungary, the quantity of dead wood has an ever-increasing significance in the forests. The decomposition of wood starts with the xylophagous insects, followed by the appearance tinder fungus, which transforms the wood into a form suitable for decomposers. Fungus beetles decompose most of the fungus. Therefore, besides consumer organizations, demolition organizations also play an essential role in building the forest ecosystem. In Central Europe, we have a little information about the beetle communities of tinder fungi. During our research, we investigated the beetle communities of Fomes fomentarius and Trametes gibbosa, which were collected from the Sopron-mountains in West Hungary. In F. fomentarius, the most common beetle species that we found was Bolitophagus reticulatus with about 100 individuals in four fruiting bodies, while in T. gibbosa, Cis boleti had the largest number of individuals with more than 5300 in four specimens. The beetle communities in the two tinder fungi were different, the difference probably caused by the structure and the nutritional value of the fungi.
Nitrergic myenteric neurons are especially susceptible to the development of neuropathy in functional gastrointestinal disorders. Investigations of the similarities and dissimilarities in the organization of nitrergic neurons in the various mammalian species are therefore important in an effort to determine the extent to which the results obtained in different animal models can be generalized. In the present work, the density and the spatial organization of the nitrergic neurons in the myenteric plexus of the duodenum were investigated in 7 mammalian species. After nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry, the Plexus Pattern Analysis software (PPAs) was applied to count the nuclei of nitrergic neurons, calculate the proportions of the areas covered by the plexus and perform randomization analysis. All 7 species exhibited a large population of nitrergic myenteric neurons, with densities in the range 12–56 cells/mm 2 . The distribution patterns of these neurons differed markedly in the different species, however, the rat was the only species in which the nitrergic neurons appeared to be randomly distributed. The PPAs in conjunction with NADPH-d histochemistry proved to be a simple and fast tool with which to reveal similarities and dissimilarities in the spatial arrangement of the nitrergic neurons in the different species.
Our attention was focused on the changes occurring in the cell surface network linked to the induction of embryogenic competence of pre- and pro-embryogenic stages of indirect somatic embryogenesis in the callus tissue of Drosera spathulata Labill., which originated from isolated leaves. This surface network forms as a distinct and compact layer on globular somatic embryos before formation of protoderm. Young protodermal cells had a typical furrowed surface, whilst mature protodermal cells were practically smooth. Embryogenic cells show changes in structural organisation and chemical composition of cell surface network, during different stage formation of somatic embryogenesis. Using SEM, TEM analysis and enzymatic digestion of proteins and pectins, we have shown that granular components, which represent pectic polysaccharides, were linked to induction and acquisition of embryogenic competence and pre-embryogenic stage. Fibrillar network was linked to proembryogenic stage of somatic embryogenesis. Our study has revealed that combined effect of protease and pectinase after 5 hours caused a complete disappearance and removal of the cell surface network.
