Specificity and localised distribution of mycorrhizal fungi in the soil may contribute to co-existence of orchid species

Co-occurring orchid species tend to occupy different areas and associate with different mycorrhizal fungi, suggesting that orchid mycorrhizal (OrM) fungi may be unevenly distributed within the soil and, therefore, impact the aboveground spatial distribution of orchids. To test this hypothesis, we investigated spatial variations in the community of potential OrM associates within the roots of three co-habitating orchid species (Anacamptis morio, Gymnadenia conopsea, and Orchis mascula) and the surrounding soil in an orchid-rich calcareous grassland in Southern Belgium using 454 amplicon pyrosequencing. Putative OrM fungi were broadly distributed in the soil, although variations in community composition were strongly related to the proximal host plant. The diversity and frequency of sequences corresponding to OrM fungi in the soil declined with increasing distance from orchid plants, suggesting that the clustered distribution of orchid species may to some extent be explained by the localised distribution of species-specific mycorrhizal associates.     

Effect of intrahippocampal administration of anti-melanin-concentrating hormone on spatial food-seeking behavior in rats

Melanin-concentrating hormone (MCH) is a hypothalamic peptide that plays a critical role in the regulation of food intake and energy metabolism. In this study, we investigated the potential role of dense hippocampal MCH innervation in the spatially oriented food-seeking component of feeding behavior. Rats were trained for eight sessions to seek food buried in an arena using the working memory version of the food-seeking behavior (FSB) task. The testing day involved a bilateral anti-MCH injection into the hippocampal formation followed by two trials. The anti-MCH injection did not interfere with the performance during the first trial on the testing day, which was similar to the training trials. However, during the second testing trial, when no food was presented in the arena, the control subjects exhibited a dramatic increase in the latency to initiate digging. Treatment with an anti-MCH antibody did not interfere with either the food-seeking behavior or the spatial orientation of the subjects, but the increase in the latency to start digging observed in the control subjects was prevented. These results are discussed in terms of a potential MCH-mediated hippocampal role in the integration of the sensory information necessary for decision-making in the pre-ingestive component of feeding behavior.     

Long-term monitoring data meet freshwater species distribution models: Lessons from an LTER-site

Long-term monitoring datasets provide a solid framework for ecological research. Such a dataset from the German long-term ecological research (LTER) site Rhine-Main-Observatory was used to set up a species distribution model (SDM) for the Kinzig catchment. The extensive knowledge on the monitoring data provided by the LTER-site framework allowed to calibrate a robust model for 175 taxa of stream macroinvertebrates and to project their distributions on the Kinzig River stream network using bioclimatic, topographical, hydrological, land use and geological predictors. On average, model performance was good, with a TSS of 0.83 (±0.09 SD) and a ROC of 0.95 (±0.03 SD). The model delivered valuable insights on three sources of bias that plague SDMs in general: (a) level of taxonomic identification of the modeled organisms, (b) the spatial arrangement of sampling sites, and (c) the sampling intensity at each sampling site. Taxonomic resolution did not affect SDM performance. The distribution of high predicted probabilities of occurrence in the stream network coincided with those segments in the stream network most densely and frequently sampled, indicating both a spatial and temporal sampling bias. Species richness curves confirmed the temporal sampling bias. Next to spatial bias, sampling frequency also plays an important role in data collection, affecting further analysis and modeling procedures. Results indicate an underrepresentation of low order streams, an important aspect that should be addressed by both monitoring schemes and modeling approaches.     

Incorporating spatial autocorrelation in rarefaction methods: Implications for ecologists and conservation biologists

Recently, methods for constructing Spatially Explicit Rarefaction (SER) curves have been introduced in the scientific literature to describe the relation between the recorded species richness and sampling effort and taking into account for the spatial autocorrelation in the data. Despite these methodological advances, the use of SERs has not become routine and ecologists continue to use rarefaction methods that are not spatially explicit. Using two study cases from Italian vegetation surveys, we demonstrate that classic rarefaction methods that do not account for spatial structure can produce inaccurate results. Furthermore, our goal in this paper is to demonstrate how SERs can overcome the problem of spatial autocorrelation in the analysis of plant or animal communities. Our analyses demonstrate that using a spatially-explicit method for constructing rarefaction curves can substantially alter estimates of relative species richness. For both analyzed data sets, we found that the rank ordering of standardized species richness estimates was reversed between the two methods. We strongly advise the use of Spatially Explicit Rarefaction methods when analyzing biodiversity: the inclusion of spatial autocorrelation into rarefaction analyses can substantially alter conclusions and change the way we might prioritize or manage nature reserves.     

Influence of Stimuli Spatial Proximity on a SSVEP-Based BCI Performance

Objective: Steady-State Visual Evoked Potentials based Brain-Computer Interfaces (SSVEP-based BCIs) systems have been shown as promising technology due to their short response time and ease of use. SSVEP-based BCIs use brain responses to a flickering visual stimulus as an input command to an external application or device, and it can be influenced by stimulus properties, signal recording, and signal processing. We aim to investigate the system performance varying the stimuli spatial proximity (a stimulus property).Material and methods: We performed a comparative analysis of two visual interface designs (named cross and square) for an SSVEP-based BCI. The power spectrum density (PSD) was used as feature extraction and the Support Machine Vector (SVM) as classification method. We also analyzed the effects of five flickering frequencies (6.67, 8.57, 10, 12 e 15 Hz) between and within interfaces.Results: We found higher accuracy rates for the flickering frequencies of 10, 12, and 15 Hz. The stimulus of 10 Hz presented the highest SSVEP amplitude response for both interfaces. The system presented the best performance (highest classification accuracy and information transfer rate) using the cross interface (lower visual angle).Conclusion: Our findings suggest that the system has the highest performance in the spatial proximity range from 4° to 13° (visual angle). In addition, we conclude that as the stimulus spatial proximity increases, the interference from other stimuli reduces, and the SSVEP amplitude response decreases, which reduces system accuracy. The inter-stimulus distance is a visual interface parameter that must be chosen carefully to increase the efficiency of an SSVEP-based BCI.     

Analysis of intranuclear binding process of glucocorticoid receptor using fluorescence correlation spectroscopy

The diffusion properties of EGFP-hGRalpha and mutants C421G, A458T and I566 in living cells were analyzed. The wild type and mutants C421G and A458T translocated from the cytoplasm to the nucleus after addition of Dex; however, the Brownian motions of the proteins were different. The diffusion constant of wild-type GRalpha after addition of Dex slowed to 15.6% of that in the absence of Dex, whereas those of A458T and C421G slowed to 34.8% and 61.7%, respectively. This is the first report that dimer formation is less important than the binding activity of GRalpha to GRE in the living cell.     

Subpopulation genetic structure of a plant panmictic population of Castanea sequinii as revealed by microsatellite markers

Castanea squinii Dode, an endemic tree widely distributed in China, plays an important role both in chestnut breeding and forest ecosystem function. The spatial genetic structure within and among populations is an important part of the evolutionary and ecological genetic dynamics of natural populations, and can provide insights into effective conservation of genetic resources. In the present study, the spatial genetic structure of a panmictic natural population of C. sequinii in the Dabie Mountain region was investigated using microsatellite markers. Nine prescreened microsatellite loci generated 29–33 alleles each, and were used for spatial autocorrelation analysis. Based on Moran’s I coefficient, a panmictic population of C. sequinii in the Dabie Mountain region was found to be lacking a spatial genetic structure. These results suggest that a high pollen-mediated gene flow among subpopulations counteract genetic drift and/or genetic differentiation and plays an important role in maintaining a random and panmictic population structure in C. sequinii populations. Further, a spatial genetic structure was detected in each subpopulation’s scale (0.228 km), with all three subpopulations showing significant fine-scale structure. The genetic variation was found to be nonrandomly distributed within 61 m in each subpopulation (Moran’s I positive values). Although Moran’s I values varied among the different subpopulations, Moran’s I in all the three subpopulations reached the expected values with an increase in distances, suggesting a generally patchy distribution in the subpopulations. The fine-scale structure seems to reflect restricted seed dispersal and microenvironment selection in C. sequinii. These results have important implications for understanding the evolutionary history and ecological process of the natural population of C. sequinii and provide baseline data for formulating a conservation strategy of Castanea species. __________ Translated from Acta Phytoecologica Sinica, 2006, 30(1): 147–156 [译自: 植物生态学报]     

Local adaptation in dispersal in multi‐resource landscapes

The distribution of resources in space has important consequences for the evolution of dispersal‐related traits. Dispersal moderates patterns of gene flow and, consequently, the potential for local adaptation to spatially differentiated resource types. We lack both models and experiments that evaluate how dispersal evolves in landscapes with multiple resources. Here, we investigate the evolution of dispersal in landscapes that contain two resource types that differ in their spatial autocorrelations. Individuals may possess ecological traits that give them a fitness advantage on one or the other resource. We find that resources differing in their spatial autocorrelation select for different optimal dispersal strategies and, further, that some multi‐resource landscapes can support the stable coexistence of distinct dispersal strategies. Whether divergence in dispersal strategies between resource specialists occurs depends on the underlying structure of the resources and the degree of linkage between dispersal strategies and ecological specialization. This work indicates that the spatial autocorrelation of resources is an important factor in determining when evolutionary branching is likely to occur, and sheds light on when secondary isolating mechanisms should arise between locally adapted specialists.     

Morphological correlates of necromass accumulation in the traps of an Eastern tropical pitcher plant, Nepenthes ampullaria Jack, and observations on the pitcher infauna and its reconstitution following experimental removal

I studied the trap morphology, necromass accumulation rates and pitcher infauna of an eastern tropical pitcher plant, Nepenthes ampullaria, that grew in `kerangas' heath forest in the Sungei Ingei Conservation Area, Brunei. I surveyed 164 pitchers distributed among 35 plants and extracted the necromass and larval infauna from the pitchers and then resampled the pitcher contents after 14 days. Plants varied significantly in the morphology of their pitchers, in their rate of necromass accumulation per pitcher and in the abundance and composition of the pitcher infaunas. On average, pitchers accumulated 11.5 mg dry weight over 14 days, but larger pitchers accumulated more necromass than smaller ones. Pitcher morphology explained 45% of the variation in necromass accumulation among plants. On average, pitchers initially contained 26.3 individual larval inquilines. Collectively, the larval infauna was composed of nine taxa of dipteran larvae and infrequent anuran tadpoles. These ten taxa were never found together in a single pitcher and the mean species richness per pitcher was 4.0. Of the six taxa that could be assessed, all except Toxorhynchites spp. had a contagious distribution among the pitchers. Pitcher morphology and necromass accumulation explained only 15% of the variation in inquiline abundance among plants. I found little evidence for the existence of density-dependent interactions between inquiline species: a partial correlation analysis detected only one statistically significant pairwise relationship between the abundances of inquiline taxa, which was a positive association. Fourteen days after being emptied, pitchers contained an average of 9.6 inquilines. There was no evidence that the species composition of the infauna recolonising each pitcher was related to that of its pre-removal infauna. Received: 2 June 1997 / Accepted: 9 September 1997     

Assignment and evaluation of ground beetle (Coleoptera: Carabidae) assemblages to sites on different scales in a grassland landscape

Carabid beetles and environmental parameters were investigated in 52 grassland sites with three replicate pitfall traps in each site and in the valley of the River Eider in Schleswig–Holstein (northern Germany) with 61 pitfall traps. Environmental parameters included water content of soil, sand content, organic matter content and pH. Ground beetle assemblages were derived by detrended correspondence analyses (DCA) and characterised by the specific environmental conditions as means for each assemblage. On the regional scale including all investigated sites of Schleswig–Holstein, five assemblages were differentiated. On the local scale including the investigated sites in the valley of the River Eider, three assemblages were found corresponding well with those found on the regional scale. Environmental conditions at the sites of the five assemblages were correlated with land use data, soil types, and water level stages provided by three maps of a geographic information system (GIS). The GIS maps were combined to develop smaller areas with land use, soil type and water level stage information. The characteristic environmental conditions were assigned to each area to derive the spatial distribution of the five ground beetle assemblages. Spatial prediction was correct for 65% of investigated sites. The potential area of each assemblage was estimated for the valley. The different grassland areas were evaluated as potential habitats for ground beetle species comparing total species richness with the regional species richness of each assemblage. The comparison shows that species richness in the evaluated assemblages is relatively low compared to the regional potential.