Studies on the paradox of seedling rarity in Vaccinium myrtillus L. in NE Scotland

Summary

On the moors studied Vaccinium myrtillus produced many berries containing highly viable seed, yet seedlings were rare. Offtake of berries by birds or mammalian herbivores was apparently minor, most berries simply falling from the bushes when ripe. Fallen berries quickly disappeared, probably being removed by small rodents. Berries were fed experimentally to captive field voles and capercaillies, and it was found that only c. 1% of the seeds survived. For the voles, most of these viable seeds probably resulted from contamination of the droppings with partially-eaten berries or discarded extracted seeds, processes which must contribute to dispersal in the wild. The soil seed-bank was shown to be small, and the viability of buried seed declined from c. 90% to c. 20% in 3 years, due to decay in the soil H horizon and premature germination in the litter layer. Fewer seedlings established from experimental sowings on grass and Vaccinium myrtillus turf than on bare peat. We conclude that Vaccinium myrtillus has a seed-dispersal strategy which secures some long-distance movement by frugivores at the expense of much lost seed, and that the small seed-bank and low numbers of seedlings result from poor defence of the seeds and weak competitive ability of the seedlings; other attributes of Vaccinium myrtillus, e.g. efficient vegetative reproduction, compensate for these losses and enable it to be a successful species.     

Diversity patterns of leaf-associated aquatic hyphomycetes along a broad latitudinal gradient

Information about the global distribution of aquatic hyphomycetes is scarce, despite the primary importance of these fungi in stream ecosystem functioning. In particular, the relationship between their diversity and latitude remains unclear, due to a lack of coordinated surveys across broad latitudinal ranges. This study is a first report on latitudinal patterns of aquatic hyphomycete diversity associated with native leaf-litter species in five streams located along a gradient extending from the subarctic to the tropics. Exposure of leaf litter in mesh bags of three different mesh sizes facilitated assessing the effects of including or excluding different size-classes of litter-consuming invertebrates. Aquatic hyphomycete evenness was notably constant across all sites, whereas species richness and diversity, expressed as the Hill number, reached a maximum at mid-latitudes (Mediterranean and temperate streams). These latitudinal patterns were consistent across litter species, despite a notable influence of litter identity on fungal communities at the local scale. As a result, the bell-shaped distribution of species richness and Hill diversity deviated markedly from the latitudinal patterns of most other groups of organisms. Differences in the body-size distribution of invertebrate communities colonizing the leaves had no effect on aquatic hyphomycete species richness, Hill diversity or evenness, but invertebrates could still influence fungal communities by depleting litter, an effect that was not captured by the design of our experiment.     

On Cannabis indica,Indian hemp

Background: The South Aegean Volcanic Arc (SAVA), one of the most notable geological structures of the Mediterranean Sea, is floristically well known. Nevertheless, the factors that contribute to shaping the plant species richness of the SAVA remain unclear.

Aims: To investigate the factors that affect plant species richness and identify plant diversity hotspots in the SAVA and other central Aegean islands.

Methods: We used stepwise multiple regression to test the relationship between a number of environmental factors and plant species richness in the SAVA, as well as the residuals from the species–area linear regressions of native, Greek and Cycladian endemic taxa as indicators of relative species richness.

Results: The area was confirmed to be the most powerful single explanatory variable of island species richness, while geodiversity, maximum elevation and mean annual precipitation explained a large proportion of variance for almost all the species richness measures. Anafi, Amorgos and Folegandros were found to be endemic plant diversity hotspots.

Conclusions: We have demonstrated that geodiversity is an important factor in shaping plant species diversity in the Cyclades, while mean annual precipitation, human population density and maximum elevation were significant predictors of the Greek endemics present in the Cyclades. Finally, Anafi was found to be a plant diversity hotspot in the South Aegean Sea.     

山西省重点保护野生植物资源及区系特征研究

以《国家重点保护野生植物名录(第一批)》和《山西省重点保护野生植物名录(第一批)》为依据,建立山西省重点保护野生植物名录。共记录57种保护植物,隶属于38科45属（其中国家Ⅰ级保护2种,国家Ⅱ级保护6种,省级保护49种）。分析结果得出,山西省重点保护野生植物在全省的分布不集中,零散分布于全省61个县区境内,且绝大多数物种的分布范围很狭窄。山西省重点保护野生植物区系具有复杂多样、起源古老、孑遗植物和单种属多等特点,科、属植物区系成分以温带分布型占优势,同时也有较明显的热带性质,过渡性特征比较明显,有其独特的地理优势和保护价值。本研究旨在对山西省重点保护野生植物资源现状及区系特征进行初步研究,从而为野生植物资源的保护和合理有效地利用提供科学的理论依据与参考。     

Data gaps in anthropogenically driven local‐scale species richness change studies across the Earth's terrestrial biomes

There have been numerous attempts to synthesize the results of local‐scale biodiversity change studies, yet several geographic data gaps exist. These data gaps have hindered ecologist's ability to make strong conclusions about how local‐scale species richness is changing around the globe. Research on four of the major drivers of global change is unevenly distributed across the Earth's biomes. Here, we use a dataset of 638 anthropogenically driven species richness change studies to identify where data gaps exist across the Earth's terrestrial biomes based on land area, future change in drivers, and the impact of drivers on biodiversity, and make recommendations for where future studies should focus their efforts. Across all drivers of change, the temperate broadleaf and mixed forests and the tropical moist broadleaf forests are the best studied. The biome–driver combinations we have identified as most critical in terms of where local‐scale species richness change studies are lacking include the following: land‐use change studies in tropical and temperate coniferous forests, species invasion and nutrient addition studies in the boreal forest, and warming studies in the boreal forest and tropics. Gaining more information on the local‐scale effects of the specific human drivers of change in these biomes will allow for better predictions of how human activity impacts species richness around the globe.     

Species traits and catchment‐scale habitat factors influence the occurrence of freshwater mussel populations and assemblages

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Tree diversity,tree height and environmental harshness in eastern and western North America

Does variation in environmental harshness explain local and regional species diversity gradients? We hypothesise that for a given life form like trees, greater harshness leads to a smaller range of traits that are viable and thereby also to lower species diversity. On the basis of a strong dependence of maximum tree height on site productivity and other measures of site quality, we propose maximum tree height as an inverse measure of environmental harshness for trees. Our results show that tree species richness is strongly positively correlated with maximum tree height across multiple spatial scales in forests of both eastern and western North America. Maximum tree height co‐varied with species richness along gradients from benign to harsh environmental conditions, which supports the hypothesis that harshness may be a general mechanism limiting local diversity and explaining diversity gradients within a biogeographic region.