Filtern
Dokumenttyp
Sprache
- Englisch (5)
Volltext vorhanden
- ja (5)
Gehört zur Bibliographie
- nein (5)
Schlagworte
- species turnover (5) (entfernen)
Institut
Wet grasslands once covered a large area in the lowlands of northern Germany, but have declined since several decades as a result of land use intensification. Permanent plot data from such grasslands in the region that would allow to assess the extent of changes in species composition and richness are still rare. Here, we present a re-visitation study of 52 quasi-permanent plots from the Stedinger Land area in the basin of the river Weser near Bremen, comparing quadrat data between 1948 and 2015. In 1948, the grasslands were characterized by species typical of wet, moderately fertile grasslands belonging to the Bromo-Senecionetum aquatici (Bromion racemosi), including 15 species currently classified as threatened. Until 2015, the vegetation had changed strongly: almost all indicators of wet grasslands had either declined or completely vanished, whereas more nutrient-demanding species of less wet soils had increased, especially grasses. The cumulative number of species had declined by 50%, while mean plot species richness had decreased by 64.6%, mainly resulting from the pronounced loss of many herbs. A comparison of mean Ellenberg indicator values suggested that the plots had become drier, but also more base- and nutrient-rich, most likely triggered by the intensification of land use with drainage and fertilization as well as more frequent and earlier cutting. Our study reflects the dramatic loss of plant species diversity in wet grasslands over the past 60−70 years in areas not preserved and properly managed, and it documents the need for protecting remnants of these grasslands and for restoring wet grassland areas by re-wetting, nutrient removal and the transition to a less intensive land use.
A recent survey of the mangroves around Hong Kong revealed the presence of seven species of the genus Elaphropeza Macquart, 1827. All belong to a group of yellow species that occur exclusively in mangroves. Three species were previously known: Elaphropeza calcarifera Bezzi, 1912 and E. xanthocephala Bezzi, 1912, both from Taiwan, and E. riatanae Shamshev & Grootaert, 2007 from Singapore. Four species are new to science: Elaphropeza furcatella sp. nov., E. guenardi sp. nov., E. hongkongensis sp. nov. and E. hongshulin sp. nov. All seven species are described or an extended diagnosis is provided. All species are figured and NGS barcodes are made available. A key is given for the Hong Kong species and their siblings from Singapore and Taiwan. Remarkable is that five of the seven species are more or less closely related to species occurring in Singapore. Genetic distances and morphologic differences are congruent. The species turnover between the northern part and the southern part of the South China Sea is high, with only one of the seven species present in both regions.
Using a qualitative sampling approach to survey for Odonata along water systems inside and outside of four major protected areas in Southern Ghana (viz; Atewa Range Forest Reserve, Ankasa Forest Reserve, Owabi Wildlife Sanctuary and Bobiri Forest Reserve), a total of 66 Odonata species in seven families encompassing 28 Zygoptera and 38 Anisoptera were recorded. Libellulidae (n= 36) exhibited the highest number of species, followed by Coenagrionidae (n= 10), and Calopterygidae (n= 5). In considering the observed number of species exhibited by each protected area, the Atewa Range Forest Reserve exhibited the highest number of species (n= 51), followed by the Ankasa Forest Reserve (n= 47), the Owabi Wildlife Sanctuary (n= 44) and Bobiri Forest Reserve (n= 43). Disturbance tolerance species dominated in habitats outside the various forest reserves, whiles forest specialists predominated inside the reserves, indicating the quality of the forest cover therein.
Questions: Habitat islands are often characterized by the presence of more or less sharp boundaries to adjacent matrix habitats. However, knowledge on boundaries of natural habitat islands is scarce, especially regarding patterns of beta diversity and its two underlying components: species turnover and nestedness. We therefore aim to quantify the effects of fine-scaled and sharp boundaries of quartz islands (quartz gravel-covered soils) on the different components of plant beta diversity and how they are linked to different soil environmental drivers. Location: Knersvlakte, Western Cape, South Africa. Methods: We sampled plant species richness in 56 fine-scale transects of 6 m × 1 m plots across eight different boundary types (four quartz island to matrix, four between habitats on quartz islands). Soil depth and chemistry (pH, electrical conductivity) were analyzed for each 1 m2 plot. Differences in the two beta diversity components (turnover and nestedness) for each boundary type were tested by t tests. We used linear models to test relationships between species and environmental dissimilarity. Results: All boundary types showed high beta diversity. Species turnover was the prevailing component for six boundary types, the nestedness component was only important for two boundary types. We found a significant linear increase of species dissimilarity with increasing dissimilarity in soil pH and distinct plant communities for the habitat types, but no significant increase for electrical conductivity or soil depth. Conclusions: The spatial distinctiveness of the quartz islands leads to sharp boundaries, which result in high beta diversity, mainly through species turnover. This reflects the high levels of diversification and adaptation of the local plant communities. Nestedness occurred at two boundaries to the matrix, indicating that the latter does not necessarily represent an impermeable boundary for all species of the respective ecosystem. Studying diversity patterns across boundaries contributes to the question of applicability of island biogeography theory to habitat islands.
Questions: Both species turnover and intraspecific trait variation can affect plant assemblage dynamics along environmental gradients. Here, we asked how community assemblage patterns in relation to species turnover and intraspecific variation differ between endemic and non-endemic species. We hypothesized that endemic species show lower intraspecific variation than non-endemic species because they tend to have high rates of in situ speciation, whereas non-endemic species are expected to have a larger gene pool and higher phenotypic plasticity.
Location: La Palma, Canary Islands.
Methods: We established 44 sampling sites along a directional gradient of precipitation, heat load, soil nitrogen, phosphorus and pH. Along this gradient, we estimated species abundances and measured three traits (plant height, leaf area and leaf thickness) on perennial endemic and non-endemic plant species. In total, we recorded traits for 1,223 plant individuals of 43 species. Subsequently, we calculated community-weighted mean traits to measure the relative contribution of species turnover, intraspecific variation and their covariation along the analysed gradient.
Results: The contribution of intraspecific variation to total variation was similar in endemic and non-endemic assemblages. For plant height, intraspecific variation explained roughly as much variation as species turnover. For leaf area and leaf thickness, intraspecific variation explained almost no variation. Species turnover effects mainly drove trait responses along the environmental gradient, but intraspecific variation was important for responses in leaf area to precipitation.
Conclusions: Despite their distinct evolutionary history, endemic and non-endemic plant assemblages show similar patterns in species turnover and intraspecific variation. Our results indicate that species turnover is the main component of trait variation in the underlying study system. However, intraspecific variation can increase individual species’ fitness in response to precipitation. Overall, our study challenges the theory that intraspecific trait variation is more important for the establishment of non-endemic species compared with endemic species.