The nymphs of spittlebugs (Hemiptera, Cercopidae) are xylem-feeders and live on herbs, grasses or woody plants within their self-produced spittle masses. Nymphs of the spittlebug Neophilaenus albipennis live aggregated in these spittle masses on their host plant Brachypodium pinnatum, a common grass in dry grassland. The objective of this study was to estimate nymphal mortality rates and to examine what role aggregation and vegetation structure play in the mortality of the nymphs. The aggregation and mortality were measured using two different methods, direct monitoring and caging of nymphs. The nymphs passively aggregated with up to 4 nymphs per spittle and aggregation decreased with instar. The aggregation of the nymphs resulted in a reduced mortality in all instars. Although it has already been argued that aggregation may be an advantage, this study is the first direct evidence (i.e. direct measurement of single individuals) for the benefit of aggregation to individual spittlebug nymphs. Despite a clumped distribution of N. albipennis nymphs in tall vegetation, nymphal mortality was not correlated with vegetation height.
One way of reducing the rapid decline in biological diversity in agricultural landscapes is to establish wildflower areas. The species richness and abundance of heteropteran bugs in twenty 1- to 4-year-old wildflower areas and winter wheat fields were compared, and the effects of succession in the wildflower areas investigated. Vegetation and environmental parameters (plant species richness, vegetation structure, flower abundance, field size, surrounding landscape) and their effects on bug species were explored. Total species richness and abundance of bugs were significantly lower in wheat fields than in wildflower areas but did not differ in the wildflower areas of different ages. The numbers of zoophagous bugs in the wildflower areas were positively correlated with the age of the wildflower areas. Correspondence analysis showed that the bug species composition in the winter wheat fields was very similar but strongly separated from that in the wildflower areas. The species composition of bugs in the wildflower areas became increasingly dissimilar with advancing successional age. In a partial canonical correspondence analysis, the bug assemblage was significantly associated with the number of perennial plant species, the number of annual plant species and vegetation structure, which accounted for 13.4%, 12.6% and 7.2% of the variance, respectively. As wildflower areas clearly increased heteropteran diversity on arable land and bug species composition changed with increasing successional stage, the establishment of a mosaic of wildflower areas of different age is recommended as it enables the survival of heteropteran bugs with different life history traits.
The evolution of different foraging strategies, corresponding echolocation signals and adaptations of wing morphologies allowed niche differentiation and sympatric foraging habitat use of bat species. We investigated how different habitat selection transferred into sympatric species groups (“bat communities”). The occurrence of bat species at different transects and landscape structures of five sites of a low mountain range forest in the south west of Germany was determined. Species were present at transects in the following descending order: Pipistrellus pipistrellus > Myotis myotis > Nyctalus leisleri > N. noctula > Myotis daubentonii > Eptesicus serotinus > Plecotus austriacus. We analyzed patterns of habitat use and evaluated differences in community structure. Landscape structures (patch types) influenced more than geographical location of sites within the landscape the bat community structure. Bat communities at individual forest sites disaggregated into different smaller species groups of one to at least eight species at different landscape structures. The results confirm previously proposed models of foraging habitat use of bats. Species groups clustered in correlation with the landscape structures “open area” (clearance or grassland), “closed or open canopy forest”, and “still water”. The highest bat diversity foraged predominantly at open canopy forest, which may fulfil best the requirements of several distinct functional groups (guilds) of bats.
In this paper simulated rainfall experiments in laboratory were conducted to quantify the effects of patchy distributed Artemisia capillaris on spatial and temporal variations of the Darcy-Weisbach friction coefficient (f). Different intensities of 60, 90, 120, and 150 mm h-1 were applied on a bare plot (CK) and four different patched patterns: a checkerboard pattern (CP), a banded pattern perpendicular to slope direction (BP), a single long strip parallel to slope direction (LP), and a pattern with small patches distributed like the letter ‘X’ (XP). Each plot underwent two sets of experiments, intact plant and root plots (the above-ground parts were removed). Results showed that mean f for A. capillaris patterned treatments was 1.25-13.0 times of that for CK. BP, CP, and XP performed more effectively than LP in increasing hydraulic roughness. The removal of grass shoots significantly reduced f. A negative relationship was found between mean f for the bare plot and rainfall intensity, whereas for grass patterned plots fr (mean f in patterned plots divided by that for CK) increased exponentially with rainfall intensity. The f -Re relation was best fitted by a power function. Soil erosion rate can be well described using f by a power-law relationship.
Small-scale soil disturbance, such as animal mounds created by subterraneous ecosystem engineers are important microhabitats for species of conservation concern. There are many studies on the effects of ecosystem engineers on plant species diversity and soil properties, but the influence of such organisms on other taxa, such as insects, are rarely analyzed. In this paper, we demonstrate for the first time the role of molehills produced by the European Mole (Talpa europaea) (Linnaeus, 1758) as a larval habitat for a threatened butterfly species within central European calcareous grasslands. We selected the grizzled skipper (Pyrgus malvae) (Linnaeus, 1758) as a study species as previous studies revealed that it prefers warm and open microhabitats for oviposition. Our study clearly showed that host plants occurring on or in the close vicinity of molehills were regularly occupied by immature stages of P. malvae. Occupied host plants at these disturbed sites were characterized by a more open vegetation structure with a higher proportion of bare ground or stones and a lower cover of the herb layer compared with available host plants (control samples). Among molehills those were preferred that had the highest cover of host plants, especially Agrimonia eupatoria. Molehills are important larval habitats for P. malvae in calcareous grasslands on deeper soils. At these sites succession occurs rapidly and the amount of bare ground is usually low, even when they are managed. In contrast to other known breeding sites in calcareous grasslands, molehills with a high cover of host plants provide ideal conditions for the successful larval development of P. malvae: (i) sufficient food during the larval period and (ii) warm microclimatic conditions., Merle Streitberger, Thomas Fartmann., and Obsahuje seznam literatury
Interactions between herbivorous insects and their parasitoids occur in highly structured and complex environments. Habitat structure can be an important factor affecting ecological interactions between different trophic levels. In this study the influence of plant architecture and surrounding vegetation structure on the interaction between the tansy leaf beetle, Galeruca tanaceti L. (Coleoptera: Chrysomelidae) and its egg parasitoid, Oomyzus galerucivorus Hedqvist (Hymenoptera: Eulophidae), was investigated at two small spatial scales in the field. It was expected that high and structurally complex plants or vegetation represent an enemy free space for the herbivore by making host search more difficult for the parasitoid. At the scale of individual plants, plant height had a positive influence on herbivore oviposition and egg clutch height a negative impact on parasitism. In addition, the beetle was more likely to oviposit on simple plants than on plants with branches, while the parasitoid remained unaffected by the degree of branching. At the microhabitat scale (r = 0.1 m around an oviposition site), both height and density of the vegetation affected beetle oviposition positively and egg parasitism negatively. The herbivore and its parasitoid, therefore, were influenced in opposite ways by habitat structure at both spatial scales investigated, suggesting the existence of an enemy free space for the herbivores' eggs on tall plants and in tall and complex vegetation. This study indicates that structural components of the environment are important for interactions among organisms of different trophic levels.
Various disturbances in forests often result in the formation of open habitats with characteristics that are distinctly different from those of the original forest (microclimate, illumination, stand age and composition). These disturbances affect the habitat heterogeneity in time and space and seem to drive forest succession and changes in biodiversity in forests. Little is known about how the colonization of deforested habitats by Orthoptera is influenced by environmental factors. We studied the association between the structure of orthopteran assemblages and the age of clear-cuts, vegetation structure and other environmental parameters (size, elevation, altitude). This involved 33 clear-cuts of three age categories in broadleaved forests dominated by European beech. The Orthoptera were sampled using sweep netting and by counting individuals recorded along transects that ran parallel to those used for recording the structure of the vegetation. We recorded significant differences in the number and abundance of species in the three age categories of clear-cuts. Grasshopper species were more abundant than bush-crickets in first year clear-cuts. Species capable of flight occured in all three age categories of clear-cuts (>62% of the 27 species recorded). All the species of Orthoptera identified were present in two year-old clear-cuts. The species composition and abundance of Ensifera and Caelifera differed in their association with the six vegetation parameters studied. While the Caelifera occurred in habitats with bare ground the Ensifera mainly occurred in those with a higher proportion of shrubs and trees. There was also a positive correlation between number of species of Orthoptera and area of the clear-cut regardless of its age as well between the number of species of Orthoptera and elevation., Anna Sliacka, Anton Krištín, Ladislav Naďo., and Obsahuje seznam literatury