Species assembly in ground beetle (Coleoptera: Carabidae) communities in local microhabitats was studied in a forest. The following questions were addressed: are there important filters that sort the species in the assemblages? If so, what is the specific nature of these filters? In order to address these questions rarefaction analysis was used to determine whether ground beetle species are distributed non-randomly. Next, the nature of filters was determined by analyzing (1) the community matrix and searching for the consequences of competitive exclusion and (2) species-environmental relations. Rarefaction analysis revealed that the species composition is filtered: species richness was less than expected and there were fewer than expected congeneric species coexisting at high beetle population densities. However, community matrix and body size analyses did not detect significant competition among the beetle species and the matrix was significantly nested. Species-environmental analyses indicated that the ground beetle assembly was strongly linked to ground vegetation. It is concluded that spatial distribution of ground beetles across local communities in this forest habitat is determined more by local environmental conditions than competition, and ground beetles do not interact strongly among themselves so that competitive effects do not play an important role in their distribution except at high beetle population densities. and Sonomi Shibuya, Kohei Kubota, Masahiko Ohsawa, Zaal Kikvidze.
This paper examines the changes in the species composition of aphids living in dry calcareous grasslands in Central Europe over a 25-year period. To the best of our knowledge, this is the first analysis of this type in the world that takes into account both previous and current data on species richness as well as groups of aphids that are distinguishable on the basis of biological and ecological criteria such as host-alternation and feeding types, life cycle, ecological niche, symbiosis with ants and their ecological functional groups. Over the period of more than 25 years, there has been a significant decrease in aphid α-diversity, from 171 to 105 species. The gain, which is in species not previously recorded, was 17 taxa. The loss of biodiversity occurred despite the fact that these habitats are protected and are valuable regional biodiversity hotspots. The losses are mostly related to intensive human activity in adjacent areas, which, unfortunately, has resulted in the isolation of these small, protected environmental islands by the removal of ecological corridors. Since, as is shown in this study, the frequencies between individual biological and ecological groups of aphids have been retained, it would be possible to restrict this loss of biodiversity if appropriate actions are taken., Barbara Osiadacz, Roman Hałaj, Damian Chmura., and Obsahuje bibliografii
Community structure implies some features in various real-world networks, and these features can help us to analysis structural and functional properties in the complex system. It has been proved that the classic k-means algorithm can efficiently cluster nodes into communities. However, initial seeds decide the efficiency of the k-means, especially when detecting communities with different sizes. To solve this problem, we improve the classic community detection algorithm with Principal Component Analysis (PCA) mapping and local expansion k-means. Since PCA can preserve the distance information of every node pairs, the improved algorithm use PCA to map nodes in the complex network into lower dimension European space, and then detect initial seeds for k-means using the improved local expansion strategy. Based on the chosen initial seeds, the k-means algorithm can cluster nodes into communities. We apply the proposed algorithm in real-world and artificial networks, the results imply that the improved algorithm is efficient to detect communities and is robust to the initial seed of K-means.
Ants are often considered as good indicators of change of management in different habitats. They have been used sporadically to evaluate large scale transformations involving reafforestation. In the present study, the ant assemblages at 15 forest sites are compared. The sites differ in history, age and forest management. Our results show that there are clear changes in ant assemblages with developmental stage but even after 25 years not all forest species are present. Natural succession and planting of trees with or without any other management, resulted in only open country species, and some from forest and wet grassland colonizing these new forests. Sometimes gynes of target forest species arrived in new forests from nearby mature forest, but apparently were unable to start a colony. We attribute this findings to the lack of appropriate vegetation structure and litter characteristics, which determines the forest ant fauna, more than the dispersal of ant gynes. Further investigations should enable us to predict if these conditions can be produced by 50-100 or more years of forest succession and adequate management.
Studies on the effect of varying light intensity on the spatial distribution of flying insect communities are rare, particularly in complex ecosystems like forests. The horizontal and vertical distribution of Heteroptera was studied at different scales in a large deciduous forest area, the "Steigerwald", in southern Germany. Diversity was affected by (1) vertical position: it was significantly higher near the ground than in the canopy of beech-dominated forests but similar in oak-dominated forests; within the canopy of beech-dominated forests, diversity was significantly higher in the upper than in the lower canopy of intermixed oak trees but similar in beech trees; (2) canopy cover, but in oak forests the response depended on the vertical position: increasing significantly close to the forest floor with decreasing canopy cover, but showing an opposite trend in the canopy; so that in sparse stands (little canopy cover) diversity was significantly higher near the ground, whereas where the forest canopy was medium or dense diversity was higher in the canopy. Moreover, community composition of Heteroptera near the ground differed from that in the canopy in both forest types and near the ground between stands in oak-dominated forest that had canopies of different densities. Results clearly indicate that light intensity is an important direct or indirect factor structuring Heteroptera communities. While in the canopy differences in leaf quality and microhabitats might be important, near the forest floor it is more likely to be the diversity of herbaceous plants.
Clear-cutting, the main method of harvesting in many forests in the world, causes a series of dramatic environmental changes to the forest habitat and removes habitat resources for arboreal and epigeal species. It results in considerable changes in the composition of both plant and animal communities. Ants have many critical roles in the maintenance and functioning of forest ecosystems. Therefore, the response of ants to clear-cutting and the time it takes for an ant community to recover after clear-cutting are important indicators of the effect of this harvesting technique on the forest ecosystem. We investigated ground-dwelling ant communities during secondary succession of deciduous forests in Transylvania, Romania. Using space-for-time substitution, we explored a chronosequence from clear-cuts to mature forests (> 120 years). The object was to determine if cutting has measurable effects on ant community structure, and if ant species richness differs between successional stages. We recorded a total of 24 species of ants, 11 characteristic of forests and seven of open landscape. Ant species richness was higher in clear-cuts compared to closed-canopy and old stands. Number of ant individuals was highest in young age classes and lowest in closed-canopy age classes. There was no drastic change in species richness during the succession, however differences in community composition at different stages were recorded. Open landscape species are able to rapidly colonize following disturbance but disappear when the forest sites mature and many forest ant species are capable of surviving clear cutting., Ioan Tăuşan, Jens Dauber, Maria R. Trică, Bálint Markó., and Obsahuje bibliografii
We hypothesize that differences in fungal taxonomic groups may exert a direct influence on the composition of mycophagous insect communities, and that the relative importance of taxonomy compared to other fungal traits may change as the mushrooms decay. We conducted a 3-year field survey and analyzed the species composition of mycophagous insect communities using partial canonical correspondence analysis (partial CCA). We collected 2457 mushrooms belonging to 27 genera, and 4616 insects belonging to 16 families emerged from 439 of the mushrooms. For the whole insect community, fungal genera explained 10-19% of the total variance in the family composition of the insect communities of mushrooms at different developmental stages. Only the fungal genus Collybia significantly affected the community composition almost irrespective of developmental stage. In the drosophilid community, which consisted of 844 individuals from 9 species, fungal genera explained 19-34% of the total variance. Some fungal genera, such as Amanita and Collybia, affected the drosophilid community, but not at all developmental stages. The number of fungal genera that significantly affected the insect community composition did not differ among fungal stages both in the whole insect community and in the drosophilid community. Thus, our former hypothesis was supported by the present analysis, whereas the latter was not. However, the percentages of variance explained by fungal genera were rather small. This suggests that the importance of fungal genera is likely to be less significant than that of other selection pressures in determining the species composition of mycophagous insect communities.