Invasive alien species are considered to be one of the most important causes for the extinction and the reason for diminishing of the wild native species. Considering that nowadays the raccoon (Procyon lotor, Linnaeus 1758) is found in several European and Asian countries where it can amplification its ranges remarkably, but it is actually native to North and Central America. Here, we use the Maxent model to generate a preliminary map of the potential distribution of the raccoon around the world and enumerate its relative risk of invasion across all countries. In a study, MaxEnt predicted a significantly large area as the eco-climatically suitable habitat for the raccoon in the world. The predicted habitats are consistent with the wide-ranging habitat associations of the raccoon in its well-established sites. The results identified the hotspots of the raccoon invasion and indicated the possible dispersal pathways. Results also showed that both precipitation and temperature variables were strongly correlated with the raccoon distribution and the species would be absent in cold environments with average sub-zero temperatures.
Solidago canadensis, which is native to North America, is considered to be the most widespread invasive alien plant. The invasion of Solidago canadensis in China has resulted in serious environmental problems. Therefore, understanding the relationship between the geographical distribution of S. canadensis and bioclimatic variables, and then predicting the potential distribution of this species is essential for management actions and practices. Although several studies have delineated the potential distribution of S. canadensis in China, how this species would respond to variations in future climatic conditions remains unclear. In the present study, we predicted the potential distribution of S. canadensis under current and future climatic conditions using species distribution models. We also analyzed range shifting of this species under current and future climatic conditions. We arrived at several conclusions. First, the potential distribution of S. canadensis may expand 40% under future climatic condition compare with that of under current condition. Second, mean diurnal range, isothermality, mean temperature of the wettest quarter, mean temperature of the warmest quarter, precipitation of the driest month, and precipitation seasonality (coefficient of variation) are key bioclimatic variables in determine the potential distribution of S. canadensis. Third, expansion of S. canadensis can be partly attributed to the relatively warmer and wetter future bioclimatic condition than current one.
The smokybrown cockroach Periplaneta fuliginosa has spread all over the world, and is now one of the most undesired invasive alien pests in Japan. Because cockroaches are generally infected by thelastomatid nematodes, they are being distributed around the world with their parasitic nematodes. Nothing is known about parasitic nematode species in P. fuliginosa differences, or similarity of the parasite’s population structures between the different countries of the host cockroaches. Here we investigated the P. fuliginosa invasive to Japan and found that 100% of individuals were infected with one nematode species. According to the morphology and the sequence of the D2/D3 expansion segment of the 28S ribosomal RNA gene, we identified the parasite as Leidynema appendiculata. This nematode reproduced by haplodiploidy and its developmental timing under various conditions is quite divergent. Their population in the hindgut of P. fuliginosa was controlled with a few adult females and a male. This is the first report of the thelastomatid nematode isolated from the smokybrown cockroach, and is the basis for our future research examining the origin, distribution route and immigration history of the cockroach and the impact of L. appendiculata on native Japanese cockroach species.
It is a common view that increase of the trophic state of lakes has a negative effect on littoral invertebrate macrofauna, molluscs among them. However, the available data are often contradictory, and the decline of particular species is often observed only at a very pronounced raise in trophic state. The aim of this work was to present the changes of the composition and abundance of bottom malacofauna taking place during last 30 years in five small (area from 0.12 to 1.74 km²), mainly shallow (mean depth from 3.7 to 11.8 m) lakes of different trophic state (eutrophic and mesotrophic), connected by a small river (Masurian Lakeland, Northeastern Poland). The research were conducted in years 1997 and 2006 and were compared with published data, collected in 1976. The trophic state of the lakes studied was still constant during the period of investigations. In the studied lakes the decrease of number of bottom mollusc species was observed in subsequent years. The previously recorded there alien, invasive species, Potamopyrgus antipodarum (J.E. Gray, 1843) and Lithoglyphus naticoides (C. Pfeiffer, 1828) also disappeared. Dreissena polymorpha (Pallas, 1771) remained the dominant species in most of the lakes. These changes were recorded in four eutrophic lakes as well as inone mesotrophic lake. The decline of the species in individual lakes didn’t follow any regularity. Some mollusc species disappeared and value of similarity index between malacocenoses in these lakes decreased. It seems, that the trophic state was not the cause of disappearance of some mollusc species from the studied lakes. However, the effect of frequent anoxia in littoral zone related to eutrophication was raised up as the possible cause. The decline is of long-term character, probably resulting from small size and relative isolation of the lakes, which impede their recolonisation.
Long-term changes in groundlayer vegetation of unique stand of Carpathian beech forest Dentario glandulosae-Fagetum considered partly as a natural succession due to climatic changes and partly as a response to canopy dynamics, were investigated in the Ojcow National Park (South Poland). Species composition and structure of the herb layer in the permanent research area were compared in 1993 and after ten years. About 77% of the study area was changed in this period, but the spatial pattern of distribution and intensity was highly mosaic. The mean intensity of changes calculated according to formula (1) derived from changes in percent cover of species was 42%. Herb cover decreased by about 15%, probably due to the rapid development of natural recruitment of trees in the study area (48% of area was covered by dense tree ecruitment). In the same time the number of plant species and vegetation types (homogeneous vegetation patches of the size at least 1m2, that differed from neighbouring patches in species composition and/or species share) increased substantially. It is probably due to greater variation of light condition in ground layer created as a result of canopy gaps dynamics (the area of windthrow mounds in the study area increased approximately eight times between 1993 and 2003). There was a significant decline of species typical for beech forests, especially of vernal geophytes like Dentaria glandulosa W.K. and Isopyrum thalictroides L. Although it is too early to predict any directional changes, it is possible that the beech forest community will change into the Tilio-Carpinetum association in some parts of study area. Nowadays the expansion of invasive alien species Impatiens parviflora DC. is the great threat to the forest vegetation of the protected study area and the Ojcow National Park. This species in 10 years managed to displace native species in 3% of the study area. The drastic decrease in herbaceous plants cover connected with increase in tree seedlings and saplings, systematic decline of vernal geophytes and typical beechwood species, diversification of ground vegetation structure and composition, and finally occurrence of non-native invasive plant species inform about highly dynamic nature of climax beech forests and generally of temperate forests. Changes are induced probably by both changing climate and overstorey dynamics.
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