Performance of the invasive horse-chestnut leaf miner, Cameraria ohridella Deschka & Dimic, 1986 (Lepidoptera: Gracillariidae), was studied on two host plants: the white-flowering horse-chestnut Aesculus hippocastanum L. and the Ohio buckeye Aesculus glabra Willd. C. ohridella developed successfully on both host plants; however, mine density and survival were much higher on A. hippocastanum than on A. glabra. The pupal mass and potential fecundity were strongly affected by the host plant on which the larvae fed. On A. hippocastanum pupae were significantly heavier and females more fecund than those on A. glabra. Furthermore, on both host plants there was a significant positive correlation between the number of oocytes in ovaries and pupal body mass, and as a consequence, heavier females produced more eggs. Our study demonstrates that the mine density, survival, pupal mass and potential fecundity were significantly lower on A. glabra than on A. hippocastanum. The observed lower performance of C. ohridella on the exotic host plant was assumed to be due to its poor food quality (nutritional and chemical composition)., Urszula Walczak, Edward Baraniak, Piotr Zduniak., and Obsahuje bibliografii
Invaze nepůvodních druhů žížal vede v severoamerických lesích ke komplexním změnám a to především v severních opadavých lesích, které se od posledního zalednění částečně vyvíjely zcela bez přítomnosti žížal. Článek danou problematiku zasazuje do souvislostí a představuje stav poznání z hlediska příčin, postupu a důsledků těchto invazí., Invasions of exotic earthworms into North American forests lead to complex changes, in particular, in northern deciduous forests that have partially developed after the last glaciation without the presence of earthworms. The paper explains the context of these earthworm invasions and presents the state of knowledge in respect to their causes, spread and consequences., and Jiří Schlaghamerský.
The citation frequency of papers on invasion ecology published between 1981 and 2003 and that had accumulated at least 30 citations on the Web of Science on 9 August 2006 was analysed. The dataset comprised 329 papers and 27,240 citations. For each paper, the total number of citations was recorded and the annual citation rate (number of citations per year) was calculated. Papers were classified into broad research fields: plant invasions, animal invasions, biological control, and general papers (reviews and syntheses). Eight papers were cited more than 300 times, five of them dealt with general topics, and the mean value of the total number of citations across the whole data set is 82.8±73.1. The mean annual citation rate is 11.5±11.3 citations per year; six studies received on average at least 50 citations each year. About a half (50.8%) of papers in the data set deal with plant invasions. General papers are significantly more cited than papers from the other categories. The annual citation rate increased with time over the analysed period (1981–2003), by 1.0 citations per year. To compare the trends in invasion ecology with those in other fields of ecology, comparable data were compiled for population ecology and dynamics, and global change. The annual citation rate for invasion ecology as a whole increased faster than that for population ecology and dynamics, but not exponentially as is the case with studies on global change. The best-cited papers on invasion ecology were distributed among most of the top ecology journals. Those published in Oikos, Journal of Ecology, Ecological Applications and BioScience are cited 3.8–5.8 times more than the average for these journals (based on the impact factor). Papers on biodiversity, community ecology, impact, invasibility, dispersal, population ecology, competition, resources, genetical issues, biological control and species invasiveness received the highest total number of citations. However, measured by the annual citation rate, the hottest current topics in invasion ecology are the effect of global change on invasions, the role of natural enemies, character of the invasion process, evolutionary aspects, invasibility of communities and ecosystem processes. Some topics are disproportionally more cited than studied and vice versa. Studies on plant and animal invasions differ in focus: the topics of invasibility, biodiversity, resources, species invasiveness and population genetics are more emphasized in botanical studies, dispersal, competition, impact and pathways in papers dealing with animal invasions. Studies of grasslands and marine environment are most frequently cited in botanical and zoological studies, respectively. Most of the highly cited papers deal with multiple species; only 14 plant species and four animal species are the primary focus of one or more of the highly-cited papers. Twenty-two authors (4.5% of the total involved in the papers analysed), each with seven or more contributions cited at least 30 times, together contributed 49.4% of the most-cited papers, and attracted 55.6% of the total number of citations.
Winter habitat use, niche breadth and overlap between the native and invasive species of medium sized predators, the red fox, pine marten and raccoon dog in particular, were studied in three landscapes with different habitat structure in Lithuania. Meadows were preferred by foxes but avoided by raccoon dogs and pine martens. Pine martens intensively used various forest habitats, whilst raccoon dogs tended to prefer swamps. The habitat niche breadth (Hurlbert’s standardized niche breadth) varied with respect to both the species and the study site. The habitat niche overlap was larger between raccoon dog and pine marten than that between raccoon dog and red fox. Our results suggest a low impact of the invasive raccoon dog on red fox and pine marten in studied landscapes.