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21.
We assessed the effect of geographical distance on insect species turnover in a situation where other major environmental factors, including host plant species, altitude, and climate, were constant. We sampled ambrosia beetles (Coleoptera, Curculionidae: Scolytinae and Platypodinae) from four tree species: Artocarpus altilis , Ficus nodosa , Leea indica and Nauclea orientalis , at three sites forming a 1000 km transect in lowland rainforests of northern Papua New Guinea. A standardized volume of wood from trunk, branches and twigs was sampled for ambrosia beetles from three individuals of the four tree species at each site. Each tree was killed standing and left exposed to beetle colonization for 20 days prior to sampling. We obtained 12 751 individuals from 84 morphospecies of ambrosia beetles. We surveyed most of the local species richness at each site, predicted by Chao 2 species richness estimates. The similarity of ambrosia beetle communities, estimated by Chao-Sorensen index, was not correlated with their geographical distance. Likelihood analysis and Q-mode analysis using Monte Carlo-generated null distribution of beetles among sites supported the hypothesis that the assemblages of ambrosia beetles at different sites are drawn from the same species pool, regardless of their geographical distance. Tree part (trunk, branch, or twig) was more important predictor of the composition of ambrosia beetle communities than was the host species or geographical location. All three variables, however, explained only a small portion of variability in ambrosia assemblages. The distribution of ambrosia beetles among tree parts, tree species and study sites was mostly random, suggesting limited importance of host specificity or dispersal limitation. 相似文献
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23.
Seasonality of sap-sucking insects (Auchenorrhyncha, Hemiptera) feeding on Ficus (Moraceae) in a lowland rain forest in New Guinea 总被引:1,自引:0,他引:1
Sap-sucking insects (Auchenorrhyncha, Hemiptera) were sampled quantitatively from the foliage of 15 species of Ficus (Moraceae) in a lowland rain forest in Papua New Guinea. Continuous sampling throughout 12 months produced 61,777 individuals
and 491 species. Two seasonality parameters, circular statistics and Lloyd's index, were calculated for 139 species with a
sample size of more than 36 individuals. Most of the species were present in the adult stage for at least half of the year,
and many of them continuously throughout the year. However, almost all species exhibited marked seasonal changes in abundance.
The abundance peaks of species were scattered throughout most of the year, but more species reached their population maximum
during the wet, especially early wet, season than during the dry season. Overall species richness and abundance of Auchenorrhyncha
were also higher during the wet than the dry season. A significant correlation between seasonality and host specificity was
revealed in the auchenorrhynchan community. In particular, species evenly distributed throughout the year had a tendency to
feed on a larger number of Ficus species than seasonally more restricted species. The seasonality, and the seasonality versus specificity correlation, were
independent of species abundance. Among the most abundant species (n > 300) there was a marginally significant negative correlation between abundance and host specificity, so that polyphagous
species had, on average, larger populations than specialists. There was no similar correlation among rarer species. The Auchenorrhyncha
comprises three feeding guilds, which were also analysed separately. The mesophyll-feeding guild exhibited more pronounced
seasonality than the phloem- and xylem-feeders. This difference could be explained as a part of the overall correlation between
seasonality and host specificity as mesophyll-feeders were significantly more host specific than the other two guilds.
Received: 26 January 1998 / Accepted: 9 March 1998 相似文献
24.
Vojtech Ličko 《Bulletin of mathematical biology》1972,34(1):103-112
Certain arrangements of enzymatic (bimolecular) subsystems lead to characteristic threshold-type response. Two simple cases
of such systems are studied here in terms of steady state behavior and explicit relationships between system and curve parameters.
It is found that the curvature of the threshold curve is directly related to the equivalent Michaelis constant and, in the
case of saturated threshold curve, the slope of the curve at the idealized threshold is limited by the ratio of saturation
to threshold. This slope may be appreciably increased up to a stepwise response at the threshold if a multisubstrate complex
of the enzyme is the only species which affects the enzyme mediated transport. 相似文献
25.
26.
Vlková E Rada V Trojanová I Killer J Smehilová M Molatová Z 《Archives of animal nutrition》2008,62(5):359-365
The development of faecal bacteria composition in calves fed milk or a combined diet was investigated from 4 to 21 days of age. On day 7, bifidobacteria in faeces of milk-fed calves already increased from about 7.6 to 9.2 log CFU/g and did not change until the end of the study, whereas in calves fed the combined diet bifidobacteria only moderately increased to 7.9 log CFU/g and decreased slowly until day 21. The counts of bifidobacteria in calves on a combined diet were significantly (p < 0.01) lower compared to those in milk-fed calves. Bifidobacterial counts determined by cultivation or by fluorescence in situ hybridisation (FISH) did not differ significantly. Our results showed that the occurrence of bifidobacteria in calf faeces is highly dependent on the diet composition. Faecal bacteria flora of calves fed exclusively by milk is rich in bifidobacteria, but in calves on a combined diet coliforms dominated. 相似文献
27.
Elevational species richness gradients in a hyperdiverse insect taxon: a global meta‐study on geometrid moths 下载免费PDF全文
Jan Beck Christy M. McCain Jan C. Axmacher Louise A. Ashton Florian Bärtschi Gunnar Brehm Sei‐Woong Choi Oldrich Cizek Robert K. Colwell Konrad Fiedler Cristina L. Francois Steven Highland Jeremy D. Holloway Jurie Intachat Tomas Kadlec Roger L. Kitching Sarah C. Maunsell Thomas Merckx Akihiro Nakamura Erica Odell Weiguo Sang Pagi S. Toko Jaroslav Zamecnik Yi Zou Vojtech Novotny 《Global Ecology and Biogeography》2017,26(4):412-424
28.
For healthy infants, which were born normally and fully breastfed, the dominant component of the intestinal microflora are bifidobacteria. However, infants born by caesarean section possess clostridia as a dominant intestinal bacterial group. The aim of the present study was to determine whether bifidobacteria and clostridia are able to grow on human milk oligosaccharides (HMOs) and other carbon sources - lactose, cow milk (CM) and human milk (HM). Both bifidobacteria and clostridia grew on lactose and in CM. Bifidobacteria grew in HM and on HMOs. In contrast, 3 out of 5 strains of clostridia were not able to grow in HM. No clostridial strain was able to utilise HMOs. While both bifidobacterial strains were resistant to lysozyme, 4 out of 5 strains of clostridia were lysozyme-susceptible. It seems that HMOs together with lysozyme may act as prebiotic-bifidogenic compounds inhibiting intestinal clostridia. 相似文献
29.
Krešimir Begović Jonathan S. Schurman Marek Svitok Jakob Pavlin Thomas Langbehn Kristyna Svobodová Martin Mikoláš Pavel Janda Michal Synek William Marchand Lucie Vitková Daniel Kozák Ondrej Vostarek Vojtech Čada Radek Bače Miroslav Svoboda 《Global Change Biology》2023,29(1):143-164
In a world of accelerating changes in environmental conditions driving tree growth, tradeoffs between tree growth rate and longevity could curtail the abundance of large old trees (LOTs), with potentially dire consequences for biodiversity and carbon storage. However, the influence of tree-level tradeoffs on forest structure at landscape scales will also depend on disturbances, which shape tree size and age distribution, and on whether LOTs can benefit from improved growing conditions due to climate warming. We analyzed temporal and spatial variation in radial growth patterns from ~5000 Norway spruce (Picea abies [L.] H. Karst) live and dead trees from the Western Carpathian primary spruce forest stands. We applied mixed-linear modeling to quantify the importance of LOT growth histories and stand dynamics (i.e., competition and disturbance factors) on lifespan. Finally, we assessed regional synchronization in radial growth variability over the 20th century, and modeled the effects of stand dynamics and climate on LOTs recent growth trends. Tree age varied considerably among forest stands, implying an important role of disturbance as an age constraint. Slow juvenile growth and longer period of suppressed growth prolonged tree lifespan, while increasing disturbance severity and shorter time since last disturbance decreased it. The highest age was not achieved only by trees with continuous slow growth, but those with slow juvenile growth followed by subsequent growth releases. Growth trend analysis demonstrated an increase in absolute growth rates in response to climate warming, with late summer temperatures driving the recent growth trend. Contrary to our expectation that LOTs would eventually exhibit declining growth rates, the oldest LOTs (>400 years) continuously increase growth throughout their lives, indicating a high phenotypic plasticity of LOTs for increasing biomass, and a strong carbon sink role of primary spruce forests under rising temperatures, intensifying droughts, and increasing bark beetle outbreaks. 相似文献