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981.
Khaled M. Abdel Rahman Marek Barta Ľudovít Cagáň 《Central European Journal of Biology》2010,5(4):472-480
We tested the combined effect of the fungus Beauveria bassiana and the microsporidium Nosema pyrausta on the European corn borer larvae, Ostrinia nubilalis, in the laboratory. The first instar of O. nubilalis larvae was the most sensitive to the B. bassiana infection followed by the fifth, second, third, and fourth instar (LC50s were 4.91, 6.67, 7.13, 9.15, and 6.51 × 105 conidia/ml for the first to fifth instars, respectively). Mortality of each instar increases positively with concentration
of conidia. When B. bassiana and N. pyrausta were used in combination, mortality increased significantly in all instars. Relative to the B. bassiana treatment alone, the B. bassiana + N. pyrausta treatment decreased the LC50s by 42.16%, 37.63%, 21.60%, 27.11%, and 33.95% for the first to fifth instars, respectively. The combined effects of the
two pathogens were mostly additive. However, at the two highest concentrations the pathogens interacted synergistically in
the first and second instar. Individuals that survived the B. bassiana and B. bassiana + N. pyrausta treatments and developed into adults had significantly shorter lifespans and females oviposited fewer eggs than non-exposed
insects. The effects on the longevity and the egg production were most pronounced at high concentration of B. bassiana conidia. 相似文献
982.
James S. Wakeley Michael P. Guilfoyle Terry J. Antrobus Richard A. Fischer Wylie C. BarrowJr. Paul B. Hamel 《Wetlands Ecology and Management》2007,15(5):417-439
We used an ordination approach to identify factors important to the organization of breeding bird communities in three floodplains:
Cache River, Arkansas (AR), Iatt Creek, Louisiana (LA), and the Coosawhatchie River, South Carolina (SC), USA. We used 5-min
point counts to sample birds in each study area each spring from 1995 to 1998, and measured ground-surface elevations and
a suite of other habitat variables to investigate bird distributions and community characteristics in relation to important
environmental gradients. In both AR and SC, the average number of Neotropical migrant species detected was lowest in semipermanently
flooded Nyssa aquatica Linnaeus habitats and greatest in the highest elevation floodplain zone. Melanerpes carolinus Linnaeus, Protonotaria citrea Boddaert, Quiscalus quiscula Linnaeus, and other species were more abundant in N. aquatica habitats, whereas Wilsonia citrina Boddaert, Oporornis formosus Wilson, Vireo griseus Boddaert, and others were more abundant in drier floodplain zones. In LA, there were no significant differences in community
metrics or bird species abundances among forest types. Canonical correspondence analyses revealed that structural development
of understory vegetation was the most important factor affecting bird distributions in all three study areas; however, potential
causes of these structural gradients differed. In AR and SC, differences in habitat structure were related to the hydrologic
gradient, as indexed by ground-surface elevation. In LA, structural variations were related mainly to the frequency of canopy
gaps. Thus, bird communities in all three areas appeared to be organized primarily in response to repeated localized disturbance.
Our results suggest that regular disturbance due to flooding plays an important role in structuring breeding bird communities
in floodplains subject to prolonged inundation, whereas other agents of disturbance (e.g., canopy gaps) may be more important
in headwater systems subject to only short-duration flooding. Management for avian community integrity in these systems should
strive to maintain forest zonation and natural disturbance regimes. 相似文献
983.
984.
Biological availability and humic properties of dissolved organic carbon in Lake Balaton (Hungary) 总被引:1,自引:0,他引:1
The nursery role of the Mondego estuary for marine fish species was studied between June 2003 and May 2004. The spatial and
temporal distribution and abundance patterns of 0-group Dicentrarchus
labrax (Linnaeus, 1758), Platichthys
flesus (Linnaeus, 1758) and Solea solea (Linnaeus, 1758) were analyzed based on monthly sampling surveys in five stations along the estuarine gradient. Fishing took
place during the night at low water of spring tides, using a 2 m beam trawl. The spatial patterns of estuarine colonization
were different according to species. D. labrax showed a wider distribution, but the main nursery ground was the same as for S. solea. Highest densities of S. solea juveniles were found in oligohaline areas, with muddy bottoms and high benthic invertebrates availability, while P. flesus occurred mainly in the sandy uppermost areas. D. labrax was found in both these areas. Fish abundance in the estuary mainly reflected seasonal changes. 相似文献
985.
Mikael Gyllström Thomas Lakowitz Christer Brönmark Lars-Anders Hansson 《Ecosystems》2008,11(7):1120-1132
In an experimental study we assessed if benthic bioturbating invertebrates affect the recruitment (hatching) of zooplankton
from the sediment, and if this effect persists as differences in the zooplankton community in the water column, that is, if
bioturbation quantitatively stimulates benthic–pelagic coupling. We investigated the effects of four different benthic invertebrates
(Asellus aquaticus, Chironomus plumosus, Tubifex tubifex in the presence or absence of the predator Sialis lutaria). In total, 45 zooplankton taxa hatched from the sediment and the hatching success of some of these was dependent on the
species identity of the bioturbating invertebrate. The predator Sialis reduced the abundance of all three invertebrate species, but tended to positively influence the zooplankton recruitment rates,
possibly through increasing the activity of the bioturbating invertebrates. The most striking effect of bioturbation on the
hatching and pelagic zooplankton community properties was that, on average, 11% more species hatched in the Asellus treatment than in any other treatment. This was also mirrored in the zooplankton water column community where, on average,
7% more species established a viable population in treatments with Asellus as bioturbator. In a complementary field survey, Asellus was more common in littoral than in profundal sediments. Because Asellus strongly affected recruitment of zooplankton in our experiment, we argue that bioturbation may partly explain why recruitment
of resting stages of both phyto- and zooplankton is generally higher in littoral than in profundal areas. 相似文献
986.
987.
Dispersal abilities of invading species emerge from the interaction between the species and some features of the target community. Ligustrum lucidum is a tree species invading different ecosystems. Major spatial patterns of Ligustrum invasions and their ecological consequences have been analyzed, but no study addressed the dispersal process at a fine scale, assessing the effects of different biological and environmental factors. Ligustrum lucidum is an ornithochoric species. The structure of the environment determines bird movements and thus affects seed dispersal. We used inverse modeling to analyze bird-mediated dispersal of L. lucidum seeds in a secondary Yungas forest and surrounding crop-fields. We assessed the effects of egestion mode (regurgitation and defecation) and tree density (as an environment character) on seed dispersal. Seed dispersal presented different spatial patterns depending on the egestion mode. Tree density was positively associated with the number of regurgitated dispersed seeds and negatively associated with the number of defecated dispersed seeds. In both cases, dispersal distance increased in open areas, but absence of perches inhibited seed arrival. Thus, spread of L. lucidum is facilitated in open areas with some trees; inside the native forest, short distance dispersal facilitates the gradual invasion by this exotic species. Our results suggest that processes like crop abandonment and forest succession, which are active in subtropical montane systems, may facilitate L. lucidum invasion. Our seed dispersal models should be combined with actual distribution maps of L. lucidum to identify areas vulnerable to new invasions. 相似文献
988.
Kyung-Ho Ma Anupam Dixit Young-Chang Kim Dong-Yun Lee Tae-San Kim Eun-Gi Cho Yong-Jin Park 《Conservation Genetics》2007,8(6):1507-1509
Panax ginseng C.A. Meyer, commonly known as Korean or Asian ginseng, is a perennial herb native to Korea and China. Its roots are highly
prized for several medicinal properties. The present study describes development and characterization of twenty-two polymorphic
microsatellite markers for this species. A total of 99 alleles were detected with an average of 4.5 alleles per locus across
20 accessions. Values for observed (H
O
) and expected (H
E
) heterozygosities ranged from 0.05 to 1.00 and from 0.18 to 0.73, respectively. Eleven loci deviated from Hardy–Weinberg
equilibrium (P < 0.001). Significant (P < 0.05) heterozygote deficiency was observed at 13 loci. Exact test for linkage disequilibrium showed significant values
(P < 0.05) between 12 pairs of loci. These microsatellite markers provide powerful tools for understanding population and conservation
genetics of this species and also for genetic differentiation and authentication of different Panax species being used in commercial ginseng products. 相似文献
989.
Although drug treatment of hypertension is associated with improved survival and decreased vascular complications, drug compliance is a major problem in the control of hypertension. All antihypertensive medications are associated with side effects; thus, it is a physician''s responsibility to explain to each patient the side effects of the drugs he prescribes to treat hypertension, and to instill in the patient a sense of necessity for the treatment of hypertension. The choice of antihypertensive drug should be made based on each patient''s lifestyle, overall health and ability to tolerate the drug. Ideally, the antihypertensive regimen should be simple, effective, convenient to take and have very few side effects. 相似文献
990.
Presentations at a session of the 13th Congress of the International Society for Ethnobiology (ISE, May 2012) provided a global overview of ‘maintaining resources for traditional medicine’. Two themes received special attention, transmission of traditional medical knowledge and conservation of medicinal plants. The consensus at the well attended session was that traditional medicine can play a useful role in primary healthcare, including for chronic complaints and spiritual problems. However, the use of traditional medicine is declining in many places. Some practical efforts at maintaining resources for traditional medicine are described. A case study for Buganda (Uganda), given in greater detail, shows that progress in maintaining resources for traditional medicine can be impeded by forces not directly related to its intrinsic merits. The value of making efforts to maintain resources for traditional medicine is discussed in relation to its contribution to biocultural conservation, much needed today to counter balance the homogenising and ecologically destabilising influences of globalisation. 相似文献