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181.
N fixation in feather moss carpets is maximized in late secondary successional boreal forests; however, there is limited understanding
of the ecosystem factors that drive cyanobacterial N fixation in feather mosses with successional stage. We conducted a reciprocal
transplant experiment to assess factors in both early and late succession that control N fixation in feather moss carpets
dominated by Pleurozium schreberi. In 2003, intact microplots of moss carpets (30 cm × 30 cm × 10–20 cm deep) were excavated from three early secondary successional
(41–101 years since last fire) forest sites and either replanted within the same stand or transplanted into one of three late
successional (241–356 years since last fire) forest sites and the transverse was done for late successional layers of moss.
Moss plots were monitored for changes in N-fixation rates by acetylene reduction (June 2003–September 2005) and changes in
the presence of cyanobacteria on moss shoots by microscopy (2004). Forest nutrient status was measured using ionic resin capsules
buried in the humus layer. Late successional forests exhibit high rates of N fixation and consistently high numbers of cyanobacteria
on moss shoots, but low levels of available N. Conversely, early successional forests have higher N availability and have
low rates of N fixation and limited presence of cyanobacteria on moss shoots. Transplantation of moss carpets resulted in
a significant shift in presence and activity of cyanobacteria 1 year after initiation of the experiment responding to N fertility
differences in early versus late successional forests. 相似文献
182.
We tested whether selection by pollinators could explain the parapatric distribution of coastal red- and inland yellow-flowered races of Mimulus aurantiacus (Phrymaceae) by examining visitation to natural and experimental populations. As a first step in evaluating whether indirect selection might explain floral divergence, we also tested for local adaptation in early life stages using a reciprocal transplant experiment. Hummingbirds visited flowers of each race at similar rates in natural populations but showed strong (>95%) preference for red flowers in all habitats in experimental arrays. Hawkmoths demonstrated nearly exclusive (>99% of visits) preference for yellow flowers and only visited in inland regions. Strong preferences for alternative floral forms support a direct role for pollinators in floral divergence. Despite these preferences, measures of plant performance across environments showed that red-flowered plants consistently survived better, grew larger and received more overall pollinator visits than yellow-flowered plants. Unmeasured components of fitness may favour the yellow race in inland habitats. Alternatively, we document a marked recent increase in inland hummingbird density that may have caused a change in the selective environment, favouring the eastward advance of red-flowered plants. 相似文献
183.
Grooming and agonistic support are 2 common primate behaviorsthat have been hypothesized to constitute examples of reciprocalaltruism. In particular, because primates often direct theirgrooming up the dominance hierarchy, it has been suggested thatthey may exchange grooming for agonistic support. Empiricaltests of this hypothesis have resulted in highly inconsistentfindings. I synthesized the published literature on the relationbetween grooming and agonistic support in primates using modernmeta-analytical techniques. A meta-analysis of 36 studies carriedout on 14 different species showed that a significant positiverelation exists between grooming and agonistic support (weightedaverage r = 0.154, corrected for publication bias). These findingssuggest that grooming and agonistic support may have evolvedas part of a system of low-cost reciprocal altruism. They alsohighlight the potential of meta-analysis in tackling the studyof behavioral phenomena characterized by low overall frequencyand small effect sizes. 相似文献
184.
Disentangling the effect of host genetics and gut microbiota on resistance to an intestinal parasite
Bruno Faivre Jérôme Bellenger Aurélie Rieu Emmanuel Guivier Maxime Galan Anthony Ollivier Lauriane Poloni Gabriele Sorci 《International journal for parasitology》2019,49(11):873-883
Resistance to infection is a multifactorial trait, and recent work has suggested that the gut microbiota can also contribute to resistance. Here, we performed a fecal microbiota transplant to disentangle the contribution of the gut microbiota and host genetics as drivers of resistance to the intestinal nematode Heligmosomoides polygyrus. We transplanted the microbiota of a strain of mice (SJL), resistant to H. polygyrus, into a susceptible strain (CBA) and vice-versa. We predicted that if the microbiota shapes resistance to H. polygyrus, the FMT should reverse the pattern of resistance between the two host strains. The two host strains had different microbiota diversities and compositions before the start of the experiment, and the FMT altered the microbiota of recipient mice. One mouse strain (SJL) was more resistant to colonization by the heterologous microbiota, and it maintained its resistance profile to H. polygyrus (lower parasite burden) independently of the FMT. On the contrary, CBA mice harbored parasites with lower fecundity during the early stage of the infection, and had an up-regulated expression of the cytokine IL-4 (a marker of H. polygyrus resistance) after receiving the heterologous microbiota. Therefore, while host genetics remains the main factor shaping the pattern of resistance to H. polygyrus, the composition of the gut microbiota also seems to play a strain-specific role. 相似文献
185.
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187.
Ling-Fei Li Ke-Qing Shi Yi-Qian Lin Li-Ren Wang Jiang-Ping He Martin Braddock Yong-Ping Chen Ming-Hua Zheng 《Gene》2014
Hepatitis C virus (HCV) infection is the major cause of chronic liver disease after renal transplantation (RT), which reduces both graft and patient survival. After RT, the most widely used approach is interferon (IFN)-based therapy of hepatitis C which may be unsatisfactory with both poor efficacy and an increasing risk of allograft rejection. Thus, it is not recommended unless patients develop fibrosing cholestatic hepatitis. Several recent studies, however, suggest that treatment was possible with preservation of both renal and liver functions. From the limited studies on HCV infection after RT, several factors have been identified as important tools for the management of therapy in these patients. Infection with HCV genotypes 2 and 3, low baseline viral load and absence of advanced fibrosis/cirrhosis in the liver are associated with a sustained virologic response (SVR). After initiation of treatment, initial viral decline with undetectable HCV-RNA at week 4 of therapy (RVR) is the best predictor of SVR independent of HCV genotype. Furthermore, some factors must be taken into consideration in order to avoid allograft rejection, such as the time between transplantation and therapy for HCV, the dose and duration of regimen and renal function. Careful evaluation of predictions of stable renal function and SVR for those patients helps to reduce inefficient treatment regimes and to increase the cure rate in addition to reducing the possible risk. In this review, the latest information was collected and we focus on the discussion of the factors influencing the attainment of SVR after RT. 相似文献
188.
Cameron D. Siler Jamie R. Oaks Kerry Cobb Hidetoshi Ota Rafe M. Brown 《Diversity & distributions》2014,20(7):756-772
189.
Species‐specific responses to climate change will lead to changes in species interactions across multiple trophic levels. Interactions between plants and their insect herbivores, in particular, may become increasingly disrupted if mobile herbivores respond more rapidly to climatic change than their associated host plants. We present a multispecies transplant experiment aimed at assessing potential climatic impacts on patterns of leaf herbivory. Four shrubby understorey plant species were transplanted outside their native range into a climate 2.5°C warmer in annual mean temperature. After 12 months, we assessed the types and amount of herbivore leaf damage, compared with plants transplanted to a control site within their native range. The overall amount of foliage loss to herbivores ranged from approximately 3–10% across species and sites, a range consistent with most estimates of leaf loss in other studies. The most common types of leaf damage were sucking and chewing and this pattern was consistent for all four plant species at all sites. There were no significant differences in levels and patterns of herbivory between control and warm sites for three out of four plant species. This suggests that with moderate climate warming, most herbivory will continue to be dominated by chewers and suckers, and that the overall level of foliage loss will be similar to that experienced presently. 相似文献
190.
The changes in species' geographical distribution demanded by climate change are often critically limited by the availability of key interacting species. In such cases, species' persistence will depend on the rapid evolution of biotic interactions. Understanding evolutionary limits to such adaptation is therefore crucial for predicting biological responses to environmental change. The recent poleward range expansion of the UK brown argus butterfly has been associated with a shift in female preference from its main host plant, rockrose (Cistaceae), onto Geraniaceae host plants throughout its new distribution. Using reciprocal transplants onto natural host plants across the UK range, we demonstrate reduced fitness of females from recently colonised Geraniaceae‐dominated habitat when moved to ancestral rockrose habitats. By contrast, individuals from ancestral rockrose habitats show no reduction in fitness on Geraniaceae. Climate‐driven range expansion in this species is therefore associated with the rapid evolution of biotic interactions and a significant loss of adaptive variation. 相似文献