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991.
Functional diversity: back to basics and looking forward 总被引:16,自引:0,他引:16
Functional diversity is a component of biodiversity that generally concerns the range of things that organisms do in communities and ecosystems. Here, we review how functional diversity can explain and predict the impact of organisms on ecosystems and thereby provide a mechanistic link between the two. Critical points in developing predictive measures of functional diversity are the choice of functional traits with which organisms are distinguished, how the diversity of that trait information is summarized into a measure of functional diversity, and that the measures of functional diversity are validated through quantitative analyses and experimental tests. There is a vast amount of trait information available for plant species and a substantial amount for animals. Choosing which traits to include in a particular measure of functional diversity will depend on the specific aims of a particular study. Quantitative methods for choosing traits and for assigning weighting to traits are being developed, but need much more work before we can be confident about trait choice. The number of ways of measuring functional diversity is growing rapidly. We divide them into four main groups. The first, the number of functional groups or types, has significant problems and researchers are more frequently using measures that do not require species to be grouped. Of these, some measure diversity by summarizing distances between species in trait space, some by estimating the size of the dendrogram required to describe the difference, and some include information about species' abundances. We show some new and important differences between these, as well as what they indicate about the responses of assemblages to loss of individuals. There is good experimental and analytical evidence that functional diversity can provide a link between organisms and ecosystems but greater validation of measures is required. We suggest that non-significant results have a range of alternate explanations that do not necessarily contradict positive effects of functional diversity. Finally, we suggest areas for development of techniques used to measure functional diversity, highlight some exciting questions that are being addressed using ideas about functional diversity, and suggest some directions for novel research. 相似文献
992.
Ecosystem productivity can be predicted from potential relative growth rate and species abundance 总被引:4,自引:0,他引:4
We show that ecosystem-specific aboveground net primary productivity (SANPP, g g−1 day−1 , productivity on a per gram basis) can be predicted from species-level measures of potential relative growth rate (RGRmax ), but only if RGRmax is weighted according to the species' relative abundance. This is in agreement with Grime's mass-ratio hypothesis. Productivity was measured in 12 sites in a French Mediterranean post-agricultural succession, while RGRmax was measured on 26 of the most abundant species from this successional sere, grown hydroponically. RGRmax was only weakly correlated ( r 2 = 0.12, P < 0.05) with field age when species abundance was not considered, but the two variables were strongly correlated ( r 2 = 0.81, P < 0.001) when the relative abundance of species in each field was taken into account. SANPP also decreased significantly with field age. This resulted in a tight relationship ( r 2 = 0.77, P < 0.001) between productivity and RGRmax weighted according to species relative biomass contribution. Our study shows that scaling-up from the potential properties of individual species is possible, and that information on potential and realized species traits can be integrated to predict ecosystem functioning. 相似文献
993.
Each species generally has a close relationship with one or more habitats and can therefore be classified as either specialist or generalist. We studied whether specialist and generalist species are spatially distributed independently of each other. Repeating the analysis for 100 of the most frequent terrestrial bird species recorded over the 10 000 sampled sites of the French Breeding Bird survey, we found that specialists were more abundant if the rest of the community was specialized, and that the inverse was also true. This pattern was far subtler than just a simple dichotomy: most species actually presented a maximum abundance at a value of community specialization similar to their own level of specialization. Bird communities appear very well defined along a specialist–generalist gradient. We believe this pattern becomes more apparent with habitat degradation. The consequences on both ecological services and community resilience may well be considerable. 相似文献
994.
Abstract To characterize the structure and species density of termite assemblages in tropical forests, we developed a sampling protocol based on a single large quadrat (belt transect) that standardises sampling effort and area. Emphasizing the estimation of species richness, Roisin and Leponce (2004, Austral Ecology, 29 : 637–46) recommend sampling numerous small quadrats, and varying the number of quadrats depending on local species density. However, their method would result in the loss of standardisation and speed, taking up to four times longer to collect and process the samples. We show that even for a subtropical forest with low species density, our protocol produces robust results. 相似文献
995.
996.
Modular design of artificial transcription factors 总被引:6,自引:0,他引:6
997.
Moss transcriptome and beyond 总被引:11,自引:0,他引:11
998.
Zhang D Chen J Yao Q Pan Z Chen J Zhang W 《Archives of insect biochemistry and physiology》2012,79(4-5):220-234
Insect chitinases are a multigene family that is encoded by a rather large and diverse group of genes. The main function of chitinases is to digest the chitin contained in tissues such as the cuticles and gut lining during molting. In this study, we examined the role of a chitinase (SeChi) and a bacterial type chitinase (SeChi-h) during the pupation and eclosion stages of Spodoptera exigua. First, efficient silencing of the SeChi and SeChi-h genes through specific double-stranded RNA (dsRNA) injection led to a significant reduction in the mRNA levels of SeChi and SeChi-h. Additionally, different phenotypic defects were observed at the pupal and adult stages after injection of the SeChi and SeChi-h dsRNAs. After injecting SeChi dsRNA in the pupal stage, the cuticle of the head split open and the pupal cuticle was visible under the old larval cuticle. However, after injecting the SeChi-h dsRNA, animals died without exhibiting any special phenotypes. At the adult death stage, animals injected with dsSeChi could not shed their pupal shell completely, and their old cuticles remained attached to their head or chest. However, the main lethal phenotype was that insects did not emerge after dsSeChi-h injection. Additionally, the average survival rates of S. exigua were 52.02% and 40.38% at the pupal and adult stages, respectively, after injection with SeChi dsRNA. For the insects injected with SeChi-h dsRNA, the survival rates were 72.38% and 48.52%, respectively. These results suggest that SeChi and SeChi-h may have different biologic functions during the pupal-adult molting. 相似文献
999.
Long-term functional plasticity in plant hydraulic architecture in response to supplemental moisture
Background and Aims
Plasticity in structural and functional traits related to water balance may determine plant performance and survival in ecosystems characterized by water limitation or high levels of rainfall variability, particularly in perennial herbaceous species with long generation cycles. This paper addresses whether and the extent to which several such seasonal to long-term traits respond to changes in moisture availability.Methods
Using a novel approach that integrates ecology, physiology and anatomy, a comparison was made of lifetime functional traits in the root xylem of a long-lived perennial herb (Potentilla diversifolia, Rosaceae) growing in dry habitats with those of nearby individuals growing where soil moisture had been supplemented for 14 years. Traditional parameters such as specific leaf area (SLA) and above-ground growth were also assessed.Key Results
Individuals from the site receiving supplemental moisture consistently showed significant responses in all considered traits related to water balance: SLA was greater by 24 %; roots developed 19 % less starch storing tissue, an indicator for drought-stress tolerance; and vessel size distributions shifted towards wider elements that collectively conducted water 54 % more efficiently – but only during the years for which moisture was supplemented. In contrast, above-ground growth parameters showed insignificant or inconsistent responses.Conclusions
The phenotypic changes documented represent consistent, dynamic responses to increased moisture availability that should increase plant competitive ability. The functional plasticity of xylem anatomy quantified in this study constitutes a mechanistic basis for anticipating the differential success of plant species in response to climate variability and change, particularly where water limitation occurs. 相似文献1000.
Combined use of leaf size and economics traits allows direct comparison of hydrophyte and terrestrial herbaceous adaptive strategies 总被引:1,自引:0,他引:1