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The shape of the species–area relationship (SAR) often varies with the amount of available energy; SARs from high‐energy habitats typically have higher intercepts and steeper slopes than SARs from low‐energy habitats. Such patterns are often assumed to result from a shift in the mechanisms of coexistence between high and low energy habitats. However, a plausible but unexplored alternative mechanism emerges from proportional sampling, if there are simply more individuals in larger or more productive habitats, without the need to invoke differing coexistence mechanisms. Here, we examined proportional versus disproportional responses of a diverse assemblage of freshwater zooplankton to manipulations of experimental pond size and energy inputs. We found that higher energy treatments had higher species richness in large, but not small, ponds, leading to a steeper SAR with higher energy input. The total abundances of individuals also increased with energy in large, but not small ponds. By using a sample‐independent rarefaction technique (probability of interspecific encounter), we found that SAR patterns resulted from changes in the total, but not relative, abundance of individuals, and thus proportional, rather than disproportional, responses of species. Overall, our results emphasize the need to consider how both the total and relative abundances of species respond to ecological drivers such as energy and area before inferring the underlying mechanisms that lead to biodiversity patterns. Further, our results may implicate a proportionally smaller influence of energy on patterns of biodiversity when habitats are destroyed.  相似文献   

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土壤微生物多样性海拔格局研究进展   总被引:12,自引:4,他引:8  
厉桂香  马克明 《生态学报》2018,38(5):1521-1529
生物多样性的海拔分布格局与维持机制是生物多样性与生态系统功能研究的热点领域。相比动植物多样性海拔分布格局,土壤微生物多样性海拔分布格局的研究还处在起步阶段。近年来,随着以罗氏454、Illumina Mi Seq等为代表的高通量测序平台的发展,土壤微生物海拔梯度分布格局的研究进展较快。对土壤微生物多样性海拔分布格局最新研究综述发现,土壤微生物海拔分布模式并不明确,表现为无趋势、下降、单峰或者下凹型等多种海拔分布模式。这与大型动植物并不相同,暗示其驱动机制可能存在一定的差异。微生物由于其个体微小、扩散能力强以及较高的多样性和个体丰度而在局域尺度上可能更易受到气候环境因素的影响。土壤pH、碳、氮等因子是影响微生物多样性和群落组成在海拔梯度上变异的重要因素。此外,温度和降水也具有重要作用。另外,除微生物自身属性以及取样限制外,测序深度可能是影响土壤微生物物种丰富度海拔分布格局的重要因素。目前,对土壤微生物群落的研究在功能基因、群落构建机制以及生态学理论的验证方面还存在着不足。未来的研究应进一步加大测序深度,增加取样密度,着重关注全球气候变化及生物多样性丧失背景下土壤微生物群落的构建和维持机制及其生态系统功能等方面。  相似文献   

4.
We examine whether rain forest dung beetle species found in plantations in Sabah, northern Borneo, tend to be endemic or geographically widespread. In addition, linear regressions of abundance vs. distance from a major river in primary rain forest are calculated to see if species found in plantation forest show affinity to one specific biotope (riverine vs. interior forest) in their natural habitat. Results show that 14 of the 40 species recorded from plantations are endemic to Borneo. Only edge‐specialist endemic species are found in plantation forest, with no interior‐forest specialists recorded. Data suggest that endemic species that are adapted to more exposed conditions in primary rain forest, such as riverine species, can in some instances tolerate man‐made habitats. Twenty‐nine species (±SE 4.0) per transect are recorded from plantation transects, whereas 44.2 (±1.7 SE) are recorded in primary rain forest. As species richness is much lower in plantations than natural forest, implying loss of biodiversity, we conclude that measures of biogeographic distinctiveness, whereby endemic species confer higher values, may be misleading unless they take into account edge‐affinity. Local‐ as well as regional‐distributional data may therefore be needed to interpret correctly patterns of species assemblages in derived forest ecosystems.  相似文献   

5.
Islands are vulnerable ecosystems worldwide, increasingly exposed to human pressure, global climate change and invasive species. Thus, understanding island species diversity is key for nature conservation. Recent studies on insular plant communities indicated that habitat-specific species composition and richness might largely affect diversity patterns observed at the island scale. In consequence, habitat-based approaches are needed to (i) estimate how environmental changes at the habitat scale may affect island diversity, and to (ii) estimate the contribution of different patches of the same habitat to island diversity with respect to habitat-specific environmental constraints.In the present study, we tested these habitat-to-island diversity relationships for shoreline habitats (brackish reeds, salt marsh, rocky shore, tall herbs) and island interior habitats (rocks, semi-natural grassland, pioneer forest, coniferous forest, mixed forest) using 108 islands of three Baltic archipelagos in Sweden. These islands differed in terms of island-scale variables describing effects of island configuration and distance, and habitat-scale variables representing the effects of habitat area, abiotic environment and land-use.The studied habitats differed in their contribution to island species diversity, called habitat specificity. Shoreline habitats shared many common specialist species adapted to extreme conditions like sea salt or bird grazing, while habitats of the island interior harbored mainly species adapted to the specific conditions of a single habitat. We found high variability in habitat specificity as a consequence of habitat-specific environmental factors. Variability was highest for grasslands, where it was related to abandonment and soil fertility, stressing the importance of grassland management for maintaining island biodiversity. Habitats with high habitat specificity through either high species richness or many habitat-specific specialists should be the primary targets for biodiversity management.  相似文献   

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While it is generally assumed that specialist species are more vulnerable to disturbance compared with generalist counterparts, this has rarely been tested in coastal marine ecosystems, which are increasingly subject to a wide range of natural and anthropogenic disturbances. Habitat specialists are expected to be more vulnerable to habitat loss because habitat availability exerts a greater limitation on population size, but it is also possible that specialist species may escape effects of disturbance if they use habitats that are generally resilient to disturbance. This study quantified specificity in use of different coral species by six coral‐dwelling damselfishes (Chromis viridis, C. atripectoralis, Dascyllus aruanus, D. reticulatus, Pomacentrus moluccensis, and P. amboinensis) and related habitat specialization to proportional declines in their abundance following habitat degradation caused by outbreaks of the coral eating starfish, Acanthaster planci. The coral species preferred by most coral‐dwelling damselfishes (e.g., Pocillopora damicornis) were frequently consumed by coral eating crown‐of‐thorns starfish, such that highly specialized damselfishes were disproportionately affected by coral depletion, despite using a narrower range of different coral species. Vulnerability of damselfishes to this disturbance was strongly correlated with both their reliance on corals and their degree of habitat specialization. Ongoing disturbances to coral reef ecosystems are expected, therefore, to lead to fundamental shifts in the community structure of fish communities where generalists are favored over highly specialist species.  相似文献   

7.
Conversion of formerly continuous native habitats into highly fragmented landscapes can lead to numerous negative demographic and genetic impacts on native taxa that ultimately reduce population viability. In response to concerns over biodiversity loss, numerous investigators have proposed that traits such as body size and ecological specialization influence the sensitivity of species to habitat fragmentation. In this study, we examined how differences in body size and ecological specialization of two rodents (eastern chipmunk; Tamias striatus and white‐footed mouse; Peromyscus leucopus) impact their genetic connectivity within the highly fragmented landscape of the Upper Wabash River Basin (UWB), Indiana, and evaluated whether landscape configuration and complexity influenced patterns of genetic structure similarly between these two species. The more specialized chipmunk exhibited dramatically more genetic structure across the UWB than white‐footed mice, with genetic differentiation being correlated with geographic distance, configuration of intervening habitats, and complexity of forested habitats within sampling sites. In contrast, the generalist white‐footed mouse resembled a panmictic population across the UWB, and no landscape factors were found to influence gene flow. Despite the extensive previous work in abundance and occupancy within the UWB, no landscape factor that influenced occupancy or abundance was correlated with genetic differentiation in either species. The difference in predictors of occupancy, abundance, and gene flow suggests that species‐specific responses to fragmentation are scale dependent.  相似文献   

8.
Assessing the extent to which changes in lacustrine biodiversity are affected by anthropogenic or climatic forces requires extensive palaeolimnological data. We used high‐throughput sequencing to generate time‐series data encompassing over 2200 years of microbial eukaryotes (protists and Fungi) diversity changes from the sedimentary DNA record of two lakes (Lake Bourget in French Alps and Lake Igaliku in Greenland). From 176 samples, we sequenced a large diversity of microbial eukaryotes, with a total 16 386 operational taxonomic units distributed within 50 phylogenetic groups. Thus, microbial groups, such as Chlorophyta, Dinophyceae, Haptophyceae and Ciliophora, that were not previously considered in lacustrine sediment record analyses appeared to be potential biological markers of trophic status changes. Our data suggest that shifts in relative abundance of extant species, including shifts between rare and abundant taxa, drive ecosystem responses to local and global environmental changes. Community structure shift events were concomitant with major climate variations (more particularly in Lake Igaliku). However, this study shows that the impacts of climatic fluctuations may be overpassed by the high‐magnitude eutrophication impacts, as observed in the eutrophicated Lake Bourget. Overall, our data show that DNA preserved in sediment constitutes a precious archive of information on past biodiversity changes.  相似文献   

9.
With the advent of molecular methods, it became clear that microbial biodiversity had been vastly underestimated. Since then, species abundance patterns were determined for several environments, but temporal changes in species composition were not studied to the same level of resolution. Using massively parallel sequencing on the 454 GS FLX platform we identified a highly dynamic turnover of the seasonal abundance of protists in the Austrian lake Fuschlsee. We show that seasonal abundance patterns of protists closely match their biogeographic distribution. The stable predominance of few highly abundant taxa, which previously led to the suggestion of a low global protist species richness, is contrasted by a highly dynamic turnover of rare species. We suggest that differential seasonality of rare and abundant protist taxa explains the—so far—conflicting evidence in the ‘everything is everywhere’ dispute. Consequently temporal sampling is basic for adequate diversity and species richness estimates.  相似文献   

10.
The niche is a fundamental ecological concept that underpins many explanations of patterns of biodiversity. The complexity of niche processes in ecological systems, however, means that it is difficult to capture them accurately in theoretical models of community assembly. In this study, we build upon simple neutral biodiversity models by adding the important ingredient of overlapping niche structure. Our model is spatially implicit and contains a fixed number of equal-sized habitats. Each species in the metacommunity arises through a speciation event; at which time, it is randomly assigned a fundamental niche or set of environments/habitats in which it can persist. Within each habitat, species compete with other species that have different but overlapping fundamental niches. Species abundances then change through ecological drift; each, however, is constrained by its maximum niche breadth and by the presence of other species in its habitats. Using our model, we derive analytical expressions for steady-state species abundance distributions, steady-state distributions of niche breadth across individuals and across species, and dynamic distributions of niche breadth across species. With this framework, we identify the conditions that produce the log-series species abundance distribution familiar from neutral models. We then identify how overlapping niche structure can lead to other species abundance distributions and, in particular, ask whether these new distributions differ significantly from species abundance distributions predicted by non-overlapping niche models. Finally, we extend our analysis to consider additional distributions associated with realized niche breadths. Overall, our results show that models with overlapping niches can exhibit behavior similar to neutral models, with the caveat that species with narrow fundamental niche breadths will be very rare. If narrow-niche species are common, it must be because they are in a non-overlapping niche or have countervailing advantages over broad-niche species. This result highlights the role that niches can play in establishing demographic neutrality.  相似文献   

11.
Anthropogenic habitats are increasingly prevalent in coastal marine environments. Previous research on sessile epifauna suggests that artificial habitats act as a refuge for nonindigenous species, which results in highly homogenous communities across locations. However, vertebrate assemblages that live in association with artificial habitats are poorly understood. Here, we quantify the biodiversity of small, cryptic (henceforth “cryptobenthic”) fishes from marine dock pilings across six locations over 35° of latitude from Maine to Panama. We also compare assemblages from dock pilings to natural habitats in the two southernmost locations (Panama and Belize). Our results suggest that the biodiversity patterns of cryptobenthic fishes from dock pilings follow a Latitudinal Diversity Gradient (LDG), with average local and regional diversity declining sharply with increasing latitude. Furthermore, a strong correlation between community composition and spatial distance suggests distinct regional assemblages of cryptobenthic fishes. Cryptobenthic fish assemblages from dock pilings in Belize and Panama were less diverse and had lower densities than nearby reef habitats. However, dock pilings harbored almost exclusively native species, including two species of conservation concern absent from nearby natural habitats. Our results suggest that, in contrast to sessile epifaunal assemblages on artificial substrates, artificial marine habitats can harbor diverse, regionally characteristic assemblages of vertebrates that follow macroecological patterns that are well documented for natural habitats. We therefore posit that, although dock pilings cannot function as a replacement for natural habitats, dock pilings may provide cost‐effective means to preserve native vertebrate biodiversity, and provide a habitat that can be relatively easily monitored to track the status and trends of fish biodiversity in highly urbanized coastal marine environments.  相似文献   

12.
Despite the well‐documented impacts of consumers on seed abundance the link between seed predation and plant population dynamics remains poorly understood because experimental studies linking patterns of predation with seedling establishment are rare. We used experimental manipulations with six woody plant species to elucidate the effects of seed predator type, habitat, and plant species identity on rates of seed predation and seedling recruitment in the Neotropical savannas known as the Cerrado. We found that seed predation rates are consistently high across a diversity of local habitat types, with important inter‐habitat variation in seed predation for three of the six species used in our experiments. We also found that seed predation has a clear demographic signal – experimentally excluding predators resulted in higher rates of seedling establishment over the course of two seasons. Because the intensity of seed predation varied between species and habitats, it may play a role in structuring local patterns of plant abundance and community composition. Finally, our results lend support to the recent hypothesis that herbivores have major and underappreciated impacts in Neotropical savannas, and that top–down factors can influence the demography of plants in this extensive and biodiversity‐rich biome in previously unexplored ways.  相似文献   

13.
Assessing how natural environmental drivers affect biodiversity underpins our understanding of the relationships between complex biotic and ecological factors in natural ecosystems. Of all ecosystems, anthropogenically important estuaries represent a ‘melting pot'' of environmental stressors, typified by extreme salinity variations and associated biological complexity. Although existing models attempt to predict macroorganismal diversity over estuarine salinity gradients, attempts to model microbial biodiversity are limited for eukaryotes. Although diatoms commonly feature as bioindicator species, additional microbial eukaryotes represent a huge resource for assessing ecosystem health. Of these, meiofaunal communities may represent the optimal compromise between functional diversity that can be assessed using morphology and phenotype–environment interactions as compared with smaller life fractions. Here, using 454 Roche sequencing of the 18S nSSU barcode we investigate which of the local natural drivers are most strongly associated with microbial metazoan and sampled protist diversity across the full salinity gradient of the estuarine ecosystem. In order to investigate potential variation at the ecosystem scale, we compare two geographically proximate estuaries (Thames and Mersey, UK) with contrasting histories of anthropogenic stress. The data show that although community turnover is likely to be predictable, taxa are likely to respond to different environmental drivers and, in particular, hydrodynamics, salinity range and granulometry, according to varied life-history characteristics. At the ecosystem level, communities exhibited patterns of estuary-specific similarity within different salinity range habitats, highlighting the environmental sequencing biomonitoring potential of meiofauna, dispersal effects or both.  相似文献   

14.
Research frontiers in null model analysis   总被引:4,自引:0,他引:4  
Null models are pattern‐generating models that deliberately exclude a mechanism of interest, and allow for randomization tests of ecological and biogeographic data. Although they have had a controversial history, null models are widely used as statistical tools by ecologists and biogeographers. Three active research fronts in null model analysis include biodiversity measures, species co‐occurrence patterns, and macroecology. In the analysis of biodiversity, ecologists have used random sampling procedures such as rarefaction to adjust for differences in abundance and sampling effort. In the analysis of species co‐occurrence and assembly rules, null models have been used to detect the signature of species interactions. However, controversy persists over the details of computer algorithms used for randomizing presence–absence matrices. Finally, in the newly emerging discipline of macroecology, null models can be used to identify constraining boundaries in bivariate scatterplots of variables such as body size, range size, and population density. Null models provide specificity and flexibility in data analysis that is often not possible with conventional statistical tests.  相似文献   

15.
European forest management guidelines include conservation and enhancement of biodiversity. Within plantation forestry, trackways provide contiguous permanent open-habitat with potential to enhance biodiversity. We examined the ground-active spider assemblage in the trackway network of Thetford Forest, Eastern England, the largest lowland conifer forest in the UK, created by afforestation of heathland and farmland. Results are relevant to other forests in heath regions across Europe. We used pitfall trapping to sample the spider assemblage of trackways within thicket-aged stands (n = 17), mature stands (n = 13) and heathland reference sites (n = 9). A total of 9,314 individuals of 71 species were recorded. Spider assemblages of the trackway network were distinct from those of the heathland reference sites; however, trackways were found to support specialist species associated with grass-heath habitats, including nationally scarce species. Richness of grass-heath species was similar for trackways in thicket-aged forest and heathland reference sites, although the abundance of individuals was three times greater in the reference sites. Trackways in mature stands had lower grass-heath species richness and abundance than both thicket trackways and heath reference sites. Wide trackways within thicket stands contained greater richness and abundance of specialist xeric species than narrower trackways. However, fewer xeric individuals were found in trackways compared to heathland reference sites. Either inferior habitat quality in trackways or poor dispersal ability of specialist xeric species may largely restrict these to relict areas of heathland. Targeted widening of trackways to allow permanent unshaded habitat and creating early successional stages by mechanical disturbance regimes could improve trackway suitability for specialist species, helping to restore connectivity networks for grass-heath biodiversity.  相似文献   

16.
Habitat structure determines spider diversity in highland ponds   总被引:1,自引:0,他引:1  
Wetlands (e.g. ponds, meadows) can be found in many landscapes, playing an important role in maintaining regional biodiversity and supporting heterogeneous communities. Spiders are diversified predators that are highly influenced by changes in plant community structure, heterogeneous habitats sustain high spider diversity and abundance. We investigated the characteristics of spider biodiversity in ponds with different habitat structures, by examining patterns across habitats of ponds with different vegetation levels. Sampling took place in four occasions over a year. We compared spider abundance, species richness and composition among ponds including distinct vegetation variables, related to life form, type of leaves, coverage and height. Overall 1174 individuals (194 adults) of 11 families and 37 morphospecies were sampled. We found mostly expected differences in the manner that communities were structured between different habitats. Thus, higher variability of abundance was explained for higher habitat structure of ponds. We also found differences in species composition between ponds with low emergent vegetation and higher habitat structures. Additionaly, spiders were consistently structured more by turnover than nestedness components, with a greater beta diversity of web-builders. Our results suggest varying levels of habitat structures and species substitution shape pond spider communities, depending on habitat heterogeneity and spider guild. Those findings demonstrate the clear role of spatial habitat structure, with more spider species preferring to build webs or actively hunt at vegetated environments on ponds.  相似文献   

17.
Insects are particularly vulnerable to rapid environmental changes, which are disproportionally affecting high latitudes. Increased temperature could influence insect species differentially and reshape assemblages over time. We quantified temporal assemblage turnover of Arctic Diptera (flies) in the Muscidae, one of the most diverse and abundant families of Arctic insects, using time series data from Zackenberg, north‐east Greenland. We measured temporal patterns of abundance, diversity, and composition of muscid assemblages in wet fen, mesic and arid heath habitats from yearly collections spanning 1996–2014 and tested their relationship to climate. A total of 18 385 individuals representing 16 species of muscid flies were identified. A significant decrease of 80% of total muscid abundance was observed during the study period. Species richness declined in each habitat type but this trend was not significant across habitats. The number of common and abundant species also decreased significantly over time across habitats revealing a temporal modification of species evenness. Significant temporal changes in composition observed in the wet fen and across habitats were mainly driven by a change in relative abundance of certain species rather than by species replacement. Shift in composition in each habitat and decline in muscid abundance across habitats were associated with summer temperature, which has significantly increased over the study period. However, relationships between temperature and muscid abundance at the species level were noticeable for a few species only. Significant directional change in composition was documented in the wet fen but no biotic homogenization across habitats was observed. As one of the few studies of species‐level changes in abundance, diversity and composition of an insect taxon in the Arctic over the past two decades, our study shows that habitat types may modulate insect species responses to recent climate change and that contrasting species responses can alter species assemblages within a few decades.  相似文献   

18.
Species colonization in a new habitat patch is an efficiency indicator of biodiversity conservation. Colonization is a two‐step process of dispersal and establishment, characterized by the compatibility of plant traits with landscape structure and habitat conditions. Therefore, ecological trait profiling of specialist species is initially required to estimate the relative importance of colonization filters. Old planted parks best satisfy the criteria of a newly created and structurally matured habitat for forest‐dwelling plant species. We sampled species in 230 ancient deciduous forests (source habitat), 74 closed‐canopy manor parks (target habitats), 151 linear wooded habitats (landscape corridors), and 97 open habitats (isolating matrix) in Estonia. We defined two species groups of interest: forest (107 species) and corridor specialists (53 species). An extra group of open habitat specialists was extracted for trait scaling. Differing from expectations, forest specialists have high plasticity in reproduction mechanisms: smaller seeds, larger dispersules, complementary selfing ability, and diversity of dispersal vectors. Forest specialists are shorter, less nutrient‐demanding and mycorrhizal‐dependent, stress‐tolerant disturbance‐sensitive competitors, while corridor specialists are large‐seeded disturbance‐tolerant competitors. About 40% of species from local species pools have immigrated into parks. The historic forest area, establishment‐related traits, and stand quality enhance the colonization of forest specialists. The openness of landscape and mowing in the park facilitate corridor specialists. Species traits in parks vary between a forest and corridor specialist, except for earlier flowering and larger propagules. Forest species are not dispersal limited, but they continue to be limited by habitat properties even in the long term. Therefore, the shady parts of historic parks should be appreciated as important forest biodiversity‐enhancing landscape structures. The habitat quality of secondary stands can be improved by nurturing a heterogeneous shrub and tree layer, and modest herb layer management.  相似文献   

19.
Aim Despite the increasing pace of urbanization, little is known about how this process affects biodiversity globally. We investigate macroecological patterns of bird assemblages in urbanized areas relative to semi‐natural ecosystems. Location World‐wide. Methods We use a database of quantitative bird surveys to compare key assemblage structure parameters for plots in urbanized and semi‐natural ecosystems controlling for spatial autocorrelation and survey methodology. We use the term ‘urbanized’ instead of ‘urban’ ecosystems as many of the plots were not located in the centre of towns but in remnant habitat patches within conurbations. Results Some macroecological relationships were conserved in urbanized landscapes. Species–area, species–abundance and species–biomass relationships did not differ significantly between urbanized and non‐urbanized environments. However, there were differences in the relationships between productivity and assemblage structure. In forests, species richness increased with productivity; in both forests and open habitats, the evenness of species abundances declined as productivity increased. Among urbanized plots, instead, both species richness and the evenness of species abundances were independent of variation in productivity. Main conclusions Remnant habitats within urbanized areas are subject to many ecological alterations, yet key macroecological patterns differ remarkably little in urbanized versus non‐urbanized plots. Our results support the need for increased conservation activities in urbanized landscapes, particularly given the additional benefits of local experiences of biodiversity for the human population. With increasing urbanization world‐wide, broad‐scale efforts are needed to understand and manage the effects of this driver of change on biodiversity.  相似文献   

20.
Frequent low‐intensity fires are used in management of Australian forests to reduce fuel loads and protect natural resources and human property. Low‐intensity fires are typically patchy and unburned litter microhabitats are often associated with large objects such as logs, which may act as refuges both for vertebrate and for invertebrate fauna. The aim of this study was to determine whether ants were using unburned leaf litter microhabitats associated with logs as a refuge after fire. The study was carried out in Bulls Ground State Forest, New South Wales, Australia, where experimentally burned and unburned sites had previously been established. Species richness and abundance of ants in leaf litter did not differ between habitats adjacent to logs and away from logs, in burned and unburned sites. Fifteen of the 42 ant species were found in all four habitats, and contributed 94% of total ant abundance. Every habitat had a group of unique species, which together made up 30% of the total species richness. There was also a distinct group of species that was not found in the leaf litter associated with the burned/open habitat. However, as 45% of all species were found in low abundance (less than 10 individuals), care must be taken in inferring patterns for these groups. When functional groups were used to assess community structure, ‘cryptic’ species were found to be common in all habitats, whereas ‘subordinate Camponotini’ were found in burned habitats only. This study indicates that in an area where frequent burning is applied on a broad scale, preserving a range of microhabitats, including those associated with retained logs, may make a substantial contribution to conserving ant biodiversity.  相似文献   

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