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1.
Lin Li Zhongliang Huang Wanhui Ye Honglin Cao Shiguang Wei Zhigao Wang Juyu Lian I‐Fang Sun Keping Ma Fangliang He 《Oikos》2009,118(4):495-502
The spatial dispersion of individuals in a species is an important pattern that is controlled by many mechanisms. In this study we analyzed spatial distributions of tree species in a large-scale (20 ha) stem-mapping plot in a species-rich subtropical forest of China. O-ring statistic was used to measure spatial patterns of species with abundance >10. Ω0–10 , the mean conspecific density within 10 m of a tree, was used as a measure of the intensity of aggregation of a species. Our results showed: (1) aggregated distribution was the dominant pattern in the plot. The percentage of aggregated species decreased with increased spatial scale. (2) The percentages of significantly aggregated species decreased from abundant to intermediate and to rare species. Rare species was more strongly aggregated than common species. Aggregation was weaker in larger diameter classes. (3) Seed traits determined the spatial patterns of trees. Seed dispersal mode can influence spatial patterns of species, with species dispersed by both modes being less clumped than species dispersed by animal or wind, respectively. Considering these results, we concluded that seed dispersal limitation, self-thinning and habitat heterogeneity primarily contributed to spatial patterns and species coexistence in the forest. 相似文献
2.
Summary. 1. The length of time that a gall-forming midge, Rhopalomyia califomica , was vulnerable to attack by four parasitoid species was measured in the field at two locations.
2. The midge had a restricted window of vulnerability to each of the parasitoid species, but similar windows of vulnerability were found at the two sites.
3. A stage-structured model was used to illustrate that the length of the vulnerable window should have no effect on the fraction parasitized by a single parasitoid species if that species is the only parasitoid attacking the host in a coupled host-parasitoid interaction. However, the length of the window of vulnerability can have a positive effect on the fraction parasitized by a species in competition with other parasitoid species.
4. The length of the window of vulnerability can help explain the relative field abundance of four of the common parasitoid species of R.californica. 相似文献
2. The midge had a restricted window of vulnerability to each of the parasitoid species, but similar windows of vulnerability were found at the two sites.
3. A stage-structured model was used to illustrate that the length of the vulnerable window should have no effect on the fraction parasitized by a single parasitoid species if that species is the only parasitoid attacking the host in a coupled host-parasitoid interaction. However, the length of the window of vulnerability can have a positive effect on the fraction parasitized by a species in competition with other parasitoid species.
4. The length of the window of vulnerability can help explain the relative field abundance of four of the common parasitoid species of R.californica. 相似文献
3.
东灵山辽东栎林木本植物多样性的研究 总被引:11,自引:0,他引:11
应用α多样性和β多样性指数对东灵山地区辽东栎林在不同样地环境梯度的物种多样性进行了初步研究。结果表明:不同样地梯度的辽东栎林乔灌木物种α多样性逐步降低,但变化幅度较小,群落物种组成趋于简单。不同样地梯度内辽东栎林乔木物种的β多样性的二元属性测度与数量数据测度结果反映出乔木物种和灌木物种对整个辽东栎林多样性的影响是不同的。数量数据β多样性测度综合地考虑了物种数与物种数量对β多样性变化的影响,适于对单优群落物种多样性进行分析。在中海拔样地梯度,辽东栎林乔灌木物种各样地对之间的β多样性数值较小,表明辽东栎林内物种替代速率较低,物种组成相对稳定,总体上是比较稳定的林型。 相似文献
4.
The imminent decline in species diversity coupled with increasing exotic species introductions has provoked investigation into the role of resident diversity in community resistance to exotic species colonization. Here we present the results of a field study using an experimental method in which diversity was altered by removal of less abundant species and the resulting disturbance was controlled for by removal of an equivalent amount of biomass of the most common species from paired plots. Following these manipulations, the exotic grass, Lolium temulentum , was introduced. We found that exotic species establishment was higher in plots in which diversity was successfully reduced by removal treatments and was inversely related to imposed species richness. These results demonstrate that less common species can significantly influence invasion events and highlight the potential role of less common species in the maintenance of ecosystem function. 相似文献
5.
Observation of developmental processes in loosely attached diatom (Bacillariophyceae) communities 总被引:2,自引:0,他引:2
Akihiro Tuji 《Phycological Research》2000,48(2):75-84
The succession of attached algal communities was studied in Lake Biwa and the Omiya River. After the ‘climax’ which was characterized by large numbers of Cymbella turgidula Grunow and Gomphoneis quadripunctatum (Østrup) P. Dawson, the community was dominated by species attached directly to stalks or tangled among stalks. Stalks produced by species of the previous phase are important as secondary substrata. The dominant species of the new phase were ‘loosely attached species’, as defined by Hudon and Bourget (1983). I propose a new model consisting of phase 1, characterized by the first colonizers, including large rosette‐type species and motile type species; phase 2, characterized by the stalk‐producing species; and phase 3, characterized by the growth of loosely attached species. 相似文献
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7.
The German Federal State of Saxony aims to increase forest cover, supported by the implementation of afforestation programs. To analyze consequences of an increase in forest cover, this study investigates possible trade-offs between carbon storage and plant biodiversity caused by afforestation. Six afforestation scenarios with total forest cover ranging from 27.7% to 46% were generated in the Mulde river basin in Saxony with regard to different forest types. Carbon storage was calculated by the process-based Dynamic Vegetation Model LPJ-GUESS while random forest models were used to predict changes in plant species richness. We used eight different plant groups as responses: total number of plant species, endangered species, as well as species grouped by native status (three groups) and pollination traits (three groups). Afforestation led to an increase in carbon storage that was slightly stronger in coniferous forests as compared to deciduous forests. The relationship between plant species richness and afforestation was context dependent. Species richness showed a non-linear relationship with forest cover share. The relationship was influenced by shares of land use types, climatic conditions and land use configuration expressed by the number of land use patches. The effect of forest type on plant species richness was marginal. On average the relationship between carbon storage and plant species richness was synergistic for most plant groups. However, the relationship between change in species richness and change in carbon storage varied across space. This changing relationship was used to identify priority areas for afforestation. The different plant groups responded differently to an increase in forest cover. The change in species richness for Red List species was relatively distinct from the other species groups. Neophytes and archeophytes (i.e. alien plant species introduced after and before the discovery of the Americas) showed a similar response to the afforestation scenarios. While afforestation had overall positive effects both on plant species richness and carbon storage, a number of locations were identified for which afforestation would lead to a decrease in plant species richness. Spatial planning should therefore avoid afforestation at these locations. 相似文献
8.
9.
A. L. Antsiferov 《Contemporary Problems of Ecology》2016,9(1):37-44
The ecological structure of ground beetles was studied. Its dynamics during the migration of ground beetles from one habitat to another as a result of severe ecological disturbances caused by tree felling and subsequent reforestation was considered. Some regularities in the formation and development of a ground beetle community in the early stage of secondary succession at the felling site were determined. Further trends were revealed using the simplest indices of diversity, species, abundance, distribution, and dominance of species. The species richness of ground beetles at the site one year after felling increased from 28 to 41 species. It decreased to 36 species in four years. According to the ecological preference, the basis of the complex of ground beetles at the forest site before felling was formed by spring-breeding species. Four years after felling, the proportion of forest species decreased (from 73.4 to 65.7%) and the significance of forestmarsh and meadow-field species increased. The proportion of summer- and autumn-breeding species also increased. The species and quantitative composition of ground beetles at the site during the first year after felling was mostly determined by neighboring forests. As reforestation proceeded, a separate biocenosis developed at the felling site and the influence of the forests became lower. The proportion of summer- and autumnbreeding species increased. The species and quantitative composition of ground beetles at the felling site was mostly determined by the neighboring forest during the first year. A separate biocenosis developed at the felling site in the following years, and the influence exercised by the forest diminished. 相似文献
10.
Community structure and temporal variability of ichthyoplankton in North Brazilian mangrove creeks 总被引:3,自引:0,他引:3
The species composition and dynamics of fish larvae in three mangrove creeks located in the Caeté Estuary (north Brazil) were studied monthly using a trap net during diurnal ebb tides. A total of 109 954 larvae, representing 25 families and 54 species, were collected from October 1996 to October 1997. The community was dominated numerically by a few species, a feature common for other estuarine fish populations. The most abundant taxa were estuarine species, namely the eleotrid Guavina guavina (46·7%) and the engraulid Anchovia clupeoides (14·9%). The sciaenid Cynoscion acoupa was the only marine species that used the mangroves extensively as a nursery site, occurring mainly at the postflexion stage. The size distribution of G. guavina did not produce shifting modes, indicating continuous transport out of the mangroves by tidal currents. Significantly lower species richness was observed in the late rainy season, primarily due to the emigration of marine species. Intermediate seasons were characterized by more complex larval fish assemblages. The temporal trends of the dominant species was influenced to a great degree by their life history strategy. 相似文献
11.
E. Raffaele 《Biological invasions》2004,6(4):473-481
Mallín wetland meadows are highly diverse, rare habitats in western Patagonia that are believed to be particularly susceptible to disturbance. I tested the hypothesis that exotic species reduce the rate and extent of recolonization by native species after disturbances. Open patches (50 × 50 cm) were subjected to artificial seeding with propagules of two exotic species. Cover of individual species in each plot was measured over the four following austral summers (1990–1993) and two late summers (1995 and 1998). The effect of a particular exotic species was not the same for all native species. For some native species, the presence of an exotic species in the plots was associated with a significant increase in cover, while a significant decrease in cover was observed for other species. Native species richness and diversity were not significantly affected by the introduction and establishment of exotic species. In addition, the failure of the exotic species to establish in the undisturbed control plots further suggests that the undisturbed mallín is resistant to invasion by exotic species. The results suggest that the small-scale changes that occurred in this community due to exotic species during recolonization were transient and almost undetectable after eight years. 相似文献
12.
Coldham T Rose K O'rourke J Neilan BA Dalton H Lee A Mitchell H 《Applied and environmental microbiology》2011,77(5):1581-1587
The presence of Helicobacter species in Australian marsupials was examined systematically using microscopy, culture, and PCR in different regions of the gastrointestinal tract (GIT) and in the liver of brushtail possums (BTPs) (Trichosurus vulpecula), a common Australian marsupial that feeds on eucalyptus leaves. The spatial distribution of Helicobacter species in the GIT sections also was examined microscopically in silver-stained sections and by fluorescent in situ hybridization (FISH) using a Helicobacter genus-specific probe. Helicobacter species were found colonizing the lower bowel of all BTPs studied. Good agreement was observed between the detection of Helicobacter species using culture and PCR, which was supported by the microscopic examination of silver-stained sections and FISH. The lower bowel of BTPs were colonized by one to three morphologically different (a comma-shaped species with no apparent flagella, a fusiform-shaped species entwined with periplasmic fibers and a bipolar sheathed flagella, and an S-shaped species with bipolar sheathed flagella) and potentially novel Helicobacter species, as well as in one case with a potentially novel Campylobacter species, which was a tightly coiled rod with bipolar unsheathed flagella. The isolation and characterization of these Helicobacter species in BTPs provides important information regarding the specific natural niche of these bacteria and their corelationship within their host, and it increases our understanding of the ecology of Helicobacter species. 相似文献
13.
Habitat selection and grouping of beetles (Coleoptera) 总被引:3,自引:0,他引:3
Alan Buse 《Ecography》1988,11(4):241-247
Beetles were collected by pitfall trapping for a two-year period in seven adjacent habitats in an upland site in North Wales. Positive correlations were demonstrated between number of beetle species and number and diversity of plant species. Similar correlations were shown between beetle numbers and plant species. However, only 15% of the beetle species were herbivores requiring host plants. The degree of habitat selection by individual beetle species was demonstrated, ranging from habitat specialist, being found in one habitat, lo habitat generalist, being found in most habitats. Herbivores were significantly more habitat specialist than predators or scavengers. The grouping of beetles, demonstrated by ordination analysis, was similar to, but less precise than, the grouping of plant species. The beetle groups reflect habitat selection preferences by individual species rather than a functional relationship between beetle species. They provide an example of the centrifugal structure of habitat selection theory. 相似文献
14.
Denson K. McLain Karamjit S. Rai P. Nagesh Rao 《Evolution; international journal of organic evolution》1985,39(5):998-1008
Ethological isolation among eight species of mosquitoes in the Aedes scutellaris subgroup of the south Pacific was investigated by offering females a simultaneous choice between males of their own species and males of another species. The degree of ethological isolation between these largely allopatric, island-dwelling mosquitoes was associated with time since the species had become geographically isolated by the fragmentation of the Outer Melanesian Arc 2–10 mya. The degree of ethological isolation between species pairs was observed to be significantly correlated with the degree of genetic isolation based on other published studies of allozyme variation and percentage egg hatch from interspecific hybridizations. However, ethological isolation was asymmetrical for some species pairs within the same island region. Asymmetrical isolation was especially prominent in Polynesia, where females of two older species discriminated against males of newer species, while females of the newer species failed to discriminate. 相似文献
15.
The inorganic and metal-organic growth requirements of ruminal and nonruminal Bacteroides species were compared. The heme requirement of many nonruminal Bacteroides species was similar to that of Bacteroides ruminicola subsp. ruminicola and was a general tetrapyrrole requirement. Some nonruminal Bacteroides species utilized succinate or alpha-ketoglutarate, as well as tetrapyrrole-containing compounds, in place of heme. Fe(+) as well as heme was required for maximal yields of some Bacteroides species. The divalent cation requirements of Bacteroides species are complex. Mg(2+) deletion from a medium containing Mg(2+), Ca(2+), Co(2+), and Mn(2+) reduced the yields of all isolates. Ca(2+) deletion from the same medium reduced the growth yields of Bacteroides fragilis, B. fundiliformis, and one strain of B. oralis. The effects of Mg(2+) and Ca(2+) on the growth of Bacteroides isolates was influenced by other divalent cations. Relatively large quantities of Na(+) were obligately required by all of the currently recognized predominant rumen Bacteroides species. Nonruminal Bacteroides species either did not require Na(+) or required only small amounts. The Na(+) requirement of some nonruminal Bacteroides species could be partially replaced by Li(+) or Cs(+). The Na(+) requirement of rumen Bacteroides species was absolute. The inorganic and metal-organic growth requirements of Bacteroides species appear useful as aids in species differentiation. 相似文献
16.
《农业工程》2021,41(6):524-536
This study was conducted during 2018–19 to evaluate the floristic composition and ecological characteristics of vegetation of Pashat valley, Bajaur. Floristic list of the valley contains 385 species distributed in 291 genera and 102 families. The dicotyledons having 83 families with 311 species and monocotyledons with 12 families contains 61 species. Pteridophytes having 05 families with 11 species and gymnosperm with a single family of two species. The leading family was Asteraceae with 42 species (10.90%) followed by Poaceae with 39 species (10.10%), Papilionaceae (Fabaceae) with 24 species (6.23%), Lamiaceae with 20 species (5. 19%) and Rosaceae with 15 species (3.90%). Therophytes 180 species (46.80%), hemicryptophytes 53 species (13.80%), nanophanerophytes 51 species (13.20%) and geophytes 35 species (9.09%) were the dominant life form groups. Leaf size class was dominated by microphylls (138 species, 35.84%) followed by nanophylls (124 species, 32.21%) and mesophylls (89 species, 23.12%). Habit wise the vegetation was mostly herbs (289 species) followed by shrubs (54 species), trees (38 species) and lianas (4 species). According to flowering phenology, most plants (62.30%) bloomed in spring followed by in summer (34%), in autumn (1.82%), in the whole year (1.30%) and in winter (0.52%). Based on chorological affinities, most of the species were bioregional in distribution (170 species, 44.15%) followed by mono-regional (157 species, 40.78%), pluri-regional (43 species, 11.17%) and cosmopolitan (15 species, 3.89%). The ecological characteristics like life form and leaf size spectra of the vegetation have a strong correlation with the prevailing environmental conditions such as altitude, slope, precipitation and temperature. 相似文献
17.
External morphology of spicules in several species of Trichodoridae was studied by scanning electron and light microscopy. The bristles on the spicules observed in the light microscope in several species were revealed as small scales forming a sheath which covers most of the spicule body. Some species have smooth spicules, whereas other species exhibited complicated structures formed by projections. In all of the species studied, either a ventro-terminal or terminal opening of the spicules was observed. 相似文献
18.
Flower Scent and Pollination in Selected Neotropical Palms 总被引:1,自引:0,他引:1
Abstract: The flower scents of 14 palm species were collected in the field in Ecuador and Puerto Rico by head-space adsorption and analysed by gas chromatography-mass spectrometry. Insect visitors were recorded in seven of the species in Ecuador. The floral scent of the different species was dominated by a variety of compounds, e.g., the fatty-acid derived 3-pentanone and the hydrocarbon series dodecane to pentadecane, the benzenoid compound 1,4-dimethoxybenzene, the isoprenoids ( E )-ocimene, myrcene, linalool, and ( E )-α-farnesene and the nitrogen-containing compound 2-methoxy- sec -butylpyrazine. Rather than mirroring the systematics of the studied palm species, the chemical composition of the floral scent reflected the pollination mode. The scent of beetle-pollinated species was characterized by large amounts of one or a few dominant compounds, whereas fly- and bee-pollinated species contained a mixture of several compounds in smaller total amounts. We suggest that specific scent compounds, as found in the beetle-pollinated species, have evolved as a response to pollinator preferences. The importance of olfactory cues in relation to visual cues is higher in beetle-pollinated species than in species pollinated by flies and bees. 相似文献
19.
We conducted an experiment with the dual aims of (1) examining the feasibility of establishing a species-rich grassland using a commercially available grass and wild-flower seed mixture and (2) examining the effects of different defoliation and fertilizer managements on the productivity, species richness, diversity, and composition of a species-rich grassland established on a site reclaimed after opencast coal mining. The use of the seed mixture successfully established a sward of some 18–25 species per square meter. The species composition was enriched to some extent by recruitment of unsown species, principally from the soil seed bank. Hay-type defoliation management produced greater dry matter yield and species richness than grazing defoliation, but grazing defoliation produced greater species diversity. Fertilizer application had no significant effect on dry matter production but reduced species diversity. Ordination analysis revealed that both defoliation and fertilizer management significantly affected species composition. The response obtained by individual species was explicable largely by their comparative biology. 相似文献
20.
The uptake of potassium by Carex species from swamp habitats varying from oligotrophic to eutrophic 总被引:1,自引:0,他引:1
Short-term potassium uptake by excised roots was investigated in Carex species from swamps, ranging from oligotrophic to eutrophic. The range of species from oligotrophic to eutrophic habitat is: C. rostrata Stokes, C. limosa L., C. lasiocarpa Ehrh., C. diandra Schrank, C. hudsonii A. Benn., and C. acutiformis Ehrh. After a short period of potassium starvation the species of the oligotrophic habitat showed a fast potassium uptake rate while the species of the eutrophic habitat showed lower uptake rates. Uptake by all species except C. rostrata and C. diandra was reduced at pH 4.0. Potassium uptake at low potassium concentrations was greatly increased by a period of starvation for potassium especially in the eutrophic species. The results on potassium stress are compared with the ecology of the species and with the reaction of the same Carex species to phosphate stress. 相似文献