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1.
The abundances of different species in a parasite community are never similar: there is typically one or a few numerically dominant species and many species with low abundance. Here, we determine whether basic features of parasite communities are associated with strong dominance by one or a few species, among 39 component communities of gastrointestinal helminths in marine fishes from Brazil. First, we tested whether the shape of the species abundance distribution in these communities fits that predicted by several theoretical models, using a goodness-of-fit procedure. Only the canonical lognormal model could be rejected for 5 out of 39 communities; all other comparisons of observed and predicted abundance distributions showed no significant differences, although this may be due to limited statistical power. Second, we used the ratio between the abundance of the most abundant species and either the second or third most abundant species, as indices of dominance; these show, for instance, that the dominant species in a community is typically twice, but sometimes over ten times, as abundant as the next most abundant species. We found that these ratios were not influenced by either the community's species richness, the mean number of individual parasites per host, or the taxonomic identity of the dominant species. However, the abundance ratio between the first and third most abundant species in a community was significantly correlated with an independent index of species interactivity, based on the likelihood that the different parasite species in a component community co-occur in the same host individuals: the difference in abundance between the dominant and third most abundant species was greater in communities characterized by weak interactions. These findings suggest that strong interactions may lead to greater evenness in the abundance of species, and that numerical dominance is more likely to result from interspecific differences in recruitment rates. 相似文献
2.
Although the distribution of plant species abundance in a Minnesota grassland was consistent with neutral theory, niche but not neutral mechanisms were supported by the ability of species traits to predict species abundances in three experimental grassland communities. In particular, data from 27 species grown in monoculture showed that species differed in a trait, R *, which is the level to which each species reduced the concentration of soil nitrate, the limiting soil nutrient and which is predicted to be inversely associated with competitive ability for nitrogen (N). In these N-limited habitats, species abundance ranks correlated with their predicted competitive ranks: low R * species, on average dominated. These correlations were significantly different than expected for neutral theory, which assumes the exchangeability of species traits. Additionally, we found that changes in relative abundance after environmental change (N-addition or disturbance) were not neutral but also were significantly associated with R *. 相似文献
3.
亚高寒草甸不同生境植物群落物种多度分布格局的拟合 总被引:1,自引:0,他引:1
物种多度分布是群落生态学研究的核心内容。通过对青藏高原东部亚高寒草甸3种不同生境草本植物群落的抽样调查,结合16个物种多度分布模型的两种曲线拟合优度检验得出如下结果:多种不同模型可以拟合同一生境的物种多度分布。相比于其他可拟合模型,几何级数模型在3种生境中两种拟合优度检验方法下的平均拟合效果是最好的,拟合优度值均在最优拟合优度值10左右波动。次优模型鉴于不同生境不同的检验方法表现不一。除了几何级数模型外,Sugihara分数模型在最小二乘法的拟合方法下,也可以拟合3种生境的物种多度分布。研究结果表明,仅用拟合优度检验区分产生不同物种分布格局的模型和机制是不可靠的,需要做进一步的检验性实验研究。 相似文献
4.
Species richness, endemism, and abundance patterns: tests of two fractal models in a serpentine grassland 总被引:2,自引:1,他引:1
Although scaling relationships that characterize fractal species distributions offer an exciting potential for unification in biogeography, empirical support for fractal theory remains the subject of debate. We synthesize and test multiple predictions of two interrelated fractal models and a null model of random placement using Californian serpentine grassland data describing the spatial location of over 37 000 individually identified plants. The endemics–area relationship and species‐abundance distribution recently derived from a community‐level fractal property performed poorly because of an inaccurate assumption of homogeneity among species. In contrast, a species‐level fractal model that incorporates species‐level differences predicted abundances well, but systematically overestimated endemism and predicted a species–area relationship that violated the observed power law. These findings indicate that in order to make predictions based on the existence of a power‐law species–area relationship, ecologists need a unifying theory of how the community‐level fractal property arises in the presence of species‐level distributional differences. 相似文献
5.
Enrique Núñez-Lara Pierre Legendre 《Journal of experimental marine biology and ecology》2005,324(2):157-169
Using a hierarchical multi-scale survey design, we examined the spatial patterns of reef fish communities and tested ecological models concerning the relative importance of reef geomorphology and anthropogenic pressure possibly driving community structure. Canonical redundancy analysis was used as a form of multivariate analysis of variance (MANOVA) to asses differences in reef fish community composition at two spatial scales: broad (105 m) and intermediate (104 m). Surveys were conducted on the east coast of the Yucatan Peninsula (Mexican Caribbean fringing reef), including regions and reefs which differed in geomophologic structure and human use. Seven hundred and fourteen line transects were distributed among 13 reef localities belonging to different regions established a priori. Transects covered four types of reef habitat: lagoon, front, slope, and terrace. Tests of significance were based on permutation procedures. Significant differences among regions were found for the lagoon, slope, and terrace fish communities, consistent with the geomorphologic model, but it is only in the reef lagoon that they were consistent with the anthropogenic model, which may indicate an effect of coastal human activities. Significant differences among reefs within regions were observed, which could be associated with local environmental gradients. Canonical nested MANOVA was an appropriate method for testing ecological hypotheses about the functioning of complex biological systems. The use of a surveying strategy that explicitly incorporated the spatial structure represents an important contribution of this paper to coral reef fish ecology. 相似文献
6.
This study considered a model for species abundance dynamics in two local community (or islands) connected to a regional metacommunity. The model was analyzed using continuous probabilistic technique that employs Kolmogorov-Fokker-Planck forward equation to derive the probability density of the species abundance in the two local communities. Using this technique, we proposed a classification for the species abundance dynamics in the local communities. This classification was made based on such characteristics as immigration intensity, species representation in the metacommunity and the size of local communities. We further distinguished several different scenarios for species abundance dynamics using different ecological characteristics such as species persistence, extinction and monodominance in one or both local communities. The similarity of the species abundance distributions between the two local communities was studied using the correlation coefficient between species abundances in two local communities. The correlation is a function of migration rates between local communities and between local and metacommunity. Immigration between local communities drives the homogenization of the local communities, while immigration from the metacommunity will differentiate them. This community subdivision model provides useful insights for studying the effect of landscape fragmentation on species diversity. 相似文献
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8.
Species abundance patterns of plants in Swedish semi-natural pastures 总被引:10,自引:0,他引:10
This investigation is based on a species inventory m semi-natural pastures, remnants of an "old" traditional landscape, in Sweden The aim was to examine relationships between species richness and pasture area, neighbour pasture area, distance to nearest pasture, pasture heterogeneity and fertilization Species occurrences were also investigated individually for the same parameters Pasture area, neighbour pasture area and distance to nearest pasture were not found to influence species richness Habitat heterogeneity and indications that pastures had been influenced by fertilization were however associated with both species richness and species occurrences Heterogeneity had only positive effects whereas the effects of fertilization were only negative Species regional abundance pattern tended to be bimodal, as predicted by the core-satellite hypothesis No correlation between abundance and plant height, or seed size was found, as would have been expected if competitive dominance effects determined species regional abundance There was a close to significant tendency that pasture area was positively associated with occurrences of species with features favouring a high seed dispersal capacity We suggest that the previous history of pasture distribution and management may be of vital importance for present day species abundance pattern, even though this remains obscure in the recent landscape 相似文献
9.
Leberg Samuel S Barriga Ramiro Bart Henry Olivo Alfredo Narasimhan Kaushik Karubian Jordan 《Environmental Biology of Fishes》2021,104(3):239-251
Environmental Biology of Fishes - Environmental conditions influence ecological processes that shape stream community diversity and abundance. Deforestation has the potential to limit available... 相似文献
10.
Chemical contaminants are ubiquitous in nature and a major goal of ecologists has been to understand and predict their impacts on natural communities. While direct toxic effects can be garnered from single‐species laboratory studies, the full suite of possible effects can only be observed when organisms are embedded within a community. In this study, we manipulated the concentration of malathion (a broad‐spectrum insecticide) to determine the impacts on aquatic communities containing phytoplankton, periphyton, and 27 species of animals (16 zooplankton, 5 snails, 3 tadpoles and 3 predatory insects). Using relatively low concentrations (0.13 to 0.46 mg l?1), we found important direct (and interactive) effects of predators and malathion on the food web as well as a number of apparent density‐ and trait‐mediated indirect effects. Malathion initiated an indirect effect by decreasing zooplankton diversity and abundance, which propagated an increase in phytoplankton, a decrease in periphyton, and a subsequent decrease in the growth of leopard frog tadpoles. There also was an apparent trait‐mediated indirect effect whereby increased amounts of the pesticide reduced predation rates on amphibians without affecting the survival of the primary amphibian predator (larval Anax dragonflies). In contrast, snail survival and growth was unaffected by the pesticide but there were strong, species‐specific effects from their primary predator (adult Belostoma water bugs). This is one of few studies to examine the impacts of malathion on aquatic communities across a range of concentrations, despite the fact that it is currently the most commonly applied insecticide in the United States, it is applied around the world, and it can be legally directly sprayed over aquatic habitats to control the mosquitoes that carry malaria and West Nile virus. Our results suggest several mechanisms by which a wide variety of pesticides with similar modes of action might impact aquatic communities. 相似文献
11.
Sónia A. P. Santos Armando Raimundo Albino Bento José A. Pereira 《Agricultural and Forest Entomology》2012,14(4):376-382
- 1 The patterns of abundance of coccinellid species associated to the main agricultural tree crops of north‐eastern Portugal namely olive, chestnut and almond were studied.
- 2 During three to four crop seasons, eight olive, five chestnut and one almond groves were sampled. In each grove, five samples were collected from 10 randomly selected trees using the beating technique and the coccinellids were counted and identified to species. Principal component analysis was used to establish associations among crop and coccinellid species.
- 3 The mean species richness was higher in chestnut, with 15 ± 3.81 species/grove, followed by olive and almond, with 13 ± 2.76 and 10 ± 2.97 species/grove, respectively. Scymnus mediterraneus was the most abundant species in olive and almond, whereas Scymnus interruptus was dominant in chestnut. Brumus quadripustulatus, Chilocorus bipustulatus, Scymnus subvillosus, S. mediterraneus and Rhyzobius chrysomeloides were associated with olive, whereas S. interruptus, Coccinella septempunctata and Adalia decempunctata were associated with chestnut and Hippodamia variegata, Oenopia conglobata and Adalia bipunctata with almond. Both Stethorus punctillum and Scymnus apetzi species were similarly associated with chestnut and almond.
- 4 The differences in coccinellid communities could have been related to the kind of prey item present in the different trees. This knowledge can be used to develop integrated pest management programmes that encourage greater natural enemy biodiversity in agroecosystems.
12.
Brenda Rashleigh 《Ecography》2008,31(5):612-619
The pattern of nestedness, where species present in depauperate locations are subsets of species present in locations with higher species diversity, is often found in ecological communities. Mussel communities examined in four rivers in the upper Tennessee River basin appeared significantly nested. Mussel species distributions were mostly unrelated to differences in immigration and only weakly related to downstream direction, giving some indication of structuring by differences in extinction. Mussel species distributions were not related to the number of fish species used as hosts for mussel larvae. Mussel species were more likely to overlap on common fish hosts; however, the host‐use matrix was not nested – groups of mussel species used different sets of host fish species in a pattern that appeared phylogenetically related. Sites with high fish host abundance may support high mussel diversity by promoting the survival of mussel species that are less able to attract and infect hosts. Thus, nestedness in freshwater mussel communities may be driven by the array of host fish resources, combined with differences in species’ abilities to use fish hosts. An understanding of the nested pattern in this region can aid conservation of this imperiled fauna. 相似文献
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14.
黄土高原森林群落物种多度的分布格局 总被引:6,自引:0,他引:6
选用物种多度统计模型(对数级数分布模型、对数正态分布模型)和物种多度生态位模型(分割线段模型、生态位重叠模型、随机分配模型)研究了黄土高原子午岭马栏林区不同演替阶段3种森林群落物种多度分布格局的变化。结果表明:(1)物种分布统计模型拟合显示,演替初期的白桦(Betula platyphylla)林,物种丰富,但分布不均匀;演替中期的天然油松(Pinus tabulaeformis)林,油松优势地位明显,林下灌木和草本植物数量少但分布集中;演替顶极的辽东栎(Quercus liaotungensis)林,物种分布均匀且集中,枯立木形成的林隙较多。(2)在物种多度生态位模型拟合中,3种群落均能被较好地拟合。说明在演替过程中,影响物种分布的自然和人为因素较多,不能简单地选择一个生态位模型来解释。因此,研究森林群落物种分布时,最好采用多个模型进行拟合。 相似文献
15.
The aerial prop roots of the neotropical red mangrove,Rhizophora mangle L., begin growing well above highest high water (HHW) and often extend well below lowest low water (LLW) before rooting in the benthic substratum. In Belize, Central America, prop roots growing below LLW are colonized by diverse assemblages of organisms, including macroalgae, hydrozoans, ascidians, sponges, anemones, hard corals, and isopod crustaceans. Mangroves, root-fouling epibionts, root herbivores, and benthic predators engage in complex interactions that are major determinants of mangrove growth and production. Species richness of root epibionts increases with distance from the mainland and with proximity to the barrier reef. Species richness decreases with variability in water temperature and salinity. Ascidians and sponges transplanted from Lark Cay into the coastal Placencia Lagoon failed to survive, but anemones from Lark Cay survived in Placencia Lagoon. Reciprocal transplants survived off-shore. The gastropod predator,Melongena melongena L., present only in mainland estuaries, reduced local barnacle abundance and epibiont species richness in Placencia Lagoon. Isopod species richness also increases with distance from shore, but the number of roots bored by these species decreases. These isopods can reduce root relative growth rate (RGRroot) by 55%. On off-shore cays, sponges and ascidians ameliorate negative effects of isopods. In mainland estuaries where epibionts are less common, isopod damage to roots is more severe. Experimental studies in mangrove swamps throughout the world would clarify the importance of plant-animal interactions in these widespread tropical ecosystems. 相似文献
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17.
It is not yet known whether the abundance and distribution of freshwater fish parasites form spatial patterns. Here, Rita Hartvigsen and Odd Halvorsen review the main approaches to the study of spatial patterns of these parasites, and propose an alternative approach based on meta-population theory and landscape ecology. 相似文献
18.
Macrophyte communities in unimpacted European streams: variability in assemblage patterns, abundance and diversity 总被引:5,自引:5,他引:0
Annette Baattrup-Pedersen Krzysztof Szoszkiewicz Rebi Nijboer Mattie O’Hare Teresa Ferreira 《Hydrobiologia》2006,566(1):179-196
Macrophytes are an important component of aquatic ecosystems and are used widely within the Water Framework Directive (WFD)
to establish ecological quality. In the present paper we investigated macrophyte community structure, i.e., composition, richness
and diversity measures in 60 unimpacted stream and river sites throughout Europe. The objectives were to describe assemblage
patterns in different types of streams and to assess the variability in various structural and ecological metrics within these
types to provide a basis for an evaluation of their suitability in ecological quality assessment. Macrophyte assemblage patterns
varied considerably among the main stream types. Moving from small-sized, shallow mountain streams to medium-sized, lowland
streams there was a clear transition in species richness, diversity and community structure. There was especially a shift
from a predominance of species-poor mosses and communities dominated by liverwort in the small-sized, shallow mountain streams
to more species-rich communities dominated by vascular plants in the medium-sized, lowland streams. The macrophyte communities
responded to most of the features underlying the typological framework defined in WFD. The present interpretation of the WFD
typology may not, however, be adequate for an evaluation of stream quality based on macrophytes. First and most important,
by using this typology we may overlook an important community type, which is characteristic of small-sized, relatively steep-gradient
streams that are an intermediate type between the small-sized, shallow mountain streams and the medium-sized, lowland streams.
Second, the variability in most of the calculated metrics was slightly higher when using the pre-defined typology. The consistency
of these results should be investigated by analysing a larger number of sites. Particularly the need of re-defining the typology
to improve the ability to detect impacts on streams and rivers from macrophyte assemblage patterns should be investigated.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
19.
Sally J. Holbrook 《Oecologia》1979,44(3):355-367
Summary Comparisons of prehistoric (A.D. 1100–1400) and extant cricetine-dominated rodent faunas from two locations in New Mexico and one in Arizona reveal temporal changes in both species diversity and taxonomic composition. The archaeological context of the prehistoric faunas permitted them to be dated rather accurately; paleoenvironmental inferences generated from other materials recovered in the excavations such as pollen samples, agricultural remains, and tree-ring specimens provided evidence about prehistoric environmental conditions in the study areas. Both richness and evenness components of diversity are lower in the present day faunas than in their prehistoric counterparts. At the beta (between-habitat or valley-wide) level of diversity the increased prehistoric species richness as well as the nature of the differences in present and prehistoric taxonomic composition can be accounted for by small climatic shifts which were occurring between A.D. 1100 and 1300 in the Southwest and the resultant biogeogrphic responses of certain rodent species. Alpha (or within-habitat) diversity is similar for all analyzed faunas. This suggests basic similarities in very local species packing despite observed spatial and temporal variation in valley-wide diversities. Environmental changes stemming from climatic shifts provide a reasonable explanation of the observed patterns of rodent species occurrence and diversity. Habitat destruction resulting from agricultural practies of prehistoric human populations appears to have had only a limited impact on these rodent communities. 相似文献
20.
C C Lord 《International journal for parasitology》1992,22(6):759-765
A difference equation model was developed to explore the sensitivity of the temporal pattern of relative abundance of active, host-seeking nymphal Ixodes dammini. Inputs to the model were the temporal patterns of recruitment of nymphs into the active class, mortality and successful acquisition of hosts by the ticks. Input parameters were varied both in the temporal pattern (shape) and in the cumulative level (summed over the period of activity). The output of the models, the temporal abundance pattern, was examined for (1) overall shape and (2) the timing of the peak abundance of host-seeking nymphs. The shape of the temporal pattern of nymphal abundance was not sensitive to changes in the shape of the functions used as input for host-finding. The time of peak abundance of nymphs is slightly sensitive to changes in the overall level of host-finding and mortality. When more ticks are removed from the active class (host-finding or mortality increasing), the time of the peak abundance of the nymphs shifts earlier. However, this shift is small compared to variation in field data. The general shape of the activity pattern was sensitive to changes in the temporal pattern of recruitment. A left-skewed distribution produced output which most resembles field data. The temporal pattern of nymphs entering the active class is important, and is an area which needs further empirical work. 相似文献