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1.
The purpose of this paper is to test the performance of rapid biodiversity assessment techniques in the lagoonal environment at the pan-Mediterranean scale. The multivariate techniques can produce patterns of lagoonal biodiversity along the Mediterranean. Additionally, it is shown that the polychaete inventory can preferably be used rather than the aggregation of information at the family level for the purposes of rapid biodiversity assessment. These techniques, however, appear to be weak for the environmental assessment because they cannot detect differences between the naturally disturbed and the anthropogenically impacted lagoons. Both taxonomic distinctness indices are found to be robust in providing meaningful results for rapid biodiversity/environmental assessment when the crustacean inventory and the polychaete and molluscan ones are used for the estimation of the average taxonomic distinctness and of the variation in taxonomic distinctness values, correspondingly. Conversely, information on the distribution of the macrofaunal species to the Mediterranean lagoons appears to be inadequate for the needs of such rapid biodiversity assessment at a regional scale. It is suggested that information on ecological convergence of the macrofaunal species would probably provide biodiversity indices with additional power, at least in the lagoonal environment.  相似文献   

2.
The composition and diversity of the total and intestinal component and infra-communities were determined in eels Anguilla anguilla from three shallow lagoons on the Adriatic coast of Italy to determine whether the helminth communities would differ in composition and structure from those in eels from lagoons on the Tyrrhenian coast. The lagoons differed in respect of their management regimes and the extent of freshwater influx. Both freshwater and marine species of helminths were found in the eels in all three lagoons, but the freshwater component was richer in Valle Figheri. A suite of three digenean eel specialist species occurred in all three lagoons, of which any two members dominated each community. This conferred a high degree of similarity between the communities of the three lagoons. The same three species also dominated helminth communities in eels in lagoons along the Tyrrhenian coast of Italy, and compositional similarity levels were similar within and between western and eastern groups. Species richness was higher in the component communities of the eels of the Adriatic lagoons when compared to the Tyrrhenian ones, but diversity and dominance indices were of a similar order of magnitude and range. Intestinal helminth communities were richer and more diverse in two of the Adriatic lagoons because the proportion of eels with zero or one helminth species was, unusually, in the minority. It was nevertheless concluded that infracommunity structure was similar in eels from both western and eastern lagoons and that the hypothesis that it would differ in Adriatic lagoons could not be supported. The findings provide further evidence of the similarity in composition and structure of helminth communities in eels from coastal lagoons throughout Europe.  相似文献   

3.
It is accepted that observed patterns in community structure change as analyses are carried out at higher taxonomic levels. Univariate analyses which incorporate higher taxonomic structure within assemblages have been shown to be informative. In this paper we suggest ways in which changes in multivariate relationships at higher taxonomic levels and associated with higher taxonomic/phylogenetic structure of the community may be incorporated into multivariate analyses, an aspect never occurred before in this type of analysis. Four approaches, namely: biodiversity MDS (bdMDS), number of taxa MDS (ntMDS), delta MDS (δMDS) and lambda MDS (λMDS), are proposed, and applied to theoretical data as well as to data collected from the literature on the Mediterranean lagoonal environment. Results show that these approaches have the capacity to distinguish severely impacted lagoons from naturally disturbed ones, although in practice the simplest method (ntMDS) was the most successful. Analyses based on the most abundant groups (polychaetes, molluscs, crustaceans) did not always match analyses based on the entire macrofauna, mirroring the performance of taxonomic distinctness indices in the Mediterranean lagoons. The important characteristics of the approaches introduced, as well as potential criticisms are provided. Application of these techniques on smaller scales and to other habitats, is suggested prior to their wider use in the region.  相似文献   

4.
Understanding the origin of biodiversity requires knowledge on the evolutionary processes that drive divergence and speciation, as well as on the processes constraining it. Intraspecific polymorphisms can provide insight into the mechanisms that generate and maintain phenotypic, behavioural and life history diversification, and can help us understand not only the processes that lead to speciation but also the processes that prevent local fixation of morphs. The ‘desert cichlid’ Herichtys minckleyi is a highly polymorphic species endemic to a biodiversity hotspot in northern Mexico, the Cuatro Ciénegas valley. This species is polymorphic in body shape and trophic apparatus, and eco‐morphotypes coexist in small spring‐fed lagoons across the valley. We investigated the genetic structure of these polymorphisms and their phylogeographic history by analysing the entire control region of the mitochondrial DNA and 10 nuclear microsatellite markers in several populations from different sites and morphs. We found two very divergent mitochondrial lineages that most likely predate the closing of the valley and are not associated with morphotypes or sites. One of these lineages is also found in the sister species Herichthys cyanoguttatus. Data from neutral microsatellite markers suggest that most lagoons or drainages constitute their own genetic cluster with sympatric eco‐morphotypes forming panmictic populations. Alternative mechanisms such as phenotypic plasticity and a few loci controlled traits provide possible explanations for the sympatric coexistence of discrete nonoverlapping eco‐morphotypes with apparent lack of barriers to gene flow within multiple lagoons and drainages.  相似文献   

5.
The analysis of benthic assemblages is a valuable tool to describe the ecological status of transitional water ecosystems, but species are extremely sensitive and respond to both microhabitat and seasonal differences. The identification of changes in the composition of the macrobenthic community in specific microhabitats can then be used as an “early warning” for environmental changes which may affect the economic and ecological importance of lagoons, through their provision of Ecosystem Services. From a conservational point of view, the appropriate definition of the spatial aggregation level of microhabitats or local communities is of crucial importance. The main objective of this work is to assess the role of the spatial scale in the analysis of lagoon biodiversity. First, we analyze the variation in the sample coverage for alternative aggregations of the monitoring stations in three lagoons of the Po River Delta. Then, we analyze the variation of a class of entropy indices by mixed effects models, properly accounting for the fixed effects of biotic and abiotic factors and random effects ruled by nested sources of variability corresponding to alternative definitions of local communities. Finally, we address biodiversity partitioning by a generalized diversity measure, namely the Tsallis entropy, and for alternative definitions of the local communities. The main results obtained by the proposed statistical protocol are presented, discussed and framed in the ecological context.  相似文献   

6.
7.
Synopsis The interaction of fluctuating water level and the Long Point topography is discussed with regard to the formation of lake-shore lagoons and their subsequent invasion by fishes. The species composition of fish communities in these lagoons was determined by 12 collections from lagoons (23 m2 to 25 ha) which yielded 33 fish species. The relationship of the number of fish species to lagoon area was lognormal; that is, with increasing lagoon area the number of species rose rapidly at first but soon decreased sharply, probably limited by the number of species capable of surviving in the habitat. The marked effect of area on species number in small lagoons is considered in the context of a hypothetical seasonal pattern of occasional invasion and continuous extinction.A sequence of reproductive guilds was found. In beach lagoons psammophils and lithophils were dominant. In a large vegetated lagoon in the interior phytophils and speleophils were dominant. This sequence was paralleled by an increase in the proportion of guarding and nesting species in the communities. The sequence was disrupted in the small interior lagoons where adaptations for survival were more important than reproductive strategy.  相似文献   

8.
Between 1961 and 1964 the water levels of Lake Victoria increased abruptly. This increase produced changes around the shoreline of the lake, creating new habitats in the form of lagoons. Such lagoons were cut off from the main lake by differing widths of floating vegetation. Chemically and physically these new regions resembled small tropical fish ponds, with a nocturnal reduction in both dissolved oxygen and temperature.
The lagoons were occupied shortly after their appearance by characteristic groups of fishes, which depended for their species composition on the degree of isolation of the different bodies of water from the main lake. It was generally found that the more isolated the lagoon, the more impoverished it was in numbers of species. The most successful colonizers of these waters were Tilapia leucosticta and Haplochromis nubilus , which were present in all lagoons.
Populations of these two species showed a tendency to stunt, which was more marked in the more isolated populations. This, together with the population changes associated with isolation, suggests that the mat of floating vegetation, by reason of the de-oxygenated conditions that exist under it, acts as a form of biological filter. Thus fish from the lake can only penetrate to the nearer lagoons, the populations in the more isolated waters remaining more or less segregated.  相似文献   

9.
We surveyed fish distribution in three lagoons and adjacent forereefs in the British Virgin Islands recording about 28,000 fish from 40 families and 118 species. Canonical correspondence indicated that rock, sand, fleshy algae, gorgonians, mangroves and live hard coral were the most important habitat types influencing fish assemblage composition. About 47% of fishes occurring at more than 10 stations displayed evidence of ontogenetic partitioning between reefs and lagoons but post-settlement ontogenetic life history strategies were quite varied depending on the species. For example Chaetodon striatus juveniles occurred exclusively in lagoons and all sexually mature adults were found on reefs. Some differences were less pronounced as seen in Halichoeres bivittatus where individuals of all sizes occurred on reefs and lagoons, but when analysed it was found that reefs had larger individuals than lagoons. Some species, such as Acanthurus bahianus, were primarily reef species whose juveniles also used lagoon habitats while others, such as Gerres cinereus, were generally lagoon species whose adults occasionally moved onto reefs. Even with all this variation in life-history strategies, all the species that exhibited bay-reef partitioning used the lagoons as juveniles then moved onto reefs as adults and not vice versa, supporting the hypothesis that bays are important nursery areas for reef-dwelling fishes. These results show that a detailed review of the natural life-history strategies and habitat requirements are required before making further generalisations about the role of near-shore habitat types as nurseries for reef fishes. This is especially important given the rapid changes in tropical near-shore habitats around the world.  相似文献   

10.
This article aims at studying wintering waterbirds in Tunisian coastal lagoons in order to support effective conservation measures. Species number and abundance of wintering waterbirds were assessed in January, each year from 2002 to 2007, in 10 lagoon sites belonging to four different lagoon systems. We counted 76 species and on average more than 120,000 birds per year, which represented more than 25% of the national population sizes. The most abundant taxonomic groups were waterfowls and waders, which also represented the highest species number. In general, the six most abundant bird species comprised collectively more than 77% of all birds counted. Considering all the studied lagoon systems collectively, for 13 species the lagoon systems should be considered as of international importance according the Ramsar Convention as they support regularly more than 1% of the populations. Only the lagoon system of the North held regularly more than 20,000 birds. The species abundances and species richness varied significantly among year and among lagoon systems. Based on our results we proposed priority conservation measures, these ecosystems being of major importance for wintering birds, at both national and international level.  相似文献   

11.
The ecological insurance hypothesis predicts a positive effect of species richness on ecosystem functioning in a variable environment. This effect stems from temporal and spatial complementarity among species within metacommunities coupled with optimal levels of dispersal. Despite its importance in the context of global change by human activities, empirical evidence for ecological insurance remains scarce and controversial. Here we use natural aquatic bacterial communities to explore some of the predictions of the spatial and temporal aspects of the ecological insurance hypothesis. Addressing ecological insurance with bacterioplankton is of strong relevance given their central role in fundamental ecosystem processes. Our experimental set up consisted of water and bacterioplankton communities from two contrasting coastal lagoons. In order to mimic environmental fluctuations, the bacterioplankton community from one lagoon was successively transferred between tanks containing water from each of the two lagoons. We manipulated initial bacterial diversity for experimental communities and immigration during the experiment. We found that the abundance and production of bacterioplankton communities was higher and more stable (lower temporal variance) for treatments with high initial bacterial diversity. Immigration was only marginally beneficial to bacterial communities, probably because microbial communities operate at different time scales compared to the frequency of perturbation selected in this study, and of their intrinsic high physiologic plasticity. Such local "physiological insurance" may have a strong significance for the maintenance of bacterial abundance and production in the face of environmental perturbations.  相似文献   

12.
In four lagoons at two atolls and one high island in the Tuamotu and Society Islands, French Polynesia, plankton samples were taken weekly during 4 weeks in January/February 1989. A third atoll lagoon was sampled once. The lagoons varied in size and physical openness. We also sampled in the ocean near two atolls and the high island. All locations were sampled during the day, and three lagoons (two atolls and one high island) were also sampled at night. Pelagic fish eggs were more abundant in the ocean than in the lagoons at the atolls, but not at the high island. Larvae of coastal fishes were abundant in all lagoons. In the atoll lagoons, larvae of oceanic fishes were very rare to absent, but in the high-island lagoons and in the ocean, they were commonly encountered. In the ocean, larvae of many typical reef-fish taxa were abundant (58 taxa were represented by at least 10 individuals), but in the lagoons, most of these were rare or absent, and we conclude that these rare and absent taxa normally do not complete their larval phase in lagoons.Taxa were considered to be able to complete their pelagic phase in a lagoon (i.e., were 'completers') if they were present in the lagoon plankton samples from across a full larval size range. In the high-island barrier-reef lagoon, young, preflexion larvae were abundant, but only two taxa (of 56 captured) were present over a wide size range and were considered completers in this lagoon. In the high-island lagoonal bay, 11 taxa (of 67 captured) were considered completers. The numbers of taxa captured in the three atoll lagoons ranged from 39–44, and the number of taxa considered to be completers increased with increasing lagoon size and physical openness. The 17 completer taxa in the smallest, most enclosed atoll lagoon were, with one exception, a subset of those (18) in the second lagoon which, in turn, with one exception, were a subset of those in the largest, most open lagoon (26). Completer taxa were of the families Apogonidae, Blenniidae, Bothidae, Callionymidae, Carangidae, Gobiidae, Microdesmidae, Mullidae, Pomacentridae, Schindleriidae, and Tetraodontidae. The species that can complete their pelagic periods in coral-reef lagoons are a highly predictable group, and not simply a random selection of the potential species pool. Most of these species hatch from non-pelagic eggs. Water renewal times in the atoll lagoons, unlike the high-island barrier-reef lagoon, were much longer than expected pelagic larval durations of completer taxa. Demographically, lagoon populations of completer taxa apparently self-recruit and are probably near the closed end of the open/closed population continuum. The lagoonal bay on the high island differs from the other lagoons in containing larvae of species not found elsewhere, including some completers, and lacking some species that are abundant completers in other lagoons. In French Polynesia, lagoon size is a strong predictor of the number of lagoon completer taxa. The number of completer taxa apparently peaks at intermediate lagoon water-exchange times.  相似文献   

13.
We sought to identify environmental factors influencing crustacean zooplankton species richness in brackish lagoons and to elucidate whether crustacean zooplankton species richness and trophic structure of brackish lagoons differ among two regions with contrasting temperatures. We sampled 35 and 42 brackish lagoons (salinity ranging from 0.3 to 55‰) in Mediterranean Catalonia (NE Spain) and northern-temperate Denmark, respectively. No significant differences were found in total crustacean zooplankton species richness or cladoceran richness between the climatic regions. Calanoid richness was higher in Denmark than in Catalonia, while cyclopoid richness was higher in Catalonia. Salinity was the most important variable associated with zooplankton species richness in both regions, richness of total zooplankton species, cladocerans and cyclopoids being negatively related with salinity. In both regions, a shift occurred from dominance of large filter feeding cladoceran species at low salinities to copepods and small cladoceran species at higher salinities. Cladoceran richness increased with increasing total phosphorus, but was not influenced by total nitrogen or chlorophyll-a. Trophic structure in Mediterranean brackish lagoons showed a more pronounced seasonal variation than in north temperate brackish lagoons. Our results imply that the indirect effects of climate warming, such as changes in salinity and hydrology, will have a larger impact on brackish lagoon ecosystems than the increase in temperature per se.  相似文献   

14.
Biodiversity has reached a critical state. In this context, stakeholders need indicators that both provide a synthetic view of the state of biodiversity and can be used as communication tools. Using river fishes as model, we developed community indicators that aim at integrating various components of biodiversity including interactions between species and ultimately the processes influencing ecosystem functions. We developed indices at the species level based on (i) the concept of specialization directly linked to the niche theory and (ii) the concept of originality measuring the overall degree of differences between a species and all other species in the same clade. Five major types of originality indices, based on phylogeny, habitat-linked and diet-linked morphology, life history traits, and ecological niche were analyzed. In a second step, we tested the relationship between all biodiversity indices and land use as a proxy of human pressures. Fish communities showed no significant temporal trend for most of these indices, but both originality indices based on diet- and habitat- linked morphology showed a significant increase through time. From a spatial point of view, all indices clearly singled out Corsica Island as having higher average originality and specialization. Finally, we observed that the originality index based on niche traits might be used as an informative biodiversity indicator because we showed it is sensitive to different land use classes along a landscape artificialization gradient. Moreover, its response remained unchanged over two other land use classifications at the global scale and also at the regional scale.  相似文献   

15.
Kuželová  Ilona  Chytrý  Milan 《Plant Ecology》2004,173(2):247-257
Interspecific associations detected in phytosociological data sets sampled in local areas can reflect locally specific combinations of environmental factors and may thus differ from the interspecific associations existing on a regional scale. As a result, vegetation units derived from numerical classifications of local data sets can accurately reflect local environmental gradients, but their boundaries or spectra of diagnostic species must be frequently adjusted when transferred to the regional scale. Local vegetation classifications can be useful for some purposes, but regional classifications are superior, as they facilitate communication among the researchers from different areas. We demonstrated changes in interspecific associations between regional and local scale, using a data set of 14 589 relevés of herbaceous vegetation of the Czech Republic, and 16 local subsets of this national data set. We focused on sociological species groups, derived statistically in the national data set. Changes in coherence of these groups when applied to the local data sets were described on the basis of statistical association between the relevés containing some species of these groups and the species belonging vs. not belonging to these groups. The results were summarized using the principal components analysis (PCA). In addition, relevé data sets were compared with respect to presence/absence of sociological species groups, using the principal coordinate analysis (PCoA). The results of PCA and PCoA were compared by Procrustean analysis. Local data sets differed from the national data set to different extent. The national data set was more remote to the local data sets if the analysis focused on the coherence of species group rather than on presence/absence. The species groups from the national data set retained most of their coherence in low-altitude hilly landscapes with thermophilous flora, i.e., the most diverse landscape type of the Czech Republic. On the other hand, many species groups from the national data set could not be recognized in mountainous areas or flat lowlands. These results suggest that interspecific associations existing on regional scale are best reproduced in those local areas which have a high habitat heterogeneity or which have a central position along the major gradients existing on regional scale.  相似文献   

16.
Marine biotic indices (AMBI, BENTIX) and the statistical tool M-AMBI (Multivariate AMBI) were applied as a comparative approach in assessing the Ecological Quality Status (EcoQS) of two Mediterranean coastal lakes (Caprolace and Fogliano lakes) situated in the Circeo National Park (Central Italy). The macrobenthic community was analysed using univariate indices (community structure), correspondence analysis (CA) and taxonomic distinctness indices (Δ+ and Λ+). The community composition showed a dominance of lagoonal species in both coastal lakes, while in Caprolace lake marine taxa were also found. Diversity index (H′) complies to ranges found in Mediterranean lagoons and taxonomic distinctness indices demonstrated that taxonomy structure is in accordance with natural variability ranges. Principal component analysis (PCA) on chemical parameters of water and sediment showed that both coastal lakes differ mainly in their organic matter composition. In fact, the protein fraction of bio-polymeric carbon prevails in Fogliano lake, while the ‘refractory’ component represented by carbohydrate fraction is predominant in Caprolace lake. The difference between the two coastal lakes was also demonstrated by co-inertia analysis (COIA) performed using abundance of species and concentrations of chemical parameters. The results from the application of the three biotic indices do not highlight a clear distinction between the two lagoons. However, the AMBI index provided a more suitable evaluation of EcoQS corresponding to ‘slightly polluted’ lagoons while M-AMBI and moreover BENTIX indices indicated a worsening situation. The biotic indices are widely used in assessing the EcoQS in marine environments, but their proper application in transitional waters would depend on a resettlement; thresholds established in the biotic index scale values need to be modified according to natural variability of transitional waters referring to abiotic conditions and abundance of tolerant species.  相似文献   

17.
Freshwater habitats are among the most impacted ecosystem on Earth. Consequently, reserves have been implemented in an attempt to reduce the threat to freshwater biodiversity. However, few studies have evaluated how effective these protected areas (PA) are for the conservation of freshwater organisms. In the present study, we compared species richness, community composition and density of small-bodied fishes between lagoons within an eight-year-old reserve (i.e. protected lagoons) with those outside the reserve (i.e. unprotected lagoons) in a river-floodplain system that is exposed to seasonal flooding. The unprotected lagoons have been submitted to a light fishing pressure mainly targeting small-sized fishes for sale as baits. Our results showed no differences between the lagoons inside the reserve with those outside in any of the community properties measured. However, we registered an overall tendency of abundance reduction among the species used as baits in unprotected lagoons. Considering the high degree of oversight in the PA and the low fishing pressure among unprotected lagoons, it is possible that the positive effects promoted by the reserve on fish assemblages are being exported towards unprotected lagoons and thus offsetting a portion of the anthropogenic impacts. We conclude that the protection provided by the reserve is very efficient in river-floodplain systems, because not only it protects the biota inside the reserve but also act as a source of propagules to unprotected areas during the rainy season when all the aquatic subsystems are connected by the flood.  相似文献   

18.
A good understanding of how migratory animals use their habitat network is expected to provide important insights for the prediction of population dynamics at both local and regional scales. We focused on how the physical structure of a habitat network could affect fish migration between Lake Biwa and its tributary lagoons. Although the lagoons provide suitable breeding and nursery grounds for native fishes, it is a matter of concern that they can also be a hotbed of invasive exotic fishes. Here, we assessed the migration patterns of native crucian carps (Carassius spp.) and exotic largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis macrochirus) using their carbon and nitrogen stable isotopes as migration tracers. As there were marked differences in the carbon isotope ratios of basal food webs between the main lake and its tributary lagoons, stable isotopic signatures of individual fishes collected from each lagoon enabled us to judge whether they were residents of the lagoon or recent immigrants from the main lake. The analysis revealed that native and invasive fishes showed different migration patterns across a variety of lagoons. Exotic fishes frequently immigrated from the main lake to the lagoon as the distance of the channel connecting these two habitats was short. For native crucian carps, in contrast, their migrations were unaffected by the channel distance but were promoted by narrow channels. Physical barriers of weirs and dense vegetation within the channel obstructed their migrations. Such ecological information on migration behavior will be vital to plan designs for habitat restoration to conserve native fishes.  相似文献   

19.
20.
Sexual arousal has many dimensions and has consequently been defined in various ways. In humans, sexual arousal can be assessed based in part on verbal communication. In male non-human mammalian species, it has been argued that arousal can only be definitively inferred if the subject exhibits a penile erection in a sexual context. In non-mammalian species that lack an intromittent organ, as is the case for most avian species, the question of how to assess sexual arousal has not been thoroughly addressed. Based on studies performed in male Japanese quail, we argue that several behavioral or physiological characteristics provide suitable measures of sexual arousal in birds and probably also in other tetrapods. These indices include, the performance of appetitive sexual behavior in anticipation of copulation (although anticipation and arousal are not synonymous), the activation of specific brain area as identified by the detection of the expression of immediate early genes (fos, egr-1) or by 2-deoxygucose quantitative autoradiography, and above all, by the release of dopamine in the medial preoptic area as measured by in vivo dialysis. Based on these criteria, it is possible to assess in birds sexual arousal in its broadest sense but meeting the more restrictive definition of arousal proposed for male mammals (erection in an explicit sexual context) is and will probably remain impossible in birds until refinement of in vivo imaging techniques such fMRI allow us to match in different species, with and without an intromittent organ, the brain areas that are activated in the presence of specific stimuli.  相似文献   

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