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1.
Nikos Katsimanis Michalis Dretakis Triantaphyllos Akriotis Moysis Mylonas 《Journal of Ornithology》2006,147(3):419-427
The patterns of α-diversity and the structure and organisation of breeding bird assemblages were studied in four vegetation stages (characteristic of Mediterranean shrublands) on an eastern Mediterranean island (Crete, Greece): low phrygana, tall phrygana, low maquis and tall maquis. Phrygana differed significantly from maquis, in regard to the community metrics, composition and the homogeneity of bird assemblages. Moreover, detrended correspondence analysis ordered the census plots along a continuum of increasing vegetation height. On the other hand, within-maquis differences were few, while no significant differences were found within phrygana stages. Based upon the observed patterns, we recognise three vegetation groups: (1) phrygana, with low α-diversity and abundance and homogenous bird assemblages; (2) low maquis with relatively high α-diversity and heterogenous bird assemblages; and (3) tall maquis with relatively high α-diversity and heterogenous assemblages in which “woodland” bird species contribution is prominent. 相似文献
2.
Ferenc Vilisics Péter Sólymos Antal Nagy Roland Farkas Zita Kemencei Elisabeth Hornung 《Biologia》2011,66(3):499-505
We studied abundance and diversity patterns of terrestrial isopod assemblages along a ‘micro-scale’ vertical gradient in sinkholes
in the Aggtelek National Park, Hungary. Time restricted manual sampling yielded ten native species, including endemic and
rare ones. Along the gradient we found no major differences in species richness and -composition, and abundance decreased
from the bottoms to the upper zones of the sinkholes. Species specific habitat preference on a vertical gradient showed two
distinct groups by indicator species analysis: occurrence of habitat “generalists” was irrespective of vertical zones while
“specialists” were restricted to the bottoms of the dolines. The latter group is formed mainly by rare species. We found that
both diversity and evenness of isopod assemblages were highest in the bottom zone. Our results draw the attention to the significance
of such common, yet undiscovered surficial depressions that can provide shelters for rare and specialist species and can provide
shelter for survival of populations under changing climatic conditions. 相似文献
3.
Jack T. Moyer 《Journal of Ethology》1984,2(2):85-98
Social organization and reproductive behavior were studied in 4 species of ostraciid fishes.Lactoria fornasini andLactoria diaphana from Japan andAcanthostracion polygonius from the western Atlsnyiv were usually found in single male, haremic social groups, although the latter 2 species usually
included only 2 females per harem, and individuals in all 3 species foraged solitarily. Elements of both “resource defense”
and “female defense” (Emlen & Oring 1977) were evident in the 2Lactoria species, and female defense appeared particularly intense inL. diaphana. Resource defense was apparent inA. polygonius. Lactophrys triquetor occurred in lek-like breeding assemblages at Curacao (Netherlands Antilles) and on the Atlantic coast of Panama. These variations
in social organization are discussed and a relationship with feeding habits is suggested. All 4 species appear to be gonochores
(demonstrated inLactoria by Moyer 1979). The 2Lactoria spp. showed operational sex ratios (OSR: Emlen & Oring 1977) approaching 1∶1 and a high degree of female spawning synchrony.
The occurrence of polygyny in species with 1∶1 OSRs and female spawning synchrony is discussed with reference to the Knowlton
(1979) model which predicts monogamy to occur in such situations. 相似文献
4.
Linking limitation to species composition: importance of inter- and intra-specific variation in grazing resistance 总被引:1,自引:0,他引:1
Short-term responses of producers highlight that key nutrients (e.g., N, P)—or combinations of these nutrients—limit primary
production in aquatic and terrestrial ecosystems. These discoveries continue to provide highly valuable insights, but it remains
important to ask whether nutrients always predominantly limit producers despite wide variation in nutrient supply and herbivory
among systems. After all, predictions from simple food chain models (derived here) readily predict that limitation by grazers
can exceed that by nutrients, given sufficient enrichment. However, shifts in composition of producers and/or increasing dominance
of invulnerable stages of a producer can, in theory, reduce grazer limitation and retain primacy of nutrient limitation along
nutrient supply gradients. We observed both mechanisms (inter- and intra-species variation in vulnerability to herbivory)
working in a two-part mesocosm experiment. We incubated diverse benthic algal assemblages for several months either in the
presence or absence of benthic macro-grazers in mesocosms that spread a broad range of nutrient supply. We then conducted
short-term assays of nutrient and grazer limitation on these communities. In the “historically grazed” assemblages, we found
shifts from more edible, better competitors to more resistant producers over enrichment gradients (as anticipated by the food
web model built with a tradeoff in resistance vs. competitive abilities). However, contrary to our expectations, “historically
ungrazed” assemblages became dominated by producers with vulnerable juvenile forms but inedible adult forms (long filaments).
Consequently, we observed higher resource limitation rather than grazer limitation over this nutrient supply gradient in both
“historically grazed” (expected) and “historically ungrazed” (not initially expected). Thus, via multiple, general mechanisms
involving resistance to grazing (changes in species composition or variation in stage-structured vulnerability), producer
assemblages should remain more strongly or as strongly limited by nutrients than grazers, even over large enrichment gradients.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
Lakes are common features of alpine landscapes, and the attention given to alpine lakes has increased recently in response
to increased recognition of the important role that these freshwaters play as sensible indicators of climate change. Despite
this general research interest, there is nevertheless a general lack of information about zoobenthos especially of lakes in
the Alps, and only few published data are available, which has made it nearly impossible to draw general conclusions in respect
to benthic community structure, profundal and/or littoral food webs. This paper aims to explore the relationships between
main environmental/catchment properties of 55 lakes and their littoral benthic fauna across three regions of the Alps. We
provide updated information on relative abundance, species richness, distribution and ecology of macroinvertebrates which
occur and are typical in the littoral of high-mountain lakes of the Alps. These lakes were located in the Lago-Maggiore Watershed
(Italy and Switzerland), in South Tyrol (Italy) and in North/East Tyrol (Austria), between 1840 and 2796 m a.s.l., in catchments
undisturbed by human activities. As the studied lakes are situated above the tree line, they were characterised by low nutrient
levels indicating an oligotrophic status. Lake water chemistry corresponded closely to the geo-lithology of the catchment
and some parameters (especially nutrient concentrations) differed between the regions. The macroinvertebrates were dominated
by insects which to a high degree were chironomid larvae and pupae. Other insect orders were typical cold stenotherm species
of Ephemeroptera, Plecoptera and Trichoptera. Non-insect macroinvertebrates contributed to the 144 taxa found. Other than
lake size and catchment area, the faunal parameters exhibited a clearer pattern along altitude. Macroinvertebrates per sample
increased with higher elevation, reached their maximum in lakes between 2400 and 2600 m a.s.l., but decreased strongly above
2600 m. The altitudinal pattern of species richness and Shannon diversity resembled each other being highest between 2001
and 2200 m a.s.l., but decreased when going lower and higher, respectively. Various patterns and trends along altitude were
also evident when individual groups were analysed within the individual sampling regions. The somewhat conflicting trends
of various biocoenotic indices let assume that factors other than altitude are also responsible for the structure of faunal
assemblages in the littoral of alpine lakes. Six variables (“bare rocks” and “nitrate”, “alkalinity”, “ammonia” and “peat
bog”) were selected by the CCA analysis where these three groups of lakes were identified: (1) lakes with a higher alkalinity
(higher pH, conductivity, ion concentration), a higher relative vegetation cover (compared to the “bare rocks” on the opposite
side) and lower nitrate levels; (2) lakes with a higher portion of “bare rocks” in their catchments and higher nitrate levels;
and (3) a smaller group of lakes with higher ammonia levels and a boggy environment. Geographical patterns seemed to have
weak effects on the presence of taxa while catchment properties had evident impacts on macroinvertebrate communities in these
lakes. In this way, the present study contributes to the overall understanding of environmental settings and effects on high
mountain lake ecosystems and assists in refining research and conservation strategies for an important landscape aspect in
the Alps. 相似文献
6.
Stefano Scalercio Roberto Pizzolotto Pietro Brandmayr 《Biodiversity and Conservation》2007,16(12):3463-3479
This paper is an attempt to outline a protocol for animal diversity census and evaluation aimed for areas in view of landscape
planning of territories of hundred square kilometres and more, that may work utilising different faunal groups and be anyway
useful at various scales. Many papers are addressed to elaborate tools for landscape planning starting from biodiversity evaluation
and butterflies are often utilised because of their sensitivity to landscape modifications. In this work, the biodiversity
evaluation has been performed using three hierarchically linked landscape units at micro-, meso- and macroscale. Being species
diversity values often inadequate to define the conservation interest of a landscape portion, more importance has been given
to which species compose the species assemblages. A community vulnerability Index was coded and used for evaluating potential
consequences of human disturbance on butterfly assemblages. Forty-four year samples were gained by visual census in the Sila
Greca, Southern Italy, on an area of approximately 520 square kilometres. During 5 years work, 2,535 specimens and 94 species
were recorded, equal to 75.8% of the whole Calabrian fauna. Four vulnerability levels have been established and used for mapping
butterfly assemblage vulnerability in the area, starting from a vegetation map. Species richness was found somewhat contradictory
at micro-scale, where the community vulnerability Index gives a sounder approach. S diversity gives a more reliable picture of naturalness at meso-scale, a level we identified with the “ecotope”. At this more
“geomorphic” scale level, biological functions reflected by butterfly assemblages revealed to be clearly linked to seral processes.
Similarity analysis results show that the ecotope species richness, here called “eta-diversity”, could be an useful measure
of zoological landscape (faunation) potentialities. 相似文献
7.
M. K. Zhemchuzhnikov A. N. Knyazev 《Journal of Evolutionary Biochemistry and Physiology》2011,47(6):565-570
Data are presented about the development of reproductive and defense behavior of noncopulated female crickets Gryllus argentinus Sauss. in the beginning of the imaginal ontogeny. The character of interaction of females with “virtual” males (the “supporting
ball” method-“trackball”) was studied. The forms of female motor reactions to models of intraspecies male sound signals-the
calling and aggressive songs-are described and analyzed. The character of the development of female acoustic behavior is described
as judged by change in the forms of motor reactions in the course of the imaginal ontogeny. It is shown that immediately after
the imaginal molt the reproductive behavior is not formed yet but it matures gradually within a few days. At the early stages
of the imaginal ontogeny passive defense behavior is found to be most clearly expressed. 相似文献
8.
We conducted a detail study of the photosynthetic apparatus in assimilating organs of three introduced evergreen conifer species:
Taxus cuspidate S. et Z. ex E. (Far-Eastern yew), Thuja occidentalis L. (arbovitae “green”), and Th. occidentalis f. “Reingold” (arbovitae “yellow”) at various times in their life cycle. We studied the potential photosynthesis rate; composition
and ratios of pigments, including primary carotenoids; the violaxanthin cycle (VC) activity, the synthesis of a secondary
carotenoid, rhodoxanthin; and chloroplast ultrastructure. In winter and spring, β-carotene and lutein (primary carotenoids)
contents were relatively constant in yew and arbovitae “yellow”. In December, the VC in yew was balanced and in arbovitae
“yellow” unbalanced. In arbovitae “yellow”, the zeaxanthin pool was heterogeneous, and only part of it took part in the VC.
It can be assumed that the other part of the pool can be oxidized to form a secondary carotenoid, rhodoxanthin. This secondary
carotenoid was also accumulated in arbovitae “green”; its synthesis took place during the season, when the photosynthesis
rate of plants was the lowest, and a significant chloroplast reorganization occurred (the number of thylakoids in grana decreased
and plastoglobules appeared). We suppose that rhodoxanthin forms a filter for the light under the conditions of high insolation
in winter. Thus, the evergreen conifer plants studied, which are adapted to growing at high latitudes where temperature is
low and insolation is high in winter and spring, have a system for protecting the photosynthetic apparatus against photodestruction.
In the basis of this system, the primary and secondary carotenoids lie, whose content changes during the year. 相似文献
9.
Eduardo Ribeiro Cunha Thaisa Sala Michelan Katya E. Kovalenko Sidinei Magela Thomaz 《Hydrobiologia》2012,685(1):19-26
Habitat complexity has long been known to influence animal community structure by increasing the number of available habitats.
Fifty years have passed since MacArthur brothers published the seminal paper “On bird species diversity”, which revolutionized
studies of habitat structure. This paper first evidenced and quantified the relationship between species diversity (birds)
and habitat structural complexity (the number of stratified layers of landscape vegetation). In this article, we aim to pay
homage to R. H. MacArthur’s contribution and to briefly analyze the citation history and influence of “On bird species diversity”,
focusing primarily on aquatic studies. We searched for all papers that cited “On bird species diversity” on Thomson Reuters
(ISI—Web of Knowledge) and analyzed them for temporal citation trends. In addition, considering only aquatic papers, we explored
whether and how habitat complexity was measured, as well as the ecological organization level, attributes of organisms, taxonomic
groups and study design (observational or experimental). “On bird species diversity” citations increased over time, but this
paper was less cited by limnologists compared to terrestrial and marine scientists. The majority of investigations in aquatic
ecosystems quantified habitat complexity, but few used mathematical modeling. The high number of citations, which continues
to increase, shows the great influence of “On bird species diversity” on ecological studies and typifies it as a classic in
the ecological literature. However, the low citation frequency found in papers devoted to freshwater ecosystems indicates
that limnologists in general neglect this original contribution in studies of habitat complexity. 相似文献
10.
Distribution and habitat preferences of two grapsid crab species in Mar Chiquita Lagoon (Province of Buenos Aires,Argentina) 总被引:3,自引:0,他引:3
Cyrtograpsus angulatus andChasmagnathus granulata (Grapsidae) are the two dominant decapod crustacean species in the outer parts of Mar Chiquita Lagoon, the southernmost in
a series of coastal lagoons that occur along the temperate Atlantic coasts of South America. Distribution and habitat preferences
(water and sediment type) in these crab species were studied in late spring. There is evidence of ontogenetic changes in habitat
selection of both species. Recruitment ofC. angulatus takes place mainly in crevices of tube-building polychaete (Ficopomatus enigmaticus) “reefs” and, to a lesser extent, also in other protected microhabitats (under stones). In the latter, mostly somewhat larger
juveniles were found, suggesting that these are used as a refuge for growing individuals. Adults are most frequently found
on unprotected muddy and sandy beaches.C. angulatus was found in all parts of Mar Chiquita Lagoon, including freshwater, brackish, and marine habitats.C. granulata, in contrast, was restricted to the lower parts of the lagoon, where brackish water predominates and freshwater or marine
conditions occur only exceptionally. It showed highest population density on “dry mud” flats and inSpartina densiflora grassland, where it can build stable burrows and where high contents of organic matter occur in the sediment. Such habitats
are characterized by mixed populations of juveniles (including newly settled recruits) and adults, males and females (including
a high percentage of ovigerous). Unstable “wet mud” as well as stony sand were found to be inhabited by chiefly adult populations,
with only few ovigerous females. In “dry mud” flats, the proportion of males increased vertically with increasing level in
the intertidal zone, showing a significantly increasing trend also in their average body size. These observations may be explained
by higher resistance of males, in particular of large individuals, to desiccation, salinity, and temperature stress occurring
in the upper intertidal. However, an opposite, or no such, tendency was found in the distribution of ovigerous and non-ovigerous
females, respectively. With increasing distance from the water edge, salinity increased and pH decreased significantly inC. granulata burrows, whereas temperature showed no consistent tendency within the intertidal gradient. A highly significant linear relationship
(r=−0.794; P<0.001) between salinity and pH in water from crab burrows is described. This regression line is significantly
different from one that had been observed in water from the lagoon, indicating consistently lower pH values at any salinity
level in burrow water. This is interpreted as a result of crab and/or microbial respiration. 相似文献
11.
Clara B. Jones 《Primates; journal of primatology》1980,21(3):389-405
In the dominance hierarchies of adult male and female mantled howler monkeys (Alouatta palliata
Gray), high-ranking individuals are young adults; intermediate-ranking individuals, middle-aged adults; and low-ranking individuals,
old adults. This relationship reverses the trend observed in most group-living animals and is previously unreported for this
species. A limiting supply of palatable leaves may create intense intraspecific competition for group membership which, it
is hypothesized, has resulted in this rare pattern of hierarchical relations. It is shown that individual-level selection
is sufficient to explain the evolution of this apparently “altruistic” status system, though other mechanisms are assessed.
The energetic constraints imposed by a folivorous diet appear to restrict the expression of aggression to “ritualized” forms.
Two groups of monkeys in two different habitats were studied and the rates of appeasement and aggressive behavior were found
to be higher in the more “stressful” forest. The latter group, however, displays significantly more behavioral patterns entailing
low or intermediate energy expenditure. 相似文献
12.
O. V. Yagodina 《Journal of Evolutionary Biochemistry and Physiology》2010,46(5):453-460
Comparative substrate-inhibitor analysis of catalytic properties of liver monoamine oxidases (MAO) was performed in the mature
males of the American mink Mustela vison and the European mink Mustela lutreola. The action on the MAO activity was studied of alkaloids of the benzo[c]phenanthridine group: sanguinarine and chelidonine,
diisoquinoline alkaloid berberine, medicinal agents “Ukrain” and “Sanguirythrin” as well as derivatives of 2-propylamine:
deprenyl and chlorgylin. The latter turned out to be irreversible inhibitor of the MAO A form, whereas deprenyl-irreversible
inhibitor of the MAO B form in both studied mink species. The selectivity of action of each inhibitor on the corresponding
liver MAO form for the species M. vison was one order of magnitude stronger than for the species M. lutreola. All studied alkaloids as well medicinal agents on their basis have been shown to be specific irreversible inhibitors of
the intermediate strength of the liver MAO A form of both mink species. They inhibit the enzymatic deamination of serotonin,
tyramine, and tryptamine without affecting the deamination reaction of benzylamine and β-phenylethylamine (at concentrations
of 10 mM and lower). Out of five studied isoquinoline agents, the medication “Ukrain” and alkaloid chelidonine have the highest
inhibitory action; the agent “Sanguirythrin” and alkaloids berberine and sanguinarine produce the weaker monoamine oxidase
effect. The revealed specificity of action of the studied inhibitors is an indirect evidence for the presence in the liver
enzymes of both mink species, like in the rat liver enzyme, of several molecular forms. 相似文献
13.
Bitou bush (Chrysanthemoides monilifera ssp. rotundata) is a major environmental weed of littoral habitats on the southeastern coast of Australia. This study investigates the impacts
upon selected arthropod assemblages of habitat invasion by this weed. Sixteen sites were placed at four geographic localities
within nature reserves between Forster and Budgewoi on the coast of New South Wales. The sampling design included two spatial
scales (between and within localities) and eight repeat samples (taken at two scales of temporal separation). Arthropods were
collected from both arboreal and epigaeic micro-habitats. Specimens of ants (Hymenoptera: Formicidae), beetles (Coleoptera),
true bugs (Heteroptera) and spiders (Araneae) were identified to species level. Differences in α diversity and species abundance
distributions between the taxonomic assemblages are described, along with comparisons of data contrasts between bitou bush-free
(“control”) and bitou bush-invaded (“impact”) habitats and between geographic localities. A subsidiary impact associated with
herbicide application for control of the weed is also examined. Analysis of environmental differences indicates that bitou
bush acts as a dampening agent, reducing the degree of seasonal fluctuation in factors such as leaf litter cover. Arboreal
Heteroptera were the only group to show consistent evidence of significant differences in taxon richness or abundance between
control and impact treatments within a locality, seen as a disruption of normal seasonal variation in diversity in bitou bush-impacted
sites. Significant differences between geographic localities were more common, suggesting an effect at broader spatial scales.
Evidence for arthropod assemblages characteristic of specific vegetation types was detected for several groups, as were changes
in arthropod assemblage composition following application of herbicide for bitou bush control. 相似文献
14.
Forestry is obliged to record as well as maintain and/or enhance biological diversity in forests due to national and international
agreements. Accordingly, it is necessary to work out methodological approaches for the assessment of biodiversity in forests.
In the study presented here, we focus on the total plant species pool (563 vascular plant and bryophyte species) of pine (Pinus sylvestris L.) forests in NE Germany to identify indicators for plant species richness. We distinguished several groups like “herb”,
“grass-like”, “woody”, “endangered”, and “exotic species”, for which we detected indicators for low (class #1), intermediate
(class #2), and high (class #3) species numbers. From a total of 84 species, which were identified by a three-step procedure,
most indicators were found for class #3. Only few indicators have been revealed for intermediate species numbers, i.e. class
#2. With help of Ellenberg’s ecological indicator values and information on the main occurrence in Central European vegetation
types and plant communities, respectively, we characterized the indicator species ecologically. The ecological site preferences
of the indicator species in general reflect the fact that species richness is highest in base-rich, light, and anthropogenically
disturbed pine forests. On the contrary, species-poor forests were revealed by indicators, which mainly occur on acidic sites.
It is concluded that a considerable set of indicators for species richness can help facilitate biodiversity assessments in
forestry and ecosystem restoration practice.
Electronic Supplementary Material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
15.
C. Dall’Asta S. Sforza A. Moseriti G. Galaverna A. Dossena R. Marchelli 《Mycotoxin Research》2005,21(4):218-223
Zearalenone is a mycotoxin mainly produced by severalFusarium species, which are known to colonize grains in temperate climates. The purpose of the study is to provide a reliable isotope
dilution method for the quantification of this mycotoxin. A derivative of the analyte to be used as standard is obtained by
reaction with acetic anhydride, which is available in two pure isotopic forms, a protonated (“light”) and a hexadeuterated
(“heavy”). The derivatized standards are added to the matrix split intwo parts. Then, the derivatization procedure is repeated
on both matrices derivatizing the part containing the “heavy” labelled standard with the “light” acetic anhydride and the
part containing the “light” labelled standard with the “heavy” acetic anhydride. Both extracted mixtures are analyzed by LC/MS,
monitoring the “light” and the “heavy” labelled analytes and using the former as standard for the latter in one case and viceversa
in the other case. The method allowed to obtain very good results, without the need of IAC purification.
Presented at the 27th Mykotoxin-Workshop, Dortmund, Germany, June 13–15, 2005.
Financial support: The Italian Ministry of Health 相似文献
16.
Hidden treatments in ecological experiments: re-evaluating the ecosystem function of biodiversity 总被引:68,自引:0,他引:68
Michael A. Huston 《Oecologia》1997,110(4):449-460
Interactions between biotic and abiotic processes complicate the design and interpretation of ecological experiments. Separating
causality from simple correlation requires distinguishing among experimental treatments, experimental responses, and the many
processes and properties that are correlated with either the treatments or the responses, or both. When an experimental manipulation
has multiple components, but only one of them is identified as the experimental treatment, erroneous conclusions about cause
and effect relationships are likely because the actual cause of any observed response may be ignored in the interpretation
of the experimental results. This unrecognized cause of an observed response can be considered a “hidden treatment.” Three
types of hidden treatments are potential problems in biodiversity experiments: (1) abiotic conditions, such as resource levels,
or biotic conditions, such as predation, which are intentionally or unintentionally altered in order to create differences
in species numbers for “diversity” treatments; (2) non-random selection of species with particular attributes that produce
treatment differences that exceed those due to “diversity” alone; and (3) the increased statistical probability of including
a species with a dominant negative or positive effect (e.g., dense shade, or nitrogen fixation) in randomly selected groups
of species of increasing number or “diversity.” In each of these cases, treatment responses that are actually the result of
the “hidden treatment” may be inadvertently attributed to variation in species diversity. Case studies re-evaluating three
different types of biodiversity experiments demonstrate that the increases found in such ecosystem properties as productivity,
nutrient use efficiency, and stability (all of which were attributed to higher levels of species diversity) were actually
caused by “hidden treatments” that altered plant biomass and productivity.
Received: 16 December 1996 / Accepted: 2 March 1997 相似文献
17.
Summary In order to establish a refined biostratigraphic subdivision and correlation of the Uppermost Carboniferous/Lower Permian
deposits of the Southern Alps (Carnic Alps, Karavanke Mountains; Austria/Italy/Slovenia), two major microfossil groups (fusulinoideans,
conodonts) were investigated within the same sample. The fusulinoidean species diversity (71 species, including five new species
and three new subspecies) and generic composition were reviewed and complemented. Additionally, the data on fusulinoidean
assemblages were supplemented by co-occurring conodont faunas (seven species). Accompanying studies on material from the type
sections of the Southern Urals (Russia) were made to improve the biostratigraphic correlation with the Russian standard zonation
and to discuss paleobiogeographical aspects of the faunal associations. An integrated microfacies analysis of the sampled
material in the Southern Alps serves to evaluate the relationships between certain genera and specific microfacies types.
The fusulinoidean fauna of the Lower “Pseudoschwagerina” Limestone is of late Gzhelian age. The Carboniferous/Permian boundary is close to the base of the Grenzland Formation, which
covers the entire Asselian and a part of the Sakmarian. The Upper “Pseudoschwagerina” Limestone and Trogkofel Limestone are Lake Sakmarian to Artinskian. The studies sequences in the Karavanke Mountains. formerly
known as “carbonate and clastic Trogkofel beds”, correlate to the Lower “Pseudoschwagerina” Limestone, respectively with parts of the Grenzland Formation. Due to the lithologic differences, new formation names (Dolzanova
Soteska Fm., Born Fm.) were introduced for the so-called “Trogkofel” Limestone along the Dolzanova Soteska.
Whereas late Gzhelian/Asselian fusulinoidean faunas of the Southern Alps correspond to the Southern Uralian faunas to a large
extent, Sakmarian and Artinskian faunas reveal an increasing divergence in species and genus composition. Climatic as well
as geographic barriers may have prevennted the dispersal of Paleotethyan taxa into the Southern Urals. Biostratigraphic correlation
of Sakmarian to Artinskian deposits is therefore possible only on the basis of the sparse conodont faunas. 相似文献
18.
Tardigrades have two forms of dormancy, namely cryptobiosis and encystment. The encystment is a form of diapause known for
a limited number of species of tardigrades and still little studied. To increase the knowledge on encystment, two species
of eutardigrades from Italy have been considered: the moss-dwelling Amphibolus volubilis (Eohypsibiidae), and the limnic Dactylobiotus parthenogeneticus (Murrayidae). Cysts have been collected in nature, or induced under laboratory conditions. In the latter case, it was possible
to follow the several steps of encystment processes. Two different types of cyst (“type 1” and “type 2”) have been found in
A. volubilis, while in D. parthenogeneticus only one type has been found. In general, the ovoid-shaped cysts are constituted by a series of cuticles surrounding the
animals and resemble an onion or a Matrioshka Russian doll. In all three types of cyst, the encystment processes show both
common and peculiar traits. Encystment begins with the discharging of the sclerified parts of the buccal-pharyngeal apparatus,
as in the molting process, but without the loss of the old cuticle. Then, two or three new cuticles are serially synthesized,
according to cyst type. In A. volubilis, the ultrastructure of these new cuticular involucra is similar to that of non-encysted animal cuticles, while in D. parthenogeneticus the ultrastructure of the new cuticular involucra differs from that of non-encysted animal cuticle. A modified buccal-pharyngeal
apparatus has been observed both in “type 2” cyst of A. volubilis and in the D. parthenogeneticus cyst. 相似文献
19.
This paper examines the functional relationships among species in an Australian rangeland community with mixed life forms.
It follows a previous study (Walker and others 1999) that explored the role of dominant and minor species in maintaining functional
diversity and resilience in a rangeland ecosystem. Unlike our previous results, which were based on estimates of five plant
functional attributes, the dominant species in this second community apparently are functionally no more dissimilar to each
other than to all other species. We suggest that the lack of clear results in mixed life form communities represents a confounding
of the relationships between the “hard” attributes that actually govern how a plant performs in an ecosystem and the “soft”
attributes that we use as surrogates. There are very few data on the hard functional attributes of plant species and consequently
little information on precisely how the (soft) measurable traits are related to their imputed functions. What evidence there
is shows that although the relationships are strong within life forms, they differ between life forms. This poses a problem
for the development of research relating plant biodiversity to ecosystem function. Until such a database is developed, it
will be very difficult to advance our understanding and measurement of functional diversity in mixed life form communities.
Received 30 April 2001; Accepted 23 January 2002. 相似文献
20.
Céline Labrune Antoine Grémare Jean-Michel Amouroux Rafael Sardá João Gil Sergi Taboada 《Helgoland Marine Research》2008,62(3):201-214
Samples of soft-sediment macrobenthos from 92 sites between 10 and 50 m depth were used to assess (1) the main soft-bottom
macrofauna communities in the Gulf of Lions, (2) the different components of the diversity of benthic macrofauna in this area,
and (3) the relevance of the use of major taxonomic groups as surrogates for the analysis of the structure and diversity of
total macrofauna. Three main communities were identified by cluster analysis and associated procedures. These communities
corresponded well to the assemblages recently identified on the basis of polychaete composition. The α-diversity indices were
in accordance with those reported for similar communities in the Mediterranean. Conversely, the β-diversity value was higher
than the few other data available in the literature for marine soft-bottom macrofauna. The total number of species in the
studied area estimated by the “total species accumulation curve” (TS) method was 2,319, which was only 10% higher than the
number obtained by extrapolation of the species–area curve. The similarity matrix based on polychaetes correlated best with
the one based on total macrofauna. Polychaetes and crustaceans were also the best surrogates of total macrofauna when assessing
α-diversity (except in the case of Δ*). Conversely, molluscs were the best surrogates of total macrofauna β-diversity. Our
results show that the choice of an optimal surrogate for total benthic macrofauna depends on the characteristic of the benthic
macrofauna to be studied. Moreover, this choice is also dependent on the environment to be studied. 相似文献