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1.
The distribution of genetic variance within and among socially interacting groups, often quantified as the average relatedness or r?, is an important determinant of the evolution of social behaviors. Models of social evolution often treat this average as a constant characteristic of a species. In this paper, we present data documenting the degree of temporal and spatial variation in the average relatedness of larval groups of imported willow leaf beetles, a species whose immatures display several primitive social behaviors. Collections of groups were made over three generations at three localities in Virginia and three localities in Illinois. Average relatedness was estimated from the distribution of electrophoretically determined genotypic frequencies within and among groups for each collection. Average relatedness ranged from 0.20 at one locality in Illinois to 0.65 at one locality in Virginia. Individual cases of pairwise differences between samples indicated that there were both temporal and locality effects. Further, statistical analysis showed the set of relatedness values to be heterogeneous with significant locality effects. Geographic genetic variance was also partitioned among trees sampled within localities in Illinois, among localities within each state, and between states. Notably, significant gene-frequency variation among groups of beetles occupying closely spaced trees was detected at several localities.  相似文献   

2.
Measuring floristic homogenization by non-native plants in North America   总被引:5,自引:1,他引:4  
Aim To determine if non‐native plant species are homogenizing species composition among widely dispersed plant communities. Location Twenty localities in North America. Methods Species lists among localities were compared to measure the influence of non‐native species richness at each locality on the Jaccard Index (JI) of similarity between localities. Results After removing the effects of distance, because shared native species decreased with distance, three (nonexclusive) lines of evidence indicate that non‐native species promote homogenization. First, pairs of sites with a high combined total of non‐native species tend to have higher similarity than those with a low total of non‐natives. Second, for a given distance, more non‐native than native species tended to be shared among localities. Third, whereas most of the site comparisons with high total non‐native richness have a non‐native/native JI ratio greater than 1 (often much greater), only half of the comparisons with low total non‐native richness have a ratio greater than one. Main conclusions These findings provide quantitative support for the widely held, but rarely tested, notion that non‐native species tend to homogenize biological communities because they are more commonly shared among communities. Such testing is important as non‐native species could theoretically have no impact or even reduce homogenization among communities, if non‐native colonizers consist of different species pools.  相似文献   

3.
The parasite fauna of the gray four-eyed opossum, Philander opossum (Linnaeus, 1758), and the common opossum, Didelphis marsupialis Linnaeus, 1758, in Camp du Tigre, French Guiana, is characterized. Nine species from the gastrointestinal system were recovered from both species, which shared 80% of their parasites. The parasite fauna comprised several monoxenous species (63%) and was dominated by Aspidodera raillieti Travassos, 1914, which exhibited high levels of prevalence and abundance in both communities. Only 2 species (Moennigia sp. and Spirura guianensis) had been recorded in other species of mammals. Both species richness and taxonomic composition at the level of component communities from this locality were compared against 11 communities present in the Virginia ( Didelphis virginiana ), white-bellied (Didelphis albiventris), and common opossum from Argentina, Brazil, Mexico, and the United States. Neither host phylogeny nor taxonomy accounted for statistical differences in species richness. There was no statistical difference among species richness values among the 9 localities studied. Taxonomic similarity was analyzed by means of the Jaccard's similarity index, including all, and only common species (occurring in prevalence >10%). The results suggest that sympatric species of marsupials share more species of parasites than parasite communities occurring in conspecific marsupials from different localities. As a consequence, taxonomic composition of these parasite communities varied depending on the locality. Probably, marsupials of the monophyletic Didelphini offer the same compatibility toward their parasites, by presenting them with similar habitats. Subtle differences in lifestyles of the marsupials may determine the chance of encounter between the symbionts and prevent some parasites from completing their life cycles. Further and more rigorous tests are necessary to determine the roles of encounter and compatibility filters, as well as the role of chance, in the structuring of parasite communities in marsupials.  相似文献   

4.
Spatial autocorrelation in biology 1. Methodology   总被引:25,自引:0,他引:25  
Spatial autocorrelation analysis tests whether the observed value of a nominal, ordinal, or interval variable at one locality is independent of values of the variable at neighbouring localities. The computation of autocorrelation coefficients for nominal, ordinal, and for interval data is illustrated, together with appropriate significance tests. The method is extended to include the computation of correlograms for spatial autocorrelation. These show the autocorrelation coefficient as a function of distance between pairs of localities being considered, and summarize the patterns of geographic variation exhibited by the response surface of any given variable.
Autocorrelation analysis is applied to microgeographic variation of allozyme frequencies in the snail Helix aspersa. Differences in variational patterns in two city blocks are interpreted.
The inferences that can be drawn from correlograms are discussed and illustrated with the aid of some artificially generated patterns. Computational formulae, expected values and standard errors are furnished in two appendices.  相似文献   

5.
The Middle Ordovician conodont genera that are suitable for palaeoenvironmental interpretations from the epicontinental Baltoscandian platform have been identified and evaluated to establish and describe conodont biofacies and their relationship to global cooling. The construction of biofacies was based on multivariate statistical analyses of more than 375 700 conodont specimens from 520 samples and 21 localities across Baltica. Three distinct, recurrent and laterally extensive conodont biofacies existed across the Baltoscandian platform of the Baltica continent during the Dapingian and early to middle Darriwilian stages (Middle Ordovician). A relatively shallow water conodont assemblage named the Baltoniodus–Microzarkodina Biofacies characterized the inner shelf localities in central Sweden, Estonia, Russia and Ukraine. In the distal shelf areas, patterns are more complex. Here, genera of the Periodon Biofacies characterized the shelf margin areas of the Scandinavian Caledonides facing the relatively warm Iapetus Ocean towards the north, whereas the Protopanderodus Biofacies dominated the distal shelf areas facing the cooler Tornquist Sea towards the south‐west. Although these three main biofacies continued to dominate during the succeeding Darriwilian stage, distinct changes in the distribution of biofacies took place during the transition from the Dapingian Stage to the Darriwilian. We argue that the biofacies change was triggered by a regressive event related to early Darriwilian cooling, and that the palaeoclimatological changes influenced the Baltic conodont faunas near the Tornquist Sea margin before those of the Iapetus margin (early vs middle Darriwilian).  相似文献   

6.
The diversity and similarity of parasite communities is a result of many determinants widely considered in parasite ecology. In this study, the metazoan parasite communities of 15 chub populations (Leuciscus cephalus) were sampled across a wide geographical range. Three hypotheses of biogeographical gradients in species diversity were tested: (1) latitudinal gradient, (2) a 'favourable centre' versus 'local oasis' model, and (3) decay of similarity with distance. We found that the localities in marginal zones of chub distribution showed lower parasite species richness and diversity. A latitudinal gradient, with increasing abundance of larvae of Diplostomum species, was observed. There was a general trend for a negative relationship between relative prevalence or abundance and the distance from the locality with maximum prevalence or abundance for the majority of parasite species. However, statistical support for a 'favourable centre' model was found only for total abundance of Monogenea and for larvae of Diplostomum species. The phylogenetic relatedness of host populations inferred an important role when the 'favourable centre' model was tested. Testing of the hypothesis of 'decay of similarity with geographical distance' showed that phylogenetic distance was more important as a determinant of similarity in parasite communities than geographical distance between host populations.  相似文献   

7.
A carbonate ramp in the shallow‐marine northwestern part of the Central Tarim Uplift, Bachu, NW China, exhibits an extraordinary Late Ordovician reef complex along the Lianglitag Mountains, exposed for a distance of about 25 km. Seven localities within the ‘Middle Red Limestone’ of the Upper Member of the Lianglitag Formation (Katian, Late Ordovician) illustrated the changes in biofacies and lithofacies: northern, seaward‐directed patch reefs are replaced towards the south by coeval grain banks. The patch reef units are dominated by microbial and calcareous algal components. The reefs at the northernmost locality are knoll‐shaped, kalyptra‐shaped or irregularly shaped with sizes of individual reefs increasing from about 2 m in height and diameter. Stratigraphically upward, reefs notably expand to larger structures by several mounds coalescing; they are generally about 10 m thick and tens of metres in lateral extent. The maximum thickness of the main patch reef is more than 30 m, and its diameter is around 100 m. The reefal units turn into biostromes with gentler relief southward and still further south grade into banks composed of peloids and coated grains. The southernmost locality is still a shallow‐water bank, and the coastline is not documented in the study area. The present evidence indicates that the Late Ordovician palaeo‐oceanography provided a number of environments for the optimal growth of carbonate build‐ups; microbial‐calcareous algal communities could thrive in areas where the innovative metazoan reef frameworks consisting of corals and stromatoporoids did not play a significant role. The ramp morphology, especially changes in water depth, controlled the configuration of the reef complex.  相似文献   

8.
The metazoan parasite communities of eels Anguilla anguilla were investigated in three riverine localities and one lake in Devon. Altogether 21 species of parasite, the majority of the British eel parasite fauna, were recorded. Parasite communities in the three riverine localities were more similar to each other than to that of the lake. The four parasite component communities were typical and representative of those from eels in other parts of the U.K. They were characterized by low species diversity and domination by a single species: Pseudodacytlogyrus anguillae in the rivers and Diplostomum spathaceum in the lake. Both the dominant species and the majority of parasite species, and hence individuals, in any locality infected eels directly by free swimming planktonic larval stages or indirectly by the ingestion of infected planktonic copepod intermediate hosts. Examination of other species of fish in each locality showed that only Raphidascaris acus utilized a fish species as an intermediate or paratenic host to infect eels. Increases in prevalence and intensity of infection with size of eel by helminths such as Camallanus lacustris and Paraquimperia tenerrima were observed in localities in which transmission of these parasites could not have involved another fish species. Over 63% of the specialist, specific parasites of eels throughout Europe employ planktonic transmission to their hosts, as do several species of the commoner generalists. A study of eel parasite communities thus leads to the conclusion that eels are widely and closely associated in their habits with plankton and that eels of all sizes feed regularly upon planktonic copepods: the widely accepted view of eels as being more or less exclusively benthic in habit and feeding behaviour requires re-appraisal.  相似文献   

9.
Natural populations of guppies that co-occur with the pike cichlid Crenicichla alta and associated predators mature at smaller body sizes, produce more and smaller offspring per litter reproduce more frequently, and have higher reproductive allotments (weight of developing embryos/total body weight) than guppies that co-occur with just the killifish Rivulus harti (Reznick and Endler, 1982). I here consider three forms of repeatability in these life-history patterns: i) among replicate samples collected on the same day from the same locality, ii) between Crenicichla and Rivulus communities among a new series of localities, and iii) among a smaller series of Crenicichla and Rivulus localities sampled in two wet and two dry seasons. In the analysis of replicate collections from two localities, seven of eight statistical comparisons revealed no significant difference. The usual methodology for estimating these variables therefore accurately represents guppy life-history patterns at a given locality. Differences among guppies from Rivulus and Crenicichla localities, covering a wider geographical area than considered by Reznick and Endler (1982), were virtually identical to the previous comparison. Wet-season samples were associated with significant decreases in reproductive allotment and fecundity and significant increases in the size of mature males and the minimum size of reproducing females. Differences between guppies from Rivulus and Crenicichla localities persisted across all samples and were consistent with all other observations, although they tended to be smaller during the wet season. Discriminant analyses on female reproductive traits showed that fecundity and offspring size made strong, independent contributions to discriminating between guppies from the two types of localities. The contribution from reproductive allotment was considerably smaller. There was more overlap between predator treatments during the wet season. Only 8.5% of the individuals were misclassified during the dry season, but 19.5% were misclassified during the wet season.  相似文献   

10.
We examined adaptive spatiotemporal mycobiota structure in the soil of 'Evolution Canyon' III, Nahal Shaharut, in the extreme southern Negev, Israel. A total of 223 species representing 80 genera were isolated using the soil dilution plate method. The microfungal communities in all localities and seasons were characterized by a superdominance of dark-coloured species with large multicelled conidia:  Ulocladium atrum, U. botrytis, Alternaria alternata, and Al. chlamydospora . Species of the genus Aspergillus (mainly As. fumigatus ) and teleomorphic ascomycetes comprised a basic part of the thermotolerant mycobiota obtained at a temperature of 37 °C. Isolate density displayed high positive dependence on organic matter content. Density was subject to drastic spatiotemporal (especially spatial) fluctuations, with maximum levels found in the shady valley bottom locality. The lowest biodiversity indices were estimated in localities under shrubs and in the most stressful summer and spring. The results demonstrated a clear effect of harsh desert climatic and edaphic selection on the adaptive variation of the mycobiota studied.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 263–277.  相似文献   

11.
Studies of parasites as fish population tags often apply a single round of sampling to identify potential stocks or predict harvest localities. However, the lack of replication generates pseudoreplication, implicitly assuming that infection levels are more similar between samples from the same locality than between samples from different localities. We evaluated this assumption in the case of the striped red mullet Mullus surmuletus in three localities of the Spanish Mediterranean separated by c. 300 km. Samples of 25 fish of similar size were collected in each locality in the summer and autumn of two consecutive years. Prevalence and abundance of three long-lived parasite taxa differed significantly among localities, indicating their potential as stock indicators. However, a cluster analysis (for prevalence) and a MANOVA (for abundance) indicated strong inter-sample variability, even within the same locality, with poor spatial segregation among samples. A linear discriminant analysis (LDA) based on the abundance of 17 parasite taxa correctly assigned over 80% of fish to their locality, and 95% bootstrap confidence intervals of percent classified fish per locality were narrow, indicating good and stable predictive power. However, when a LDA based on data from the first year was used to predict the locality of fish from the second year, predictive power dropped drastically (46% of correct allocation). Overall, we interpret that parasite communities of mullets change at a much lower spatial scale than that adopted in this study. This finding strongly suggests the need for proper replication to make reliable inferences about stock structure in fish populations based on parasitological data.  相似文献   

12.
Doums C  Cabrera H  Peeters C 《Molecular ecology》2002,11(11):2251-2264
In this study we investigated the population genetic structure of the queenless ant Diacamma cyaneiventre. This species, lacking winged queens, is likely to have a restricted female dispersal. We used both mitochondrial and microsatellite markers to assess the consequence of such restricted female dispersal at three geographical scales: within a given locality (< 1 km), between localities within a given region (< 10 km) and between regions (> 36 km). Within a locality, a strong population structure was observed for mitochondrial DNA (mtDNA) whereas weak or nonexistent population genetic structure was observed for the microsatellites (around 5% of the value for mtDNA). Male gene flow was estimated to be about 20-30 times higher than female gene flow at this scale. At a larger spatial scale, very strong genetic differentiation for both markers was observed between localities - even within a single region. Female dispersal is nonexistent at these scales and male dispersal is very restricted, especially between regions. The phylogeographical structure of the mtDNA haplotypes as well as the very low genetic diversity of mtDNA within localities indicate that new sites are colonized by a single migration event from adjacent localities, followed by successive colony fissions. These patterns of genetic variability and differentiation agree with what is theoretically expected when colonization events are kin-structured and when, following colonization, dispersion is mainly performed by males.  相似文献   

13.
Three species are discussed: Teloschistes hosseusianus Gyelnik, formerly known only from the type locality in Argentina is shown to have a wider distribution in South America. T. stellatus (Mey. & Flot.) Mull. Arg. known only from the type locality in Peru is reported from other localities in Peru and Chile. T. velifer F. Wils. previously known from Australia and New Zealand is reported from six localities in Chile. One of these is T. hollermayeri Ras. which is a synonym of T. velifer. A key is given to the 11 species of Teloschistes so far known from South America.  相似文献   

14.
Cherns. Lesley 1979 01 15: The environmental significance of Lingula in the Ludlow Series of the Welsh Borderland and Wales. Lethaia . Vol. 12. pp. 35–46, Oslo. ISSN 0024–1164.
The inarticulate brachiopod Lingula is commonly regarded as an indicator of very nearshore environments, particularly when found in monospecific assemblages. However, neither of the two common species in the Lower Leintwardine Beds, L. lewisii and L. lata . which occur commonly in such associations, have distributions indicative of such an environment. Their Occurrence correlates closely with the Leintwardinian palaeogeography. The former species is concentrated in shelf areas, the latter is confined to the basin; the two distributions overlap little. Individuals of both species are found articulated and perpendicular to the bedding, apparently in situ . Hence, the species may be inferred to have equivalent, infaunal modes of life comparable to living representatives of the family. The basinal distribution of L. lara is an original feature. The depth of the actively subsiding basin was relatively great, judging from sedimentological and palaeogeographical evidence. Therefore, L. lata was a species adapted to 'deep-water' environments. The lingulid distributions, reviewed against the concept of brachiopod depth-related communities previously defined for the Ludlow show the latter to be inapplicable in the Leintwardinian. The depth significance postulated for the recurrent species associations typical of the shelf sequences cannot be accepted.  相似文献   

15.
Zenetos, A. 1991 01 15: Re-evaluation of numerical classification methods for delimiting biofacies and biotopes in an estuarine environment. Lethaia . Vol. 24. pp. 13–26. Oslo. ISSN 0024–1164.
To test the applicability of numerical classificatory methods in defining biotopes and biofacies, several sets of data were combined using alternative measures of similarity and clustering techniques. In both types of analysis (biofacies and biotopes), results showed that binary data contain enough information and can give as good a picture as the quantitative data, provided [hat the appropriate techniques are used. Despite the inadequacy of the living mollusc data. biotope patterns produced by living and subfossil molluscs are similar, suggesting negligible post-mortem transportation and burial of the fauna in its place of occurrence. The biotopes delineated in this study are consistent with Eastwood's (1977) 'textural facies' patterns based on the sediment size distribution. In this line, it is suggested that the grain size of the substrate is the main factor determining the distribution of molluscs in the Eden estuary. Moreover. the fact that the same cluster analysis combination (D-coef./Ward's clustering) based on independent variables (fauna and sediment size distribution) led to similar results. emphasizes the objectivity of the methods used and the stability of the clusters generated. Mollusca. numerical taxonomy. biotopes. biofacies. Eden estuary .  相似文献   

16.
Differences between two subspecies ofBolboschoenus maritimus (L.)Palla (=Scirpus maritimus L.) in different habitats (littoral and terrestrial) are partly due to variations in the buoyancy of their achenes, caused by different anatomical structure of the fruits. This hypothesis was tested by comparing fruit buoyancy and anatomy of both subspecies at several localities. Plants were sampled fromBolboschoenus maritimus subsp.maritimus (plants with branched inflorescences and triangular fruits, 4 localities) andB. maritimus subsp.compactus (Hoffm.)Hejný (plants with compact inflorescences and prevailing concave fruits, 4 localities) in the Czech and Slovak Republics, andB. maritimus subsp.compactus (plants with compact inflorescences and convex fruits, 1 locality) from the coast of South Sweden. From each locality a plant with several tubers connected by rhizomes was taken and transferred into the experimental garden; from these cultivated plants (clones) mixed samples of fruits collected from each clone were used for buoyancy tests and a study of their anatomy. Fruit buoyancy was found to depend on the anatomical structure of the pericarp—the presence of aeriferous tissue in the exocarp serves as the main floating organ. This differentiated all plants studied into two groups: short-floating subsp.maritimus, with a thin or none acriferous tissue in the exocarp, and long-floating subsp.compactus with well developed aeriferous tissue. Differences in fruit buoyancy corresponds to differences in the prevailing habitat types of both subspecies studied in the inland sites: the frequent occurrence of subsp.compactus in temporarily flooded terrestrial habitats contrasts with the prevalence of subsp.maritimus in the littoral of water bodies. This is an example of intra-specific ecological differentiation leading to differentiation in wetland communities.  相似文献   

17.
Lower Devonian quiet-water marine benthic communities were examined to determine what parameters of community structure are maintained from locality to locality. The preserved elements of the communities are dominated by brachiopods. Each community has a characteristic taxonomic composition and diversity. From stratigraphically lowest to highest the communities include the newly proposed Dawsonelloides Community which has relatively low diversity, and is strongly dominated by a single species. The Beachia Community is less strongly dominated by a single species. The newly proposed Leptostrophia Community is very strongly dominated by a single species; less common species are rare or absent in the other communities. The Plicoplasia Community is slightly less diverse than the preceeding two communities, but unlike them has six species which dominate one or more collections and are commonly found in reduced abundance in the other collections. The gradual change in taxonomic composition and structure from one community to adjacent communities coupled with the similar structure of diversity and dominance within particular communities suggest that these characteristics are time-averaged and primary structural features of the communities.  相似文献   

18.
It is commonly asserted that exotic species promote the homogenization of biological communities. However, theoretical evidence implies that exotic species may often have the opposite effect, of differentiating biological communities where different exotic species become established in different areas. Furthermore, few empirical studies have directly measured the homogenizing effects of exotics. In this study, I used the plant inventories of 20 localities in the United States to measure whether exotic plant increased the similarity of those localities. I calculated Jaccard's index of similarity (JI) for exotic species and then for native species to see if the exotic JI was consistently higher when comparing two localities. I found that JI for both exotic and native species decline exponentially with increasing distance and latitude separation between localities so that localities that share many native species also tend to share many exotic species. More importantly, in nearly half of the pairwise locality comparisons (87 of 190), the (JIexotic/JInative) ratio is less than one, indicating a slight tendency for exotic species to differentiate rather than homogenize the localities analyzed. Also, the pattern of differentiation versus homogenization is strongly related to exotic species richness. When both localities have relatively few exotics, there is a clear tendency for exotics to produce biotic differentiation (JIexotic/JInative < 1). Much of this pattern seems related to the right-skewed frequency distribution of the geographic ranges of exotic species. As with native species, most exotics occur in few localities so there is a high probability that localities with low numbers of exotic species will share very few, if any, of those exotics. As exotic richness increases, the homogenizing effects become increasingly pronounced.  相似文献   

19.
Aethionema rhodopaeum D. Pavlova is described as a new species from the eastern Rhodope Mountains. The plant was found growing only on serpentines, in two localities, at an altitude of approximately 400 m. The localities are typical open habitats with sparsely colonized debris. The plant communities, composed mainly of xerophytes with a mosaic distribution, contain a large number of rare and endemic species for the Bulgarian flora. The new species belongs to the Aethionema saxatile group and is quite close to the species A. saxatile (L.) R. Br., in particular to ssp. creticum and ssp. graecum . The following diagnostic features are given for the new species: inner filament length always greater than half the petal length, lack of teeth of the filaments, longer [2–3(3.5) mm] style than that of A. saxatile subspecies, and dark purple petals. All leaves are broadly elliptical to suborbicular, obtuse, and fleshy. The chromosome number of the new species is 2 n  = 24. The differences between the new species and related taxa are also discussed.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 533–540.  相似文献   

20.
We describe and interpret spatiotemporal micromycete community structure and adaptive complexes in contrasting xeric and mesic microclimates in the soils of 'Evolution Canyon' II, Lower Nahal Keziv, western Upper Galilee, Israel. A total of 192 species from 60 genera belonging to Zygomycota (nine species), Ascomycota (13 species), and mitosporic fungi (170 species) were isolated. The fungal communities on the south-facing, xeric, 'African' slope (AS) demonstrated significantly greater diversity than on the north-facing, mesic, 'European' slope (ES) and the valley bottom (VB). Seasonally, winter slope communities were less heterogeneous. Forest localities on the ES and the VB in all seasons and the shady localities on the AS in the winter were overwhelmingly dominated by mesophilic Penicillium species. The sunny locality on the AS was characterized by a dominance of melanin-containing micromycetes that was most pronounced in the summer and by high occurrence and abundance of thermotolerant and thermophilic Aspergillus and Fusarium species. Ascomycetes and zygomycetes were the minor components in all local mycobiota studied; sexual ascomycetes, being stress-selected fungi, were more than ten times more abundant in the soil of the AS than in that of the ES, with the peak of abundance in the sunny summer community. The results demonstrated a microscale adaptive spatiotemporal inter- and intraslope divergence in soil mycobiota structure. Microclimatic natural selection appears to be the major factor affecting soil fungus diversity patterns.  © 2003 The Linnean Society of London . Biological Journal of the Linnean Society , 2003, 78, 527–539.  相似文献   

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