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1.
We examined changes in coral assemblages in four back-reef locations across the warm 1998 E1 Niño–Southern Oscillation (ENSO) event based on annually collected line-transect data from 3 years before and after this event. The physical locations of the reefs differed such that there was a 120%–275% warm-season range in the SDs of seawater temperatures but only minor differences in mean temperatures, based on 2 non-ENSO years. We tested the predictions that (a) rare warm-water events would produce fewer changes in eurythermal than stenothermal coral assemblages; and (b) after the disturbance, the stenothermal assemblages would more closely resemble the eurythermal ones. The 1998 event produced fewer changes in coral cover and community similarity among the assemblages in the reefs with high variation in temperature than in those with low variation in temperature. Despite the initially lower taxonomic richness in the eurythermal assemblage, there was an additional loss of taxonomic richness in the high and none in the stenothermal reefs. There was some evidence for taxonomic convergence, of the stenothermal towards the eurythermal reefs and a general loss of some of the branching taxa, such as branching Porites, Pavona, and Stylophora, and a relative increase in massive Porites and Favia. There was, however, moderate site specificity that did not produce true convergence. The eurythermal assemblages maintained the basic community structure but lost taxonomic richness, whereas the opposite was true for the stenothermal assemblages.  相似文献   

2.
Ecosystems - A fundamental goal in ecology is to understand the role of consumers in top-down (TD) and bottom-up (BU) processes that affect the functioning of ecosystems. Consumers ingest organic...  相似文献   

3.
The structure of coral reef habitat has a pronounced influence on the diversity, composition and abundance of reef-associated fishes. However, the particular features of the habitat that are most critical are not always known. Coral habitats can vary in many characteristics, notably live coral cover, topographic complexity and coral diversity, but the relative effects of these habitat characteristics are often not distinguished. Here, we investigate the strength of the relationships between these habitat features and local fish diversity, abundance and community structure in the lagoon of Lizard Island, Great Barrier Reef. In a spatial comparison using sixty-six 2m2 quadrats, fish species richness, total abundance and community structure were examined in relation to a wide range of habitat variables, including topographic complexity, habitat diversity, coral diversity, coral species richness, hard coral cover, branching coral cover and the cover of corymbose corals. Fish species richness and total abundance were strongly associated with coral species richness and cover, but only weakly associated with topographic complexity. Regression tree analysis showed that coral species richness accounted for most of the variation in fish species richness (63.6%), while hard coral cover explained more variation in total fish abundance (17.4%), than any other variable. In contrast, topographic complexity accounted for little spatial variation in reef fish assemblages. In degrading coral reef environments, the potential effects of loss of coral cover and topographic complexity are often emphasized, but these findings suggest that reduced coral biodiversity may ultimately have an equal, or greater, impact on reef-associated fish communities.  相似文献   

4.
We sampled juvenile fish approximately fortnightly using a fine mesh beach seine net to determine the recruitment patterns of Sillago ciliata, Centropogon australis and Girella tricuspidata to seagrass, Zostera capricorni, habitats in Botany Bay, south-eastern Australia. We used trends in the length frequency distributions of juveniles to estimate the timing of recruitment events, rates of post-settlement growth and the residence time of each species in seagrass. We detected discrete pulses of recruitment by each species. The timing of recruitment events by S. ciliata reflected the timing of spawning events. Recruitment by G. tricuspidata reflected lunar or tidal cycles. The factors influencing the timing of recruitment by C. australis were unclear. The growth rate of S. ciliata length cohorts varied and was positively related to estuarine water temperature. The timing of emigration from seagrass of C. australis and G. tricuspidata juveniles appeared to be length-dependant.  相似文献   

5.
In four eggs and four chicks of the North Island brown kiwi (Apteryx mantelli) we measured pre- and postnatal oxygen consumption rate (VO(2)) daily from day (d)-75 (prior to hatching) until d+25 (after hatching). The increase of embryonic VO(2) reaches a plateau phase between d-22 and d-5 (0.113 ml O(2)/g/h=59.6% of allometrically expected value of a typical 416-g egg). Mean total O(2) uptake per egg (43.01 l O(2)) corresponds to an energy turnover rate of 2.04 kJ/g during embryonic development. This is nearly identical to the expected value for all birds (2.00+/-0.8 kJ/g). Hence, the kiwi neither 'gained nor lost energy' (Calder, 1979.Biosci. 8, 461-467) by its extreme prolongation of incubation time; it is as efficient as other avian embryos. The kiwi embryo expends only approximately 17% (847 kJ) of the energy originally stored in the egg (4942 kJ). Forty-eight percent of the egg's initial yolk mass can be found as spare yolk in the hatchling and can serve as the chick's sole source of energy and substrate for tissue production for up to at least 17 days after hatching.  相似文献   

6.
Both deterministic and stochastic processes are expected to drive the assemblages of arbuscular mycorrhizal (AM) fungi, but little is known about the relative importance of these processes during the spreading of toxic plants. Here, the species composition and phylogenetic structure of AM fungal communities colonizing the roots of a toxic plant, Ligularia virgaurea, and its neighborhood plants, were analyzed in patches with different individual densities of L. virgaurea (represents the spreading degree). Community compositions of AM fungi in both root systems were changed significantly by the L. virgaurea spreading, and also these communities fitted the neutral model very well. AM fungal communities in patches with absence and presence of L. virgaurea were phylogenetically random and clustered, respectively, suggesting that the principal ecological process determining AM fungal assemblage shifted from stochastic process to environmental filtering when this toxic plant was present. Our results indicate that deterministic and stochastic processes together determine the assemblage of AM fungi, but the dominant process would be changed by the spreading of toxic plants, and suggest that the spreading of toxic plants in alpine meadow ecosystems might be involving the mycorrhizal symbionts.  相似文献   

7.
In this study, we analyse New World coral snakes in a phylogenetic framework based upon an increased molecular data set, including novel sequences for the only two sympatric species known from an island (Trinidad, West Indies). Their presence in Trinidad and absence in Tobago offers a unique system to study the phylogeography of the region. We assess the tempo and mode of colonisation of Micrurus on the island, in addition to discussing the phylogenetic relationships for the genus Micrurus concerning two phenotypic traits, body and tail banding patterns. These relationships are analysed for the first time on statistical coalescent phylogeographic discrete ancestral reconstruction. We find a robust phylogenetic component in these characteristics, where strongly supported clades are recovered: prior to the onset of the Early Miocene, a triadal and tricolour tail clade composed of species from South America, and a second clade dating to the Middle‐Late‐ Miocene with monadal and bicolour tails widely distributed from North to South America. The divergence between clades dates to the Oligocene and suggests an ancient pre‐isthmus divergence supporting the arrival of the triadal clade into South America, before the connection between Central and South America was established. We find the two coral snakes present in the West Indies, M. diutius and M. circinalis, belong to the triadal and monadal clades, respectively. Guyana and Trinidad Micrurus diutius share the same haplotypes suggesting a Late Pleistocene–Holocene vicariance when sea level rises separated Trinidad from the mainland. A second lineage of diutius‐like snakes is present in Guyana and is confirmed as M. lemniscatus which is assigned as a voucher and restricts the type locality for M. lemniscatus.  相似文献   

8.
A new species of Mollitrichosiphum Suenaga, Mollitrichosiphum tumorisiphum Qiao & Jiang, sp. n., from Fagus longipetiolata in Taiwan island is described. Siphunculi of Mollitrichosiphum tumorisiphum in alatae are distinctly swollen on the distal part, unlike those of the other known species in the genus. Updated keys to apterous and alate viviparous females of all known Chinese species of Mollitrichosiphum are provided. The specimens studied are deposited in the National Zoological Museum of China, Institute of Zoology, Chinese Academy of Sciences, Beijing, China and the Natural History Museum, London, United Kingdom.  相似文献   

9.
The present study aimed to investigate the spatial structure of fish communities at juvenile and adult stages on coral reefs at Kudaka Island (Ryukyu Archipelago, Japan) and to relate spatial patterns in the structure of the fish communities to gradients in environmental variables. Diurnal visual censuses allowed us to record 2,602 juveniles belonging to 60 species and 1,543 adults belonging to 53 species from October to December 2005. The distribution of species highlighted that the juvenile community was organised into three distinct assemblages, rather than exhibiting gradual change in community structure along the cross-reef gradient. Correlations between spatial patterns of juvenile community and environmental variables revealed that the most significant factors explaining variation in community structure were coral rubble and coral slab. In contrast, the adult community was organised into one assemblage, and the most significant variation factors in community structure were depth, live coral in massive form, live coral in branched form, dead coral and sand. Overall, the present study showed that most juvenile and adult coral reef fish at Kudaka Island exhibited striking patterns in their distribution and depth and some biological factors (e.g., abundance of live coral, dead coral and coral rubble) might exert considerable influence on the distribution of fishes.  相似文献   

10.
 CaCO3 production by reef-building organisms on Green Island Reef in the Great Barrier Reef of Australia is estimated and compared with the contribution of benthic foraminifera to the sediment mass of the vegetated sand cay. Major constituents of the cay are benthic foraminifera (mainly Amphistegina lessonii, Baculogypsina sphaerulata, and Calcarina hispida), calcareous algae (Halimeda and coralline algae), hermatypic corals, and molluscs. Among these reef-building organisms, benthic foraminifera are the single most important contributor to the sediment mass of the island (ca. 30% of total sediments), although their production of CaCO3 is smaller than other reef-building organisms. Water current measurements and sediment traps indicate that the velocity of the current around Green Island is suitable for transportation and deposition of foraminiferal tests. Abundant foraminifera presently live in association with algal turf on the shallow exposed reef flat, whose tests were accumulated by waves resulting in the formation and maintenance of the coral sand cay. Accepted: 30 June 1999  相似文献   

11.
Three species of amphibious sea kraits (Laticauda spp.) spend variable time at sea and require fresh water for water balance. Both the rate of cutaneous evaporative water loss and the extent of terrestriality are known to differ among them. Laticauda semifasciata has the greatest rate of water loss and the least extent of terrestriality, whereas L. colubrina exhibits the reverse and L. laticaudata is intermediate. These sea kraits tend to be more abundant at places where there are sources of fresh water, but other factors also influence their distribution. To further clarify the habitat requirements, we investigated the abundance of each species of sea krait at six different habitats and the availability of each type of habitat on Orchid Island, Taiwan. The six habitats were high coral reef without fresh water (HR) and with fresh water (HRF); low coral reef without fresh water (LR) and with fresh water (LRF); sand or gravel coast, which has no coral reef, without fresh water (NR) and with fresh water (NRF). The extent of safety judged from the relative availability of retreat sites, from high to low, was HR, LR, and NR among these habitats. More than 75% of individuals counted for each species were found in HRF. We found no sea kraits in NRF and NR. The most available habitat was LR, but no L. laticaudata or L. semifasciata were found in this habitat. We found 3.3% and 16.7% of L. colubrina in LR and HR, respectively. For L. colubrina, the second abundant habitat was HR, whereas for L. laticaudata and L. semifasciata, the second abundant habitat was LRF. We conclude that both safety (availability of retreat sites) and fresh water are important to the habitat selection of sea kraits. Compared with other species, L. colubrina is characterized by a greater extent of terrestrial habit and possibly greater variety of access to sources of fresh water.  相似文献   

12.
Assessment of Coleopteran diversity and abundance was carried out in the lowveld region of Swaziland by pitfall trapping in five distinct habitats. Additionally, the study was to ascertain if any of the families collected illustrated habitat fidelity. 18 coleopteran families, comprising 2903 individuals were collected, with an additional 29 unidentified specimens, totalling 2932 beetles. Numerically, the top five families were the Scarabaeidae (2425), Carabidae (211), Tenebrionidae (149), Nitidulidae (37) and Curculionidae (22). 66.6% of all specimens collected were harboured within the pine windbreak while the lowest number (2.6%) was collected from the mature citrus orchard. The highest proportion (77%) of scarabaeid beetles collected occurred within the pine windbreak. Habitat specificity was illustrated by one family, Meloidae, which was found only in the young orchard. Community analysis was further carried out to ascertain distribution patterns of the dominant coleopteran families. Three scarabaeid species were found only in the pine windbreak while three carabid species occurred only in the indigenous savanna. Significant differences between habitats were observed in the number of beetles collected while no significant differences were observed in terms of the number of families observed in each habitat (p<0.05). Results indicate that conservation of the various habitat patches within the mosaic studied could facilitate conservation of whole communities rather than individual species thus facilitating effective conservation of the agricultural landscape.  相似文献   

13.
Three groups of N2-fixing bacteria were enumerated from the top 1 cm of the surface in four vegetational areas in a Delaware salt marsh. The results over the 9-month sampling period showed that there were no discernible seasonal patterns for any of the groups enumerated (Azotobacter sp., Clostridium sp., and Desulfovibrio sp.). Azotobacter sp. was present in numbers of 107 per g of dry mud, whereas the two anaerobic fixers were present in much lower numbers (103 to 104 per g of dry mud). There were no differences in the numbers of each group among the different vegetational areas, indicating that there was a heterogeneous population of N2 fixers present. Additional studies indicate that the activity of sulfate reducers (Desulfovibrio sp.) may account for as much as 50% of the total observed acetylene reduction activity. Oxygen was found to exert little effect on the observed acetylene reduction activity, indicating that stable aerobic and anaerobic microenvironments exist in the surface layer of marsh sediments.  相似文献   

14.
Allozyme electrophoresis was used to assess temporal genetic variation in three successive generations of the Mediterranean killifish, Aphanius fasciatus. Samplings were carried out in 1995, 1996 and 1997 in a brackish-water habitat at Elba Island, Italy and a total of 212 specimens were collected. The five loci for which polymorphism has been detected in a previous study were assayed. Mean expected heterozygosity values [H=0.397 (SE 0.077), H=0.336 (SE 0.092) and H=0.313 (SE 0.092) in 1995, 1996 and 1997, respectively] were not significantly different by ANOVA test. Deviations from Hardy–Weinberg equilibrium were minimal, with only one out of the 15 probability tests showing a significant departure from the equilibrium; whereas genotypic linkage disequilibrium was not detected. Values of Nei's genetic distance were lower than 0.04. Temporal genetic variation in the A. fasciatus population at Elba Island was observed, with F-statistics indicating significant genetic divergence among samples (=0.035, SE 0.027, p<0.001). Genetic drift acting on two loci (GPD-1 * and LDH-3 *) is presumably the main force determining the temporal genetic heterogeneity observed; however, the occurrence of selection on individual loci and/or sampling error cannot be excluded. The observed allelic variation among generations in a single population of A. fasciatus is much less than levels observed among geographically discrete samples in previous studies.  相似文献   

15.
16.
We combine evolutionary biology and community ecology to test whether two species traits, body size and geographic range, explain long term variation in local scale freshwater stream fish assemblages. Body size and geographic range are expected to influence several aspects of fish ecology, via relationships with niche breadth, dispersal, and abundance. These traits are expected to scale inversely with niche breadth or current abundance, and to scale directly with dispersal potential. However, their utility to explain long term temporal patterns in local scale abundance is not known. Comparative methods employing an existing molecular phylogeny were used to incorporate evolutionary relatedness in a test for covariation of body size and geographic range with long term (1983 – 2010) local scale population variation of fishes in West Fork White River (Indiana, USA). The Bayesian model incorporating phylogenetic uncertainty and correlated predictors indicated that neither body size nor geographic range explained significant variation in population fluctuations over a 28 year period. Phylogenetic signal data indicated that body size and geographic range were less similar among taxa than expected if trait evolution followed a purely random walk. We interpret this as evidence that local scale population variation may be influenced less by species-level traits such as body size or geographic range, and instead may be influenced more strongly by a taxon’s local scale habitat and biotic assemblages.  相似文献   

17.
The relative steric size of methyl, methoxy, and methylthio groups was determined from circular dichroism (CD) spectroscopy using a sensitive system based on the bilirubin model. In the cyclohexane model, equatorial vs. axial orientation and conformational analysis led to quantitative measurements of orientation preference or steric demand: conformational A-values CH(3) > SCH(3) > OCH(3). A more sterically demanding model for assessing group size has been found in bilirubin analogs, which are yellow pigments that adopt a ridge-tile shape stabilized by a matrix of intramolecular hydrogen bonds. Optically active bilirubins have been shown to exhibit intense bisignate CD Cotton effects from exciton coupling of their two dipyrrinone chromophores held in either of two enantiomeric ridge-tile conformations. Interconversion of these M and P conformational enantiomers of helical chirality is rapid at room temperature but may be displaced toward either enantiomer by intramolecular nonbonded steric interactions that arise when substituents are introduced at equivalent sterically demanding sites, viz., the alpha or beta carbons of the pigment's propionic acid chains. Such substituents shift the conformational equilibrium toward the M or the P-chirality conformer, depending only on the S or R stereochemistry at the alpha and beta sites, and the resulting exciton CD for the approximately 430 nm transition(s) was used to evaluate the relative steric size, SCH(3) > CH(3) > OCH(3).  相似文献   

18.
Inhaca Island (southern Mozambique) is located in a high-latitude setting along the seaward margins of the estuarine Maputo Bay and is subject to fluctuations in temperature and salinity, and high sedimentation and turbidity levels. Coral reefs are developed sporadically along the margins of intertidal channels, but framework development is severely restricted. Coral growth is bathymetrically limited (never exceeding 6-m depth), and framework accumulation is only present in the upper 1–2 m. Massive Porites sp. produce a basic reef structure, with other coral genera (mainly Acropora sp., Favia sp., Platygyra sp., Pocillopora sp., and Montipora sp.) colonizing available substrata. Sediment samples also indicate restricted carbonate sediment production, with siliciclastics (mainly quartz) a major sediment contributor (often >90%) and carbonate grain assemblages differing from those normally associated with lower-latitude reefs. Although corals, molluscs and coralline algae (including rhodoliths) represent dominant grain constituents, Halimeda is absent and there is a low diversity (four species identified) of benthic foraminifera (mainly Amphistegina sp.). Grain associations are therefore somewhat transitional in character, comprising elements of both tropical (chlorozoan) and temperate (foramol) grain assemblages. These patterns of reef and associated carbonate production emphasize the marginal character of these reef environments, which form one end member in a broad spectrum of marginal reef systems that are now being identified in a range of both high- and low-latitude settings.  相似文献   

19.

Background

Seawater temperature is the main factor restricting shallow-water zooxanthellate coral reefs to low latitudes. As temperatures increase, coral species and perhaps reefs may move into higher-latitude waters, increasing the chances of coral reef ecosystems surviving despite global warming. However, there is a growing need to understand the structure of these high-latitude coral communities in order to analyze their future dynamics and to detect any potential changes.

Methodology/Principal Findings

The high-latitude (32.75°N) community surveyed was located at Tatsukushi, Shikoku Island, Japan. Coral cover was 60±2% and was composed of 73 scleractinian species partitioned into 7 functional groups. Although only 6% of species belonged to the ‘plate-like’ functional group, it was the major contributor to species coverage. This was explained by the dominance of plate-like species such as Acropora hyacinthus and A. solitaryensis. Comparison with historical data suggests a relatively recent colonization/development of A. hyacinthus in this region and a potential increase in coral diversity over the last century. Low coverage of macroalgae (2% of the benthic cover) contrasted with the low abundance of herbivorous fishes, but may be reasonably explained by the high density of sea urchins (12.9±3.3 individuals m−2).

Conclusions/Significance

The structure and composition of this benthic community are relatively remarkable for a site where winter temperature can durably fall below the accepted limit for coral reef development. Despite limited functionalities and functional redundancy, the current benthic structure might provide a base upon which a reef could eventually develop, as characterized by opportunistic and pioneer frame-building species. In addition to increasing seawater temperatures, on-going management actions and sea urchin density might also explain the observed state of this community. A focus on such ‘marginal’ communities should be a priority, as they can provide important insights into how tropical corals might cope with environmental changes.  相似文献   

20.
BACKGROUND: Lasofoxifene is a nonsteroidal selective estrogen receptor modulator (SERM) developed for the treatment of postmenopausal osteoporosis. The purpose of these studies was to evaluate the effects of lasofoxifene on the postnatal development, behavior, and reproductive performance of offspring of female rats given lasofoxifene during organogenesis and lactation. METHODS: Two range-finding studies were conducted to determine the effects of lasofoxifene at doses from 0.01-10 mg/kg on parturition and lactation in pregnant rats and on the early postnatal development of the offspring, and to optimize the dosing regimen. Maternal milk and plasma were sampled for concentrations of lasofoxifene on Lactation Days 4, 7, and 14. In the pre- and postnatal development study, lasofoxifene was administered to pregnant and lactating rats by oral gavage at dose levels of 0.01, 0.03, and 0.1 mg/kg on Gestation Days 6-17 and Lactation Days 1-20. Maternal body weight and food consumption were measured throughout pregnancy, and body weight was measured throughout lactation. Parturition was monitored closely. The F1 offspring were measured for viability, body weight, anogenital distance, the appearance of postnatal developmental indices and reflex behaviors, sensory function, in an age-appropriate functional observational battery, motor activity, auditory startle, passive avoidance, and the Cincinnati Water Maze. The F1 generation was assessed for reproductive function, and the F2 offspring were measured for body weight and viability throughout the lactation period. RESULTS: In the range-finding studies, indications of maternal toxicity included decreased body weight and food consumption, increased length of gestation, prolonged parturition, dystocia, and increased offspring mortality at birth. Concentrations of lasofoxifene in maternal plasma were similar to those in milk, increased with increasing dose, and remained consistent over a 10-day period. In the pre- and postnatal development study, maternal body weights and food consumption were decreased in all treated groups during gestation. Length of gestation was increased, parturition was prolonged, and dystocia was noted in the dams in the 0.1 mg/kg group. There was increased pup mortality in the F1 litters in the 0.1 mg/kg group and all treated groups had decreased offspring body weights beginning at 1 week of age, continuing into the postweaning period and, for the F1 males, into adulthood. Female F1 offspring in the 0.03 and 0.1 mg/kg groups had increased body weights as adults. There were delays in the age of appearance of preputial separation in the males in the 0.1 mg/kg group and vaginal opening in the females in all treated groups. Body temperature was decreased by <0.5 degrees C after weaning for male and female offspring in the 0.1 mg/kg group. The sensory, behavioral, and functional measures, including the tests of learning and memory, were unaffected by treatment. Mating success was lower for the F1 animals in the 0.1 mg/kg group, but there were no effects on the reproductive parameters. Mating, reproduction, and maternal behavior of the F1 animals in the 0.01 and 0.03 mg/kg groups and the survival and body weights of the F2 offspring in all treated groups through Postnatal Day 21 were unaffected by treatment. CONCLUSION: The maternal findings in this study were related to the pharmacologic activity of lasofoxifene. Inhibition of growth of the F1 offspring after perinatal exposure to lasofoxifene was observed, but there were no significant effects on the sensory, behavioral, or functional measures, including learning and memory. There were no effects on the F2 generation. The findings are consistent with those reported for at least one other SERM. The findings of this study do not suggest increased risk for the primary indication of use in postmenopausal women.  相似文献   

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