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991.
Rates of progression and transmission of black band disease (BBD) on the staghorn coral, Acropora muricata, were compared between months for seasonal in situ studies and between temperature treatments in experimental aquaria manipulations
at Lizard Island on the Great Barrier Reef (GBR). In situ field experiments demonstrated that BBD progressed along branches
approximately twice as fast (1.7–2.4 times) during the austral summer month of January (0.99 ± 0.04 cm/day) than in the cooler
months of July (0.58 ± 0.04 cm/day) and May (0.41 ± 0.07 cm/day). Transmission of BBD between colonies was also accelerated
in warmer months, with signs of infection becoming visible 1.2 days earlier in January compared to May. The greater seawater
temperatures by ∼2 to 3°C and light intensities by up to 650 μE/m2/s in January, suggest that rates of progression and transmission of BBD are linked to one or both of these parameters. Manipulative
experiments in summer provide corroborative evidence that elevated temperatures increase rates of BBD progression, with the
disease progressing 1.3 times more rapidly in the 32°C elevated temperature treatment than in the 30°C ambient treatment (1.17 ± 0.06 cm/day
versus 0.92 ± 0.07 cm/day; F
2,6 = 7.66, P = 0.022). In contrast, although a trend for greatest BBD progression was measured in elevated temperature treatments of 29°C
(0.46 ± 0.07 cm/day) and 31°C (0.52 ± 0.06 cm/day) in winter, these rates did not differ significantly (F
3,7 = 1.72, P = 0.249) from those measured for the ambient 27°C treatment (0.37 ± 0.06 cm/day) or the field controls (0.41 ± 0.09 cm/day).
The lower rates of BBD progression in the 31°C winter treatment (0.52 ± 0.06 cm/day) than in the 30°C (0.92 ± 0.07 cm/day)
summer treatment, may have been a response to 28-fold decreased light irradiance in the former, suggesting that high irradiance
in combination with elevated temperatures may promote progression of BBD. Results from this study indicate that the impact
of elevated temperature on BBD progression is complex with a combination of environmental factors including temperature and
light playing key roles in progression and transmission of the disease. 相似文献
992.
Bats produce echolocation signals that reflect the sensory tasks they perform. In open air or over water, bats encounter few
or no background echoes (clutter). Echolocation of such bats is the primary cue for prey perception and varies with the stage
of approach to prey, typically comprising search, approach, and terminal group calls. In contrast, bats that glean stationary
food from rough surfaces emit more uniform calls without a distinct terminal group. They use echolocation primarily for orientation
in space and mostly need additional sensory cues for finding food because clutter echoes overlap strongly with food echoes.
Macrophyllum macrophyllum is the only Neotropical leaf-nosed bat (Phyllostomidae) that hunts in clutter-poor habitat over water. As such, we hypothesized
that, unlike all other members of its family, but similar to other trawling and aerial insectivorous bats, M. macrophyllum can hunt successfully by using only echolocation for prey perception. In controlled behavioral experiments on Barro Colorado
Island, Panamá, we confirmed that echolocation alone is sufficient for finding prey in M. macrophyllum. Furthermore, we showed that pattern and structure of echolocation signals in M. macrophyllum are more similar to aerial and other trawling insectivorous bats than to close phylogenetic relatives. Particularly unique
among phyllostomid bats, we found distinct search, approach, and terminal group calls in foraging M. macrophyllum. Call structure, however, consisting of short, multiharmonic, and steep frequency-modulated signals, closely resembled those
of other phyllostomid bats. Thus, echolocation behavior in M. macrophyllum is shaped by ecological niche as well as by phylogeny. 相似文献
993.
Véronique Thériault Louis Bernatchez Julian J. Dodson 《Behavioral ecology and sociobiology》2007,62(1):51-65
Salmonids are known for the occurrence in sympatry of two life-history forms, one that undergoes migration to sea before returning
to freshwater to reproduce (anadromous) and one that inhabits freshwater without a migration phase (resident). Whereas one
breeding population is often suggested by population genetic studies, mating patterns have rarely been directly assessed,
especially when both sexes are found within each life-history form. By using highly polymorphic microsatellite loci and parentage
analysis in a natural population of sympatric anadromous and resident brook charr (Salvelinus fontinalis), we found that gene flow occurred between the two forms and was mediated by resident males mating with both resident and
anadromous females. Determinants of reproductive success, estimated by the number of surviving juveniles (ages 1 and 2 years),
differed between the sexes. No strong evidence of the influence of size on individual reproductive success was found for males,
whereas larger females (and hence most likely to be anadromous) were more successful. The higher individual reproductive success
of anadromous fish compared to residents was mainly explained by this higher reproductive success of anadromous females. We
suggest that resident males adopt a “sneaking” reproductive tactic as a way of increasing their reproductive success by mating
with females of all sizes in all habitats. The persistence of the resident tactic among females may be linked to their advantage
in accessing spatially constrained spawning areas in small tributary streams unavailable to larger females. 相似文献
994.
Xinhua Fu Fredric V. Vencl Ohba Nobuyoshi V. Benno Meyer-Rochow Chaoliang Lei Zhongning Zhang 《Chemoecology》2007,17(2):117-124
Summary. When attacked or otherwise disturbed, larvae of the aquatic firefly Luciola leii display fork-shaped glands laterally from the meso- and metathorax as well as each abdominal segment. Glandular eversion
is accompanied by a strong pine oil-like odour, thanatosis and glowing from paired larval light organs. Observations by SEM
and TEM revealed that there are numerous, almost spherical protuberances, measuring 9 μm in diameter on the surface of each
gland. Each protuberance is connected to a well developed secretory cell via a 0.1 μm thick and 0.2 μm long stalk and bears
three to six 7 μm long spines on its apex. The convoluted glandular walls measure 0.2 μm. The cytoplasm of the secretory cells
is characterized by the presence of numerous mitochondria and an extensive system of cisternae and tubular endoplasmic reticulum.
Preliminary GC-MS analysis of the glandular secretion revealed two volatile terpenoids: terpinolene and γ-terpinene. Choice
and no-choice bioassays involving fish and ants as well as other predators demonstrate that the secretions serve as an effective
deterrent against a range of ecologically relevant enemies. The larval postural adjustments, light emission, everted glands,
and glandular release of distasteful or repellent compounds, appear to function as a multi-modal, aposematic larval defence.
The tandem evolution of glandular secretions and conspicuousness in larval fireflies could partially explain their successful
radiation into both aquatic and terrestrial habitats. 相似文献
995.
A. Cafissi S. Beduschi V. Balacco B. Sacchi S. P. Trasatti 《Environmental Chemistry Letters》2007,5(2):101-106
We studied the chemical dechlorination of the polychlorinated biphenyls (PCBs) in some dielectric oils via nucleophilic substitution
of the chloro atoms by polyethylene alkoxide. The influence of temperature, ultrasounds, polyethylene glycol (PEG) and base
type was investigated. Our findings show that dechlorination of PCBs by chemical treatment is effective at moderate temperature
(90–100°C) and is strongly dependent on the nature of matrix oil. Stirring affects the process yield by influencing the homogeneity
of the oil/glycol two-phase system. Ultrasounds can improve the process efficiency by making operating conditions less severe.
Selected article from the 6th European Meeting on Environmental Chemistry, University of Belgrade, Serbia and Montenegro organized
by Prof. Dr. Branimir Jovancicevic (). 相似文献
996.
Nina H. Fefferman James F. A. Traniello Rebeca B. Rosengaus Daniel V. CalleriII 《Behavioral ecology and sociobiology》2007,61(4):565-577
Understanding the origin of disease resistance in social insects is difficult due to the lack of well-established phylogenies
of presocial and eusocial species and the absence of extant basal and intermediate forms. Moreover, comprehensive accounts
of infection-control traits in social insect lineages are not available. Therefore, to explore the evolution of pathogen control
in social insects we used cellular automata models to analyze the efficacy of immunity and nest hygiene, which we assumed
were basal traits, and allogrooming, which likely followed the transition to eusociality, and their interactions with colony
demography and patterns of worker spatial distribution. Models showed that nest hygiene provided an immediate survival benefit
and that immunity lowered overall disease susceptibility under both constant and periodic exposure scenarios. Allogrooming
increased survivorship in chronically challenged colonies but also increased pathogen transmission rates under conditions
of periodic exposure. Colonies having demographies biased towards young or old individuals had slightly higher mortality than
those with heterogeneous demographies. The distribution of older individuals relative to the nest center had no significant
effect on susceptibility and provided only a minor survival advantage. Models indicated that nest hygiene and immunity function
on different temporal scales and can interact with demography to lower disease risks. Our results suggest how infection control
systems in social insects could have been built upon the inducible immune defenses and nest hygienic behaviors of solitary
and presocial ancestors and served as important preadaptations to manage disease exposure and transmission in colonies of
eusocial species. 相似文献
997.
O. Barneah I. Brickner M. Hooge V. M. Weis T. C. LaJeunesse Y. Benayahu 《Marine Biology》2007,151(4):1215-1223
Epizoic worms were found to occur on certain coral colonies from reefs off the coast of Eilat (Red Sea). We identified 14
coral species infested by acoelomorph worms at a depth range of 2–50 m. The host corals were all zooxanthellate and included
both massive and branching stony corals and a soft coral. Worms from all hosts were identified as belonging to the genus Waminoa and contained two distinct algal symbionts differing in size. The smaller one was identified as Symbiodinium sp. and the larger one is presumed to belong to the genus Amphidinium. Worm-infested colonies of the soft coral, Stereonephthya cundabiluensis, lacked a mucus layer and exhibited distinct cell microvilli, a phenotype not present in colonies lacking Waminoa sp. In most cases, both cnidarian and Acoelomorph hosts displayed high specificity for genetically distinctive Symbiodinium spp. These observations show that the epizoic worms do not acquire their symbionts from the “host” coral. 相似文献
998.
David J Mildrexler Maosheng Zhao Faith Ann Heinsch Steven W Running 《Ecological applications》2007,17(1):235-250
The timing, location, and magnitude of major disturbance events are currently major uncertainties in the global carbon cycle. Accurate information on the location, spatial extent, and duration of disturbance at the continental scale is needed to evaluate the ecosystem impacts of land cover changes due to wildfire, insect epidemics, flooding, climate change, and human-triggered land use. This paper describes an algorithm developed to serve as an automated, economical, systematic disturbance detection index for global application using Moderate Resolution Imaging Spectroradiometer (MODIS)/Aqua Land Surface Temperature (LST) and Terra/MODIS Enhanced Vegetation Index (EVI) data from 2003 to 2004. The algorithm is based on the consistent radiometric relationship between LST and EVI computed on a pixel-by-pixel basis. We used annual maximum composite LST data to detect fundamental changes in land-surface energy partitioning, while avoiding the high natural variability associated with tracking LST at daily, weekly, or seasonal time frames. Verification of potential disturbance events from our algorithm was carried out by demonstration of close association with independently confirmed, well-documented historical wildfire events throughout the study domain. We also examined the response of the disturbance index to irrigation by comparing a heavily irrigated poplar tree farm to the adjacent semiarid vegetation. Anomalous disturbance results were further examined by association with precipitation variability across areas of the study domain known for large interannual vegetation variability. The results illustrate that our algorithm is capable of detecting the location and spatial extent of wildfire with precision, is sensitive to the incremental process of recovery of disturbed landscapes, and shows strong sensitivity to irrigation. Disturbance detection in areas with high interannual variability of precipitation will benefit from a multiyear data set to better separate natural variability from true disturbance. 相似文献
999.
Scale-dependent variation in coral community similarity across sites, islands, and island groups 总被引:2,自引:0,他引:2
Community similarity is the proportion of species richness in a region that is shared on average among communities within that region. The slope of local richness (alpha diversity) regressed on regional richness (gamma diversity) can serve as an index of community similarity across regions with different regional richness. We examined community similarity in corals at three spatial scales (among transects at a site, sites on an island, and islands within an island group) across a 10 000-km longitudinal diversity gradient in the west-central Pacific Ocean. When alpha diversity was regressed on gamma diversity, the slopes, and thus community similarity, increased with scale (0.085, 0.261, and 0.407, respectively) because a greater proportion of gamma diversity was subsumed within alpha diversity as scale increased. Using standard randomization methods, we also examined how community similarity differed between observed and randomized assemblages and how this difference was affected by spatial separation of species within habitat types and specialization of species to three habitat types (reef flats, crests, and slopes). If spatial separation within habitat types and/or habitat specialization (i.e., underdispersion) occurs, fewer species are shared among assemblages than the random expectation. When the locations of individual coral colonies were randomized within and among habitat types, community similarity was 46-47% higher than that for observed assemblages at all three scales. We predicted that spatial separation of coral species within habitat types should increase with scale due to dispersal/extinction dynamics in this insular system, but that specialization of species to different habitat types should not change because habitat differences do not change with scale. However, neither habitat specialization nor spatial separation within habitat types differed among scales. At the two larger scales, each accounted for 22-24% of the difference in community similarity between observed and randomized assemblages. At the smallest scale (transect-site), neither spatial separation within habitat types nor habitat specialization had significant effects on community similarity, probably due to the small size of transect samples. The results suggest that coral species can disperse among islands in an island group as easily as they can among sites on an island over time scales that are relevant to their establishment and persistence on reefs. 相似文献
1000.
Associations of forest bird species richness with housing and landscape patterns across the USA. 总被引:3,自引:0,他引:3
A M Pidgeon V C Radeloff C H Flather C A Lepczyk M K Clayton T J Hawbaker R B Hammer 《Ecological applications》2007,17(7):1989-2010
In the United States, housing density has substantially increased in and adjacent to forests. Our goal in this study was to identify how housing density and human populations are associated with avian diversity. We compared these associations to those between landscape pattern and avian diversity, and we examined how these associations vary across the conterminous forested United States. Using data from the North American Breeding Bird Survey, the U.S. Census, and the National Land Cover Database, we focused on forest and woodland bird communities and conducted our analysis at multiple levels of model specificity, first using a coarse-thematic resolution (basic models), then using a larger number of fine-thematic resolution variables (refined models). We found that housing development was associated with forest bird species richness in all forested ecoregions of the conterminous United States. However, there were important differences among ecoregions. In the basic models, housing density accounted for < 5% of variance in avian species richness. In refined models, 85% of models included housing density and/or residential land cover as significant variables. The strongest guild response was demonstrated in the Adirondack-New England ecoregion, where 29% of variation in richness of the permanent resident guild was associated with housing density. Model improvements due to regional stratification were most pronounced for cavity nesters and short-distance migrants, suggesting that these guilds may be especially sensitive to regional processes. The varying patterns of association between avian richness and attributes associated with landscape structure suggested that landscape context was an important mediating factor affecting how biodiversity responds to landscape changes. Our analysis suggested that simple, broadly applicable, land use recommendations cannot be derived from our results. Rather, anticipating future avian response to land use intensification (or reversion to native vegetation) has to be conditioned on the current landscape context and the species group of interest. Our results show that housing density and residential land cover were significant predictors of forest bird species richness, and their prediction strengths are likely to increase as development continues. 相似文献