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731.
José Martín Emilio Civantos Luisa Amo Pilar López 《Behavioral ecology and sociobiology》2007,62(2):173-179
Evidence for parasite-mediated sexual selection has been found in many species that use visual ornaments to attract females.
However, in many animals, variation in female responses to scents of parasitized males suggests that parasitic infections
might also affect information conveyed by pheromones (i.e., chemical ornaments). Thus, pheromones might also function in parasite-mediated
sexual selection. We show here that female lizards Psammodromus algirus responded differently to femoral gland secretions of males according to the parasite load and health of these males. Scents
of healthier males elicited more tongue flicks (a chemosensory behavior) by females, suggesting that these scents were more
attractive. Chemical analyses showed that parasite load and the T-cell-mediated immune response were related to the variability
in the proportions of some lipids in secretions of males. Further trials testing the chemosensory responses of females to
chemical standards indicated that females actually discriminated the chemicals related to males’ health from other chemicals
found in secretions. We suggest that these chemical ornaments may provide reliable information on the health and degree of
parasitic infection of a male. 相似文献
732.
P. W. Glynn S. B. Colley C. M. Eakin D. B. Smith J. Cortés N. J. Gassman H. M. Guzmán J. B. Del Rosario J. S. Feingold 《Marine Biology》1994,118(2):191-208
A comparative study of the reproductive ecology of the zooxanthellate, scleractinian corals Porites lobata Dana and P. panamensis Verrill was conducted from 1985 to 1991 in eastern Pacific reef environments that were severly impacted by the 1982–1983 El Niño warming events. P. lobata, a presumed broadcast spawner of large colony size, is widely distributed in the equatorial eastern Pacific, whereas P. panamensis, a brooder of small colony size, is abundant only on some reefs in Panamá. Both species were gonochoric with nearly 1:1 sex ratios in large study populations except for P. lobata at Caño Island that had 14% hermaphroditic colonies. Mature, unfertilized oocytes contained numerous zooxanthellae in both Porites species, and all planula developmental stages contained zooxanthellae in P. panamensis. Year-round sampling revealed high proportions of colonies with gonads, ranging from 30 to 68% in P. lobata and from 60 to 68% in P. panamensis. No clear relationship between numbers of reproductive colonies and the thermal stability of the habitat was evident in P. lobata: percent colonies with gonads at non-upwelling sites was 48 to 68% at Caño Island (Costa Rica) and Uva Island (Panamá), and at upwelling sites 30 to 50% at Saboga Island and Taboga Island (Panamá), and the Galápagos Islands (Ecuador). Similarly, 90% of all P. panamensis colonies were reproductive at Uva Island (a non-upwelling site), and 86% were reproductive at Taboga Island (an upwelling site). Upwelling at Taboga Island is seasonal, nevertheless P. panamensis produced mature gonads or planulae over most of the year (11 mo), whereas P. lobata exhibited reproductive activity during only 2 mo (May and June). No clear lunar periodicity was observed in P. panamensis (Taboga Island), but a high proportion of P. lobata showed increased gonadal development around full and new moon, especially at Caño and Uva Islands. Estimated fecundities were relatively high for P. lobata at Caño (4000 eggs cm-2 yr-1) and Uva (5200 eggs cm-2 yr-1) Islands, and notably low (70 to 110 eggs cm-2 yr-1) in the Galápagos Islands. P. panamensis mean fecundity at Taboga Island was 720 planulae cm-2 yr-1 or 4.0 mm3 cm-2 yr-1, which was lower than the egg volume production of P. lobata at Caño and Uva Islands (7.0 to 10.0 mm3 cm-2 yr-1). The capacity of P. lobata and P. panamensis to reproduce sexually supports the notion that eastern Pacific coral reef recovery may not be dependent on long-distance dispersal from central Pacific areas. However, sexual recruits of P. lobata are absent or uncommon at all eastern Pacific study sites while recruits of P. panamensis were common to abundant only at the Uva Island study site. Asexual fragmentation in P. lobata augments recruitment locally, but plays no role in P. panamensis recruitment. 相似文献
733.
Xavier Querol Josep M Parés Felicià Plana José Luis Fernández-Turiel Angel López-Solar 《Environmental geochemistry and health》1994,16(1):9-18
The bulk magnetic susceptibility of sediments from artificial and natural lakes around a large coal-fired power station in NE Spain has been measured. Higher magnetic susceptibility values are found in lake sediments located SE of the power station. This distribution of susceptibility values is compatible with environmental and meterological studies of emissions from the power station, which indicate a dominant SE plume direction. Mineralogical studies, by means of X-ray diffraction and scanning electron microscopy, show that the highest susceptibility values found in the sediments are caused by magnetic iron spinels in the fly ash that is transferred to the environment by the power station particulate emissions. After the quantitative mineralogical studies of fly ash, two different methods of fly ash content determination in the sediments have been devised, showing very similar results. The low background magnetic susceptibility of the sediments in the study area and the high susceptibility resulting from the input of magnetic fly ash particles allows both delimitation of the polluted area around the power station, and quantification of the fly ash input into the natural sediments. 相似文献
734.
Variation and persistence of the middle rocky intertidal community of central Chile,with and without human harvesting 总被引:2,自引:0,他引:2
Humans are an important intertidal predator in central Chile. Following a five-year study we report on the effects of the exclusion of humans from the rocky intertidal at Las Cruces, central Chile. The middle intertidal of harvested and non-harvested areas diverged in species diversity and composition during the experiment. In harvested areas the middle intertidal rocky shore was dominated throughout the study by a monoculture of mussels, Perumytilus purpuratus. When humans were excluded, the middle intertidal community switched to one dominated by barnacles (predominantly Jehlius cirratus and Chthamalus scabrosus); this community has persisted for at least three years, despite the presence of forces e.g. mussel larvae, that have the potential to alter the community structure. Such changes were mediated by the muricid gastropod Concholepas concholepas, a key-stone predator. As a consequence of the above changes, the species diversity, H', (primary space occupiers) in the non-harvested area increased from H'=0 at the beginning of the study in 1983 (when the middle intertidal community was dominated by mussels), to values ca H'=2 toward the middle of the study in 1984 (which coincided with the maximum predatory impact of C. concholepas) and subsequently decreasing to ca H'=0.5 at the end of the study in 1987 (when the middle intertida community was dominated by barnacles).Please address all correspondence to J. C. Castilla, Department of Zoology, University of Washington, Seattle, Washington 98195, USA, until March 1990 相似文献
735.
The effects of immigration on the behaviour of residents may have important implications for the local population characteristics. A manipulative laboratory experiment with yearlings of the common lizard (Lacerta vivipara) was performed to test whether the introduction of dispersing or philopatric individuals influences the short-term spacing behaviour of resident individuals. Staged encounters were carried out to induce interactions within dyads. The home cage of each responding individual was connected by a corridor to an unfamiliar “arrival cage” to measure the latency to leave their own home cage after each encounter. Our results showed that the time that pairs spent in close proximity was longer when a dispersing individual was introduced in the home cage. The latency to leave the home cage was longer after the introduction of a dispersing individual. These response variables were not influenced by the relative body sizes of contestants nor by the level of aggression towards each other. In contrast, the aggressive response was significantly influenced by the residency asymmetry established experimentally (“owner” of the home cage vs introduced individual). Our results suggest that the space use by resident individuals is influenced by the dispersal status of conspecifics. The potential ultimate causes driving this effect are discussed. 相似文献
736.
Summary. Geographic variations in the correspondence between diaspore phenotypes and disperser behavior are thought to determine the
evolution of plant-animal dispersal mutualisms. Helleborus foetidus is a widely distributed plant in Western Europe, which seeds bear a lipid rich elaiosome attracting ant dispersers. Laboratory
cross-tests were conducted to check the correspondence between diaspore phenotypes and ant preference in two localities of
the Iberian Peninsula, Caurel and Cazorla, separated by 750 km. Diaspores from Caurel were systematically preferred to those
from Cazorla by Formica lugubris (the major disperser at Caurel), and Aphaenogatser iberica and Camponotus cruentatus (both major dispersers at Cazorla). Further bioassays conducted on A. iberica only showed that differences in elaiosome traits were sufficient to explain ant preference. Separation of the lipid fractions
composing the elaiosome revealed that triglycerides, diglycerides and free fatty acids were all dominated by oleic acid. The
elaiosomes from Caurel contained relatively more free oleic acid but were less concentrated in linoleyl-containing triglycerides,
free palmitic acid and free linoleic acid than those from Cazorla. The three lipid fractions were attractive to ants but dummies
soaked with the free fatty acids extracted from Caurel were preferred to those from Cazorla. Taken together, these results
reinforce the idea that oleic acid is a major releaser of seed collection by ants and suggest that geographic variations in
free fatty acid composition affect the probability of diaspore removal by ants which in turn potentially determine plant demography. 相似文献
737.
Analyzing and predicting the development of foliar nutrient concentrations are important and challenging tasks in environmental monitoring. This article presents how linear sparse regression models can be used to represent the relations between different foliar nutrient concentration measurements of coniferous trees in consecutive years. In the experiments the models proved to be capable of providing relatively good and reliable predictions of the development of foliage with a considerably small number of regressors. Two methods for estimating sparse models were compared to more conventional linear regression models. Differences in the prediction accuracies between the sparse and full models were minor, but the sparse models were found to highlight important dependencies between the nutrient measurements better than the other regression models. The use of sparse models is, therefore, advantageous in the analysis and interpretation of the development of foliar nutrient concentrations. 相似文献
738.
The structure of megabenthic decapod crustacean assemblages on the Galician (north-west Spain) continental shelf (100 to
200 depth) and upper slope (200 to 500 m) was analyzed based on surveys carried out in autumn and spring, from 1980 to 1987.
Forty species belonging to 19 families were caught. The portunid crab Polybius henslowii, a species with pelagic phases, was the most abundant species, but displayed strong spatial and temporal fluctuations. Other
dominant species were the Norway lobster Nephrops norvegicus, the portunid Liocarcinus depurator, the galatheids Munida intermedia and M. sarsi, and the shrimps Solenocera membranacea, Plesionika heterocarpus, Pasiphaea sivado and Dichelopandalus bonnieri. Total abundance and biomass (average values excluding Polybius henslowii = 255 individuals and 2.06 kg/30 min tow) and species richness and diversity, H′ (6.85 species and H′ = 1.45 per tow) displayed a significant positive correlation with depth, and strong interannual fluctuations. The factors
determining community organization were depth and, to a lesser extent, spatial structure. There was clear evidence of bathymetric
zonation, differentiating between species characteristic of the slope (D. bonnieri and Pasiphaea sivado), shelf-slope edge (Macropipus tuberculatus, Pontophilus spinosus, Munida sarsi, S. membranacea, Processa spp.) and shelf (L. depurator, Macropodia tenuirostris, Paguridae and Chlorotocus crassicornis). The spatial zonation was related to changes in oceanography and sediment along the continental margin. Goneplax rhomboides, N. norvegicus, C. crassicornis and Alpheus glaber are benthic species which generally exhibit burrowing behaviour, and they were found mainly in the southern area where there
are fine sediments due to the outwelling from the Rías Baixas. Different benthopelagic shrimps (Pontophilus spinosus, Plesionika heterocarpus,Processa spp. and Pasiphaea sivado) were typical of the zone just north of Fisterra, characterized by a convergence of water masses bringing about an increase
in productivity due to upwelling. The benthic anomuran and brachyuran crabs Munida intermedia, M.␣sarsi, L.␣depurator and Macropipus tuberculatus were characteristic of the northwestern zone between Fisterra and Estaca, where the infauna reaches high biomass despite
coarser sediments with a lower concentration of organic material than in the southern area. Lastly, both the Paguridae and
Macropodia tenuirostris were species typically found in the waters in the northern shelf. Based on interannual changes in assemblage structure, two
periods could be distinguished: between 1980 and 1984, when Polybius henslowii, D. bonnieri and Pasiphaea sivado had abundance peaks; and another period from 1985 to 1987 when L. depurator, Munida intermedia, M.␣sarsi and Macropipus tuberculatus increased in abundance.
Received: 21 May 1996 / Accepted: 9 August 1996 相似文献
739.
In the asperillo dune system, Southwest Spain, lichen vegetation covering the dune sand, has a low species diversity but is
an important component of the perennial vegetation, providing stability, nutrients, and moisture to the soil layer. The Asperillo
dunes harbour (1) natural ecosystems, (2) disturbed systems affected by forestry activities where the natural vegetation is
eliminated, and (3) pine forest resulting from afforestation withPinus pinea since the end of the 1940s where the composition and abundance of the lichen flora has been drastically changed.
Our hypothesis was that the lichen species composition and distribution are influenced by the type and period of human intervention.
To test this hypothesis a 1.2 km × 1.1 km area, which includes zones with different degrees of conservation and perturbation,
consisting of five different habitats, was selected: well preservedJuniperus woodland,Pinus pinea plantations with dense scrub, dense scrub,P. pinea plantations cleared from scrub, and pioneer scrub in recent pine afforestation. In each area, randomly located 5m × 5 m homogeneous
plots were sampled. In each plot the cover of shrub and lichen species was recorded.
The first results show that lichen cover is higher in the most preserved areas,Cladonia mediterranea being the dominant species under theJuniperus phoenicea canopy. The lichen community changes in composition and abundance depending on the time elapsed since the last perturbation. 相似文献
740.
Malia Chevolot Peter H. J. Wolfs Jónbjörn Pálsson Adriaan D. Rijnsdorp Wytze T. Stam Jeanine L. Olsen 《Marine Biology》2007,151(4):1275-1286
Population genetic structure of the thorny skate (Amblyraja radiata) was surveyed in >300 individuals sampled from Newfoundland, Iceland, Norway, the Kattegat and the central North Sea. A 290-bp
fragment of the mt cytochrome-b gene was first screened by SSCP. Sequences of SSCP haplotypes revealed 34 haplotypes, 14 of
which were unique to Iceland, 3 to Newfoundland, 1 to Norway and 3 to the Kattegat. The global F
ST was weak but significant. Removal of the two Kattegat locations, which were the most differentiated, resulted in no significant
genetic differentiation. Haplotype diversity was high and evenly distributed across the entire Atlantic (h = 0.8) with the exception of the North Sea (h = 0.48). Statistical parsimony revealed a star-like genealogy with a central widespread haplotype. A subsequent nested clade
analysis led to the inference of contiguous expansion with evidence for long distance dispersal between Newfoundland and Iceland.
Historical demographic analysis showed that thorny skates have undergone exponential population expansion that started between
1.1 million and 690,000 years ago; and that the Last Glacial Maximum apparently had little effect. These results strongly
differ from those of a parallel study of the thornback ray (Raja clavata) in which clear structure and former refugial areas could be identified. Although both species have similar life history
traits and overlapping ranges, the continental shelf edge apparently does not present a barrier to migration in A. radiata, as it does for R. clavata. 相似文献