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501.
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503.
The spiny lobster, Panulirus argus, is predominantly nocturnal, remaining inside shelters during the day and foraging outside at night, presumably to minimize
predation risk. Predation risk generally decreases with increasing lobster size. Therefore, this study examined the hypothesis
that size would influence this basic circadian pattern. Video cameras continuously recorded the shelter occupancy of juvenile
lobsters (n = 72) having a carapace length (CL) of 30–62 mm that were tethered to shelters in a shallow reef lagoon. The lobsters’ shelter
occupancy was 100% during the day, but declined linearly from shortly before sunset to a minimum of 50% shortly after midnight
and then increased linearly, reaching 100% by 1 h after sunrise. The percent time the lobsters spent in the shelters followed
a similar trend, but there was wide variability at night (0–100%) for individual lobsters. Lobsters left their shelters 2–30
times night−1, with a majority of excursions lasting <10 min. These results suggest that juvenile P. argus minimize predation risk by remaining in their shelters as long as possible but offset the energetic cost of this behavior
by foraging close to their shelters for several short periods at night. This emergence pattern contrasts with those of early
benthic phase lobsters (<15 mm CL), which seldom leave their shelters, and adults (>80 mm CL), which have a dusk/early evening
peak in activity and leave the shelter for extended periods of time during the night. Furthermore, a minimum shelter occupancy
in the middle of the night appears especially well adapted to avoid exposure to daytime predators. Videotaped observations
also included interactions between lobsters and two dominant lobster predators, the triggerfish, Balistes capriscus, and the octopus Octopus cf. vulgaris. Lobsters responded differently to these predators: remaining in the shelter when attacked by a triggerfish and fleeing the
shelter when attacked by an octopus. Triggerfish were nearly twice as likely to attack a lobster that was outside of the shelter
than inside. Once under attack, however, a lobster had nearly the same chance of surviving if it was inside or outside. Results
suggest that the patterns of shelter use and emergence change as lobsters grow, probably reflecting the interplay between
perception of predation risk and the need to forage.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
504.
Olivier Monga Mamadou Bousso Patricia Garnier Valrie Pot 《Ecological modelling》2008,216(3-4):291-302
During the past 10 years, soil scientists have started to use 3D Computed Tomography in order to gain a clearer understanding of the geometry of soil structure and its relationships with soil properties. We propose a geometric model for the 3D representation of pore space and a practical method for its computation. Our basic idea consists in representing pore space using a minimal set of maximal balls (Delaunay spheres) recovering the shape skeleton. In this representation, each ball could be considered as a maximal local cavity corresponding to the “intuitive” notion of a pore as described in the literature. The space segmentation induced by the network of balls (pores) was then used to spatialize biological dynamics. Organic matter and microbial decomposers were distributed within the balls (pores). A valuated graph representing the pore network, organic matter and distribution of micro-organisms was then defined. Microbial soil organic matter decomposition was simulated by updating this valuated graph. The method was implemented and tested using real CT images. The model produced realistic simulated results when compared with data in the literature in terms of the water retention curve and carbon mineralization. A decrease in water pressure decreased carbon mineralization, which is also in accordance with findings in the literature. From our results we showed that the influence of water pressure on decomposition is a function of organic matter distribution in the pore space. As far as we know, this is the approach to have linked pore space geometry and biological dynamics in a formal way. Our next goal will be to compare the model with experimental data of decomposition using different soil structures, and to define geometric typologies of pore space shape that can be attached to specific biological and dynamic properties. 相似文献
505.
Amélia Viricel Allan E. Strand Patricia E. Rosel Vincent Ridoux Pascale Garcia 《Behavioral ecology and sociobiology》2008,63(2):173-185
Compared to terrestrial mammals, little is known of cetacean social systems as they are generally less accessible to behavioral
investigations due to their aquatic environment. The present study investigates group structure of the pelagic common dolphin,
Delphinus delphis, using genetic markers. Tissue samples from 52 individuals representing a recent live mass-stranding event were compared
to 42 single strandings taken from presumably different groups. The mass-stranding event occurred in 2002 on the French coast
of the English Channel, whereas the single strandings were collected between 1993 and 2003 along the western coast of France
(Bay of Biscay and English Channel). Analysis of mitochondrial DNA control region sequences indicated that genetic variability
within the mass-stranded pod was similar to variability observed in single strandings. The mass-stranded group was composed
of 41 different mitochondrial haplotypes or matrilines while the single strandings revealed 29 different haplotypes. Analysis
of 11 microsatellite loci revealed that average relatedness of the mass-stranded pod was not different from average relatedness
among all single strandings suggesting that individuals within the group had no closer kin relationships than animals taken
from presumably different groups. These results do not support a matriarchal system and suggest that common dolphins constituting
a pod are not necessarily genetically related. 相似文献
506.
María J Lombardero Patricia Vázquez-Mejuto Matthew P Ayres 《Ecological applications》2008,18(5):1171-1181
Plantations of rapidly growing trees are becoming increasingly common because the high productivity can enhance local economies, support improvements in educational systems, and generally improve the quality of life in rural communities. Landowners frequently choose to plant nonindigenous species; one rationalization has been that silvicultural productivity is enhanced when trees are separated from their native herbivores and pathogens. The expectation of enemy reduction in nonindigenous species has theoretical and empirical support from studies of the enemy release hypothesis (ERH) in the context of invasion ecology, but its relevance to forestry has not been evaluated. We evaluated ERH in the productive forests of Galicia, Spain, where there has been a profusion of pine plantations, some with the indigenous Pinus pinaster, but increasingly with the nonindigenous P. radiata. Here, one of the most important pests of pines is the indigenous bark beetle, Tomicus piniperda. In support of ERH, attacks by T. piniperda were more than twice as great in stands of P. pinaster compared to P. radiata. This differential held across a range of tree ages and beetle abundance. However, this extension of ERH to forestry failed in the broader sense because beetle attacks, although fewer on P. radiata, reduced productivity of P. radiata more than that of P. pinaster (probably because more photosynthetic tissue is lost per beetle attack in P. radiata). Productivity of the nonindigenous pine was further reduced by the pathogen, Sphaeropsis sapinea, which infected up to 28% of P. radiata but was absent in P. pinaster. This was consistent with the forestry axiom (antithetical to ERH) that trees planted "off-site" are more susceptible to pathogens. Fungal infections were positively correlated with beetle attacks; apparently T. piniperda facilitates S. sapinea infections by creating wounds and by carrying fungal propagules. A globally important component in the diminution of indigenous flora has been the deliberate large-scale propagation of nonnative trees for silviculture. At least for Pinus forestry in Spain, reduced losses to pests did not rationalize the planting of nonindigenous trees. There would be value in further exploration of relations between invasion ecology and the forestry of nonindigenous trees. 相似文献
507.
Leeann T. Reaney Golo Maurer Patricia R. Y. Backwell Celeste C. Linde 《Behavioral ecology and sociobiology》2012,66(7):1017-1024
The fiddler crab Uca mjoebergi mates both underground in male-defended burrows and on the surface near female-defended burrows. The reproductive tract of Uca species facilitates last-male precedence, suggesting that males that do not guard-mated females are likely to gain very little paternity if the female re-mates with another male. Here, we test the reproductive success of burrow and surface matings using paternity analysis. We found that 100?% of the females that mated in burrows extruded a clutch of eggs. Furthermore, we show conclusively, for the first time in a fiddler crab species, that last-male sperm precedence results in the majority of the female’s eggs being fertilised by the burrow-mated male. In contrast, surface matings resulted in significantly fewer females extruding eggs (5.6?%). Paternity analysis also revealed that more than half of the clutches from burrow-mated females showed low levels of extra-pair paternity from previous matings. Although multiple matings appear common in U. mjoebergi, burrow-mated males that guard females are guaranteed a successful mating with extremely high rates of assured paternity. Surface matings therefore appear to be an opportunistic tactic that may increase male reproductive success in a highly competitive environment. 相似文献
508.
Management in fire-prone ecosystems relies widely upon application of prescribed fire and/or fire surrogate (e.g., forest thinning) treatments to maintain biodiversity and ecosystem function. Recently, published literature examining wildlife response to fire and fire management has increased rapidly. However, none of this literature has been synthesized quantitatively, precluding assessment of consistent patterns of wildlife response among treatment types. Using meta-analysis, we examined the scientific literature on vertebrate demographic responses to burn severity (low/moderate, high), fire surrogates (forest thinning), and fire and fire surrogate combined treatments in the most extensively studied fire-prone, forested biome (forests of the United States). Effect sizes (magnitude of response) and their 95% confidence limits (response consistency) were estimated for each species-by-treatment combination with two or more observations. We found 41 studies of 119 bird and 17 small-mammal species that examined short-term responses (< or =4 years) to thinning, low/moderate- and high-severity fire, and thinning plus prescribed fire; data on other taxa and at longer time scales were too sparse to permit quantitative assessment. At the stand scale (<50 ha), thinning and low/moderate-severity fire demonstrated similar response patterns in these forests. Combined thinning plus prescribed fire produced a higher percentage of positive responses. High-severity fire provoked stronger responses, with a majority of species possessing higher or lower effect sizes relative to fires of lower severity. In the short term and at fine spatial scales, fire surrogate forest-thinning treatments appear to effectively mimic low/moderate-severity fire, whereas low/moderate-severity fire is not a substitute for high-severity fire. The varied response of taxa to each of the four conditions considered makes it clear that the full range of fire-based disturbances (or their surrogates) is necessary to maintain a full complement of vertebrate species, including fire-sensitive taxa. This is especially true for high-severity fire, where positive responses from many avian taxa suggest that this disturbance (either as wildfire or prescribed fire) should be included in management plans where it is consistent with historic fire regimes and where maintenance of regional vertebrate biodiversity is a goal. 相似文献
509.
Tracking habitat and resource use for the jumbo squid Dosidicus gigas: a stable isotope analysis in the Northern Humboldt Current System 总被引:1,自引:0,他引:1
Juan Argüelles Anne Lorrain Yves Cherel Michelle Graco Ricardo Tafur Ana Alegre Pepe Espinoza Anatolio Taipe Patricia Ayón Arnaud Bertrand 《Marine Biology》2012,159(9):2105-2116
To determine the habitat and resource use of Dosidicus gigas in the Northern Humboldt Current System, we analysed carbon and nitrogen stable isotopes of 234 individuals collected during 2008–2010. Large variations in mantle stable isotope ratios were recorded, with values ranging from −19.1 to −15.1 ‰ (δ13C) and from 7.4 to 20.5 ‰ (δ15N). Most of the variation was explained by latitude, followed by distance to shelf break for carbon and by squid size for nitrogen. Latitudinal variations with increasing values from north to south were also found in zooplankton samples and were related to changes in isotope baseline values probably due to oxygen minimum zones that occur off Peru. This similar latitudinal trend in both zooplankton and D. gigas samples reveals that D. gigas is a relatively resident species at the scale of its isotopic turnover rate (i.e. a few weeks), even if this is not necessarily the case at the scale of its life. A small but significant size effect on δ13C values suggests that jumbo squid perform offshore–onshore ontogenic migration, with juveniles distributed offshore. For nitrogen, the high inter-individual variability observed with mantle length indicates that D. gigas can prey on a high variety of resources at any stage of their life cycle. This large-scale study off the coast of Peru provides further evidence that D. gigas have the capability to explore a wide range of habitats and resources at any stage of their life. 相似文献
510.
Michael R. Elliott Patricia F. Waller Trivellore E. Raghunathan Jean T. Shope Roderick J. A. Little 《Journal of Safety Research》2000,31(4):229-242
This analysis examines the ability of previous offenses to predict future high-risk offenses, and similarly, the ability of crashes to predict future high-risk crashes, using the complete driver history data (up to 9 years) for a set of young Michigan subjects. As expected, those with previous ticketed offenses or reported crashes are at greater risk for future offenses or crashes; with a previous-year serious offense doubling the odds of serious offenses during the subsequent year, and a previous-year at-fault crash increasing the odds of subsequent-year at-fault crashes by nearly 50%. There is modest evidence that serious offenses and at-fault crashes may better predict subsequent behavior in females and in more experienced drivers. This latter finding is also evidenced by the fact that records of these young drivers are less predictive of subsequent driving history than is true for records of all drivers in general found in other studies. This suggests that, in the early stages of driving, offenses and crashes are, at least in part, attributable to inexperience, and hence, characteristic of all beginning drivers. 相似文献