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51.
The barnacle, Balanus glandula has recently invaded along the Pacific coast of eastern Hokkaido, Japan. To evaluate the direct and indirect effects of endemic seaweeds, barnacles, and invertebrate predators on the abundance of B. glandula on the rocky intertidal coast of eastern Hokkaido, we conducted a field experiment from June 2011 to October 2012 in which we manipulated the presence or absence of these factors. Seaweeds showed no significant effect on the abundance of B. glandula. The endemic barnacle Chthamalus dalli and the invertebrate predator Nucella lima reduced the abundance of B. glandula. However, the simultaneous influence of N. lima and C. dalli was compensative rather than additive, probably due to keystone predation. These findings suggest that competition by the endemic barnacle C. dalli and predation by the invertebrate predator N. lima decreased the abundance of B. glandula, but that N. lima predation on C. dalli weakened the negative influence of C. dalli on B. glandula. The implications of these findings are twofold: the endemic competitor and invertebrate predator may have played important roles in decreasing the abundance of B. glandula in natural habitats, and conservation of endemic invertebrate predators may be crucial to impede the establishment and survival of introduced barnacles in rocky intertidal habitats. 相似文献
52.
We conducted an artificial pond experiment to assess the direct and indirect effects of predation on Bufo viridis tadpoles. We ran three treatments: free Anax (unrestrained predatory dragonfly nymph Anax imperator), caged Anax (non-consumptive effects), and control (no Anax). Anax showed both strong consumptive and non-consumptive effects on Bufo tadpoles. Free Anax eliminated all of the tadpoles within six days. Tadpoles preferred the shady side of the ponds. Caged Anax caused tadpoles to increase their spatial preferences. Tadpoles avoided the center of the pond, and in the presence of the
caged predator, they were found in the center even less. Tadpoles also showed a strong preference for crowding together, and
in the presence of a caged Anax, they tended to crowd more. Moreover, Bufo metamorphosed earlier and at a larger size in the caged Anax ponds, possibly by providing extra food resources due to the extra organic matter excreted by the predators.
Handling editor: K. Martens 相似文献
53.
This article explores factors that shape population structure in novel environments that have received scant theoretical attention: cities. Urban bird populations exhibit higher densities and lower diversity. Some work suggests this may result from lower predation pressure and more predictable and abundant resources. These factors may lead to populations with few winners and many losers regarding access to food, body condition, and reproductive success. We explore these hypotheses with an individual-energy-based competition model with two phenotypes of differing foraging ability. We show that low frequency resource fluctuations favor strong competitors and vice versa. We show that low predation skews equilibrium populations in favor of weak competitors and vice versa. Increasing the time between resource pulses can thus shift population structure from weak to strong competitor dominance. Given recent evidence for more constant resource input and lower predation in urban areas, the model helps understand observed urban bird population structure. 相似文献
54.
Baldauf SA Thünken T Frommen JG Bakker TC Heupel O Kullmann H 《International journal for parasitology》2007,37(1):61-65
Many parasites with complex life cycles increase the chances of reaching a final host by adapting strategies to manipulate their intermediate host's appearance, condition or behaviour. The acanthocephalan parasite Pomphorhynchus laevis uses freshwater amphipods as intermediate hosts before reaching sexual maturity in predatory fish. We performed a series of choice experiments with infected and uninfected Gammarus pulex in order to distinguish between the effects of visual and olfactory predator cues on parasite-induced changes in host behaviour. When both visual and olfactory cues, as well as only olfactory cues were offered, infected and uninfected G. pulex showed significantly different preferences for the predator or the non-predator side. Uninfected individuals significantly avoided predator odours while infected individuals significantly preferred the side with predator odours. When only visual contact with a predator was allowed, infected and uninfected gammarids behaved similarly and had no significant preference. Thus, we believe we show for the first time that P. laevis increases its chance to reach a final host by olfactory-triggered manipulation of the anti-predator behaviour of its intermediate host. 相似文献
55.
Studies of inducible defenses have traditionally examined prey responses to one predator at a time. However, prey in nature
encounter combinations of predators that should force them to produce phenotypic compromises. We examined how snails (Helisoma trivolvis) alter their phenotype in the presence of three different predator species that were presented alone and in pairwise combinations.
When snails were exposed to each predator alone, they formed predator-specific defenses that reflected the differences in
each predator’s foraging mode. When snails were exposed to pairwise combinations of predators, their phenotype was dependent
on their ability to detect each predator, the risk posed by each predator, and the effectiveness of a given defense against
each predator. Consequently, responses to combined predators were typically biased towards one of the predators in the pair.
This suggests that prey facing combined predators do not form simple intermediate defenses and, as a result, may experience
enhanced mortality risk when they encounter natural predator regimes. 相似文献
56.
Risk-sensitive hatching is adaptive for species facing a trade-off between egg-stage and post-hatching risks, and environmental
variation in one or both stages. Such plasticity has been found in amphibians, fishes, reptiles and spiders, with red-eyed
treefrogs (Agalychnis callidryas) being the best-studied case. We assessed hatching plasticity and egg- and larval-stage risks in a closely related, syntopic
species, the gliding leaf-frog (Agalychnis spurrelli). We found a lower hatching response to egg-eating snakes in A. spurrelli (9–28% of embryos escaped) than in A. callidryas (59–80% escaped). Levels of snake predation were similarly high for clutches of both species monitored at a pond in Costa
Rica, and in fish predation experiments early-hatched A. spurrelli tadpoles were more vulnerable than later hatchlings, as has been shown for A. callidryas. A. spurrelli thus face a risk trade-off similar to A. callidryas, and likely would benefit from predator-induced hatching; their lower responsiveness to snakes appears nonadaptive. A. spurrelli embryos showed a stronger hatching response (57% hatched in 1 h) to submergence underwater than to snake attacks even though
submergence is a less frequent risk. This suggests they have a greater capacity for early hatching than is expressed in the
context of snake attacks, but have much lower sensitivity to snake cues than to flooding cues. Development in A. spurrelli is accelerated compared to syntopic A. callidryas, and spontaneous hatching is earlier and more synchronous. This is congruent with predictions based on selection by egg predators
in the absence of a strong escape hatching response. 相似文献
57.
First Passage Time Analysis of Animal Movement and Insights into the Functional Response 总被引:2,自引:0,他引:2
Movement plays a role in structuring the interactions between individuals, their environment, and other species. Although
movement models coupled with empirical data are widely used to study animal distribution, they have seldom been used to study
search time. This paper proposes first passage time as a novel approach for understanding the effect of the landscape on animal
movement and search time. In the context of animal movement, first passage time is the time taken for an animal to reach a
specified site for the first time. We synthesize current first passage time theory and derive a general first passage time
equation for animal movement. This equation is related to the Fokker–Planck equation, which is used to describe the distribution
of animals in the landscape. We illustrate the first passage time method by analyzing the effect of territorial behavior on
the time required for a red fox to locate prey throughout its home range. Using first passage time to compute search times,
we consider the effect of two different searching modes on a functional response. We show that random searching leads to a
Holling type III functional response. First passage time analysis provides a new tool for studying how animal movement may
influence ecological processes. 相似文献
58.
Erika P. J. Britto Manoel G. C. GondimJr. Jorge B. Torres Komi K. M. Fiaboe Gilberto J. Moraes Markus Knapp 《BioControl》2009,54(3):363-368
Predatory behaviour and reproductive output of the ladybird beetle Stethorus tridens Gordon as function of the tomato red spider mite (TRSM), Tetranychus evansi Baker & Pritchard, densities was investigated in the laboratory. Adult female of S. tridens were isolated in cylindrical plastic arenas, containing a leaf disc of Solanum americanum Mill. with 5, 20, 40, 60, 80 or 100 T. evansi nymphs. The number of prey consumed and eggs laid were evaluated daily for ten consecutive days, starting at the oviposition.
Oviposition of S. tridens was positively correlated with prey consumption and lower threshold prey consumption for S. tridens laying eggs was 16.3 mites per day. The instantaneous rate of attack (ca. discovery area) and the handling time were 0.0062 h−1 and 0.83 h, and 0.00254 h−1 and 0.78 h, respectively, for predators at the 1st- and 10th-oviposition day. The predator exhibited a type II functional
response at 1st- and 10th-oviposition day with a maximum consumption per predator of 33 T. evansi nymphs per day at the highest prey density. The ladybird beetle S. tridens is often collected associated with red spider mite colonies on solanaceous wild plants and the results suggest the potential
of this ladybird beetle to control T. evansi in tomatoes crops.
Handling editor: Eric Lucas. 相似文献
59.
M. Kosloski 《Journal of experimental marine biology and ecology》2011,396(2):115-121
The ability to assign lethal traces left on prey to particular durophagous predators enhances our understanding of predation pressure in the fossil record. To determine whether stone crabs (Menippe mercenaria Say 1818) leave diagnostic traces in the act of feeding on hard clams (Mercenaria mercenaria Linnaeus 1758), live clams were offered to crabs in laboratory aquaria over several months and the fragments produced during predation were examined for diagnostic breakage patterns. These fragments were then compared both macroscopically and using scanning electron microscopy to the fracture patterns produced by tumbling clams in a rock tumbler which simulated breakage during transport in the surf zone, and crushing clams using an Instron which simulated breakage resulting from sediment compaction. Fossil specimens of Mercenaria mercenaria were also examined to determine whether the criteria for recognizing predation traces generated experimentally could be recognized. While not all acts of predation produce diagnostic traces, when larger fragments (greater than 50% shell remaining) are produced during feeding, predatory-diagnostic breakage ranges from 70 to 80%. Macroscopic breakage patterns generated during the predation experiments were also present in fossil specimens. Damage caused by abiotic mechanisms (tumbling and crushing) is highly unlikely to be confused with damage produced by this predator. 相似文献
60.
Peter McHugh Phaedra Budy Gary Thiede Erin VanDyke 《Environmental Biology of Fishes》2008,81(1):63-75
Nonnative trout invasions have caused the widespread decline of cutthroat trout populations in western North America. In contrast
to other nonnative salmonids, the role of nonnative brown trout in native cutthroat trout decline is poorly understood. Specifically,
the level of ecological similarity that occurs between these species and the importance of other trophic mechanisms (e.g.,
predation) in their interactions are key uncertainties. We evaluated the trophic relationships of brown trout and cutthroat
trout in a northern Utah river using a combination of diet and stable isotope analyses. We compared the dietary habits of
these two species using multiple and complementary measures. Based on both stomach contents and δ13C signatures, we found that these species consumed a similar and opportunistic diet (i.e., they were nonselective in their
foraging patterns). However, at most sizes, brown trout ingested larger prey—including fishes—and occupied a higher relative
trophic position (i.e., δ15N) than cutthroat trout. Overall, these results demonstrate a high degree of dietary similarity and therefore strengthen earlier
conclusions regarding interspecific competition between these two species. Our study, when considered alongside the work of
others, suggests there is potential for predatory interactions between these species (i.e., brown trout preying on small cutthroat
trout). We believe that future research on brown trout–cutthroat trout interactions should consider predatory effects in greater
detail.
相似文献
Peter McHughEmail: |