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1.
In the present study, the effect of chemical cues from two fish species (mosquitofish and pumpkinseed), at different concentrations,
was tested in life history experiments with Daphnia longispina. The two fish species used represent the most abundant planktivores of many Mediterranean shallow lakes (SW Europe), where
the indigenous fish communities have been replaced by such exotic assemblages. Results have shown a similar response of D. longispina to both fish species: kairomones stimulated daphnids to produce more offspring, which resulted in higher fitness (r), relatively to a fishless control. Fish presence also induced an earlier first reproduction, a smaller size at maturity
of daphnids, and the production of smaller-sized neonates. Significant correlations with fish concentration (indirect measure
of fish kairomone concentration) were found for size at maturity and neonate size, for both fish species. These results are
in accordance to the “positive response” observed by other authors, which represents a defence mechanism to face losses caused
by fish predators. The chemically mediated size reduction of mature females and neonates is an adaptive response to the size-selective
predation exerted by fish. Pumpkinseed introduction is very recent in the lake of origin of the daphnids used in the experiments
and its kairomone produced similar effects to mosquitofish in the life history of D. longispina. These results are contrary to the existence of a species-specific kairomone and support the hypothesis of a general fish
kairomone.
Guest editor: Piet Spaak
Cladocera: Proceedings of the 7th International Symposium on Cladocera 相似文献
2.
Species with complex life cycles (e.g., aquatic larvae, terrestrial adults) are expected to shorten the time spent in the
larval stage if mortality risks are high, a trade-off that lowers predation risk at the cost of reduced time for growth and
thus smaller adult size. We tested these predictions by comparing the timing of and size at emergence for two relatively large
and common invertebrate mesopredator species (Isoperla montana and Rhyacophila vibox) that inhabit small coastal streams, with and without predatory fish, in eastern Canada. Contrary to expectations based on
predation risk–foraging trade-off theory, individuals of both invertebrate species tended to be larger rather than smaller
in streams with fish than in fishless streams. The patterns were consistent, however, with the expected ecological effects
of top predators on food webs, where fish lower abundances of invertebrate mesopredators, increasing resource availability
and thus growth rates for the remaining individuals. We conclude that variation among streams in size at emergence is better
explained by the impact of fish on resource availability than to behavioural or life history trade-offs occurring under risk
of predation. 相似文献
3.
Landmark‐based geometric morphometric analysis was used to detect differences in scale shape between ecologically distinct phenotypes of Arctic charr Salvelinus alpinus coexisting in the same lake. Relative warp analysis and standard multivariate analyses of the partial warps, obtained after a Procrustes superimposition, showed that scale landmarks were efficient in discriminating among two closely related alternative phenotypes within each of the two lakes. In Loch Tay, S. alpinus exhibited a bimodal body size‐frequency distribution among sexually mature fish, whereas in Loch Awe, S. alpinus are unimodal in body size but segregated into two distinct spawning phenotypes. In both lakes, alternative phenotypes showed significant differences in foraging ecology, habitat use and life history. It is probable that differences in scale shape reflect differences in ecology of these forms. 相似文献
4.
5.
G.L. Poletta A. Larriera E. Kleinsorge M.D. Mudry 《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》2008,650(2):202-209
Caiman latirostris is one of the two crocodilian species that inhabit Argentina. In this country, as a consequence of agricultural frontiers expansion during the last years, many areas of the geographic distribution of the broad snouted caiman overlap with regions of intensive agricultural activity. Contaminants released to the environment may induce genetic alterations in wildlife, which could lead to mutations and/or carcinogenesis. Up to the moment, no studies had been made concerning the possibbility to apply biomarkers of genotoxic evaluation in C. latirostris.The aim of this study was to adapt two widely used genotoxic techniques, the comet assay and the micronucleus test, for their application in C. latirostris and to determine the baseline values in this species, in order to establish its suitability as a sentinel organism for future genotoxic monitoring of environmental pollutants.A total of 41 juvenile caimans of 4 months old (FMO) and 10 months old (TMO) were used. Genotoxic techniques were applied on peripheral blood erythrocytes introducing the necessary modifications required by the material, which are presented here.Our results show that baseline values of DNA damage are quite stable among juvenile caimans (MN: FMO animals 0.87 ± 0.74 and TMO animals 1.04 ± 0.92; DI: FMO animals 103.40 ± 3.36 and TMO animals 120.08 ± 11.33), being independent of the nest of origin, sex and size of the animals and confirm the potential value of both short term tests as accurate screening tools for the evaluation of genotoxic agents in C. latirostris. This is the first reference to the application of genotoxic techniques on C. latirostris and the second in crocodilians.Data provided here will be useful for future studies involving the biomonitoring of natural regions where C. latirostris occurs, employing this species as a sentinel organism for genotoxic assessment of environmental pollutants. 相似文献
6.
Synopsis The behaviour of three piranha species,Serrasalmus marginatus, S. spilopleura, andPygocentrus nattereri, and their prey fishes was studied underwater in the Pantanal region, Mato Grosso, Brazil. General habits, predatory tactics, feeding behaviour, and social interactions while foraging, as well as defensive tactics of prey fishes were observed.S. marginatus is solitary whereas the other two species live in shoals; their agonistic behaviour varies accordingly, the simplest being displayed by the solitary species. Predatory tactics and feeding behaviour also vary:S. spilopleura shows the most varied diet and highly opportunistic feeding strategy, which includes aggressive mimicry. The solitaryS. marginatus, besides fin and scale-eating, occasionally cleans larger individuals ofP. nattereri. Several cichlid species display defensive tactics clearly related to piranha attacks: tail protecting, watching, and confronting the predator are the most commonly observed behaviours. Piranhas seem to strongly influence use of habitat, social structure, and foraging mode of the fish communities. 相似文献
7.
We review recent works on different life history variables of cladoceran taxa in tropical and temperate freshwater bodies,
comparing the strategies that cladocerans have evolved to adapt to contrasting environmental conditions in the two geographical
regions. These life-history parameters relate to age and size at maturity, survival, fecundity, life-expectancy at birth,
lifespan, gross, and net reproductive rates, generation time, the rate of population increase, peak population density and
day of peak abundance. We also discuss the role of photoperiod and temperature on some of these life history parameters. We
found a general paucity of experimental work and field data in tropics on cladocerans. There is very limited information on
the few Daphnia species found in the tropics. The misconception of low species diversity of cladocerans in the tropics arose due to several
reasons including lack of extensive and intensive field collections. Higher water temperatures apparently promote permanent
infestation of tropical waters with toxic cyanobacteria, which reduce the zooplankton diversity. In addition to higher temperatures
in the tropics, the year-round high predation pressure of planktivorous fish probably causes the tropical species, particularly
in pelagic habitats, to reach maturity earlier (< 3 days) than in temperate regions. Species of Daphnia in temperate regions are particularly adapted to living at food concentrations that are much lower and seasonably more variable
than those for tropical genera such as Diaphanosoma. This is further corroborated by the more than an order of magnitude higher threshold food concentration (TFC) for tropical
Cladocera than for their temperate counterparts. Fecundity patterns differ between tropical and temperate cladoceran taxa:
cultured under optimal temperature regimes, tropical taxa have fewer eggs than temperate species of a comparable body size.
Predation pressure may act differently depending on the size of the cladoceran neonates and thus on their population size
structure. Global warming and climate changes seem to affect the behaviour (migration), distribution, and abundance of cladocerans.
Apparently, in direct response to these changes, the possibility of encountering the tropical cladocerans in the northern,
temperate hemisphere (bioinvasions) is on the rise. 相似文献
8.
9.
Synopsis Vision plays an important role in the early life history of fishes. We investigated the ontogenetic changes in visual acuity
of early life history stages of alewife,Alosa pseudoharengus, yellow perch,Perca flavescens and bloater,Coregonus hoyi, across a range of sizes. Acuities were determined through histological examination of the retinae of larvae. Reactive distances
of larvae to prey were estimated through videophotography of their response to prey and were then converted to measurements
of visual angle. Both measures of visual ability improved with size (age) for all species. When behavioural and anatomical
measures of ability were compared as a function of size, the data indicate that fish are anatomically more capable of seeing
objects than the behavioural response suggests. In two of the three species, the relationship between histological acuity
and visual angle was not constant. These results may indicate that while vision may limit initial rates of encounter and feeding,
increases in visual acuity mean that in older stages limitations on encounter and feeding are more likely to be behavioural.
Furthermore, these results indicate that encounter rates based upon histological estimates of visual acuity will be greater
than comparable estimates based upon reactive distances. We recommend calculation of encounter rates based upon reactive distances.
Present address: Department of Biology, McGill University, 1205 Ave, Dr. Penfield, Montreal, PQ H3A 1B1, Canada 相似文献
10.
The peak echolocation frequency of insectivorous bats generally declines as body size increases. However, there are notable
exceptions to this rule, with some species, such as Rhinolophus clivosus, having a higher than expected peak frequency for their body size. Such deviations from allometry may be associated with
partitioning of foraging habitat (the foraging habitat hypothesis) or insect prey (the prey detection hypothesis). Alternatively,
the deviations may be associated with the partitioning of sonar frequency bands to allow effective communication in a social
context (the acoustic communication hypothesis). We tested the predictions of these hypotheses through comparisons at the
family, clade and species level, using species of rhinolophids in general and R. clivosus, a species with a wide distribution, as a specific test case. We compared the wing parameters, echolocation frequency and
ecology of R. clivosus to those of the sympatric R. capensis. Rhinolophus clivosus has a much higher echolocation frequency than predicted from its wing loading or body mass. Furthermore, contrary to the
predictions of the foraging habitat hypothesis, we found no difference in foraging habitat between R. clivosus and R. capensis. The size range of insect prey taken by the two species also overlapped almost completely, contrary to the prey detection
hypothesis. On the other hand, the variation of echolocation frequencies around the allometric relationship for rhinolophids
was smaller than that for Myotis spp., supporting the prediction of the acoustic communication hypothesis. We thus propose that the relatively high peak frequency
of R. clivosus is the result of partitioning of sonar frequency bands to minimize the ambiguity of echolocation calls during social interactions. 相似文献
11.
Jean‐Bernard Dongmo Champlain Djieto‐Lordon Pierre Ngassam 《African Journal of Ecology》2015,53(3):312-319
Evidence of sexual dimorphism in body size and the existence of morphological differences were studied in the yellow‐whiskered Greenbul Andropadus latirostris. We measured fresh body weight and seven linear parameters of external morphology in mature individuals of this species from three localities in Cameroon and two localities in Ghana. Based on general linear model analysis, we showed that males are significantly larger than females. We applied a discriminant analysis on eight morphometric parameters to create two discriminant functions, one for each country. The overall rate of well‐classified birds was 93.3% for Cameroon and 92.7% for Ghana. Wing length was the most accurate character for separating the sexes in both study areas. Significant sexual size dimorphism might be explained by sexual selection on male competitive ability and intraspecific competition. We also found morphological divergence in this species between the two study areas, including marked differences in size of the beak. This work provides statistical evidence of a substantial sexual size dimorphism in A. latirostris and geographic variation in morphology. 相似文献
12.
Different growth responses to temperature and resource limitation in three fly species with similar life histories 总被引:3,自引:0,他引:3
Wolf U. Blanckenhorn 《Evolutionary ecology》1999,13(4):395-409
Growth responses to temperature and resource limitation in three dipteran species with similar life histories were compared.
With respect to current life history theory, two points are raised. First, growth rate in real time increased steeply with
temperature in all species, following the standard pattern. However, when expressed in physiological time growth rate increased
as temperature decreased in the yellow dung fly Scathophaga stercoraria, remained approximately constant in Sepsis cynipsea, and increased in Drosophila melanogaster. These responses can be understood as adaptations to climate and seasonality. It is concluded that some patterns of adaptation
may be more easily interpreted if, and some may even go undetected unless, they are analysed in physiological time. Second,
a decrease in body size, development rate and growth rate when resources are limited is believed to be nearly universal and
generally predicted by life history models. Despite their similar life histories, the three species investigated showed qualitatively
different growth responses to larval food shortage. At unlimited resources, yellow dung flies showed the fastest initial larval
body mass gain per unit time, while those of S. cynipsea and D. melanogaster were lower and about equal. The period of no body mass gain at the end of larval development was longest in S. stercoraria and shortest in S. cynipsea. When facing resource limitation, S. stercoraria emerged smaller but earlier (thus nearly maintaining their growth rate), S. cynipsea smaller after the same development period, and D. melanogaster smaller and later (showing reduced and much reduced growth, respectively). It is concluded that whether growth really slows
when resources are limited depends on the precise ecological circumstances of the species in question. More refined models,
particularly those where mortality costs are independent of time, and more experiments are necessary to account for the variation
in growth and size and age at maturity present in nature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Foraging behavior as a determinant of asymmetric competitive interaction between two ant species in a tropical agroecosystem 总被引:4,自引:0,他引:4
Ivette Perfecto 《Oecologia》1994,98(2):184-192
This work is concerned with elucidating competitive interactions between two neotropical ants, Solenopsis geminata and Pheidole radoszkowskii, focusing on their foraging behavior. When released from competition from P. radoszkowskii, S. geminata increased its foraging activity. On the other hand, when released from competition from S. geminata, P. radoszkowskii did not respond, demonstrating asymmetric competition between the two species. Foraging experiments showed that P. radoszkowskii is more efficient at finding food resources, whereas S. geminata is better at defending the resources once they are encountered. These differences in foraging behavior appear to permit the coexistence of these two species. The practical implications of the results for the management of ant communities in tropical agroecosystems is discussed with respect to the potential use of ants as natural enemies. 相似文献
14.
Life history theory predicts that individuals will allocate resources to different traits so as to maximize overall fitness. Because conditions experienced during early development can have strong downstream effects on adult phenotype and fitness, we investigated how four species of synovigenic, larval-pupal parasitoids that vary sharply in their degree of specialization (niche breadth) and life history (Diachasmimorpha longicaudata, Doryctobracon crawfordi, Opius hirtus and Utetes anastrephae), allocate resources acquired during the larval stage towards adult reproduction. Parasitoid larvae developed in a single host species reared on four different substrates that differed in quality. We measured parasitoid egg load at the moment of emergence and at 24 h, egg numbers over time, egg size, and also adult size. We predicted that across species the most specialized would have a lower capacity to respond to changes in host substrate quality than wasps with a broad host range, and that within species, females that emerged from hosts that developed in better quality substrates would have the most resources to invest in reproduction. Consistent with our predictions, the more specialized parasitoids were less plastic in some responses to host diet than the more generalist. However, patterns of egg load and size were variable across species. In general, there was a remarkable degree of reproductive effort-allocation constancy within parasitoid species. This may reflect more “time-limited” rather than “egg-limited” foraging strategies where the most expensive component of reproductive success is to locate and handle patchily-distributed and fruit-sequestered hosts. If so, egg costs, independent of degree of specialization, are relatively trivial and sufficient resources are available in fly larvae stemming from all of the substrates tested. 相似文献
15.
For insects that develop inside discrete hosts, both host size and host quality constrain offspring growth, influencing the evolution of body size and life history traits. Using a two-generation common garden experiment, we quantified the contribution of maternal and rearing hosts to differences in growth and life history traits between populations of the seed-feeding beetle Stator limbatus that use a large-seeded host, Acacia greggii, and a small-seeded host, Pseudosamanea guachapele. Populations differed genetically for all traits when beetles were raised in a common garden. Contrary to expectations from the local adaptation hypothesis, beetles from all populations were larger, developed faster and had higher survivorship when reared on seeds of A. greggii (the larger host), irrespective of their native host. We observed two host plant-mediated maternal effects: offspring matured sooner, regardless of their rearing host, when their mothers were reared on P. guachapele (this was not caused by an effect of rearing host on egg size), and females laid larger eggs on P. guachapele. This is the first study to document plasticity by S. limbatus in response to P. guachapele, suggesting that plasticity is an ancestral trait in S. limbatus that likely plays an important role in diet expansion. Although differences between populations in growth and life history traits are likely adaptations to their host plants, host-associated maternal effects, partly mediated by maternal egg size plasticity, influence growth and life history traits and likely play an important role in the evolution of the breadth of S. limbatus’ diet. More generally, phenotypic plasticity mediates the fitness consequences of using novel hosts, likely facilitating colonization of new hosts, but also buffering herbivores from selection post-colonization. Plasticity in response to novel versus normal hosts varied among our study populations such that disentangling the historical role of plasticity in mediating diet evolution requires the consideration of evolutionary history. 相似文献
16.
We hypothesize that foraging stream salmonids move during summer because (1) they monitor habitat conditions at a reach scale (100s of m), and (2) dominant fish move when conditions in their present foraging location become sub-optimal relative to conditions at other locations in the reach. To test these ideas, we quantified temporal variation in foraging habitat quality between late spring and early fall in a reach of a small Rocky Mountain brook charr, Salvelinus fontinalis, stream, predicted optimal-foraging fish distributions within the reach, and experimentally manipulated access to foraging sites and measured fish responses. Our results show that high-quality foraging sites were located at certain places in the reach during one period, but at different places during others, consistent with the hypothesis that fish movement is required if dominant fish are to occupy high-quality foraging sites throughout summer. The optimal foraging model was able to predict foraging locations within study pools, but not the exact location of individual fish within the pools or the reach. However, empirical evidence suggests that fish were distributed in order to maximize energy intake at the reach scale. Finally, dominant fish excluded from their preferred foraging location either left the pools (three of six cases), or began to occupy focal points of the next largest fish which, in turn, exited the pool (two of six cases). If habitat selection was occurring only within habitat units, then large fish, when excluded from their preferred locations, would select the next best locations within the pool. Taken together, these results suggest that charr use summertime movements to both monitor habitat conditions at a large spatial scale, and to gain access to optimal foraging locations even as conditions change temporally. 相似文献
17.
Andrzej Engelmayer 《Hydrobiologia》1995,307(1-3):203-206
The effects of chemicals released by fish and Chaoborus larvae on some life history traits in Daphnia pulex were studied in an in situ enclosure experiment. The mean size of Daphnia individuals was smaller in the presence of fish-released cues. Also the minimal size of an egg bearing female in the presence of fish exudates was smaller than in the population exposed to the chemicals released by Chaoborus larvae as well as in the control population. Fish-released chemicals caused the increase in clutch size in Daphnia. There were no statistically significant differences between the studied life history parameters of the control and Chaoborus treatments. The results are discussed in reference to recent laboratory research. 相似文献
18.
Optimal foraging: the difficulty of exploiting different feeding strategies simultaneously 总被引:2,自引:0,他引:2
Lennart Persson 《Oecologia》1985,67(3):338-341
Summary The foraging efficiency of a visually feeding fish, perch (Perca fluviatilis) was studied on two prey species (Daphnia magna and Chaoborus obscuripus) presented either separately or combined. It is shown that when both prey species are present, the foraging efficiency of the predator is reduced. This is due to the predator's inability to simultaneously cope with prey species with different anti-predatory behaviour. In the mixed-meal experiment the predator captured both prey species in equal proportions in disagreement with optimal foraging models assuming that handling time and encounter rate for a prey species are independent of other prey species. The results are, however, in agreement with optimal foraging models assuming that handling time and encounter rate are influenced by short time learning. 相似文献
19.
We tested if pelagic crustaceans of the genus Daphnia use different anti-predator defences in environmental conditions that do or do not offer deep refuge from planktivorous fish.
We kept Daphnia catawba in two series of 9-m deep enclosures with and without caged cyprinid fish Phoxinus eos. In one series of enclosures, Daphnia could select its depth of residence and hide in deep dark water layers to avoid anticipated fish predation, while in another
series of enclosures, a plankton net barrier fixed at 2-m depth forced them to stay in subsurface zone exposed to fish kairomones.
We compared depth residence and migratory behaviour strategies with life history strategies (body size and size at first reproduction,
diapause induction) in Daphnia exposed or not to fish kairomones with or without deep refuge. In deep enclosures with fish, Daphnia spent daytime hours in deep dark layers while at night, they resided closer to the water surface. Yet, no change in life
history parameters of migrating individuals was observed compared to the fish-free conditions. In enclosures with fish, where
the net barrier forced Daphnia to reside in subsurface zone, they produced smaller offspring, matured at smaller size and achieved lower maximum body length
compared to the fish-free conditions. However, they did not produce diapausing eggs. Our experimental study supports the hypothesis
that diel vertical migration behaviour with daytime residence in deep, dark water are the preferred antipredator strategy
chosen by Daphnia facing anticipated fish predation over life history changes such as reduced size and low growth rate which are used when
dark deep refuge is not present or accessible. 相似文献
20.
Links between morphology and foraging strategies have been well established for many vertebrate groups. Foraging strategies
of Melanerpes woodpeckers are especially variable, with at least six species being proficient flycatchers; the remainder of the better
known species do not flycatch. Our objective was to examine variation in foraging tactics as it relates to skull morphology
and other life history traits among these species to better understand the biology of these diverse woodpeckers. We measured
eight skull characters from 241 individuals representing 19 species, but focused on eight species for which we had the most
data. We used the log-geometric mean and a principal components analysis (PCA) to calculate size-scaled shape variables. Cluster
analysis based on PCA scores clearly separated birds by foraging behavior. Species with similar foraging behaviors (i.e.,
flycatchers vs non-flycatchers) also share a number of other life history characteristics including similar plumage, diets,
and migratory behavior. Diversity within Melanerpes may imply a high degree of plasticity or that species have been incorrectly placed in a polyphyletic group. Woodpeckers currently
in the genus Melanerpes share few uniting characters and historically have been placed in as many as eight different genera. Additional life history,
morphological, and genetic studies of the group, especially of Caribbean and Neotropical species, is warranted. 相似文献