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1.
Consumer-specific responses to riverine subsidy pulses in a riparian arthropod assemblage 总被引:3,自引:0,他引:3
1. Aquatic resource fluxes from streams can provide significant subsidies for riparian consumers. Because aquatic resource fluxes can be highly variable in space and time, the subsidy efficiency (i.e. transfer to the recipient food web) is controlled by the short‐term aggregative response of riparian consumers. 2. Field manipulations of stream‐derived invertebrate prey subsidies were used to examine specific aggregative responses of ground‐dwelling arthropods to riverine subsidy pulses in a braided‐river (Tagliamento River, NE Italy). Subsidy manipulation comprised short‐term reductions of natural stream‐derived subsidies and increased subsidies of stream‐derived invertebrate prey during four seasons. 3. We hypothesised that specific aggregative responses of riparian arthropods depend on their specialisation on aquatic insects which was inferred from stable isotope analysis. Natural riverine subsidy sources including aquatic insect emergence and surface‐drifting organisms were quantified. 4. Arthropods responded significantly with a reduction in abundance by 51%, at reduced subsidies and an increase by 110% at increased subsidies, when averaged over all seasons. Different arthropod taxa responded differently to subsidy manipulations in relation to their specialisation on aquatic subsidies: ground beetles with a diet consisting predominantly of aquatic insects responded only to subsidy reductions, indicating that their local abundance was not limited by natural stream‐derived subsidies; lycosid spiders with a partly aquatic diet showed no significant response; and ants, although relying on a terrestrial diet, responded positively to added stream‐derived invertebrate prey, indicating that stranding of surface‐drifting terrestrial invertebrates represented an important subsidy pathway. 5. Ground beetles and lycosid spiders were seasonally separated in their use of aquatic subsidies. Results indicate that the life‐history characteristics of riparian consumers can control the subsidy efficiency for the recipient community. By the effective uptake of pulsed riverine‐derived subsidies, riparian arthropods can enhance the transfer of riverine food sources to the riparian food web. 相似文献
2.
Adult aquatic insects emerging from streams can subsidize riparian food webs, but little is known of the spatial extent of these subsidies. Stable isotope (15 N) enrichment of aquatic insects, principally a species of stonefly (Plecoptera: Leuctridae), emerging from an upland stream was used to trace the subsidy from the stream ecosystem to riparian spiders (Lycosidae). The downstream profile of spider δ15 N correlated closely with that of adult stoneflies, indicating that they were deriving nutrition from aquatic sources. The contribution of adult aquatic insects to spider diets was determined using a two-source mixing model. Adult aquatic insects made up over 40% of spider diets adjacent to the stream, but <1% at 20 m from the stream. Enrichment of riparian spiders declined exponentially with distance from the stream channel. Aquatic-terrestrial subsidies were spatially restricted, but locally important, to riparian lycosid spiders at the study site. 相似文献
3.
We examined the relationship between body size of the riparian spider Nephila clavata and the contribution of allochthonous (aquatic insects) and autochthonous (terrestrial insects) sources to its diet using
stable isotope analysis. During the study period from July to September, the body size of the females increased remarkably
(about 60-fold) but that of males remained small. The biomass of both aquatic and terrestrial insects trapped on the spider
webs increased with spider size, with the biomass of the former ranging between 30 and 70% of that of the terrestrial insects.
The average relative contribution of aquatic insects to the diet of the spiders, calculated from δ13C values, was 40–50% in spiders in the early juvenile and juvenile stages, 35% in adult males and 4% in adult females. There
was a significant negative relationship between the relative contribution of aquatic insects and body size of the female spiders.
We conclude that aquatic insects might be an important seasonal dietary subsidy for small spiders and that these allochthonous
subsidies may facilitate the growth of riparian spiders, which may in turn enable the spiders to feed on larger prey. 相似文献
4.
Prey use by web-building spiders: stable isotope analyses of trophic flow at a forest-stream ecotone
A forest-stream trophic link was examined by stable carbon isotope analyses which evaluated the relationship of aquatic insects emerging from a stream to the diets of web-building spiders. Spiders, aquatic and terrestrial prey, and basal resources of forest and stream food webs were collected in a deciduous forest along a Japanese headwater stream during May and July 2001. The 13C analyses suggested that riparian tetragnathid spiders relied on aquatic insects and that the monthly variation of such dependence is partly associated with the seasonal dynamics of aquatic insect abundance in the riparian forest. Similarly, linyphiid spiders in the riparian forest exhibited 13C values similar to aquatic prey in May. However, their 13C values were close to terrestrial prey in both riparian and upland (150m away from the stream) forests during June to July, suggesting the seasonal incorporation of stream-derived carbon into their tissue. In contrast, araneid spiders relied on terrestrial prey in both riparian and upland forests throughout the study period. These isotopic results were consistent with a previous study that reported seasonal variation in the aquatic prey contribution to total web contents for each spider group in this forest, implying that spiders assimilate trapped prey and that aquatic insect flux indeed contributes to the energetics of riparian tetragnathid and linyphiid spiders. 相似文献
5.
Alterations to river flow conditions have wide impacts on riparian organisms in terms of behavior and biomass. However, little
is known about natural flood impacts on prey use and individual growth of riparian predators. Using stable carbon isotope
analysis, we investigated flood impacts on aquatic-prey use and the size structure of an orb-web spider, Nephila clavata, during 3 years under different flood conditions in a black locust forest in the middle reaches of the Chikuma River. Large
floods depressed aquatic-prey abundance, but did not affect terrestrial-prey abundance in the riparian forest. Consequently,
spider growth was stunted after large floods. Spider body size was positively correlated with the body sizes of both aquatic
and terrestrial insects in spider webs, where terrestrial insects were significantly larger than aquatic insects. The δ13C of aquatic insects was about 8‰ higher than that of terrestrial insects, and the δ13C of both insect groups did not vary significantly between months or among years. A negative relationship was found between
body size and δ13C in spiders under different subsidies levels. Our results showed that flow regime altered spider growth through changes in
aquatic subsidies level, but not aquatic-prey use by the spiders due to relative body sizes of predators and prey. Changes
in relative body sizes of predator and prey may be an important factor in understanding nutrients, materials, and energy flows
in aquatic and terrestrial linkages in the context of flow regime. 相似文献
6.
Cross-ecosystem movement of nutrients and biomass can have important effects on recipient systems. Emerging aquatic insects are subsidies to terrestrial ecosystems and can influence foodweb interactions in riparian systems. In a 2-year field experiment, we simulated aquatic insect deposition by adding adult midge carcasses (150?g dry mass m?2 year?1) to 1-m2 heathland plots at a site with low natural midge deposition. We established four levels of midge-addition treatments and measured stable isotopes (??13C and ??15N) in plants and arthropods within each treatment. We used a multiple-source isotope Bayesian mixing model to estimate the terrestrial versus aquatic contribution to the diets of arthropods. Aquatic resources were incorporated into plant, detritivore, and predator biomass. Detritivorous Collembola showed the greatest difference in isotope values (+3??? ??15N and +4??? ??13C) between midge-addition and reference treatments. Isotope values of small spiders followed the same trend of enrichment as Collembola while other arthropods (mites and large spiders) were only enriched after 2?years of midge addition. Although predator diets did not change, they became isotopically enriched via their likely prey (Collembola). Plants also had elevated ??15N (+1???) in midge-addition treatments. The time required and amount of midge-derived C and N detected varied and depended on trophic position. Midge-derived nutrients were no longer present in arthropod biomass in the year following midge addition. Aquatic insect carcasses can be rapidly incorporated into terrestrial food webs in nearshore habitats, and repeated inputs can be detected at multiple trophic levels, thus highlighting the importance of the detrital pathway for aquatic to terrestrial cross-ecosystem subsidies. 相似文献
7.
8.
Dietary Dependence of Predatory Arthropods on Volant Aquatic Insects in Tropical Stream Riparia
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The dietary dependence on volant aquatic insects of eight species of predatory arthropods from three different orders was determined by stable isotope analyses in combination with three‐source, two‐isotope (C and N) Bayesian mixing models. The predators were collected from riparian zones along three streams in tropical Hong Kong during both the wet and dry seasons. Dietary importance of aquatic insects varied according to predator hunting modes, and showed a consistent pattern across all sites during the wet season. The web‐building tetragnathid spider (Orsinome diporusa) had the greatest reliance (~40–55%) on this water‐to‐land subsidy, followed by two species of damselflies (40–50%), three cursorial spiders (Lycosidae, Pisauridae, and Sparassidae: 32–51%) and two neustic gerrids (17–36%). Such reliance also varied according to the microhabitat preferences of different cursorial spiders. Four species of predators (gerrids and cursorial spiders) that were active year‐round showed generally consistent reliance on aquatic insects between seasons, which probably reflected the observed lack of seasonal variability in the relative proportions of aquatic and terrestrial prey. There was a marked overlap in isotopic signatures of aquatic and terrestrial prey at all sites which, combined with the absence of data on the extent to which isotopic fractionations may vary among individual species of prey and predators, contributes some uncertainty to the estimates of dietary compositions derived by mixing models. The findings of the present study are thus likely to be indicative rather than definitive. 相似文献
9.
Investigations into trophic ecology and aquatic food web resolution are increasingly accomplished through stable isotope analysis.
The incorporation of dietary and metabolic changes over time results in variations in isotope signatures and turnover rates
of producers and consumers at tissue, individual, population and species levels. Consequently, the elucidation of trophic
relationships in aquatic systems depends on establishing standard isotope values and tissue turnover rates for the level in
question. This study investigated the effect of diet and food quality on isotopic signatures of four mussel tissues: adductor
muscle, gonad, gill and mantle tissue from the brown mussel Perna perna. In the laboratory, mussels were fed one of the two isotopically distinct diets for 3 months. Although not all results were
significant, overall δ13C ratios in adductor, mantle and gill tissues gradually approached food source signatures in both diets. PERMANOVA analyses
revealed significant changes over time in tissue δ13C (mantle and gill) with both diets and in δ15N (all tissues) and C:N ratios (mantle and gill) for one diet only. The percentage of replaced carbon isotopes were calculated
for the 3 month period and differed among tissues and between diets. The tissue with the highest and lowest amount of replaced
isotopes over 81 days were mantle tissue on the kelp diet (33.89%) and adductor tissue on the fish food diet (4.14%), respectively.
Percentages could not be calculated for any tissue in either diet for δ15N due to the lack of significant change in tissue nitrogen. Fractionation patterns in tissues for both diets can be linked
to nutritional stress, suggesting that consumer isotopic signatures are strongly dependent on food quality, which can significantly
affect the degree of isotopic enrichment within a trophic level. 相似文献
10.
11.
Grasshoppers must gather food while avoiding size-selective predation from other arthropods, especially spiders, potentially leading to a trade-off between foraging and defensive behaviors. This trade-off becomes less intense as prey grow larger and are less susceptible to arthropod predation. Activity budgets were constructed for three nymphal (third- to fifth- instar) and adult life cycle stages of Ageneotettix deorum, a common rangeland grasshopper, for three conditions of predation risk by lycosid spiders (spider absence, spider presence, and presence of a nonlethal, chelicerae-modified spider). In third and fourth instars, exposure to predators resulted in reduced feeding activity, increased time spent in antipredator and defensive behaviors, and reduced general activity compared to individuals not exposed to spiders. No significant shifts in behaviors were observed for fifth-instar nymphs and adult A. deorum in response to spider presence. Activity levels in functional spiders and chelicerae-modified spiders were statistically indistinguishable. 相似文献
12.
Allyson K. Jackson Collin A. EaglesSmith W. Douglas Robinson 《Ecology and evolution》2021,11(11):7003
Cross‐ecosystem subsidies move substantial amounts of nutrients between ecosystems. Emergent aquatic insects are a particularly important prey source for riparian songbirds but may also move aquatic contaminants, such as mercury (Hg), to riparian food webs. While many studies focus on species that eat primarily emergent aquatic insects, we instead study riparian songbirds with flexible foraging strategies, exploiting both aquatic and terrestrial prey sources. The goal in this study is to trace reliance on aquatic prey sources and correlate it to Hg concentrations in common riparian arachnids (Families Tetragnathidae, Opiliones, and Salticidae) and songbirds (Common Yellowthroat Geothlypis trichas, Spotted Towhee Pipilo maculatus, Swainson''s Thrush Catharus ustulatus, Song Sparrow Melospiza melodia, and Yellow Warbler Setophaga petechia). We used stable isotopes of δ13C and δ15N and Bayesian mixing models in MixSIAR to determine the reliance of riparian predators on aquatic prey sources. Using mixed effects models, we found that arachnid families varied in their reliance on aquatic prey sources. While songbird species varied in their reliance on aquatic prey sources, songbirds sampled earlier in the season consistently relied more on aquatic prey sources than those sampled later in the season. For both arachnids and songbirds, we found a positive correlation between the amount of the aquatic prey source in their diet and their Hg concentrations. While the seasonal pulse of aquatic prey to terrestrial ecosystems is an important source of nutrients to riparian species, our results show that aquatic prey sources are linked with higher Hg exposure. For songbirds, reliance on aquatic prey sources early in the breeding season (and subsequent higher Hg exposure) coincides with timing of egg laying and development, both of which may be impacted by Hg exposure. 相似文献
13.
The dietary basis for temporal partitioning: food habits of coexisting Acomys species 总被引:5,自引:0,他引:5
Two rodent species of the genus Acomys coexist on rocky terrain in the southern deserts of Israel. The common spiny mouse (A. cahirinus) is nocturnally active whereas the golden spiny mouse (A. russatus) is diurnally active. An early removal study suggested that competition accounts for this pattern of temporal partitioning:
the golden spiny mouse is forced into diurnal activity by its congener. Theoretically, temporal segregation should facilitate
coexistence if the shared limiting resources differ at different times (primarily among predators whose prey populations have
activity rhythms), or if they are renewed within the period of the temporal segregation. We studied food preferences of the
two Acomys species in a controlled cafeteria experiment in order to assess resource overlap and the potential for competition for food
between the two species. We found no significant difference in food preferences between species. The dietary items preferred
by both were arthropods. We also carried out a seasonal study of the percentage and identity of arthropods taken in the field
by individuals of the two species. Individuals of both species took on annual average a high percentage of arthropods in their
diets. Seasonal diet shifts reflect seasonal abundance of arthropods at Ein Gedi during day and night. Diurnal activity may
also reduce interspecific interference competition between A. russatus and A. cahirinus. However, the strong interspecific dietary overlap in food preference, the heavy reliance on arthropods in spiny mouse diets,
and the seasonal and circadian differences in arthropod consumption suggest that prey partitioning may be a viable mechanism
of coexistence in this system.
Received: 6 July 1998 / Accepted: 10 May 1999 相似文献
14.
Antarctic soil ecosystems are amongst the most simplified on Earth and include only few soil arthropod species, generally
believed to be opportunistic omnivorous feeders. Using stable isotopic analyses, we investigated the food choice of two common
and widely distributed Antarctic soil arthropod species using natural abundances of 13C and 15N and an isotope labelling study. In the laboratory we fed the isotomid springtail Cryptopygus antarcticus six potential food sources (one algal species, two lichens and three mosses). Our results showed a clear preference for algae
and lichens rather than mosses. These results were corroborated by field data comparing stable isotope signatures from the
most dominant cryptogams and soil arthropods (C. antarcticus and the oribatid mite Alaskozetes antarcticus). Thus, for the first time in an Antarctic study, we present clear evidence that these soil arthropods show selectivity in
their choice of food and have a preference for algae and lichens above mosses. 相似文献
15.
Tsungai Alfred Zengeya Anthony J. Booth Armanda D. S. Bastos Christian T. Chimimba 《Environmental Biology of Fishes》2011,92(4):479-489
The stable isotope ratio and seasonal changes in diet of two indigenous (Oreochromis mossambicus, Tilapia rendalli) and one exotic (Oreochromis niloticus) tilapiine cichlids in the subtropical Limpopo River, South Africa were investigated to determine patterns of resource partitioning.
Stomach contents of O. niloticus and O. mossambicus indicated high dietary overlap across size class, habitat and season, with both species primarily feeding on vegetative detritus.
However, stable isotope analysis revealed that the two Oreochromis species had different stable isotope ratios derived from different food sources. The relatively δ13C-depleted O. niloticus indicates a phytoplankton-based diet, while the δ13C-enriched O. mossambicus indicates a macrophagous diet dominated by vegetative detritus and periphyton. The high similarity in stomach contents and
the interspecific differences in isotopic composition reveal fine-scale patterns of food resource partitioning that could
be achieved through selective feeding. Tilapia rendalli was largely macrophagous and fed mainly on aquatic macrophytes and had a low dietary overlap with both O. niloticus and O. mossambicus. In the Limpopo River, detritus and algae are probably the most abundant food resources and the causal factors responsible
for the observed patterns of resource partitioning among the tilapiines are usually difficult to ascertain. Fish may be able
to perceive food resources in terms of the dynamics that determine their availability. Detailed studies of variation in food
resource availability and fish habitat use within the system are needed to evaluate this hypothesis. 相似文献
16.
We analyzed the food source of riparian spiders in a middle reach of the Chikuma River, Japan, by using stable isotope ratios of carbon and nitrogen. The carbon and nitrogen isotope ratios of attached algae were higher than those of terrestrial plants, reflecting a large carbon isotope fractionation in terrestrial plants and a difference in nitrogen sources. The carbon isotope ratios of terrestrial insects were similar to those of the terrestrial plants, and the ratios of aquatic insects were scattered between those of the terrestrial plants and the attached algae. The carbon and nitrogen isotope ratios of spiders were intermediate between those of the terrestrial and aquatic insects. The two-source mixing model using the carbon isotope ratio showed that the web-building spiders utilized both the terrestrial and aquatic insects, with large contribution by the aquatic insects (54% on average with a maximum of 92% among spiders taxa collected in each zone), in the riparian area in a middle reach of the Chikuma River. The large contribution of the aquatic insects was often observed for the spiders collected near river channel (<5m) and for the horizontal web-building spiders collected across the riparian area. The relative contribution of the aquatic insects might be related with food availability (distance from river channel) and spiders food preference reflected in their web types (horizontal vs. vertical). Our results showed that organic materials produced in the river channel, in the riparian area, and in the terrestrial area surrounding the riparian area were mixed at the carnivorous trophic level of riparian spiders. 相似文献
17.
Ants are prominent components of most terrestrial arthropod food webs, yet due to their highly variable diet, the role ants
play in arthropod communities can be difficult to resolve. Stable isotope analysis is a promising method for determining the
dietary history of an organism, and has the potential to advance our understanding of the food web ecology of social insects.
However, some unique characteristics of eusocial organisms can complicate the application of this technique to the study of
their trophic ecology. Using stable isotopes of N and C, we investigated levels of intraspecific variation both within and
among colonies. We also examined the effect of a common preservation technique on δ15N and δ13C values. We discuss the implications of our results on experimental design and sampling methods for studies using stable
isotopes to investigate the trophic ecology of social insects.
Received 4 February 2005; revised 23 June 2005; accepted 4 July 2005. 相似文献
18.
Riparian vegetation typically provides substantial allochthonous material to aquatic ecosystems where micro-organisms can
play an important role in organic matter degradation which can support consumer biomass. We examined the effects of leaf litter
quality (e.g., leaf nutrients, lignin and cellulose content), leaf species mixing, and microbial community diversity on in-stream
breakdown rates of litter from dominant riparian trees (Melaleuca
argentea, M. leucadendra, and Nauclea
orientalis) in both a perennial and intermittent river in Australia’s wet-dry tropics. Leaf mass remaining after 82 days of in-stream
incubation was negatively correlated (P < 0.05) with initial leaf N and P content while initial lignin and cellulose content had no statistically significant effect.
Breakdown rates of incubated leaves of both Melaleuca and Nauclea were significantly higher in mixed litter bags compared with single species litter bags. Although it was expected that leaf
N content would decrease from initial levels during decomposition, we found either similar or slightly higher N content following
in-stream incubation suggesting microbial colonisation increased overall N content. Stable isotopes of δ13C and δ15N for the major sources and consumers in both rivers provide evidence that leaf litter was an important macroinvertebrate
food source in the perennial river where heavy shading may limit algal production. However, in the intermittent river where
riparian cover was low, benthic algae were the major organic carbon source for consumers. Our findings suggest that riparian
tree species influence rates of in-stream organic matter processing, microbial community composition, and aquatic food web
dynamics in tropical wet-dry streams. 相似文献
19.
Stable oxygen and hydrogen isotope analyses of fossil aquatic organisms, such as the chitinous head capsules of chironomid
larvae (Chironomidae: Diptera), are promising proxies for inferring paleoecological conditions. In order for analyses of stable
oxygen (δ18O) and hydrogen isotope ratios (δ2H) of fossil chironomid head capsules to be used effectively in paleoecological research, it is necessary to understand the
factors controlling their stable oxygen and hydrogen composition. We cultured chironomid larvae in two isotopically distinct
waters under controlled, replicated laboratory conditions. Chironomid larvae were fed on identical diets, to examine the degree
to which water and diet influence the δ18O and δ2H of these organisms. We used a two-end member mixing model to determine the proportional contributions of oxygen and hydrogen
from water to the oxygen and hydrogen of chironomid larvae. Our experiment demonstrated that 69.0 ± 0.4% of oxygen and 30.8 ± 2.6%
of hydrogen in chironomid larvae are derived from habitat water. Our results show that oxygen isotopes from chironomid remains
can better constrain past habitat water isotopic changes compared to hydrogen, due to 69% of the chironomid oxygen being influenced
by habitat water. Our data add to a small but growing suite of comparative data on the sources of oxygen and hydrogen in animal
tissues, and provide the first such analyses from aquatic insects. 相似文献
20.
Carbon and nitrogen stable isotopes are frequently used to study energy sources and food web structure in ecosystems, and
more recently, to study the effects of anthropogenic stress on aquatic ecosystems. We investigated the effect of nutrient
enrichment on δ13C and δ15N in fine (FPOM), coarse (CPOM) particulate organic matter, periphyton, invertebrates and fish in nine boreal streams in south-central
Sweden. In addition, we analysed the diet of benthic consumers using stable isotope data. Increases in δ15N of periphyton (R
2 = 0.88), CPOM (0.78), invertebrates (0.92) and fish (0.89) were related to nutrient enrichment. In contrast, δ13C signatures did not change along the nutrient gradient. Our results show that δ15N has potential as a sensitive indicator of nutrient enrichment in boreal streams. Carbon and nitrogen isotopes failed to
elucidate putative diets of selected aquatic consumers. Indeed, comparison of low- and high-impact sites showed that δ13C of many consumers were found outside the ranges of basal resource δ13C. Moreover, ranges of basal resource δ13C and δ15N overlapped at both low and high sites, making discrimination between the importance of allochthonous and autochthonous production
difficult. Our findings show that a fractionation rate of 3.4‰ is not always be appropriate to assess trophic interactions,
suggesting that more studies are needed on fractionation rates along gradients of impairment.
Handling editor: M. Power 相似文献