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1.
Cinclodes nigrofumosus and C. oustaleti are two closely related songbirds that inhabit the northern Chilean coast during the austral fall and winter.This stretch spans a dramatic north to south latitudinal gradient in rainfall and temperature. Whereas C. nigrofumosus lives exclusively on coastal environments, C. oustaleti shifts seasonally from coastal environments to inland freshwater ones. We used the δ13C of these two species’ tissues to investigate whether the reliance on marine versus terrestrial sources varied from the hyper-arid north to the wet south. We also investigated latitudinal variation in the renal traits that mediate how these birds cope with dehydration and a salty marine diet. Both species increased the incorporation of terrestrial carbon, as measured by δ13C, as terrestrial productivity increased southwards. However, C. nigrofumosus had consistently more positive (i.e. more marine) and less variable δ13C values than C. oustaleti. The osmoregulatory traits of both species varied with latitude as well. Urine osmolality decreased from extremely high values in the north to moderate values in the south, while C. nigrofumosus produced more concentrated urine than C. oustaleti. In both species, the proportion of kidney devoted to medullary tissue decreased from north to south, and kidney size increased significantly with latitude. Cinclodes nigrofumosus had larger kidneys with larger proportions of medullary tissue than C. oustaleti. C. nigrofumosus and C. oustaleti are terrestrial organisms subsidized by a rich marine environment where it is adjacent to an unproductive terrestrial. Variation in the reliance on marine food sources seems to be accompanied by adjustments in the osmoregulatory mechanisms used by these birds to cope with salt and dehydration. 相似文献
2.
Stable-carbon and nitrogen isotopic compositions (δ13C, δ15N) of baleen plates of two juvenile and four adult gray whales (Eschrichtius robustus) were examined. High variance in isotopic composition of baleen plates was detected among individuals and, unlike other migratory
species of baleen whales examined isotopically, δ13C and δ15N values of most whales showed no regular oscillations. Only one baleen plate reflected the assumed principal Arctic prey
(ampeliscid amphipods) during growth on the summer grounds. The rate of baleen growth inferred for one of the juveniles in
the last 5 months of life (4.7 mm/week) was similar to the rate calculated previously for a rehabilitating gray whale calf.
Autumn corresponded to the timing of the formation of lowest δ15N values measured along plates. We estimate that the baleen length in all adult gray whales recorded around a year of information
(1.3 ± 0.3; Mean ± SD). This short period of dietary integration precludes long time series analyses in this species and reflects
the extensive wear on baleen plates due to benthic foraging.
Handling editor: M. Power 相似文献
3.
C. P. Chamberlain J. D. Blum R. T. Holmes Xiahong Feng T. W. Sherry G. R. Graves 《Oecologia》1996,109(1):132-141
To determine whether stable isotopes can be used for identifying the geographic origins of migratory bird populations, we
examined the isotopic composition of hydrogen (deuterium, δD), carbon (δ13C), and strontium (δ87Sr) in tissues of a migratory passerine, the black-throated blue warbler (Dendroica caerulescens), throughout its breeding range in eastern North America. δD and δ13C values in feathers, which are grown in the breeding area, varied systematically along a latitudinal gradient, being highest
in samples from the southern end of the species’ breeding range in Georgia and lowest in southern Canada. In addition, δD
decreased from east to west across the northern part of the breeding range, from New Brunswick to Michigan. δ87Sr ratios were highest in the Appalachian Mountains, and decreased towards the west. These patterns are consistent with geographical
variation in the isotopic composition of the natural environment, i.e., with that of precipitation, plants, and soils for
δD, δ13C, and δ87Sr, respectively. Preliminary analyses of the δD and δ13C composition of feathers collected from warblers in their Caribbean winter grounds indicate that these individuals were mostly
from northern breeding populations. Furthermore, variances in isotope ratios in samples from local areas in winter tended
to be larger than those in summer, suggesting that individuals from different breeding localities may mix in winter habitats.
These isotope markers, therefore, have the potential for locating the breeding origins of migratory species on their winter
areas, for quantifying the degree of mixing of breeding populations on migratory and wintering sites, and for documenting
other aspects of the population structure migratory animals – information needed for studies of year-round ecology of these
species as well as for their conservation. Combining information from several stable isotopes will help to increase the resolution
for determining the geographic origins of individuals in such highly vagile populations.
Received: 24 April 1995 / Accepted: 2 June 1996 相似文献
4.
δ13C and δ15N measurements are still poorly conducted in benthic invertebrate larvae. To assess the δ13C and δ15N changes occurring after a dietary shift, experiments were conducted on veliger larvae of Crepidula fornicata fed with two cultured microalgae (Isochrysis galbana and Pavlova lutheri) of known isotopic composition, 13C-enriched and 15N-depleted compared to the initial values of the larvae. Rapid changes in larval δ13C and δ15N were observed after the dietary shift, with an increase in δ13C and a decrease in δ15N. After 19 days of feeding, isotopic equilibrium was still not reached, a period which is close to the duration of the pelagic life of the larvae. This implies that the isotopic composition measured in field-collected larvae might only partly reflect actual larval feeding but also the parental isotopic signature, especially during the early developmental stages. Isotopic measurements in marine invertebrate larvae should thus be interpreted cautiously. In planktonic food web investigations, the study of field-collected larvae of different size/developmental stage may reduce potential misinterpretations. 相似文献
5.
The use of stable isotopes to investigate animal diets, habitat use, and trophic level requires understanding the rate at
which animals incorporate the 13C and 15N from their diets and the factors that determine the magnitude of the difference in isotopic composition between the animal’s
diet and that of its tissues. We determined the contribution of growth and catabolic turnover to the rate of 13C and 15N incorporation into several tissues that can be sampled non-invasively (skin, scute, whole blood, red blood cells, and plasma
solutes) in two age classes of a rapidly growing ectotherm (loggerhead turtles, Caretta caretta). We found significant differences in C and N incorporation rates and isotopic discrimination factors (Δ13C = δ13Ctissues − δ13Cdiet and Δ15N = δ15Ntissues − δ15Ndiet) among tissues and between age classes. Growth explained from 26 to 100% of the total rate of incorporation in hatchling
turtles and from 15 to 52% of the total rate of incorporation in juvenile turtles. Because growth contributed significantly
to the rate of isotopic incorporation, variation in rates among tissues was lower than reported in previous studies. The contribution
of growth can homogenize the rate of isotopic incorporation and limit the application of stable isotopes to identify dietary
changes at contrasting time scales and to determine the timing of diet shifts. The isotopic discrimination factor of nitrogen
ranged from −0.64 to 1.77‰ in the turtles’ tissues. These values are lower than the commonly assumed average 3.4‰ discrimination
factors reported for whole body and muscle isotopic analyses. The increasing reliance on non-invasive and non-destructive
sampling in animal isotopic ecology requires that we recognize and understand why different tissues differ in isotopic discrimination
factors. 相似文献
6.
Stable isotope data are often used to assess diet, trophic level, trophic niche width and the extent of omnivory. Notwithstanding
ongoing discussions about the value of these approaches, variations in isotopic signatures among individuals depend on inherent
variability as well as differences in feeding habitats. Remarkably, the relative contributions of diet variation and inherent
variability to differences in δ15N and δ13C among individuals have not been quantified for the same species at the same life history stages, and inherent variability
has been ignored or assumed. We quantified inherent variability in δ13C and δ15N among individuals of a marine fish (the European sea bass, Dicentrarchus labrax) reared in a controlled environment on a diet of constant isotopic composition and compared it with variability in δ13C and δ15N among individuals from wild bass populations. The analysis showed that inherent variability among reared individuals on
a controlled diet was equivalent to a large proportion of the observed variability among wild individuals and, therefore,
that inherent variability should be measured to establish baseline variability in wild populations before any assumptions
are made about the influence of diet. Given that inherent variability is known to be dependent on species, life history stage
and the environment, our results show that it should be quantified on a case-by-case basis if diet studies are intended to
provide absolute assessments of dietary habits. 相似文献
7.
Concentration and isotopic composition (δ13C and δ18O) of ambient CO2 and water vapour were determined within a Quercus petraea canopy, Northumberland, UK. From continuous measurements made across a 36-h period from three heights within the forest canopy,
we generated mixing lines (Keeling plots) for δa
13CO2, δa C18O16O and δa H2
18O, to derive the isotopic composition of the signal being released from forest to atmosphere. These were compared directly
with measurements of different respective pools within the forest system, i.e. δ13C of organic matter input for δa
13CO2, δ18O of exchangeable water for δa C18O16O and transpired water vapour for δa H2
18O. [CO2] and δa
13CO2 showed strong coupling, where the released CO2 was, on average, 4 per mil enriched compared to the organic matter of plant material in the system, suggesting either fractionation
of organic material before eventual release as soil-respired CO2, or temporal differences in ecosystem discrimination. δa C18O16O was less well coupled to [CO2], probably due to the heterogeneity and transient nature of water pools (soil, leaf and moss) within the forest. Similarly,
δa H2
18O was less coupled to [H2O], again reflecting the transient nature of water transpired to the forest, seen as uncoupling during times of large changes
in vapour pressure deficit. The δ18O of transpired water vapour, inferred from both mixing lines at the canopy scale and direct measurement at the leaf level,
approximated that of source water, confirming that an isotopic steady state held for the forest integrated over the daily
cycle. This demonstrates that isotopic coupling of CO2 and water vapour within a forest canopy will depend on absolute differences in the isotopic composition of the respective
pools involved in exchange and on the stability of each of these pools with time.
Received: 21 March 1998 / Accepted: 10 December 1998 相似文献
8.
Continent-wide variation in hydrogen isotopic composition of precipitation is incorporated into animal diets, providing an
intrinsic marker of geographic location at the time of tissue growth. Feathers from migratory birds are now frequently analyzed
for stable-hydrogen isotopes (δD) to estimate the location of individuals during a preceding molt. Using known-origin birds,
we tested several assumptions associated with this emerging technique. We examined hydrogen isotopic variation as a function
of age, sex, feather type and the timing of molt in a marked population of American redstarts (Setophaga ruticilla) breeding in southeastern Ontario. We measured δD in feathers and blood from individuals that bred or hatched at our study
site during the year in which those tissues were grown. Juvenile tissues from 5- to 10-day-old birds had more negative δD
values than those from adults, which most likely reflected age-related differences in diet. Within adults, primary feathers
had more negative δD values than contour feathers. The mean δD value in adult primary feathers was relatively consistent among
years and with the value expected for our study population. However, among-individual variation in δD corresponded to an estimated
latitudinal range of 6–8° (650–900 km). We conclude that feathers sampled from recently hatched juveniles may not provide
a reliable estimate of expected local isotopic signatures for comparison with adult feathers of unknown origin. Furthermore,
we urge researchers to use caution when using δD values in feathers to infer geographic origin, and suggest that the best
approach is to assign individuals to broad geographic zones within a species’ potential molting range. 相似文献
9.
Linking isotopic and migratory patterns in a pelagic seabird 总被引:1,自引:0,他引:1
The value of stable isotope analysis in tracking animal migrations in marine environments is poorly understood, mainly due
to insufficient knowledge of isotopic integration into animal tissues within distinct water masses. We investigated isotopic
and moult patterns in Cory’s shearwaters to assess the integration of different stable isotopes into feathers in relation
to the birds’ transoceanic movements. Specimens of Mediterranean Cory’s shearwater Calonectris diomedea diomedea caught accidentally by Catalan longliners were collected and the signatures of stable isotopes of C (δ13C), N (δ15N) and S (δ34S) were analysed in 11 wing and two tail feathers from 20 birds, and in some breast feathers. Based on isotopic signatures
and moult patterns, the feathers segregated into two groups (breeding and wintering), corresponding to those grown in the
Mediterranean or Atlantic regions, respectively. In addition, feathers grown during winter, i.e. moulted in Atlantic waters,
were grouped into two isotopically distinct profiles, presumably corresponding to the two main wintering areas previously
identified for Mediterranean Cory’s shearwater in tracking studies. N signatures mainly indicated the Mediterranean-to-Atlantic
migration, whereas C and S signatures differed according to the Atlantic wintering area. Our results indicate that isotopic
signatures from distant oceanic regions can integrate the feathers of a given bird and can indicate the region in which each
feather was grown. This study thus underscores how stable isotope analysis can link marine animals to specific breeding and
wintering areas, and thereby shed new light on studies involving assignment, migratory connectivity and carry-over effects
in the marine environment.
Xavier Ruiz deceased 27 April 2008. 相似文献
10.
Trophic patterns of omnivorous freshwater shrimps, Exopalaemon modestus and Macrobrachium nipponensis, were investigated in two shallow eutrophic lakes by using stable isotope analysis. δ15N and δ13C of M. nipponensis and E. modestus increased with increasing body weight, which might be attributed to larger individuals ingesting organisms that feed higher
up the food chain and/or increased assimilation of benthic food items with enriched isotopic signatures. Of the freshwater
shrimps occurring in the studied lakes, those from Lake Taihu had significantly elevated δ15N and δ13C values (4.3‰ and 1.8‰, respectively) compared with those from the less eutrophic Lake Chaohu, indicating that the isotopic
signature might partially reflect the trophic states of their habitats. Mixing model results suggested that the benthic food
web provides the primary carbon source for both shrimp species, and that E. modestus assimilated relatively more pelagic food sources than M. nipponensis in these lakes.
Handling editor: S. Wellekens 相似文献
11.
Stable carbon and nitrogen isotope ratio profiling of sperm whale teeth reveals ontogenetic movements and trophic ecology 总被引:1,自引:0,他引:1
Teeth from male sperm whales (Physeter macrocephalus) stranded in the North-eastern Atlantic were used to determine whether chronological profiles of stable isotope ratios of
C (δ13C) and N (δ15N) across dentine growth layers could be used to detect known ontogenetic benchmarks in movements and trophic ecology. Profiles
showed a general decrease in δ13C (median = 1.91‰) and an increase in δ15N (median = 2.42‰) with age. A marked decline in δ13C occurred for all 11 teeth around 9–10 years and again for six individuals around 20 years. After the early twenties the
δ13C continued to decline with age for all teeth. These results are consistent with males segregating from natal groups in low
latitudes with the onset of puberty between 4 and 15 years and gradually dispersing pole-ward into 13C-depleted temperate waters. Penetration into further depleted, productive high latitudes after the age of 20 might facilitate
the spurt of accelerated growth rate observed around this age. Breeding migrations back to lower latitudes were not reflected
in the δ13C profiles possibly due to being short compared to the time spent feeding in high latitudes. The timings of marked isotopic
change in the δ15N profiles reflect those of the δ13C profiles, suggesting a link between dietary changes and movements. The observed increase in δ15N with age is likely to be caused by a trophic level increase as males grow in size, probably feeding on larger prey. An additional
explanation could be that, in the higher latitudes of the North Atlantic, the main prey source is the high trophic level squid
Gonatus fabricii. Also, the lower latitudes from where males disperse are depleted in basal 15N. Profiles of δ13C and δ15N in sperm whale teeth gathered from different regions, sexes, and periods in time, could provide a unique way to understand
the ecology of this species across different oceans. 相似文献
12.
Using eggshell membranes as a non-invasive tool to investigate the source of nutrients in avian eggs
Development of minimally invasive techniques to collect nutritional information from free-living birds is desirable for both
ethical and conservation reasons. Here, we explore the utility of waterfowl eggshell membranes to determine the nutrient source
of egg formation by using stable isotope ratios. We compared δ13C and δ15N of membranes from complete king eider (Somateria spectabilis) eggs to membranes of hatched or depredated eggs of the same clutch remaining after incubation. Despite large variation among
membranes (δ13C: −26 to −14‰) we found a highly predictable relationship between δ13C of complete egg membranes and remaining (hatched or depredated) membranes from the same clutch. We did not find a consistent
change in either δ13C or δ15N of eggshell membranes during incubation. We suggest that isotope ratios of membranes can be used to determine the source
of exogenous nutrients for egg production in income breeders, and that membranes may offer a clutch-specific reference point
for dietary nutrients (‘income endpoint’) in isotopic mixing models quantifying nutrient allocation in capital or mixed-strategy
breeders. 相似文献
13.
‘Are fish what they eat’ all year round? 总被引:4,自引:0,他引:4
Isotope turnover in muscle of ectotherms depends primarily on growth rather than on metabolic replacement. Ectotherms, such
as fish, have a discontinuous pattern of growth over the year, so the isotopic signature of muscle (δ13C and δ15N) may only reflect food consumed during periods of growth. In contrast, the liver is a regulatory tissue, with a continuous
protein turnover. Therefore, the isotopic composition of liver should respond year round to changes in the isotopic signature
of food sources. Therefore, we predicted that (1) Whitefish in Lake Geneva would have larger seasonal variation in the isotopic
variation of the liver compared to that of the muscle tissue, and (2) the isotope composition of fish muscle would reflect
a long-term image of the isotope composition of the food consumed only throughout the growth period. To test these expectations,
we compared the isotope compositions of Whitefish muscle, liver and food in a 20-month study. We found that the seasonal amplitude
of isotope variation was two to three times higher in liver compared to muscle tissue. During the autumn and winter, when
growth was limited, only the isotopic signature of liver responded to changes in the isotope composition of the food sources.
The δ13C and δ15N of muscle tissue only reflected the food consumed during the spring and summer growth period. 相似文献
14.
We studied the nutritional modes of the orchid Serapias strictiflora and its mycorrhizal fungus Epulorhiza sp. using the differences in carbon isotopic composition (δ13C) of C3 orchid and C4 maize tissues. We found that if cultivated in substrate lacking any organic compounds, the mycorrhizal extraradical mycelia
(δ13C = −26.3 ± 0.2 ‰) developed well, despite being fully dependent on nutrition from orchid roots (δ13C = −28.6 ± 0.1 ‰). If the mycorrhizal fungus had additional access to and colonized decaying maize roots (δ13C = −14.6 ± 0.1 ‰), its isotopic composition (δ13C = −21.6 ± 0.4 ‰) reflected a mixture of biotrophy and saprotrophy. No statistically significant differences in δ13C of new storage tubers were found between Epulorhiza-associated orchids with (δ13C = -28.2 ± 0.1 ‰) and without access to maize roots (δ13C = −28.6 ± 0.2 ‰). We conclude that autotrophy is the predominant nutritional mode of mature S. strictiflora plants and that they supply their mycorrhizal fungus with substantial amount of carbon (69 ± 3 % of the fungus demand), even
if the fungus feeds saprotrophically. 相似文献
15.
Use of saguaro fruit by white-winged doves: isotopic evidence of a tight ecological association 总被引:1,自引:0,他引:1
We report the use of stable isotope and crop content analyses to quantify the use of saguaro (Carnegiea gigantea) nectar and fruit by migratory desert white-winged doves (Zenaida asiatica mearsnii). Saguaro resources had characteristically 13C-enriched CAM values (δ13C=–12.8±0.7‰ SD VPDB and –13.1±0.5‰ SD VPDB for nectar and fruit, respectively) relative to other food plants used by doves
(δ13CC3=–24.9±3.3‰ SD VPDB). The water contained in saguaro nectar and fruit was deuterium enriched (δD=19.6±2.0‰ SD VSMOW and 48.4±1.6‰
SD VSMOW for nectar and fruit, respectively) relative to other water sources (ranging from –41 to –19‰ VSMOW). During the
fruiting season, there was a positive correlation between δ13C in dove liver tissues and percent of saguaro in crop contents. A two-point mixing model indicated that during the peak of
saguaro fruit use, most of the carbon incorporated in dove tissues was from saguaro. Desert white-winged doves appear to be
saguaro specialists. Averaged over the period when doves were resident, saguaro comprised about 60% of the total carbon incorporated
into dove tissues. Tissue δ13C and δD of body water showed a significant positive correlation, indicating that doves were using saguaro as a source of
both nutrients and water. However, at the peak of saguaro utilization, the doves’ body-water δD was more positive (by about
20‰) than saguaro fruit water. We hypothesize that this enrichment is due to fractionated evaporative water losses by doves.
Using dove carbon isotope data and a two end-point mixing model we estimate that, on average, doves consume the equivalent
of 128 saguaro fruits per season; each fruit contains on average 26.0±14.8 g SD of pulp (wet mass) of which 19.4 g is water.
Stable isotopes have been used to produce qualitative re-constructions of animal diets. Our study shows that they can be used
to provide quantitative estimates of the flow of nutrients from resources into consumers as well.
Received: 30 September 1999 / Accepted: 23 March 2000 相似文献
16.
Summary Stable carbon isotope ratios in bone collagen have been used in a variety of dietary studies in modern and fossil animals,
including humans. Inherent in the stable isotope technique is the assumption that the isotopic signature is a reflection of
the diet and is persistent in collagen because this is a relatively inert protein. Carbon isotope analyses of bones from a
southern Indian population of Asian elephant (Elephas maximus), a long-lived mammal that alternates seasonally between a predominantly C3 (browse) and C4 (grass) plant diet, showed two patterns that have important implications for dietary interpretation based on isotopic studies.
Relative to the quantity of the two plant types consumed on average, the δ13C signal in collagen indicated that more carbon was incorporated from C3 plants, possibly due to their higher protein contribution. There was a much greater variance in δ13C values of collagen in sub-adult (range -10.5‰ to-22.7‰, variance=14.51) compared to adult animals (range -16.0‰ to -20.3‰,
variance=1.85) pointing to high collagen turnover rates and non-persistent isotopic signatures in younger, growing animals.
It thus seems important to correct for any significant relative differences in nutritive value of food types and also consider
the age of an animal before drawing definite conclusions about its diet from isotope ratios. 相似文献
17.
The species composition, abundance, and isotopic signature of millipedes (Myriapoda, Diplopoda) were investigated in seven
biotopes of Kaluzhskie Zaseki State Nature Reserve. Nine Diplopoda species were found in total, and the local species diversity
(within a sampling plot) reached seven species. The Diplopoda tissues were similar to the plant litter in the isotopic composition
of nitrogen (δ15N was by 0.4‰ higher, on average), but were strongly enriched in heavy carbon (δ13C was by 4‰ higher, on average). Removal of mineral carbon from the cuticle reduced δ13C of Diplopoda by about 1.4‰ on average. Differences in the δ15N and δ13C values between the species did not exceed 2.5‰. Differences in the isotopic compositions of the considered species were
small, and, it is impossible to distinguish particular trophic guilds in the Diplopoda community. Analysis of the published
data confirmed that isotopic differentiation of millipedes was much less pronounced than in other investigated groups of soil
animals. Hence, millipedes of the deciduous forest form a uniform trophic group. 相似文献
18.
Keith A. Hobson 《Oecologia》1999,120(3):314-326
To understand the ecology of migratory animals it is important to link geographic regions used by individuals including breeding,
wintering, and intermediate stopover sites. Previous conventional approaches used to track animal movements have relied on
extrinsic markers and typically the subsequent recovery of individuals. This approach has generally been inappropriate for
most small, or non-game animals. The use of intrinsic markers such as fatty acid profiles, molecular DNA analyses, and the
measurement of naturally occurring stable isotopes in animal tissues offer alternative approaches. This paper reviews the
use of stable isotope analyses (primarily δ13C, δ15N, δ34S, δD, δ87Sr) to trace nutritional origin and migration in animals. This approach relies on the fact that foodweb isotopic signatures
are reflected in the tissues of organisms and that such signatures can vary spatially based on a variety of biogeochemical
processes. Organisms moving between isotopically distinct foodwebs can carry with them information on the location of previous
feeding. Such an approach has been used to track animal use of inshore versus offshore, marine versus freshwater, terrestrial
C3 versus marine, terrestrial mesic versus xeric, and C3 versus C4 or Crassulacean acid metabolism foodwebs. More recently, the use of stable hydrogen isotope analyses (δD) to link organisms
to broad geographic origin in North America is based on large-scale isotopic contours of growing-season average δD values
in precipitation. This technique, especially when combined with the assay of other stable isotopes, will be extremely useful
in helping to track migration and movement of a wide range of animals from insects to birds and mammals. Future research to
refine our understanding of natural and anthropogenic-induced isotopic gradients in nature, and to explore the use of stable
isotopes of other elements, is recommended.
Received: 1 July 1998 / Accepted: 9 December 1998 相似文献
19.
It is widely accepted that stable isotope ratios in inert tissues such as feather keratin reflect the dietary isotopic signature
at the time of the tissue synthesis. However, some elements such as stable nitrogen isotopes can be affected by individual
physiological state and nutritional stress. Using malaria infection experiment protocols, we estimated the possible effect
of malaria parasite infections on feather carbon (δ13C) and nitrogen (δ15N) isotope signatures in juvenile common crossbills Loxia curvirostra. The birds were experimentally infected with Plasmodium relictum (lineage SGS1) and P. ashfordi (GRW2), two widespread parasites of passerines. Experimental birds developed heavy parasitemia of both parasites and maintained
high levels throughout the experiment (33 days). We found no significant difference between experimental and control birds
in both δ13C and δ15N values of feathers re-grown. The study shows that even heavy primary infections of malaria parasites do not affect feather
δ13C and δ15N isotopic signatures. The results of this experiment demonstrate that feather isotope values of wild-caught birds accurately
reflect the dietary isotopic sources at the time of tissue synthesis even when the animal’s immune system might be challenged
due to parasitic infection. 相似文献
20.
Rune Knudsen Anna Siwertsson Colin E. Adams Monica Garduño-Paz Jason Newton Per-Arne Amundsen 《Evolutionary ecology》2011,25(3):589-604
There is now strong evidence that foraging niche specialisation plays a critical role in the very early stages of resource
driven speciation. Here we test critical elements of models defining this process using a known polymorphic population of
Arctic charr from subarctic Norway. We test the long-term stability of niche specialisation amongst foraging predators and
discuss the possibility that contrasting foraging specialists are exposed to differing selection regimes. Inter-individual
foraging niche stability was measured by combining two time-integrated ecological tracers of the foraging niche (each individual’s
δ13C and δ15N stable isotope (SI) signatures and their food borne parasite fauna) with a short-term measure of foraging niche use (stomach
contents composition). Three dietary subgroups of predators were identified, including zooplankton, gammarid and benthivore
specialists foragers. Zooplanktivorous specialists had muscle low in δ 13C, a high abundance of parasites transmitted from pelagic copepods, a smaller head, longer snout and a more slender body-form
than gammaridivorous specialist individuals which had muscle more enriched in δ 13C and high abundance of parasites transmitted from benthic Gammarus. Benthivorous individuals were intermediate between the other two foraging groups according to muscle SI-signals (δ13C) and loadings of parasites transmitted from both copepods and Gammarus. The close relationship between subgroups identified by stomach contents, time-integrated tracers of niche use (SI and parasites)
and functional trophic morphology (niche adaptations) demonstrate a long-term temporally stable niche use of each individual
predator. Differential habitat use and contrasting parasite communities and loadings, show differential exposure to different
suites of selection pressures for different foraging specialists. Results also show that individual specialisation in trophic
behaviour and thus exposure to different suites of selection pressures are stable over time, and thus provide a platform for
disruptive selection to operate within this sympatric system. 相似文献