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1.
To understand the consequences of the invasion of the nonnative rainbow trout Oncorhynchus mykiss on the native marble trout Salmo marmoratus, we compared two distinct headwater sectors where marble trout occur in allopatry (MTa) or sympatry (MTs) with rainbow trout
(RTs) in the Idrijca River (Slovenia). Using data from field surveys from 2002 to 2009, with biannual (June and September)
sampling and tagging from June 2004 onwards, we analyzed body growth and survival probabilities of marble trout in each stream
sector. Density of age-0 in September over the study period was greater for MTs than MTa and very similar between MTs and
RTs, while density of trout ≥age-1 was similar for MTa and MTs and greater than density of RTs. Monthly apparent survival
probabilities were slightly higher in MTa than in MTs, while RTs showed a lower survival than MTs. Mean weight of marble and
rainbow trout aged 0+ in September was negatively related to cohort density for both marble and rainbow trout, but the relationship
was not significantly different between MTs and MTa. No clear depression of body growth of sympatric marble trout between
sampling intervals was observed. Despite a later emergence, mean weight of RTs cohorts at age 0+ in September was significantly
higher than weight of both MTs and MTa. The establishment of a self-sustaining population of rainbow trout does not have a
significant impact on body growth and survival probabilities of sympatric marble trout. The numerical dominance of rainbow
trout in streams at lower altitudes seem to suggest that while the low summer flow pattern of Slovenian streams is favorable
for rainbow trout invasion, the adaptation of marble trout to headwater environments may limit the invasion success of rainbow
trout in headwaters. 相似文献
2.
Julien Cucherousset Jean-Marc Paillisson Jean-Marc Roussel 《Die Naturwissenschaften》2013,100(8):761-768
Natal departure timing represents one of the first crucial decisions for juveniles born in spatially varying environments that ultimately disappear, but our knowledge on its determinants is limited. The present study aimed at understanding the determinants of juvenile natal departure by releasing individually tagged juvenile pike (Esox lucius L.) with variable body size and trophic position in a temporary flooded grassland. Specifically, we investigated whether natal departure depends on individual competitive status (‘competition hypothesis’), physiological tolerance to environmental conditions (‘physiological hypothesis’) or individual trophic position and the spatial heterogeneity of trophic resources (‘trophic hypothesis’). The results indicated that departure timing was negatively correlated with body size at release, showing that the dominance status among competing individuals was not the main trigger of juvenile departure. A positive correlation between departure timing and individual body size at departure was observed, suggesting that inter-individual variability in physiological tolerance did not explain departure patterns. While individual growth performances were similar irrespective of the timing of natal departure, stable isotope analyses revealed that juveniles with higher trophic position departed significantly earlier than individuals with lower trophic position. Therefore, the trade-off driving the use of spatially varying environments was most likely dependent upon the benefits associated with energetic returns than the costs associated with inter-individual competition or physiological stress. This result highlighted how ontogeny, and particularly ontogenetic niche shift, can play a central role in juvenile’s decision to depart from natal habitats in a predatory species. 相似文献
3.
Among the order of primates, torpor has been described only for the small Malagasy cheirogaleids Microcebus and Cheirogaleus. The nocturnal, gray mouse lemur, Microcebus murinus (approx. 60 g), is capable of entering into and spontaneously arousing from apparently daily torpor during the dry season
in response to reduced temperatures and low food and water sources. Mark–recapture studies indicated that this primate species
might also hibernate for several weeks, although physiological evidence is lacking. In the present study, we investigated
patterns of body temperature in two free-ranging M. murinus during the austral winter using temperature-sensitive data loggers implanted subdermally. One lemur hibernated and remained
inactive for 4 weeks. During this time, body temperature followed the ambient temperature passively with a minimum body temperature
of 11.5°C, interrupted by irregular arousals to normothermic levels. Under the same conditions, the second individual displayed
only short bouts of torpor in the early morning hours but maintained stable normothermic body temperatures throughout its
nocturnal activity. Reduction of body temperature was less pronounced in the mouse lemur that utilized short bouts of torpor
with a minimum value of 27°C. Despite the small sample size, our findings provide the first physiological confirmation that
free-ranging individuals of M. murinus from the humid evergreen littoral rain forest have the option to utilize short torpor bouts or hibernation under the same
conditions as two alternative energy-conserving physiological solutions to environmental constraints. 相似文献
4.
Population dynamics and regulation in the cave salamander <Emphasis Type="Italic">Speleomantes strinatii</Emphasis> 总被引:1,自引:0,他引:1
Salvidio S 《Die Naturwissenschaften》2007,94(5):396-400
Time series analysis has been used to evaluate the mechanisms regulating population dynamics of mammals and insects, but has
been rarely applied to amphibian populations. In this study, the influence of endogenous (density-dependent) and exogenous
(density-independent) factors regulating population dynamics of the terrestrial plethodontid salamander Speleomantes strinatii was analysed by means of time series and multiple regression analyses. During the period 1993–2005, S. strinatii population abundance, estimated by a standardised temporary removal method, displayed relatively low fluctuations, and the
autocorrelation function (ACF) analysis showed that the time series had a noncyclic structure. The partial rate correlation
function (PRCF) indicated that a strong first-order negative feedback dominated the endogenous dynamics. Stepwise multiple
regression analysis showed that the only climatic factor influencing population growth rate was the minimum winter temperature.
Thus, at least during the study period, endogenous, density-dependent negative feedback was the main factor affecting the
growth rate of the salamander population, whereas stochastic environmental variables, such as temperature and rainfall, seemed
to play a minor role in regulation. These results stress the importance of considering both exogenous and endogenous factors
when analysing amphibian long-term population dynamics. 相似文献
5.
Carotenoid-based integument colour in animals has been hypothesised to signal individual phenotypic quality because it reliably
reflects either foraging efficiency or health status. We investigated whether carotenoid-derived yellow plumage coloration
of fledgling great tits (Parus major) reflects their nestling history. Great tit fledglings reared in a poor year (1998) or in the urban habitat were less yellow
than these reared in a good year (1999) or in the forest. The origin of nestlings also affected their coloration since nestlings
from a city population did not improve their coloration when transferred to the forest. Brood size manipulation affected fledgling
colour, but only in the rural population, where nestlings from reduced broods developed more yellow coloration than nestlings
from increased and control broods. Effect of brood size manipulation on fledgling plumage colour was independent of the body
mass, indicating that growth environment affects fledgling body mass and plumage colour by different pathways.
Received: 20 March 2000 / Accepted in revised form: 4 September 2000 相似文献
6.
We analyzed the relationships among spleen size, body condition (measured as kidney fat), and larval counts of the nematode
Elaphostrongylus cervi in red deer (Cervus elaphus). The aim was to investigate the interaction between host body condition and intensity of infection with parasites. As red
deer are highly polygynous, we also tested whether these relationships varied with sex and age of the hosts. Kidney fat and
spleen size were positively correlated in subadults (2–3 years old) and adults (>3 years old), but not in calves (<1 year
old) or yearlings (1–2 years old). Spleen size was negatively associated with nematode load in subadult females and in adult
males. These two age classes are potentially the most nutritionally stressed, as subadult hinds are still growing and often
engaging in rearing their first calf, and adult stags were sampled just after the rut, which is recognized as a substantial
energy drain in this age–sex class, as they compete to hold females during the mating season. Body condition related negatively
to parasite count only in adult males. In the context of red deer life history, these findings suggest that spleen size is
dependent on body condition and that it could be affected by variation in resource partitioning among immune defense, growth,
and reproductive effort in red deer. For the first time in a wild mammal, the spleen mass is shown to be positively related
to body condition and negatively related to parasite infection. We conclude that elucidating whether spleen mass reflects
immune defense investment or a measure of general body condition should contribute to understanding topical issues in mammal
ecology. 相似文献
7.
8.
Glycogen is a vital energy substrate for anaerobic organisms, and the size of glycogen stores can be a limiting factor for
anoxia tolerance of animals. To this end, glycogen stores in 12 different tissues of the crucian carp (Carassius carassius L.), an anoxia-tolerant fish species, were examined. Glycogen content of different tissues was 2–10 times higher in winter
(0.68–18.20% of tissue wet weight) than in summer (0.12–4.23%). In scale, bone and brain glycogen stores were strongly dependent
on body mass (range between 0.6 and 785 g), small fish having significantly more glycogen than large fish (p < 0.05). In fin and skin, size dependence was evident in winter, but not in summer, while in other tissues (ventricle, atrium,
intestine, liver, muscle, and spleen), no size dependence was found. The liver was much bigger in small than large fish (p < 0.001), and there was a prominent enlargement of the liver in winter irrespective of fish size. As a consequence, the whole
body glycogen reserves, measured as a sum of glycogen from different tissues, varied from 6.1% of the body mass in the 1-g
fish to 2.0% in the 800-g fish. Since anaerobic metabolic rate scales down with body size, the whole body glycogen reserves
could provide energy for approximately 79 and 88 days of anoxia in small and large fish, respectively. There was, however,
a drastic difference in tissue distribution of glycogen between large and small fish: in the small fish, the liver was the
major glycogen store (68% of the stores), while in the large fish, the white myotomal muscle was the principal deposit of
glycogen (57%). Since muscle glycogen is considered to be unavailable for blood glucose regulation, its usefulness in anoxia
tolerance of the large crucian carp might be limited, although not excluded. Therefore, mobilization of muscle glycogen under
anoxia needs to be rigorously tested. 相似文献
9.
香溪河流域微塑料的分布特征及其迁移规律分析 总被引:4,自引:4,他引:0
微塑料作为水体中一种普遍存在的污染物已引起社会的广泛关注.为探究微塑料在淡水河流中的时空分布特征及其迁移规律,以长江支流香溪河为例,分别在2020年11月和2021年4月对香溪河表层水体、沉积物和消落带进行取样分析.结果表明,香溪河表层水体中微塑料的平均丰度为(6.64±1.32)n·L-1(平水期)和(5.00±1.07)n·L-1(枯水期),沉积物中微塑料的平均丰度为(0.56±0.13)n·g-1(平水期)和(0.41±0.09)n·g-1(枯水期),消落带中微塑料的平均丰度为(0.53±0.15)n·g-1(平水期)和(0.68±0.18)n·g-1(枯水期),表层水体、沉积物和消落带中微塑料丰度分布存在显著差异性(P<0.05).在表层水体和沉积物中微塑料粒径主要分布在0.1~0.5 mm,消落带中主要分布在1~5 mm;表层水体和消落带中微塑料颜色以透明为主,沉积物中以蓝色为主;香溪河流域微塑料的形态以纤维为主,材质主要是聚乙烯(PE)和... 相似文献
10.
In this paper, the role played by habitat diversity in the landscape on species richness and on the stability of farmland bird communities was investigated. Species richness was estimated on 374 samples monitored in farmland by the French breeding bird survey during the 2001–2005 period. A capture–recapture approach was used to estimate species richness accounting for the variation in detection probability among species of the 100 most common species detected in farmland. Landscape structure and composition were measured both in farmland and in adjacent habitats. The independent effect of each variable on community richness and stability was further assessed using hierarchical variance partitioning and taking spatial autocorrelation into account. A strong matrix effect was detected: non-cropped land deeply influenced richness and stability of bird assemblages. 相似文献
11.
Kikuchi T Miyazaki S Ohnishi H Takahashi J Nakajima Y Tsuji K 《Die Naturwissenschaften》2008,95(10):963-968
Evolution of caste is a central issue in the biology of social insects. Comparative studies on their morphology so far suggest
the following three patterns: (1) a positive correlation between queen–worker size dimorphism and the divergence in reproductive
ability between castes, (2) a negative correlation among workers between morphological diversity and reproductive ability,
and (3) a positive correlation between queen–worker body shape difference and the diversity in worker morphology. We conducted
morphological comparisons between castes in Pachycondyla luteipes, workers of which are monomorphic and lack their reproductive ability. Although the size distribution broadly overlapped,
mean head width, head length, and scape length were significantly different between queens and workers. Conversely, in eye
length, petiole width, and Weber’s length, the size differences were reversed. The allometries (head length/head width, scape
length/head width, and Weber’s length/head width) were also significantly different between queens and workers. Morphological
examinations showed that the body shape was different between queens and workers, and the head part of workers was disproportionately
larger than that of queens. This pattern of queen–worker dimorphism is novel in ants with monomorphic workers and a clear
exception to the last pattern. This study suggests that it is possible that the loss of individual-level selection, the lack
of reproductive ability, influences morphological modification in ants. 相似文献
12.
Yang Christopher Schneider Stephen H. 《Mitigation and Adaptation Strategies for Global Change》1997,2(4):373-404
Carbon dioxide emissions from 1990 to 2100 AD are decomposed into the product of four factors: population size, affluence
(measured here as GDP per capita), energy intensity (energy use per unit GDP) and carbon intensity (carbon dioxide emissions
per unit energy). These emissions factors are further subdivided into three regions: more developed countries (MDCs), China,
and the remaining less developed countries (LDCs). Departures from a baseline scenario (based on IPCC, 1992a — the so-called
‘business-as-usual’ scenario) are calculated for a variety of alternative assumptions concerning the four emissions factors
in the three regions. Although the IPCC scenario is called a ‘non-intervention’ scenario, it is shown, for example, that large
decreases in energy intensity in China or carbon intensity in MDCs are built into the ‘business as usual’ case — and such
large changes vary considerably from region to region. We show what CO2 emissions would look like if each of these four emissions factors projected in the baseline case somehow remained constant
at 1990 levels. Certain factors like energy intensity improvements and long-term population growth in LDCs, or GDP growth
and carbon intensity improvements in MDCs, are shown to have a big contribution to cumulative global emissions to 2100 AD,
and consequently, changes in these projected factors will lead to significant deviations from baseline emissions. None of
the scenarios examined in this analysis seems to indicate that any one global factor is clearly dominant, but cultural, economic,
and political costs or opportunities of altering each factor may differ greatly from country to country. 相似文献
13.
Elena Cantarello Claude E. Steck Paolo Fontana Diego Fontaneto Lorenzo Marini Marco Pautasso 《Die Naturwissenschaften》2010,97(3):265-271
Recent large-scale studies have shown that biodiversity-rich regions also tend to be densely populated areas. The most obvious
explanation is that biodiversity and human beings tend to match the distribution of energy availability, environmental stability
and/or habitat heterogeneity. However, the species–people correlation can also be an artefact, as more populated regions could
show more species because of a more thorough sampling. Few studies have tested this sampling bias hypothesis. Using a newly
collated dataset, we studied whether Orthoptera species richness is related to human population size in Italy’s regions (average
area 15,000 km2) and provinces (2,900 km2). As expected, the observed number of species increases significantly with increasing human population size for both grain
sizes, although the proportion of variance explained is minimal at the provincial level. However, variations in observed Orthoptera
species richness are primarily associated with the available number of records, which is in turn well correlated with human
population size (at least at the regional level). Estimated Orthoptera species richness (Chao2 and Jackknife) also increases
with human population size both for regions and provinces. Both for regions and provinces, this increase is not significant
when controlling for variation in area and number of records. Our study confirms the hypothesis that broad-scale human population–biodiversity
correlations can in some cases be artefactual. More systematic sampling of less studied taxa such as invertebrates is necessary
to ascertain whether biogeographical patterns persist when sampling effort is kept constant or included in models. 相似文献
14.
Miwa T 《Die Naturwissenschaften》2007,94(7):551-560
I studied the conditions controlling the timing of breeding migration of the Japanese mountain stream frog Rana sakuraii, an explosive breeder, over 9 years (1992, 1993 and 1999–2005). I analysed two factors: the daily cumulative temperature
(DCT) during hibernation and the triggering temperature on the day of migration onset. Frogs hibernated in shallow running
water in streams in December. A total of 53,155 breeding migrating adults were captured by traps. Every year, breeding migration
was induced by a rise in daily maximum water temperature to about 5°C. However, its date was limited to 1 February at the
earliest, and the onset needed a DCT (from 20 January, using 3°C as the threshold for daily effective temperature) of at least
about 15°C. Earlier (e.g. in mid- or late January), even if the maximum temperature rose to 5–8°C, migration did not begin.
Moreover, even in early February, if the maximum temperature rose to 5°C, if it had been too cold in January and the DCT was
low, migration would not begin until mid- or late February. Thus, the earliest date of readiness for migration varied from
1 February to mid-February, depending on the winter DCT. Logistic regression analyses showed that both factors, the DCT and
the daily temperature, were significant. I propose that in temperate-zone amphibian explosive breeders, both the passing of
an essential number of days and an essential DCT during hibernation are prerequisites for the onset of breeding migration
before the daily temperature rises to the threshold. 相似文献
15.
Increased turbidity reduces visibility in the water column, which can negatively affect vision-oriented fish and their ability to detect prey. Young fish could consequently benefit from high turbidity levels that can provide a protective cover, reducing predation pressure. Perch (Perca fluviatilis) are commonly found in littoral zones of temperate lakes and coastal areas of the Baltic Sea. Pikeperch (Sander lucioperca) spawn in these areas, so perch is a potential predator for pikeperch larvae. We conducted laboratory experiments to test the predation of perch on pikeperch larvae at different turbidity levels (5–85 nephelometric turbidity units), densities of pikeperch larvae (2–21 individuals l−1) and volumes of water (10–45l). The logistic regression showed that the probability of larvae eaten depended significantly on turbidity and volume of water in the bags, while density of larvae was not significant. However, because container size is known to affect predation, the data was divided into two groups based on water volume (10–20 and 25–45l) to reduce the effects of container size. In either group, probability of predation did not significantly depend on volume, whereas turbidity was significant in both groups, while density was significant in larger water volumes. Thus, high turbidity impaired perch predation and protected pikeperch larvae from perch predation. Because density of larvae was also a significant factor affecting predation of perch, the dispersal of pikeperch larvae from spawning areas should also increase the survival of larvae. 相似文献
16.
Elena P. Kruchenkova Michael Goltsman Sergei Sergeev David W. Macdonald 《Die Naturwissenschaften》2009,96(4):457-466
The Arctic Fox Alopex lagopus semenovi population on Mednyi Island is completely isolated and subsists largely by scavenging on seabird colonies, which have remained
abundant and spatio-temporally predictable for many years. We compared population data at the beginning of 1976/1978 and some
time after 1994–2005, finding an 85% decline in fox numbers due to disease, to assess the effect of population size on social
structure. A total of 81 groups of known size and composition was observed during this 29-year period. Overall, helpers (usually
non-lactating yearling females) occurred in 25.7% of groups, and in 32.4% of groups there were two or three lactating females.
Female engagement in alloparental behaviour decreased, but not statistically significantly, after the decline in population
density. Total food availability was apparently constant throughout the study period, and therefore, the amount available
per individual was much higher later in the study. Both communally nursing females and helpers brought food and helped to
guard the litter. However, the benefits of communal rearing were unclear. While cubs were left without guards significantly
more rarely in the groups with an additional adult, the number of cubs weaned per lactating female was greater in groups with
one (3.93 ± 1.60), as opposed to two or three (3.06 ± 0.92), lactating females. Survival of cubs to 1 year of age in the groups
with two lactating females and/or with helpers was lower than that in the families with one lactating female without helpers (22.2% vs 32.2%). Fewer second-generation litters were
born to foxes produced by composite families than to those produced by pairs. Reproductive adults producing by pairs had,
on average, 1.23 (±1.72) second-generation litters. In groups that initially included additional adults, the average number
of second-generation litters per reproductive female was 0.21 (±0.49) and 0.46 (±0.81) litters per male. Thus, according to
three measures, increased group size had no apparent positive impact on reproductive success. The increased parental investment
and enhanced guarding of the cubs in the larger families could be beneficial under conditions of high population density and
a saturated biotope to which the island fox population was presumably adapted before the population crash in the late 1970s. 相似文献
17.
Genetic variability among males is a necessary precondition for the evolution of female choice based on indirect genetic benefits.
In addition to mutations and host–parasite cycles, migration of locally adapted individuals offers an explanation for the
maintenance of genetic variability. In a previous study, conducting a reciprocal transplant experiment on a grasshopper, Chorthippus biguttulus, we found that environmental conditions significantly influenced not only body condition but also an important trait of male
calling song, the amplitude of song. Although not significant, all other analysed physical and courtship song traits and attractiveness
were superior in native than in transferred males. Thus, we concluded that local adaptation has a slight but consistent influence
on a range of traits in our study populations, including male acoustic attractiveness. In our present study, we scanned male
grasshoppers from the same two populations for amplification fragment length polymorphism (AFLP) loci connected with acoustic
attractiveness to conspecific females. We found greater differences in allele frequencies between the two populations, for
some loci, than are expected from a balance between drift and gene flow. These loci are potentially connected with locally
adapted traits. We examined whether these alleles show the proposed genotype environment interaction by having different associations
with attractiveness in the two populations. One locus was significantly related to sexual attractiveness; however, this was
independent of the males’ population affiliation. Future research on the evolution of female choice will benefit from knowledge
of the underlying genetic architecture of male traits under intraspecific sexual selection, and the ‘population genomics’
approach can be a powerful tool for revealing this structure. 相似文献
18.
Diapause in arthropods is a physiological state of dormancy that is generally thought to promote survival during harsh seasons
and dispersal, but it may also serve to avoid predation in space and time. Here, we show that predation-related odours induce
diapause in female adult spider mites. We argue that this response allows them to move into an area where they are free of
enemies, yet forced to survive without food. Spider mites are specialised leaf feeders, but—in late summer—they experience
severe predation on leaves. Hence, they face a dilemma: to stay on the leaf and risk being eaten or to move away from the
leaf and risk death from starvation and thirst. Female two-spotted spider mites solve this dilemma by dramatically changing
their physiology when exposed to predation-associated cues. This allows them to disperse away from leaves and to survive in
winter refuges in the bark of trees or in the soil. We conclude that the mere presence of predation-associated cues causes
some herbivorous mites to seek refuge, thereby retarding the growth rate of the population as a whole: a trait-mediated indirect
effect that may have consequences for the stability of predator–prey systems and for ecosystem structure. 相似文献
19.
本文研究了温度(29℃、31℃、33℃、35℃和37℃)对中国鲎(Tachypleus tridentatus)幼鲎蜕壳同步性、机体免疫力和抗氧化能力等的影响。研究结果显示:(1)当温度高于33℃时幼鲎的成活率显著降低(P<0.05),蜕壳增重率随温度的升高而显著降低(P<0.05),蜕壳率则随着温度升高呈先显著升高(P<0.05)后显著降低(P<0.05)的趋势,33℃试验组蜕壳率最高;(2)温度较高试验组幼鲎开始蜕壳的时间较早,33℃试验组的幼鲎最先蜕壳;一、二龄幼鲎能值随温度升高而显著降低(P<0.05);(3)37℃高温组一、二幼鲎的ACP活力均显著降低(P<0.05),而AKP活力变化没有明显规律;(4)一龄幼鲎CAT活性随温度升高而显著降低(P<0.05),37℃试验组二龄幼鲎的TAOC和CAT活性均显著低于其他试验组(P<0.05)。研究结果表明,当温度低于33℃时,适当升高温度有利于中国鲎幼鲎的蜕壳与生长;当温度超过33℃时,幼鲎的免疫力、抗氧化能力显著降低,成活率下降。本文的结果可以为中国鲎人工育苗和放流活动开展提供基础... 相似文献
20.
The evolution of bird migration—a synthesis 总被引:1,自引:1,他引:0
We approach the problem of the evolution of bird migration by asking whether migration evolves towards new breeding areas
or towards survival areas in the non-breeding season. Thus, we avoid the ambiguity of the usually discussed “southern-home-theory”
or “northern-home-theory”. We argue that migration evolved in birds that spread to seasonal habitats through gradual dispersal
to enhance survival during the non-breeding season; this in contrast to the alternative idea suggesting that migration evolved
towards new breeding areas to increase reproductive success. Our synthesis is based on the threshold model explaining how
migratory traits can change rapidly through microevolutionary processes. Our model brings former theories together and explains
how bird migration, with the appropriate direction and time program, evolves through selection after genetically non-directed
events such as dispersal and colonization. The model does not need the former untested assumptions such as competition as
a reason for migration and for the disappearance of sedentary populations or higher reproductive success in temperate breeding
areas. Our theory offers answers to questions such as how birds with a southern origin may gradually reach northern latitudes,
why migration routes may follow historical expansion routes and why birds leave an area for the non-breeding season and move
back instead of breeding on their wintering grounds. The theory proposes gradual change through selection and not sudden changes
such as long distance dispersal or mutations and can be applied to migration at all latitudes and in all directions. The scenario
provides a reasonable concept to understand most of the existing migratory phenomena on the basis of the ecology and genetics
of migratory behaviour. 相似文献