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1.
Although avoidance behavior is thought to be one of the major strategies for arthropods to cope with cold, there is a general lack of data supporting its use. This study tested the suggestion that Collembola migrate deeper into the soil to avoid cooling temperatures during the transition from summer to winter. We released mature hemi‐edaphic Folsomia candida Willem (Collembola: Isotomidae) in large (5 301 cm3) and small (306 cm3) soil microcosms exposed to ambient temperatures ranging between 5 and 20 °C. Springtails released in the large microcosms for periods of 2, 3, and 4 weeks dispersed throughout the soil column but remained more abundant in the upper third layer of the soil column whether exposed to weekly decreasing temperatures or a constant ambient temperature of 20 °C. Both small (juvenile) and large (mature) springtails exposed to cooling were more abundant in the upper third than in the middle or lower third of the soil columns after 2, 3, or 4 weeks. Groups of F. candida released in small microcosms provided with a positive soil temperature gradient displayed the same vertical distribution, with 90% of individuals clustered in the top 4.5 cm of the 15‐cm column whether exposed to air temperatures of 5, 10, 15, or 20 °C. Results from the two types of microcosms demonstrated that the vertical distribution of springtails remains strongly biased to the upper soil layer regardless of the temperature of their environment and whether the temperature in the soil column was uniform or graduated. This supports our prediction that hemi‐edaphic species such as F. candida do not relocate to warmer deeper soil layers, but tend to remain in the surface soil layer where they can acclimate to the cooling temperature. 相似文献
2.
Springtails are closely related to insects, but they differ from these with respect to water balance, in particular because springtails are small and have high integumental permeability to water. Here we report a series of experiments addressing the dynamics of osmoregulation, water content and accumulation of free amino acids (FAAs) in three springtail species during exposure to a gradually increasing environmental desiccation simulating conditions in drought exposed soil. Folsomia candida and Protaphorura fimata (both living in the deeper soil layers; euedaphic species) were active throughout the 3 week exposure, with the developing drought regime ending at −3.56 MPa (the soil water activity at the permanent wilting point of plants is −1.5 MPa) and remained hyperosmotic (having an body fluid osmolality higher than the corresponding environment) to their surrounding air. Sinella curviseta (living in upper soil/litter layers; hemiedaphic species) also survived this exposure, but remained hypoosmotic throughout (i.e. with lower osmolality than the environment). The body content of most FAAs increased in response to drought in all three species. Alanine, proline and arginine were the most significantly upregulated FAAs. By combining our results with data in the literature, we could account for 82% of the observed osmolality at −3.56 MPa in F. candida and 92% in P. fimata. The osmolality of S. curviseta was only slightly increased under drought, but here FAAs were considerably more important as osmolytes than in the two other species. We propose that FAAs probably have general importance in drought tolerance of springtails. 相似文献
3.
4.
Background
In lakes with a deep-water algal maximum, herbivorous zooplankton are faced with a trade-off between high temperature but low food availability in the surface layers and low temperature but sufficient food in deep layers. It has been suggested that zooplankton (Daphnia) faced with this trade-off distribute vertically according to an "Ideal Free Distribution (IFD) with Costs". An experiment has been designed to test the density (competition) dependence of the vertical distribution as this is a basic assumption of IFD theory. 相似文献5.
Nocturnal increases in water potential (ψ) and water content (θ) in the upper soil profile are often attributed to root water efflux, a process termed hydraulic redistribution
(HR). However, unsaturated liquid or vapor flux of water between soil layers independent of roots also contributes to the
daily recovery in θ (Δθ), confounding efforts to determine the actual magnitude of HR. We estimated liquid (J
l) and vapor (J
v) soil water fluxes and their impacts on quantifying HR in a seasonally dry ponderosa pine (Pinus ponderosa) forest by applying existing datasets of ψ, θ and temperature (T) to soil water transport equations. As soil drying progressed, unsaturated hydraulic conductivity declined rapidly such that
J
l was irrelevant (<2E−05 mm h−1 at 0–60 cm depths) to total water flux by early August. Vapor flux was estimated to be the highest in upper soil (0–15 cm),
driven by large T fluctuations, and confounded the role of HR, if any, in nocturnal θ dynamics. Within the 15–35 cm layer, J
v contributed up to 40% of hourly increases in nocturnal soil moisture. While both HR and net soil water flux between adjacent
layers contribute to θ in the 15–65 cm soil layer, HR was the dominant process and accounted for at least 80% of the daily
recovery in θ. The absolute magnitude of HR is not easily quantified, yet total diurnal fluctuations in upper soil water content
can be quantified and modeled, and remain highly applicable for establishing the magnitude and temporal dynamics of total
ecosystem water flux. 相似文献
6.
Zn uptake by maize plants may be affected by the presence of arbuscular mycorrhizal fungi (AMF). Collembola often play an important controlling role in the inter-relationship between AMF and host plants. The objective of this experiment was to examine whether the presence of Collembola at different densities (0.4 and 1 individuals g−1 dry soil) and their activity have any effect on Zn uptake by maize through the plant–AMF system. The presence of the AMF (Glomus intraradices) and of the Collembola species Folsomia candida was studied in a laboratory microcosm experiment, applying a Zn exposure level of 250 mg kg−1 dry soil. Biomass and water content of the plants were no different when only AMF or when both AMF and Collembola were present. In the presence of AMF the Zn content of the plant shoots and roots was significantly higher than without AMF. This effect was reduced by Collembola at both low and high density. High densities of Collembola reduced the extent of AMF colonization of the plant roots and hyphal length in the soil, but low densities had no effect on either. The results of this experiment reveal that the F. candida–G. intraradices interaction affects Zn uptake by maize, but the mechanisms are still unknown. 相似文献
7.
Hayashi M Wharton DA 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(3):335-342
The cold tolerance abilities of only a few nematode species have been determined. This study shows that the oatmeal nematode,
Panagrellus redivivus, has modest cold tolerance with a 50% survival temperature (S
50) of −2.5°C after cooling at 0.5°C min−1 and freezing for 1 h. It can survive low temperatures by freezing tolerance and cryoprotective dehydration; although freezing
tolerance appears to be the dominant strategy. Freezing survival is enhanced by low temperature acclimation (7 days at 5°C),
with the S
50 being lowered by a small but significant amount (0.42°C). There is no cold shock or rapid cold hardening response under the
conditions tested. Cryoprotective dehydration enhances the ability to survive freezing (the S
50 is lowered by 0.55°C, compared to the control, after 4 h freezing at −1°C) and this effect is in addition to that produced
by acclimation. Breeding from survivors of a freezing stress did not enhance the ability to survive freezing. The cold tolerance
abilities of this nematode are modest, but sufficient to enable it to survive in the cold temperate environments it inhabits. 相似文献
8.
Meryem Beklioglu Ayse Gul Gozen Feriha Yıldırım Pelin Zorlu Sertac Onde 《Hydrobiologia》2008,614(1):321-327
Vertical migration of Daphnia represents the best-studied predator-avoidance behaviour known; yet the mechanisms underlying the choice to migrate require
further investigation to understand the role of environmental context. To investigate the optimal habitat choice of Daphnia under fish predation pressure, first, we selected the individuals exhibiting strong migration behaviour. The animals collected
from the hypolimnion during the daytime were significantly larger, being more conspicuous, and in turn performed stronger
diel vertical migration (DVM) when exposed to fish cue. We called them strong migrants. Second, we provided the strong migrant
D. pulex with food at high and intermediate (1 and 0.4 mg C l−1, respectively) levels, which were well above the incipient limiting level and of high quality. They traded the benefits of
staying in the warm water layer and moved down to the cold water in response to fish cue indicating fish predation. The availability
of food allowed the animals to stay in the cold hypolimnion. However, at the low food level (0.1 mg C l−1), which is an additional constraint on fitness, Daphnia moved away from the cold hypolimnion. Poor food condition resulted in strong migrant Daphnia to cease migration and remain in the upper warmer water layer. Although temperature is known to be a more important cost
factor of DVM than food, our results clearly show that this is only true as long as food is available. It becomes clear that
food availability is controlling the direction of vertical positioning when daphnids experience a dilemma between optimising
temperature and food condition while being exposed to fish cue. Then they overlook the predation risk. Thus, the optimal habitat
choice of Daphnia appears to be a function of several variables including temperature, food levels and fish predation.
Handling editor: S. I. Dodson 相似文献
9.
Xiao-Hong Guo Jing Jiang Shi-Jie Lin Bai-Chen Wang Yu-Cheng Wang Gui-Feng Liu Chuan-Ping Yang 《Biotechnology letters》2009,31(7):1079-1087
The ThCAP gene, which encodes a cold acclimation protein, was isolated from a Tamarix hispida NaCl-stress root cDNA library; its expression patterns were then assayed by qRT-PCR in different T. hispida tissues treated with low temperature (4°C), salt (400 mM NaCl), drought (20% PEG6000) and exogenous abscisic acid (100 μM).
Induction of ThCAP gene was not only responsive to different stress conditions but was also organ specific. When transgenic Populus (P. davidiana × P. bolleana) plants were generated, expressing ThCAP under regulation of the cauliflower mosaic virus CaMV 35S promoter, they had a greater resistance to low temperature than
non-transgenic seedlings, suggesting that ThCAP might play an important role in cold tolerance. 相似文献
10.
Development time, reproduction, survival and sex ratio were determined for the omnivorous mite Amblyseius swirskii at nine constant temperatures (13, 15, 18, 20, 25, 30, 32, 34 and 36°C) on pepper leaf disks with cattail, Typha latifolia, pollen for food. These data were used to derive life table parameters at these constant temperatures. No development was
observed at 13°C. The lower development threshold, based on the fit to the linear portion of the development curve, was 11.3°C.
The upper development threshold was 37.4 ± 1.12°C, and the optimum temperature was calculated to be 31.5°C. Average lifetime
fecundity ranged from a low of 1.3 ± 0.24 eggs/female at 15°C to a high of 16.1 ± 0.34 eggs/female at 25°C, and r
m was greatest at 32°C. Non-linear regression of the relationship between temperature and r
m produced an estimate of 15.49 ± 0.905°C for the lower threshold for population growth and 36.99 ± 0.816°C for the upper threshold
for population growth, and an optimum temperature of 30.1°C. These values suggest that A. swiskii populations should grow quickly in response to food availability (pollen or prey) between 20 and 32°C, but that, especially
below 20°C, population growth could be slow and impacts on prey populations should be monitored carefully. 相似文献
11.
Transcriptional regulatory network triggered by oxidative signals configures the early response mechanisms of japonica rice to chilling stress 总被引:3,自引:0,他引:3
Kil-Young Yun Myoung Ryoul Park Bijayalaxmi Mohanty Venura Herath Fuyu Xu Ramil Mauleon Edward Wijaya Vladimir B Bajic Richard Bruskiewich Benildo G de los Reyes 《BMC plant biology》2010,10(1):16
12.
13.
In spring and early summer, a small population of the large-bodied Daphnia pulicaria coexists with a much larger population of the medium-sized hybrid Daphnia galeata × hyalina in the epilimnion of Lake Maarsseveen (The Netherlands). When large shoals of juvenile perch (Perca fluviatilis) appear in the open water, both species start to migrate vertically. Since D. pulicaria has a larger body-size than D. galeata × hyalina, and is therefore competitive dominant over the hybrid, it is unlikely that both species interact via their common food resource, but they react both to fish predation. However, since they differ in size, and therefore in vulnerability for fish predation, both species adopt different strategies. The smaller bodied, and less vulnerable D. galeata × hyalina exhibits diel vertical migration ascending to the surface at dusk, and staying there during the night. In this way, benefiting from the higher temperatures of the surface layers. In contrast, the large-bodied, and more vulnerable D. pulicaria selects the deep cold hypolimnion water layers as refuge against fish predation. In this way it benefits from a safe habitat, free from fish predators, but on the other hand suffers from low water temperatures, which decrease its fitness. It is likely that the relatively higher temperature in the upper water layers serves as a proximate factor for the downward migration of D. pulicaria. 相似文献
14.
Land degradation affects shrub growth responses to precipitation in a semiarid rangeland of north‐eastern Patagonia (Argentina)
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María Victoria Campanella César Mario Rostagno Lina Sonia Videla Alejandro Jorge Bisigato 《Austral ecology》2018,43(3):280-287
Arid land degradation diminishes the proportion of precipitation conducted to infiltration and increases the proportion lost to run‐off and evaporation. Consequently, we expect that the effects of annual precipitation on shrub growth vary with land degradation as a result of changes in soil available water. Chuquiraga avellanedae is the dominant shrub and the main indicator of land degradation in semiarid rangelands of north‐eastern Patagonia. We chose two communities with a different degree of land degradation: an herbaceous steppe with shrubs (HSS) and a degraded shrub steppe (SS). Vegetative growth of C. avellanedae was determined nondestructively using a double‐sampling approach. Soil water content was estimated for the two communities using a soil water balance model. Linear regressions were used to evaluate the relationships between shrub growth and (i) annual precipitation and (ii) mean available water during the period of high vegetative growth in the soil layer that each plant community concentrates their roots. In SS, with elevated clay content, there were more roots of C. avellanedae in the upper layers of soil while in HSS, with coarse‐textured soil, C. avellanedae had more roots in deeper layers. Vegetative growth of C. avellanedae, both in HSS and SS communities, was positively related to annual precipitation but, for a given precipitation, C. avellanedae presented higher vegetative growth in HSS than in SS. We also found a positive relationship between vegetative growth and soil available water, and this relationship did not differ between communities. SS presented lower water availability because of lower infiltration rates. Our results showed that, irrespective of the degree of land degradation, plants respond directly to water content of the soil layers where most roots are present at a specific window of time. 相似文献
15.
Yukio Nakasone 《Population Ecology》1982,24(1):97-109
Field observations on the behaviour of Uca (Thalassuca) vocans vocans were made in the estuary of the Okukubi river, Okinawa Island. The formation of the feeding aggregation of wandering individuals or drove was found in warm seasons above an average monthly air temperature 20°C from April to early November, while the aggregation was little observed in cold seasons below the temperature from the middle of November to March. The members of the aggregation tended to move down from the upper levels of burrow area, rather than lower levels. This may be related to the richness of organic matters in the substratum of the lower levels as compared with the upper levels. The feeding aggregation was mostly composed of males, but in June females were numerously seen and its peak occurred in June. It suggested that the peak in June is related to both feeding and copulation. Behaviour different from warm seasons was observed in cold seasons. When feeding on surface soil or Enteromorpha the crabs carried a mass of surface soil or the alga into their burrow. It was though that this behaviour was related to the storage of food. It seems likely that the crabs maintain the population by the formation of the aggregation of wandering feeders in warm seasons when there are no algae and by feeding abundant algae as well as surface soil or by storing up food in good weather for bad one in cold seasons. 相似文献
16.
Pollinator‐independent orchid attracts biotic pollinators due the production of lipoidal substances
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E. R. Pansarin P. J. Bergamo M. J. Ferreira‐Caliman 《Plant biology (Stuttgart, Germany)》2018,20(2):182-190
- Flowering plants often depend on the attraction of biotic pollinators for sexual reproduction. Consequently, the emergence and maintenance of selected floral attributes related to pollinator attraction and rewarding are driven by pollinator pressure.
- In this paper we explore the effect of pollinators, rainfall, temperature and air humidity on the reproduction of a Brazilian terrestrial orchid, Cranichis candida based on data of phenology, flower resources, olfactory and visual attraction cues, pollinators and breeding system.
- The flowers of C. candida are strongly protandrous and pollinated by workers of the social native bee Tetragonisca angustula. The bees collect labellar lipoidal substances (wax scales), which are transported to the nest. The lipoidal substance is composed of sterols, hydrocarbons and terpenes. The last presumably protects the bees and their nests against pathogens and other arthropods. C. candida sets fruits through biotic self‐ and cross‐pollination, and spontaneously due the action of raindrops on flowers.
- Our results indicate that in C. candida, although rain‐mediated spontaneous self‐pollination happens, fructification mediated by biotic pollinations also occurs, which may result in fruit set by cross‐pollination. A mixed pollination system must result in higher genetic variability when compared to species whose fruits are produced entirely by self‐pollination. On the other hand, autogamy is a form of reproductive assurance, and has commonly evolved where pollination services are rare or absent.
17.
Arundo donax L. (Poaceae) is an aggressive invader in California’s riparian habitats. Field experiments were conducted to examine invader
and site attributes important in early invasion. One hundred A. donax rhizomes were planted along five transects into each of three southern California riparian habitats. Pre-planting rhizome
weight was recorded, along with site variables including percent bare ground, litter depth, PAR, soil moisture, soil temperature,
incidence of herbivory, native canopy cover, and plant community richness and diversity. A. donax shoot emergence, survival time, and shoot height were recorded for approximately 10 months. The experiment was repeated over
three years in different locations within each site. When years and sites were pooled to reveal large-scale patterns, A. donax performance was explained by rhizome weight, soil moisture, bare ground, soil temperature, and herbivory. When each site
was considered singly, A. donax was positively correlated with different variables in each location. Species richness was correlated with A. donax performance in only one site. Our results indicate that A. donax establishment in riparian habitats is promoted by both vegetative reproduction and favorable abiotic environmental factors
and relatively unaffected by the composition of the native community. The positive response of A. donax to disturbance (bare ground) and high resource availability (soil moisture), combined with a competitive perennial habit
suggest that this species takes advantage of a competitive-ruderal life history. The ability of A. donax to respond to different conditions in each site combined with low genetic and phenotypic variation seen in other studies
also suggests that a high degree of environmental tolerance contributes to invasion success. 相似文献
18.
Disentangling effects of air and soil temperature on C allocation in cold environments: A 14C pulse‐labelling study with two plant species
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Carbon cycling responses of ecosystems to global warming will likely be stronger in cold ecosystems where many processes are temperature‐limited. Predicting these effects is difficult because air and soil temperatures will not change in concert, and will affect above and belowground processes differently. We disentangled above and belowground temperature effects on plant C allocation and deposition of plant C in soils by independently manipulating air and soil temperatures in microcosms planted with either Leucanthemopsis alpina or Pinus mugo seedlings. Daily average temperatures of 4 or 9°C were applied to shoots and independently to roots, and plants pulse‐labelled with 14CO2. We traced soil CO2 and 14CO2 evolution for 4 days, after which microcosms were destructively harvested and 14C quantified in plant and soil fractions. In microcosms with L. alpina, net 14C uptake was higher at 9°C than at 4°C soil temperature, and this difference was independent of air temperature. In warmer soils, more C was allocated to roots at greater soil depth, with no effect of air temperature. In P. mugo microcosms, assimilate partitioning to roots increased with air temperature, but only when soils were at 9°C. Higher soil temperatures also increased the mean soil depth at which 14C was allocated. Our findings highlight the dependence of C uptake, use, and partitioning on both air and soil temperature, with the latter being relatively more important. The strong temperature‐sensitivity of C assimilate use in the roots and rhizosphere supports the hypothesis that cold limitation on C uptake is primarily mediated by reduced sink strength in the roots. We conclude that variations in soil rather than air temperature are going to drive plant responses to warming in cold environments, with potentially large changes in C cycling due to enhanced transfer of plant‐derived C to soils. 相似文献
19.
20.
Daria M. Martynova Natalia A. Kazus Ulrich V. Bathmann Martin Graeve Alexey A. Sukhotin 《Polar Biology》2011,34(8):1175-1195
We have studied the seasonal dynamics of abundance and feeding characteristics of three species of calanoid copepods (Acartia spp., Centropages hamatus and Temora longicornis) in the White Sea from the surface water layer (0–10 m), in order to assess their role in the pelagic food web and to determine
the major factors governing their population dynamics during the productive season. These species dominated in the upper water
layer (0–10 m) from June through September, producing up to 3 generations per year. Data on the food spectra revealed all
species to be omnivorous; but some inter- and intraspecific differences were observed. Generally, copepods consumed diatoms,
dinoflagellates and microzooplankton. The omnivory index ‘UC’ (i.e., fatty acid unsaturation coefficient) varied from 0.2
to 0.6, which implied ingestion of phytoplankton. The different degree of selectivity on the same food items by the studied
species was observed, and therefore, successful surviving strategy with minimal overlapping could be assumed. In total, the
populations of the three studied copepod species grazed up to 2.15 g C m−2 day−1 and released up to 0.68 g C m−2 day−1 in faecal pellets. They consumed up to 50% of particulate organic carbon, or up to 85% of phytoplankton standing stock (in
terms of Chl. a), and thus played a significant role in the transformation of particulate organic matter. Seasonal changes in abundance of
the studied species depended mostly on water temperature in the early summer, but were also affected by food availability
(Chl. a concentration) during the productive season. 相似文献