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1.
Vidar Selås Geir A. Sonerud Erik Framstad John Atle Kålås Sverre Kobro Helge B. Pedersen Tor K. Spidsø Øystein Wiig 《Population Ecology》2011,53(2):361-371
Grouse and vole numbers may peak after peaks in the seed crop of bilberry (Vaccinium myrtillus) because of reduced levels of feeding deterrents in bilberry plants. We predicted that grouse reproduction depends also on
summer (June–September) temperatures in the 2 previous years, because bilberry plants will be less exhausted after a high
seed crop in or after warm summers, and thus rebuild their chemical defence more quickly. After berry peak years, population
indices of capercaillie (Tetrao urogallus) and bank vole (Myodes glareolus) in southern Norway were negatively related to summer temperatures in the previous year or previous 2 years. Willow grouse
(Lagopus lagopus) chick production in five areas in Norway was negatively related to summer temperatures in the 2 previous years when controlling
for vole density. A similar pattern was found for the bilberry-feeding moth (Eulithis populata), an important prey for grouse chicks. In eastern Norway, autumn densities of capercaillie and black grouse (Tetrao tetrix) were more likely to peak in vole peak years at high altitudes, where summer temperatures are low. We conclude that high
summer temperatures may limit grouse reproduction through the effect on bilberry plants and that a warm climate thus adversely
affects population levels of grouse. 相似文献
2.
Berry production drives bottom–up effects on body mass and reproductive success in an omnivore
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Anne G. Hertel Richard Bischof Ola Langval Atle Mysterud Jonas Kindberg Jon E. Swenson Andreas Zedrosser 《Oikos》2018,127(2):197-207
Obligate herbivores dominate studies of the effects of climate change on mammals, however there is limited empirical evidence for how changes in the abundance or quality of plant food affect mammalian omnivores. Omnivores can exploit a range of different food resources over the course of a year, but they often rely on seasonally restricted highly nutritious fruiting bodies during critical life stages. Brown bears Ursus arctos in Sweden are dependent on berries for fattening before entering hibernation. We used a ten‐year time series to evaluate the effect of temperature and snow on annual variation in berry abundance and how this variation affected bears. We found marked interannual variation in berry production of bilberry Vaccinium myrtillus and lingonberry V. vitis‐idaea, that we could attribute in part to temperature during plant dormancy and flowering and precipitation during fruit ripening. Both, autumn weights of female bears and spring weights of yearling bears increased linearly with bilberry abundance. When bilberry abundance was low, lightweight female bears had a lower reproductive success than females in better condition. This effect vanished when food abundance was above average, indicating that lightweight females could compensate for their initial weight during good bilberry years. Our study highlights the importance of considering individuals’ dynamic responses to variation in food availability, which leave some more vulnerable to food shortage than others. Individual life‐history heterogeneity in response to resource variation likely affects long‐term population recruitment. Our findings emphasize that Scandinavian bears can be dependent on a single food resource during a critical period of the year and are therefore less resilient to environmental change than expected for an omnivore. Future climate scenarios predict ambiguous trends for weather covariates that affected crucial stages of berry phenology, preventing a clear prognosis of how climate change may affect long‐term bilberry production. 相似文献
3.
Vidar Selås Geir A. Sonerud Olav Hjeljord Lars Erik Gangsei Helge B. Pedersen Erik Framstad Tor Kristian Spidsø Øystein Wiig 《European Journal of Wildlife Research》2011,57(3):523-535
The plant stress hypothesis states that plant stress factors other than herbivory improve herbivore performance due to changes
in the content of nutritive or defensive compounds in the plants. In Norway, the bilberry (Vaccinium myrtillus) is important forage for the bank vole (Myodes glareolus) in winter and for the moose (Alces alces) in summer and autumn. The observed peaks in bank vole numbers after years with high production of bilberries are suggested
to be caused by increased winter survival of bank voles due to improved forage quality. High production of bilberries should
also lead to higher recruitment rates in moose in the following year. We predict, however, that there is an increasing tendency
for a 1-year delay of moose indices relative to vole indices with decreasing summer temperatures, because low temperatures
prolong the period needed by plants to recover in the vole peak year, and thus positively affect moose reproduction also in
the succeeding year. In eight out of nine counties in south-eastern Norway, there was a positive relationship between the
number of calves observed per female moose during hunting and a bilberry seed production index or an autumn bank vole population
index. When dividing the study area into regions, there was a negative relationship between a moose-vole time-lag index and
the mean summer temperature of the region. These patterns suggest that annual fluctuations in the production of bilberries
affect forage quality, but that the effect on moose reproduction also depends on summer temperatures. 相似文献
4.
Vidar Sels 《Acta theriologica》2020,65(2):267-275
Animals that feed on forest tree seeds, such as Apodemus mice, increase in number after a mast year. At high latitudes, there is a similar delayed response by Myodes voles to high seed crops of bilberry (Vaccinium myrtillus), but here the mechanism is hypothesised to be increased forage quality, caused by a trade-off between reproduction and defence in the plants. Both Apodemus mice and Myodes voles eat berries, but only the latter feed on bilberry plants. Hence, only Myodes voles are predicted to respond to bilberry peak years. A second prediction is that the effect should last longer than any possible direct impacts of bilberries, because the plants would not be able to rebuild their defence until the succeeding summer. During a 21-year snap-trapping study of small rodents in Southern Norway, the spring population of bank vole (Myodes glareolus) was positively related to a bilberry seed index of the previous year, indicating increased winter survival, whereas the wood mouse (Apodemus sylvaticus) was not affected. Also the succeeding autumn population index of the bank vole was positively related to the bilberry index of the previous year, even when controlling for spring population levels. The wood mouse population responded to mast years of sessile oak (Quercus petraea), whereas seeds of Norway spruce (Picea abies) seemed to have some impact on both species. It is concluded that these rodents are mainly limited from below, but by different mechanisms for the granivorous and the herbivorous species. 相似文献
5.
The mast depression hypothesis (MDH) proposes that cyclic population fluctuations of microtines and other herbivores are
an effect of cyclic seed cropping of plants. This is because high seed crops, termed masts, are produced at the expense of
chemical defence against herbivores. It has generally been assumed that bird-hunting raptors produce high numbers of offspring
when microtine prey are abundant because of reduced competition from generalist predators. However, this may also be caused
by higher production of herbivorous insects, and thus insectivorous bird prey, because of lower contents of chemical defence
compounds in some plant species, such as bilberry Vaccinium myrtillus and cowberry V. vitis-idaea. In Aust-Agder county, southern Norway, the mean brood size of pied flycatcher Ficedula hypoleuca, sparrowhawk Accipiter nisus and goshawk A. gentilis was higher in peak vole years than in other years. The effect was not due to variation in nest predation, as only successful
nesting attempts were included in the analyses. For the pied flycatcher, the annual proportion of large broods (>6 fledglings)
was positively correlated with the vole trapping index. No correlation was found between the offspring production of goshawks
and the proportion of voles in their diet. During a 3-year light-trapping study of nocturnal moths prior to our study, four
moth species whose larvae ate Vaccinium were commonest in the vole peak year. All these results are consistent with the MDH.
Received: 16 March 1998 / Accepted: 20 April 1998 相似文献
6.
Synchrony in short-term fluctuations of moose calf body mass and bank vole population density supports the mast depression hypothesis 总被引:1,自引:0,他引:1
Inter-annual variations in body mass of moose, Alces alces , in Norway and Sweden have been considered as most likely due to direct or indirect effects of weather, but so far predictions of autumn body mass of moose calves on the basis of weather data have given a poor fit to data. A striking, but hitherto unnoticed, feature of several time series on body mass of moose calves from south-eastern Norway is an apparently regular 3–4-year fluctuation pattern. This short-term fluctuation could be due to regular variations in forage quality, e.g. caused by a cyclic seed production of some important food plants, as envisaged by the "mast depression" hypothesis. One plant species important as food for moose calves in autumn is bilberry, Vaccinium myrtillus , which usually produces high seed crops (masts) at intervals of 3–4 years. Populations of the bank vole, Clethrionomys glareolus, which feeds on bilberry shoots in winter, are known to peak in bilberry post-mast years. In two study areas in Norway, there was a positive correlation between the autumn body mass of moose calves and the autumn population index of bank vole in the succeeding year. In the northern area there was an additional positive effect of summer precipitation, whereas in the southern area there was an additional negative effect of summer temperature. In both areas, however, the effect of weather was less pronounced than that of the bank vole index. These results support the mast depression hypothesis. 相似文献
7.
Two recent studies on territory occupancy rates of goshawk Accipiter gentilis and gyrfalcon Falco rusticolus report a 2–3-year-delayed numerical response to grouse numbers, which is a requirement for a hypothesis of predator-generated
grouse cycles. The time lags were assumed to reflect the average age of sexual maturity in the raptor species. In southern
Norway, however, subadult (two-year-old) goshawk hens occupied only 18–25% of territories where occupancy was not recorded
in the preceding year, and there was no significant relationship between the proportion of subadults among recruits and grouse
indices two years earlier. We argue that territory occupancy rates are not appropriate indices of total raptor population
levels, but rather reflect the proportion of territorial pairs that attempt to nest. Because this depends on the body condition
of the hens, fluctuations in other important winter resident prey species (most important for the goshawk) and winter weather
(most important for the gyrfalcon) should also be addressed. During 1988–2006, the annual proportion of goshawk territories
with recorded nesting attempts in southern Norway was most closely related to the preceding autumn’s population indices of
black grouse Tetrao tetrix and mountain hare Lepus timidus, whereas the annual proportion of gyrfalcon territories with observations of falcons or with confirmed breeding attempts
in central Norway were best explained by population indices of willow grouse Lagopus lagopus and ptarmigan L. mutus from the previous autumn, and by December temperatures. Hence, our studies do not support the predation hypothesis for grouse
cycles. 相似文献
8.
Mustonen AM Saarela S Nieminen P 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2008,178(2):199-208
Arvicolinae voles are small herbivores relying on constant food availability with weak adaptations to tolerate prolonged food
deprivation. The present study performed a comparative analysis on the responses to 4–18 h of food deprivation in the common
vole (Microtus arvalis) and the tundra vole (Microtus oeconomus). Both species exhibited rapid decreases in the plasma and liver carbohydrate concentrations during phase I of fasting and
the decline in the liver glycogen level was more pronounced in the tundra vole. The plasma thyroxine concentrations of the
common vole decreased after 4 h. Lipid mobilization (phase II of fasting) was indicated by the increased plasma free fatty
acid levels after 8–18 (the common vole) or 4–18 h (the tundra vole) and by the elevated lipase activities. In the tundra
vole, the plasma ghrelin concentrations increased after 12 h possibly to stimulate appetite. Both species showed increased
liver lipid concentrations after 4 h and plasma aminotransferase and creatine kinase activities after 12–18 h of food deprivation
implying liver dysfunction and skeletal muscle damage. No signs of stimulated protein catabolism characteristic to phase III
of fasting were present during 18 h without food. 相似文献
9.
Jaakola Laura Tolvanen Anne Laine Kari Hohtola Anja 《Plant Cell, Tissue and Organ Culture》2001,66(1):73-77
Buds and shoot tips of wild bilberry (Vaccinium myrtillus L.) and lingonberry (V. vitis-idaea L.) plants were cultured on a modified MS medium containing N6-isopentenyladenine (2iP), 9.8–78.4 μM, in order to study the effect of the 2iP-concentration on the initiation of growth.
The experiment was first performed in the autumn and repeated in the spring to determine the influence of season on growth
initiation. To optimise rooting, three different rooting treatments were tested for the bilberry and lingonberry microshoots.
Shoots were rooted either in vitro with 0.49 μM IBA (indole-3-butyric acid) or ex vitro, incubating microshoots in 2.07 mM KIBA-solution (potassium salt of IBA) before planting, or microshoots were planted directly
on peat without exogenous auxin. The best 2iP concentration for the initiation of the growth for bilberry was 49.2 μM and
for lingonberry 24.6 μM. It was observed that increasing the 2iP concentration at the growth initiation stage increased the
number of brownish explants both in bilberry and in lingonberry microcultures. Spring was a considerably better time than
autumn for the initiation of new growth, for both species. The results of the rooting test showed that the KIBA-treatment
before planting on peat increases rooting efficiency in both bilberry and lingonberry.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
The plant cycle hypothesis says that poor-quality food affects both herbivorous voles (Microtinae spp.) and grouse (Tetraonidae
spp.) in vole decline years, leading to increased foraging effort in female grouse and thus a higher risk of predation by
the goshawk Accipiter gentilis. Poor-quality food (mainly the bilberry Vaccinium myrtillus) for these herbivores is induced by seed masting failure in the previous year, when the bilberry is able to allocate resources
for chemical defence (the mast depression hypothesis; MDH). The predation facilitation hypothesis (PFH) in turn states that
increased searching activity of vole-eating predators during or after the decline year of voles disturbs incubating and brooding
grouse females. The behaviours used by grouse to avoid these terrestrial predators make them more vulnerable to predation
by goshawks. We tested the main predictions of the MDH and PFH by collecting long-term (21-year) data from black grouse Tetrao tetrix hens and cocks killed by breeding goshawks supplemented with indices of bilberry crop, vole abundance and small carnivores
in the vicinity of Oulu, northern Finland. We did not find obvious support for the prediction of the MDH that there is a negative
correlation of bilberry crop in year t with vole abundance and with predation index of black grouse hens in year t + 1. We did find obvious support for the prediction of the PFH that there is a positive correlation between predator abundance
and predation index of grouse hens, because the stoat Mustela erminea abundance index was positively related to the predation index of black grouse hens. We suggest that changes in vulnerability
of grouse hens may mainly be caused by the guild of vole-eating predators, who shift to alternative prey in the decline phase
of the vole cycle, and thus chase grouse hens and chicks to the talons of goshawks and other avian predators. 相似文献
11.
The degradation and utilization of solid waste (SW) from anaerobic digestion of poultry litter by Agrocybe aegerita was evaluated through mushroom production, loss of organic matter (LOM), lignocellulolytic enzymes activity, lignocellulose
degradation and mushroom nutrients content. Among the substrate combinations (SCs) tested, substrates composed of 10–20% SW,
70–80% wheat straw and 10% millet was found to produce the highest mushroom yield (770.5 and 642.9 g per 1.5 kg of substrate).
LOM in all SCs tested varied between 8.8 and 48.2%. A. aegerita appears to degrade macromolecule components (0.6–21.8% lignin, 33.1–55.2% cellulose and 14–53.9% hemicellulose) during cultivation
on the different SCs. Among the seven extracellular enzymes monitored, laccase, peroxidase and CMCase activities were higher
before fruiting; while xylanase showed higher activities after fruiting. A source of carbohydrates (e.g., millet) in the substrate
is needed in order to obtain yield and biological efficiency comparable to other commercially cultivated exotic mushrooms. 相似文献
12.
K. P. Singh R. K. Jaiswal Niranjan Kumar 《World journal of microbiology & biotechnology》2007,23(2):291-294
Summary
Catenaria anguillulae parasitized and killed the eggs and second stage juveniles (J2) of Meloidogyne graminicola under natural conditions. The percentage of infection in eggs was higher than J2 of M.␣graminicola, which ranged between 0–50.3% and 0–18.9% in 2004 and 0–46.6% and 0–21.7% in 2005, respectively. The higher parasitism of
eggs and J2 was recorded from those fields in which plants were severely infected with M. graminicola. The degree of parasitism of eggs and J2 by C. anguillulae varied with severity of root knot disease. The fields with a higher root gall index recorded a higher percentage of infection
in eggs and J2 of M. graminicola. In general, old galls when teased and incubated, recorded higher parasitism of eggs and juveniles than young galls. 相似文献
13.
Clotfelter ED Pedersen AB Cranford JA Ram N Snajdr EA Nolan V Ketterson ED 《Oecologia》2007,154(3):493-503
Resource pulses can have cascading effects on the dynamics of multiple trophic levels. Acorn mast is a pulsed resource in
oak-dominated forests that has significant direct effects on acorn predators and indirect effects on their predators, prey,
and pathogens. We evaluated changes in acorn mast, rodent abundance, raptor abundance, and reproductive success of a ground-nesting
songbird over a 24-year period (1980–2004) in the southern Appalachian Mountains in an effort to determine the relationships
among the four trophic levels. In particular, we examined the following: acorn mast from red oaks (Quercus rubra) and white oaks (Q. alba), abundance of white-footed mice (Peromyscus leucopus) and deer mice (P. maniculatus), population estimates of seven raptor species from three feeding guilds, and nest failure and number of juveniles of dark-eyed
juncos (Junco hyemalis). Finally, we recorded seasonal temperature and precipitation to determine the effects of weather on each trophic level.
We found that weather patterns had delayed effects of up to 3 years on these trophic interactions. Variation in acorn mast,
the keystone resource in this community, was explained by weather conditions as far back as 2 years before the mast event.
Acorn mast, in turn, was a strongly positive predictor of rodent abundance the following year, whereas spring and summer temperature
and raptor abundance negatively affected rodent abundance. Dark-eyed junco nests were more likely to fail in years in which
there were more rodents and raptors. Nest failure rate was a strong predictor of the number of juvenile juncos caught at the
end of the summer. Our results improve our understanding of the complex ecological interactions in oak-dominated forests by
illustrating the importance of abiotic and biotic factors at different trophic levels.
Ethan D. Clotfelter and Amy B. Pedersen contributed equally to the writing of this paper. 相似文献
14.
Santos LO Gonzales TA Ubeda BT Monte Alegre R 《Applied microbiology and biotechnology》2007,77(4):763-769
A strategy of experimental design using a fractional factorial design (FFD) and a central composite rotatable design (CCRD)
were carried out with the aim to obtain the best conditions of temperature (20–30°C), agitation rate (100–300 rpm), initial
pH (5.0–7.0), inoculum concentration (5–15%), and glucose concentration (30–70 g/l) for glutathione (GSH) production in shake-flask
culture by Saccharomyces cerevisiae ATCC 7754. By a FFD (25–2), the agitation rate, temperature, and pH were found to be significant factors for GSH production. In CCRD (22) was obtained a second-order model equation, and the percent of variation explained by the model was 95%. The results showed
that the optimal culture conditions were agitation rate, 300 rpm; temperature, 20°C; initial pH, 5; glucose, 54 g/l; and inoculum
concentration, 5%. The highest GSH concentration (154.5 mg/l) was obtained after 72 h of fermentation. 相似文献
15.
Camelini CM Maraschin M de Mendonça MM Zucco C Ferreira AG Tavares LA 《Biotechnology letters》2005,27(17):1295-1299
β-Glucans of Agaricus brasiliensis fruiting bodies in different stages of maturity were isolated and characterized by FTIR and NMR. These fractions had greater
amount of (1→6)-β-glucan and the (1→3)-β-glucan increased with fruiting bodies maturation. Yields of β-glucans increased from 42 mg β-glucans g−1 fruiting bodies (dry wt) in immature stage to 43 mg g−1 in mature stage with immature spores, and decreased to 40 mg g−1 in mature stage with spore maturation. Mature fruiting bodies, which included these glucans, have potential therapeutical benefits for use in nutraceutical products. 相似文献
16.
Kazuaki Takahashi Tadatoshi Shiota Hiroo Tamatani Masaru Koyama Izumi Washitani 《Ecological Research》2008,23(2):471-478
Fruit use by the Japanese black bear (Ursus thibetanus japonicus) and seed clumping in bear scat were studied in central Japan using fecal analyses. Between May and November 2003 and 2004,
the life form and fruit size of plants consumed by bears and the species composition and intactness of seeds contained in
scat were examined in five transects (approximately 10 km × 10 m) in broad-leaved deciduous forests. In 2003, scats with seeds
were found only in the autumn, when fruiting trees and shrubs were abundant. In 2004, scats with seeds occurred intermittently
from the summer, when fruiting plants were rare, up to the autumn. Yearly and seasonal variation in fruit use reflects the
opportunistic foraging behavior of Japanese black bears. Seven of the nine plant species detected in scats had medium-sized
fruits (6–15 mm width), whereas the other two species had relatively large fruits (20–100 mm width). In total, 14,492 seeds
were detected, of which 97.6% were intact; the remainder were damaged. Intact seeds of one or two species were found in each
scat. The number of intact seeds per scat ranged from 1 to 5476. Japanese black bears seldom digest ingested seeds, thereby
contributing to the seed dispersal of their food plants, including species with fruits that are too large to be swallowed
by frugivorous birds. 相似文献
17.
Zulima González-Parrado Carmen Reyes Fuertes-Rodríguez Ana M. Vega-Maray Rosa M. Valencia-Barrera F. Javier Rodríguez-Rajo Delia Fernández-González 《Aerobiologia》2006,22(1):47-53
Winter-flowering trees such as the alder (Alnus glutinosa (L.) Gaertner) can survive periods of adverse climatic conditions, entering a period of dormancy in the early fall. The end
of dormancy and the start of the pollen season require a period of low temperatures followed by another of warm temperatures.
These requirements were studied from 1995 to 2002, in order to develop a model to predict the onset of the alder pollen season
in Ponferrada (Spain). Chilling accumulation took place from late October to late December or early January. The best result
was obtained with a threshold temperature of 6.5 °C and an average of 848 chilling hours (CH). Heat requirements were calculated
at maximum temperature, an average 143 growth degree days (GDD) were needed, with a threshold temperature of 0 °C. In order
to validate models, predicted values were compared with real values for 2002–2003, 2003–2004 and 2004–2005, years not used
in developing the models. Predictions for the pollen-season start-date differed only slightly from observed dates: in 2002–2003
predicted and observed dates were the same, in 2003–2004 there was a difference of 7 days and in 2004–2005 a difference of
3 days. 相似文献
18.
Seasonal variation in the light environment on the forest floor of a deciduous forest was investigated with special reference
to sunflecks. Diurnal variations and seasonal changes in frequency and irradiation period of the sunflecks (sunfleck duration)
were measured. The hourly total sunfleck duration varied seasonally; that is, 30–40 min in spring and autumn and about 15–20
min in summer. There was no large variation in the hourly sunfleck duration during daytime hours (from 9.00 to 15.00 h). The
emergence frequency of sunflecks was 1.3–4.8 per h with two peaks, one in the morning and one in the afternoon. The mean duration
of a sunfleck, however, showed a characteristic daily pattern with a peak around noon. Sunfleck duration was long around noon,
ranging from 12 to 18 min, and short around 10.00 and 14.00 h, ranging from 6 to 10 min. Using the light photosynthesis curves
ofPyrola japonica andSyneilesis palmata (Koizumi & Oshima 1985), the contribution of sunflecks to the dry matter production of these understory species was evaluated.
It was shown that the sunflecks contributed 7–10% of the carbon gain inS. palmata, but only 2–3% of that inP. japonica. 相似文献
19.
The temporal availability of propagules is a critical factor in sustaining pioneer riparian tree populations along snowmelt-driven
rivers because seedling establishment is strongly linked to seasonal hydrology. River regulation in semi-arid regions threatens
to decouple seed development and dispersal from the discharge regime to which they evolved. Using the lower Tuolumne River
as a model system, we quantified and modeled propagule availability for Populus fremontii (POFR), Salix gooddingii (SAGO), and Salix exigua (SAEX), the tree and shrub species that dominate near-channel riparian stands in the San Joaquin Basin, CA. A degree-day
model was fit to field data of seasonal seed density and local temperature from three sites in 2002–2004 to predict the onset
of the peak dispersal period. To evaluate historical synchrony of seed dispersal and seasonal river hydrology, we compared
peak spring runoff timing to modeled peak seed release periods for the last 75 years. The peak seed release period began on
May 15 for POFR (range April 23–June 10), May 30 for SAGO (range May 19–June 11) and May 31 for SAEX (range May 8–June 30).
Degree-day models for the onset of seed release reduced prediction error by 40–67% over day-of-year means; the models predicted
best the interannual, versus site-to-site, variation in timing. The historical analysis suggests that POFR seed release coincided
with peak runoff in almost all years, whereas SAGO and SAEX dispersal occurred during the spring flood recession. The degree-day
modeling approach reduce uncertainty in dispersal timing and shows potential for guiding flow releases on regulated rivers
to increase riparian tree recruitment at the lowest water cost. 相似文献
20.
Julie Deter Nathalie Charbonnel Jean-François Cosson Serge Morand 《European Journal of Wildlife Research》2008,54(1):60-70
The goal of this study is to determine whether a parasitic nematode may regulate, or destabilise by inducing demographic cycles,
its host populations. We explore three host–parasite systems through population dynamic models. The hosts considered are the
fossorial water vole, Arvicola terrestris, the common vole Microtus arvalis and the bank vole Myodes (Clethrionomys) glareolus and the parasitic nematode is Trichuris arvicolae. Three differential equation-based mathematical models are developed including host immunity and the existence of trade-off
between immunity and host survival. Using parameters estimated from field data and laboratory observations, all these models
show that T. arvicolae can induce host population regulation but not demographic cycles. The regulation effect of the nematode is un-ambiguous for
the water vole (reduction of 50.2% of the host population size), but less obvious for the common vole (5.9%) and even less
for the bank vole (1.4%). Important biological parameters to be taken into account in such models are discussed. Experimental
confirmation of the regulatory potential of the nematode and of the costs of mounting an immune response against this nematode
are now required.
Communicated by W. Lutz 相似文献