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1.
Emilio Civantos 《Acta ethologica》2002,4(2):91-95
In some species, more aggressive individuals are more successful in resource competition. High testosterone level is associated
with increased activity and aggressive behavior, and this may have a direct effect on metabolic rate and cause an increase
in energy expenditure. Here, I examined the influence of exogenously administered testosterone on aggressiveness and body
growth in juvenile Psammodromus algirus male lizards. Juvenile males were given testosterone-filled (experimental) or empty (control) implants. Testosterone produced
an increase in aggressiveness and activity in the experimental males. However, despite being more aggressive, experimental
males did not acquire larger home ranges than control males. Experimental males also experienced a significant reduction in
growth rate over the 2-month period following implantation. Experimental males also were in poorer condition at the completion
of the experiment, compared to control males. These results suggest that although an elevated testosterone level may have
positive effects on aggressiveness and activity, it also may have negative effects manifested as reduced growth rate and body
condition.
Received in revised form: 15 June 2001
Electronic Publication 相似文献
2.
Tail loss reduces home range size and access to females in male lizards, Psammodromus algirus 总被引:3,自引:0,他引:3
Numerous lizard species use caudal autotomy as an antipredatordevice even though there must be significant costs during theperiod of tail regeneration. Strategies used by tailless individualsto enhance survival in natural populations are still poorlyunderstood. We experimentally examine tail loss in large, dominantmales of Psammodromus algirus in the middle of the breedingseason in the field. We report data showing home range reductionof large dominant males after autotomy, reduction in the numberof females in the home ranges of manipulated males, and a potentialincrease in mating opportunities of small subordinate maleswith complete tails. We conclude that changes in home rangeuse because of desertion of areas with less cover can resultin decreased predation risk at the cost of decreased accessto females. 相似文献
3.
In Idotea baltica, a marine isopod that lives and feeds on the brown alga Fucus vesiculosus, microhabitat choice differs between sexes so that males are found more often than females on the light-coloured and exposed
apical parts of the alga. We investigated how the requirements of avoiding visual predators and feeding were related to microhabitat
choice in relation to diurnal and life-cycle stage in males and females. Faced with a choice between an apical and a basal
piece of the alga, females spent more time than males on the basal piece, but this difference was not due to food choice.
Faced with a choice between a dark, concealing and a light, exposing background, the preference for a dark background was
stronger at day than at night, and stronger in females than in males. This suggests that a sex difference in the importance
of avoiding visual predators can explain the sex difference in microhabitat choice. Further, the preference for a dark background
and night feeding both increased with age, suggesting that feeding is increasingly subordinated to the need to avoid visual
predators. Our experiment found no effect of the presence of the opposite sex on microhabitat choice. Our results support
the hypothesis that the sexes trade off feeding against predation risk differently, presumably because growth is more important
to males than to females, which have more to gain by protection and therefore spend more time on the lower parts of the alga.
Received: 22 March 1999 / Accepted: 7 October 1999 相似文献
4.
In the lizard Psammodromus algirus, larger and older males show
orangenuptial coloration on most of the head and are dominant oversmaller
and younger, albeit sexually mature, males which donot show such extensive
nuptial coloration. This raises thequestion of why young, small males delay
the development ofnuptial coloration until a later breeding season. We tested
thehypothesis of social costs by manipulating the color of thehead of small
males. The results of agonistic interactions suggestedthat small males may
pay a cost in terms of being punished bylarge males. Small males with heads
painted orange were stillrecognized as small by other small males, suggesting
that theywould not gain in social status relative to normal, dull, small
males.We also manipulated the coloration of large males. Small malesshowed a
similar response toward all large males, independentof coloration. This
suggests that in short-distance communication,males used other cues, such as
body size and behavior, whenjudging fighting ability. In staged experiments
without malecompetition, female acceptance of matings was influenced bymale
body size but not by coloration because large males weremore successful in
obtaining matings than were small males,and within each age/size category
there was no difference inmating success between experimental and control
males. 相似文献
5.
Life history theory predicts that organisms should only invest resources into intrinsic components of life span to the degree
that it pays off in terms of reproductive success. Here, we investigate if the temporal distribution of mating opportunities
may have influenced the evolution of intrinsic mortality rates in the butterfly Pararge aegeria (Satyrinae). In this species, females mate only once and the frequency of male mating opportunities depends on the temporal
emergence pattern of virgin females. As expected, in a population from Madeira where females emerge continuously throughout
the year, there was no sex difference in adult life span, while in a Swedish population with synchronised female emergence,
males had significantly shorter life spans compared to females. A logistic mortality model provided the best fit to the observed
change in age-specific mortality and all categories reached an asymptotic mortality rate of a similar magnitude. However,
the Swedish males reached this mortality plateau more rapidly than the other categories. External mortality, due to water
and food limitation, affected the pattern of sex-specific mortality but males from Sweden still had higher rates of mortality
compared to all other categories. We argue that selection on male longevity is likely to be weaker in Sweden because under
synchronised emergence, all females emerge and mate within a short period of time, after which male reproductive value will
quickly approach zero. On Madeira, however, male reproductive value decrease more slowly with age since the probability of
finding a receptive female is constant over the year.
Received: 29 July 1999 / Accepted: 23 August 1999 相似文献
6.
《Biochemical Systematics and Ecology》2006,34(9):691-697
In spite of the importance of chemoreception in social organization of lizards, only a few studies have examined chemical composition of secretions of lizards. The secretion of the femoral glands of male lizards Psammodromus algirus contains 59 lipophilic compounds, mainly carboxylic acids between n-C9 and n-C20, and steroids (mainly campesterol, ergosterol and cholesterol), and minor components such as five alcohols, six aldehydes, squalene, α-tocopherol, ketones, and a furanone. These compounds were identified on the basis of mass spectra, obtained by GC–MS. Secretions of adult males of different age were different. Older lizards had secretions with relatively lower proportions of octadecadienoic, oleic and eicosatetraenoic acids, and higher proportions of campesterol, ergosterol, ergostenol, 4,4-dimethy-cholest-7-en-3-ol, and ergosta-5,22-dien-3-ol. These differences might allow conspecifics to get information on the age of the sender based on chemicals alone, which may have an important role in social behavior of this lizard. 相似文献
7.
To evaluate the potential impact of our research activities on guanacos (Lama
guanicoe), we tested for effects of radiocollaring on juvenile (≤1 year of age) survival in Torres del Paine National Park, Chile
during 1992–1996. The survival of collared (40.1%) and uncollared (38.2%) juveniles was not significantly different (G=0.08; P=0.77). Our results suggest that radiocollaring does not adversely affect the survival of juvenile guanacos. Although we observed
no effect of radiocollaring, we still underline the importance of testing for effects of radiocollars in other wildlife investigations
when feasible.
Received: 20 September 1999 / Accepted: 8 March 2000 相似文献
8.
The arrangement of resources in patchy landscapes: effects on distribution, survival, and resource acquisition of chironomids 总被引:3,自引:0,他引:3
The spatial arrangement of resources in patchy habitats influences the distribution of individuals and their ability to acquire
resources. We used Chironomus riparius, a ubiquitous aquatic insect that uses leaf particles as an important resource, to ask how the dispersion of resource patches
influences the distribution and resource acquisition of mobile individuals in patchy landscapes. Two experiments were conducted
in replicated laboratory landscapes (38×38 cm) created by arranging sand and leaf patches in a 5×5 grid so that the leaf patches
were either aggregated or uniformly dispersed in the grid. One-day-old C. riparius larvae were introduced into the landscapes in one of three densities (low, medium, high). In experiment 1, we sampled larvae
and pupae by coring each patch in each landscape 3, 6, 12, or 24 days after adding larvae. In experiment 2, emerging adults
were collected daily for 42 days from each patch in each landscape. In aggregated landscapes, individuals were aggregated
in one patch type or the other during a particular developmental stage, but the ”preferred” type changed depending on developmental
stage and initial density. Adult emergence was lower by about 30% in all aggregated landscapes. In dispersed landscapes, individuals
used both types of patch throughout their life cycles at all initial densities. Thus, patch arrangement influences the distribution
of mobile individuals in landscapes, and it influences resource acquisition even when average resource abundance is identical
among landscapes. Regardless of patch arrangement, high initial density caused accumulation of early instars in edge patches,
75% mortality of early instars, a 25% increase in development time, and a 60% reduction in adult emergence. Because mortality
was extremely high among early-instar larvae in high-density treatments, we do not have direct evidence that the mechanism
by which patch arrangement operates is density dependent. However, the results of our experiments strongly suggest that dispersion
of resource patches across a landscape reduces local densities by making non-resource patches available for use, thereby reducing
intraspecific competition.
Received: 20 July 1999 / Accepted: 28 January 2000 相似文献
9.
C. Thouzeau S. Massemin Y. Handrich 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(1):17-24
To assess the role of bone marrow fat in survival during a period of negative energy balance, we investigated the relationship
between the time-course of marrow fat mobilization and the metabolic states associated with body fuel utilization during a
prolonged fast. In order to mimic the winter fast of the barn owl (Tyto alba), captive birds were subjected to fasts of various durations at 5 °C ambient temperature. Body mass and plasma metabolites
were used to determine the metabolic state at the end of fasting. Skeleton composition remained unchanged throughout phase
II of fasting, during which the birds essentially rely on lipid fuels. During the following phase III, characterized by an
increase in net body protein breakdown, the lipid mass in skeleton marrow decreased sharply by 78%, concomitant with an increase
of the bone water content. This marrow fat mobilization occurred in all parts of the skeleton. This observation supports the
hypothesis that bone marrow fat is not only involved in local nutrition, but can also be used as a lipid reserve for total
energy requirements. However, in contrast to other fat deposits, marrow fat is mobilized only during phase III of the fast,
when the last shift from lipid to protein fuel metabolism occurs. Thus, metabolic and/or hormonal changes associated with
this transition could be involved in bone marrow fat mobilization. Lastly, our results suggest that the measurement of bone
marrow fat can be used as an accurate index of the nutritional status (i.e. phase II or phase III) in barn owls.
Accepted: 4 July 1996 相似文献
10.
Understanding the evolution of growth rate requires knowledge of the physiology of growth. This study explored the physiological
basis of countergradient variation (CnGV) in somatic growth across latitudinal populations of the Atlantic silverside, Menidia menidia. Energetics of northern (Nova Scotia, Canada) and southern (South Carolina, USA) genotypes were compared across resource
levels, temperatures, and fish sizes to identify trade-offs to rapid growth. Offered unlimited resources, genotypes differed
in both energy acquisition and allocation. Food consumption, growth, and efficiency of northern genotypes were consistently
higher than in southern genotypes, across temperatures and body sizes. Feeding metabolism (specific dynamic action; SDA) was
proportional to meal size, differing between genotypes to the extent that food consumption differed. Given limited resources,
northern and southern genotypes displayed similar growth, efficiency, routine activity, and SDA across temperatures and fish
sizes. Routine metabolism was equal at 17°C and 22°C, yet was significantly higher in northern fish at 28°C. Growth rates
in M. menidia do not appear to trade off across environments or body sizes, i.e., at no temperature, ration, or size do southern fish outgrow
northern conspecifics. Nor does submaximal growth result from increased costs of maintenance, tissue synthesis, or routine
activity. Based on our findings, we propose that CnGV consumption and growth in M. menidia likely result from trade-offs with other energetic components, namely sustained and burst swimming.
Received: 26 January 1999 / Accepted: 14 September 1999 相似文献
11.
Foraging theory predicts that dietary niche breadth should expand as resource availability decreases. However, Galápagos marine iguanas often die during algae shortages (El Niños) although land plants abound where they rest and reproduce. On Seymour Norte island, a subpopulation of iguanas exhibited unique foraging behavior: they consistently included the succulent beach plant B. maritima in their diet. We investigated the consequences of land-plant feeding for body size and survival. Batis-eaters supplemented their algae diet both before and after intertidal zone foraging, and more Batis was eaten during tides unfavorable for intertidal zone foraging (dawn and dusk). Larger, energy-constrained iguanas fed more on land than did smaller animals. Compared to intertidal zone algae, Batis was 39% lower in caloric content (1.6 vs. 2.6 kcal g–1 dry mass), 56% lower in protein (8.3 vs. 18.9% dry mass) and 57% lower in nitrogen (1.3 vs. 3.0% dry mass). In spite of its lower nutrient value, iguanas that supplemented their diet with this plant were able to attain nearly twice the body size of other iguanas on the island. Age estimates indicate that many Batis-eaters survived repeated El Niño episodes during which animals of their relative size-class experienced high mortality on other islands. The larger animals were, however, completely dependent upon this supplementary source of food to maintain condition, and all perished in the 1997–1998 El Niño when high tides inundated and killed Batis on Seymour Norte Island. We hypothesize that Batis feeding developed as a local foraging tradition, and that dietary conservatism and strong foraging site fidelity explain why the inclusion of land plants in the diet has been observed in only a single population. Ultimately, a unique algae-adapted hindgut morphology and physiology may limit a switch from marine to terrestrial diet. 相似文献
12.
Altitudinal life history variation in the dung flies Scathophaga stercoraria and Sepsis cynipsea 总被引:2,自引:0,他引:2
W. U. Blanckenhorn 《Oecologia》1997,109(3):342-352
Field phenologies of high- (ca. 1500 m) and low- (ca. 500 m) altitude populations of the two most common European species
of dung flies, Scathophaga stercoraria and Sepsis cynipsea, differ quite markedly due to differences in climate. To differentiate genetic adaptation due to natural selection and phenotypic
plasticity, I compared standard life history characters of pairs of high- and low-altitude populations from three disjunctive
sites in Switzerland in a laboratory experiment. The F1 rearing environment did not affect any of the variables of the F2
generation with which all experiments were conducted; hence, there were no carry-over or maternal effects. In Sc. stercoraria, high-altitude individuals were smaller but laid larger eggs; the latter may be advantageous in the more extreme (i.e. more
variable and less predictable) high-altitude climate. Higher rearing temperature strongly decreased development time, body
size and the size difference between males and females (males are larger), produced female-biased sex ratios and led to suboptimal
adult emergence rates. Several of these variables also varied among the three sites, producing some interactions complicating
the patterns. In Se. cynipsea, high-altitude females were marginally smaller, less long-lived and laid fewer clutches. Higher rearing temperature strongly
decreased development time and body size but tended to increase the size difference between males and females (males are smaller);
it also increased clutch size but decreased physiological longevity. Again, interpretation is complicated by variation across
sites and some significant interactions. Overall, genetic adaptation to high-altitude conditions appears weak, probably prevented
by substantial gene flow, and may be swamped by the effects of other geographic variables among populations. In contrast,
phenotypic plasticity is extensive. This may be due to selection of flexible, multi-purpose genotypes. The results suggest
that differences in season length between high- and low-altitude locations alone do not explain well the patterns of variation
in phenology and body size.
Received: 21 March 1996 / Accepted: 1 September 1996 相似文献
13.
L. J. Vitt S. S. Sartorius T. C. S. Avila-Pires M. C. Espósito D. B. Miles 《Oecologia》2000,122(3):410-420
We examined standard niche axes (time, place, and food) for three sympatric teiid lizards in the Amazon rain forest. Activity
times during the day were similar among species. Ameiva ameiva were in more open microhabitats and had higher body temperatures compared with the two species of Kentropyx. Microhabitat overlaps were low and not significantly different from simulations based on Monte Carlo analysis. Grasshoppers,
crickets, and spiders were important in the diets of all three species and many relatively abundant prey were infrequently
eaten (e.g., ants). Dietary overlaps were most similar between the two species of Kentropyx even though microhabitat overlaps were relatively low. A Monte Carlo analysis on prey types revealed that dietary overlaps
were higher at all ranks than simulated overlaps indicating that use of prey is not random. Although prey size was correlated
with lizard body size, there were no species differences in adjusted prey size. A. ameiva ate more prey items at a given body size than either species of Kentropyx. Body size varies among species, with A. ameiva being the largest and K. altamazonica the smallest. The two species of Kentropyx are most distant morphologically, with A. ameiva intermediate. The most distant species morphologically are the most similar in terms of prey types. A morphological analysis
including 15 species from four genera revealed patterns of covariation that reflected phylogenetic affinities (i.e., taxonomic
patterns are evident). A cluster analysis revealed that A. ameiva, K. pelviceps, and K. altamazonica were in the same morphological group and that within that group, A. ameiva differed from the rest of the species. In addition, K. pelviceps and K. altamazonica were distinguishable from other species of Kentropyx based on morphology.
Received: 26 December 1998 / Accepted: 15 September 1999 相似文献
14.
Characteristics of genetic variation in the progenies of protoplast-derived plants of rice, Oryza sativa cv Nipponbare 总被引:3,自引:0,他引:3
M. Yamagishi T. Koba T. Shimada K. Itoh Y. Sukekiyo K. Shimamoto 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):1-7
Genetic variation in protoplast-derived rice (Oryza sativa L.) plants was characterized using first and second generation selfed progenies. A total of 133 regenerated plants were obtained
from ten protoplasts of the japonica rice cultivar Nipponbare. Sixty two regenerated plants which set enough seeds for the subsequent field tests at the next
generation and were derived from five protoplasts were selected, and their selfed seeds were used as the first selfed-seed
progeny generation). Fifteen plants were selected from each of the 15 lines, and their selfed seeds were used for tests at the generation. Thirty seven lines (60%) segregated plants with detrimental mutant characters of yellow-green phenotype, dwarf stature, dense and short
panicle, or low seed fertility. According to the segregation patterns in the lines having mutated plants among those originated
from the same protoplasts, the stages of mutation induction were estimated. Additionally, five quantitative traits were changed
in almost all and lines. Varied quantitative traits of heading date, number of spikelets per panicle, and seed fertility, were in a heterozygous
state. However, culm and panicle lengths showed high uniformity, whereas reduced culm and panicle lengths were caused by mutational
changes in polygenes and/or multiple genes.
Received: 20 March 1996 / Accepted: 21 June 1996 相似文献
15.
The concept of body mass dynamics can be viewed as part of life history theory, but its potential has remained largely untapped
due to a lack of analytical methodology. We therefore propose a method, called contribution analysis, which enables us to
decompose a change in body mass into contributions associated with variations in individual egg mass, clutch size, and standard
somatic mass (somatic mass adjusted to body length). The advantage of contribution analysis is that various contributions
are expressed in the same units (units of mass) and show the amount of resources committed to changes in the individual traits,
while the traits themselves are measured in different units and thus incomparable on their own. The method is tuned to study
zooplankton, and is applied to examine body mass dynamics in Daphnia galeata. We found that when recovering from a poor-resource environment just above the threshold food concentration, Daphnia primarily increase their standard somatic mass, that is, restore body condition. When the trophic environment improves further
but remains below the incipient limiting level, resources are invested equally to enhance body condition and reproduction
in terms of clutch size. Finally, when food is no longer a limiting factor, almost all resources are committed to increase
clutch size. While individual egg mass also varies, it never attracts more resources than the shift in the most prioritized
trait. We suggest that the significance of this shift in resource allocation priorities is to keep an adult female alive in
a poor environment and thus to allow her to retain her reproductive potential for better conditions in the future. Contribution
analysis of body mass dynamics may allow us to detect flexible allocation strategies in a changing natural environment. 相似文献
16.
A central point in life history theory is that parental investment in current reproduction should be balanced by the costs
in terms of residual reproductive value. Long-lived seabirds are considered fixed investors, that is, parents fix a specific
level of investment in their current reproduction independent to the breeding requirements. We tested this hypothesis analysing
the consequences of an experimental increase in flying costs on the foraging ecology, body condition and chick condition in
Cory’s shearwaters Calonectris diomedea. We treated 28 pairs by reducing the wing surface in one partner and compared them with 14 control pairs. We monitored mass
changes and incubation shifts and tracked 19 foraging trips per group using geolocators. Furthermore, we took blood samples
at laying, hatching and chick-rearing to analyse the nutritional condition, haematology, muscle damage and stable isotopes.
Eighty-day-old chicks were measured, blood sampled and challenged with PHA immune assay. In addition, we analysed the effects
of handicap on the adults at the subsequent breeding season. During incubation, handicapped birds showed a greater foraging
effort than control birds, as indicated by greater foraging distances and longer periods of foraging, covering larger areas.
Eighty-day-old chicks reared by treated pairs were smaller and lighter and showed a lower immunity than those reared by control
pairs. However, oxygen demands, nutritional condition and stable isotopes did not differ between control and handicapped birds.
Although handicapped birds had to increase their foraging effort, they maintained physical condition by reducing parental
investment and transferred the experimentally increased costs to their partners and the chick. This result supports the fixed
investment hypothesis and is consistent with life history theory. 相似文献
17.
Identifying different types of de-differentiated microspores from indica-japonica F1 hybrids with subspecies-differentiating RFLP probes in rice 总被引:1,自引:0,他引:1
J. -H. Xie M. -W. Gao J. Lu J. -Y. Zhuang H. -X. Lin H. -R. Qian K. -L. Zheng 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):34-38
The indica, japonica and intermediary types of de-differentiated microspores from indica-japonica
hybrids were identified with 11 subspecies-differentiating RELP probes in rice (Oryza sativa L.). The results showed that the distribution of indica, japonica and intermediary types of de-differentiated microspores could be easily detected in a simple and quick way using the RFLP
method. Moreover, the microspores from the same hybrid but inoculated onto different media, or microspores from different hybrids when inoculated onto the same medium, often displayed distinctive distribution curves of de-differentiated microspores
types, indicating that the media employed in this experiment had high selectivity for the de-differentiation of certain types
of microspores. The application of the RELP method to de-differentiated microspore identification is of great theoretical
and practical significance in rice doubled-haploid breeding.
Received: 27 February 1996 / Accepted: 14 June 1996 相似文献
18.
Body composition in air and road inductees at high altitude during the initial days of acclimatization 总被引:1,自引:0,他引:1
This study assesses body composition changes and their time course during the initial days of acclimatization to high altitude
(HA). Comparisons were made between gradual and acute induction to HA using 60 male lowlander volunteers (24–28 years of age)
divided into two equal groups for inducting them to HA. Thirty subjects were air-lifted from sea level (SL) to 3500 m HA in
1 h. These subjects were air inductees (AI). The other 30 subjects were transported in 4 days by road to the same location
at 3500 m. These were road inductees (RI). After remaining for 15 days at 3500 m both groups were inducted to 4200 m by road.
All the subjects could not reach the various altitudes at the same time due to logistical problems. Ultimately, data for each
altitude (SL, 3500 m and 4200 m) were available for only 26 RI subjects and 10 AI subjects. Skinfold thickness (SKF) measurements
for the subscapular, thigh, triceps, biceps, juxtanipple, umbilicus, suprailiac and calf regions were taken in order to calculate
fat percentages. Measurements were taken at SL and on days 1 and 9 at both 3500 m and 4200 m. On day 1 at 3500 m, RI showed
a significant fall in body weight (BW) with respect to SL but AI maintained it. On subsequent days at HA both groups showed
a significant fall in BW and lean body mass but not in percentage fat. SKF in the biceps and triceps regions decreased significantly
but in the umbilicus and suprailiac regions it significantly increased at HA in both groups. Body composition, along with
other parameters, is discussed determining the acclimatization schedule for sojourners at HA. Possibly, translocation of body
fat takes place from the periphery to deep body fat depots in the core/main trunk due to the cold at HA.
Received: 8 May 1997 / Revised: 10 August 1997 / Accepted: 20 October 1997 相似文献
19.
G. Besnard Y. Griveau M. C. Quillet H. Serieys P. Lambert D. Vares A. Bervillé 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):131-138
A method based upon targetting of intro-gressed markers in a Phomopsis-resistant line (R) of cultivated sunflower, issuing
from a H. argophyllus cross was used to mark the Phomopsis resistance regions. Our study was based upon 203 families derived from a cross between an inbred line susceptible to Phomopsis (S1) and the introgressed resistant line (R).
Families were checked for Phomopsis resistance level in a design with replicated plots and natural infection was re-inforced
by pieces of contaminated stems. Thirty four primers were employed for RAPD analysis. Out of 102 polymorphic fragments between
(S1) and H. argophyllus, seven were still present in (R) suggesting that they marked introgressions of H. argophyllus into (R). The plants were scored for the presence or absence of 19 fragments obtained from five primers, and the relationships between
the presence/absence of fragments in plants and Phomopsis resistance/susceptiblity in the progenies was determined by using an analysis of variance. We found that at least two introgressed regions, as well as favourable
factors from sunflower, contributed to the level of Phomopsis resistance in cultivated sunflower.
Received: 28 June 1996 / Accepted: 5 July 1996 相似文献
20.
Predation against birds with low immunocompetence 总被引:8,自引:0,他引:8
Differences in the phenotypic characteristics between individuals falling prey to predators and conspecifics avoiding predation
will reflect the intensity of selection on prey. If prey are generally in poor condition, we predicted that they should have
an inferior health status in comparison to individuals dying for other reasons. We investigated this prediction for prey and
conspecifics that did not die from predation by comparing the size of the spleen, which is an important immune defence organ
reflecting one component of immunocompetence, using 18 species of passerine birds and domestic cat Felis catus predators as a model system. Prey had consistently smaller spleens than non-prey, implying that they had weak immune systems.
The data set did not indicate that sex or age, month of death, body mass, body condition, liver mass, wing length or tarsus
length differed significantly between prey and non-prey. Thus there was little evidence of confounding factors affecting the
results. These observations indirectly suggest that disease and parasitism may play an important role in predator-prey interactions.
Received: 4 August 1999 / Accepted: 7 October 1999 相似文献