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41.
Exaggerated male eye span influences contest outcome in stalk-eyed flies (Diopsidae) 总被引:3,自引:0,他引:3
Evolution of male weapons or status signals has been hypothesized to precede evolution of female mating preferences for those
traits. We used staged male fights among three species of Malaysian stalk-eyed flies (Diptera: Diopsidae) to determine if
elongated eye span, which is preferred by females in two sexually dimorphic species, influences contest outcome. Extreme sexual
dimorphism, with large males possessing longer eye span than females, is shared by Cyrtodiopsis whitei and C. dalmanni. In contrast, C. quinqueguttata exhibits a more ancestral condition – short, sexually monomorphic eye stalks. Videotape analysis of 20-min paired contests
revealed that males with larger eye span and body size won more fights in the dimorphic, but not monomorphic, species. To
determine if males from the dimorphic species use eye span directly to resolve contests, we competed male C. dalmanni from lines that had undergone artificial selection for 30 generations to increase or decrease eye span. We found that eye
span, independently of body size, determines contest outcome in selected-line males. Furthermore, in both dimorphic species,
the average encounter duration declined as the eye span difference between contestants increased, as expected if males use
eye span to assess opponent size. The number of encounters also increased with age in dimorphic, but not monomorphic, species.
Selected-line males did not differ from outbred males in either fight duration or number of encounters. We conclude that exaggerated
male eye stalks evolved to influence both competitive interactions and female mating preferences in these spectacular flies.
Received: 20 July 1998 / Received in revised form: 2 February 1999 / Accepted: 12 March 1999 相似文献
42.
Sibling aggression, hatching asynchrony, and nestling mortality in the black kite (Milvus migrans) 总被引:3,自引:0,他引:3
Javier Viñuela 《Behavioral ecology and sociobiology》1999,45(1):33-45
In siblicidal species, hatching asynchrony could act to reduce sibling rivalry or promote the death of last-hatched chicks.
The pattern of hatching asynchrony was experimentally altered in the black kite Milvus migrans. Hatching asynchrony in control broods was intermediate between those of experimentally synchronised and asynchronised broods.
Sibling aggression and wounds on the chicks were more commonly observed early in the nestling period and in synchronous nests.
Serious injuries were observed on last-hatched chicks in asynchronous nests, as were observations of intimidated or crushed
chicks. Sibling aggression was related to food abundance, but some chicks died at an early age in nests with abundant food
(cainism). Cainism was more commonly found in asynchronous nests. For species with facultative siblicide, moderate hatching
asynchrony could be a compromise between reducing sibling rivalry and avoiding large size differences between sibs that would
result in cainism. Female black kites preferentially fed the smallest chicks and exhibited behaviours to reduce sibling aggression,
contrary to observations in other siblicidal species. In a highly opportunistic forager such as the black kite, a strategy
may exist to protract the life of all the chicks in the brood, waiting for unpredictable situations of food overabundance.
This would induce the appearance of a parent-offspring conflict over brood reduction, reflected in the existence of a possible
anticipated response by some of the chicks (cainism) and in the appearance of special behaviours by the parents to selectively
feed smaller chicks or reduce sibling aggression. In this facultatively siblicidal species, cainism does not seem to be the
final stage of an evolutionary trend favouring the raising of high-quality chicks, but a manifestation of a parent-offspring
conflict over brood size.
Received: 9 March 1998 / Accepted after revision: 8 August 1998 相似文献
43.
Avian sibling aggression plays an important role in controlling food distribution among nest mates. The food-amount hypothesis
predicts that the amount of food obtained by siblings acts as a proximate cue controlling their level of aggression. The importance
of this cue to cattle egrets (Bubulcus ibis) in Oklahoma was evaluated by studying parental feeding rates, food distribution among nestlings, and nestling aggression
in three-chick broods [A-(oldest), B-, and C-chicks]. We compared nests in which siblicide occurred to nests where all three
chicks survived (nonsiblicide nests). Relative to nonsiblicide nests, siblicide nests received decreasing amounts of food
as the day of siblicide approached. Similarly, aggression levels of all three chicks in siblicide nests increased significantly
compared with nonsiblicide nests, with most of the aggressive behavior involving B- and C-chicks. As a result, on a per-day
basis, food amount and aggression exhibited a strong, negative correlation, thus providing support for the food-amount hypothesis.
Though the total amount of food delivered to siblicide nests declined on the days prior to siblicide, the amount of food received
by A-chicks in these nests did not. Relative to nonsiblicide nests, A-chicks in siblicide nests received an increased share
(percent of volume) of the food delivered at the expense of C-chicks, with the percent remaining the same for B-chicks. The
percentage of food B-chicks received the day after siblicide increased significantly from that received the day before siblicide,
with no change occurring in either the amount or percentage of food received by A-chicks; clearly, B-chicks were the beneficiary
of their aggressive actions that resulted in the death of C-chicks. We provide evidence supporting the hypothesis that aggression
is proximately linked to food amount, possibly by a relatively simple cue such as hunger.
Received: 25 November 1994/Accepted after revision: 10 February 1996 相似文献
44.
Gregory J. Robertson 《Behavioral ecology and sociobiology》1998,43(4-5):289-296
Hypotheses regarding the evolution and maintenance of intraspecific nest parasitism were tested with data collected during
a 3-year study of common eiders (Somateria mollissima) breeding near Churchill, Manitoba. The nest parasitism rate was highest (42.4% of nests) during the year with the highest
nest density and the best environmental conditions, and lowest (20.2% of nests) in the year with the lowest nest density and
the poorest environmental conditions. Over the nesting season, parasitic eggs were laid at the same time as normally laid
eggs. Most parasitic eggs (>75%) were laid before the host female laid her third egg. The majority of the parasitic eggs were
the first or second egg produced by the parasitic female. When a parasitic egg was laid before or on the same day as the host
female initiated her clutch, the probability of her first egg being depredated before incubation was significantly lowered.
First- and second-laid eggs suffered a high rate of predation probably because nesting females do not attend their clutch
until their second or third egg is laid. Hypotheses that some females use intraspecific nest parasitism to parasitize the
parental care of other females were inconsistent with these data. Egg adoption is a likely explanation for the prevalence
of females incubating parasitic eggs in this population.
Received: 30 September 1997 / Accepted after revision: 6 May 1998 相似文献
45.
C. R. Maher 《Behavioral ecology and sociobiology》2000,47(5):327-338
Whereas variation in pronghorn (Antilocapra americana) spatial organization is well documented, underlying ecological or physiological explanations are not well understood. This
study quantitatively describes spacing systems of pronghorn males and correlates of their spatial organization. I collected
behavioral data from two populations in South Dakota (Wind Cave) and Montana (Bar Diamond) to determine if males differed
in space use, response to intruders, and behavior patterns indicative of area defense. I measured sex ratio and population
density, and I examined characteristics of food resources, including forb species diversity, richness, coverage, biomass,
and nitrogen content, and how they changed during the growing season. I also collected and analyzed fecal samples to determine
if males differed in testosterone concentrations. Pronghorn males at Wind Cave were more territorial than males at Bar Diamond,
although males at Bar Diamond became more territorial during the second year. The forb community at Wind Cave was more diverse,
contained greater amounts of forbs later in summer, and had a higher nitrogen content later in summer. Population density
was lower at Wind Cave, although density dropped at Bar Diamond during the second year, and sex ratios were skewed toward
males at Bar Diamond. Finally, males at Wind Cave had higher testosterone concentrations than did Bar Diamond males, although
differences were not statistically significant. With lower population density and higher forb abundance and quality, food
resources were more economically defensible at Wind Cave, and males were more territorial there. Analyses using these and
other pronghorn populations revealed that population density and sex ratio correlated weakly with spatial organization, whereas
precipitation correlated most strongly, which suggests plant productivity has a powerful role in determining pronghorn territoriality.
Received: 16 June 1999 / Received in revised form: 21 September 1999 / Accepted: 31 December 1999 相似文献
46.
Elaeagnus umbellata, a member of the Elaeagnaceae family, is native to Pakistan, China, India, Korea, and Japan. It is found commonly at altitudes ranging from 1200 to 2100 m and thrives on eroded and degraded land due to its ability to fix nitrogen. The plant also grows under variable pH (4–8) and drought, and is used locally as fuel wood, fencing, fodder, basket making, and shelterbelts. The fruit of the plant is well known for its essential nutrients and medicinal compounds such as vitamins, minerals, essential fatty acids, carotenoids (lycopene), soluble solids, and sugars. Medicinally, it is widely believed to protect against myocardial infections, pulmonary infections, and various forms of cancers. Ten ecotypes from variable microclimatic conditions were investigated for their morphological, molecular and biochemical diversity improvement and commercialization purposes. Comparisons and disabilities indicated significant variability in terms of morphological (plant height, number of branches, thorn size and number, leaf area, fruit size, 100 fruit weight, and yield), molecular (SDS-PAGE), and micro- and macronutrient (vitamin C, Fe, mg, P, Na, K, essential oils, and sugar) bases among the ecotypes. This variability will be helpful in developing commercial varieties of the plant utilizing the conventional techniques of selection and hybridization for economic activities. The plant has ample quantities of multiple micronutrients, thus indicating their expression through a powerful promoter at one place (fruit mesocarp). Efforts to identify and isolate the micronutrient genes (vitamin A, C, E, and Fe), the deficiency of which causes malnutrition and disabilities within the population of developing countries. Micronutrient genes have also been initiated for their characterization and future transformation into staple food crops for stable bio-fortification. 相似文献
47.
Henrik Pärn Karin M. Lindström Maria Sandell Trond Amundsen 《Behavioral ecology and sociobiology》2008,62(10):1665-1677
The optimal mating system is rarely the same for males and females—whereas males usually benefit from attracting additional
females to the territory, this could incur costs for the resident female. Females should therefore prevent prospecting females
from settling on the territory. We studied the male and female behavioral and hormonal responses to simulated female territorial
intrusions in free-living bluethroats during the pre-laying period. In the study population, polygyny occurs with potential
fitness costs for the resident female. We recorded different aspects of aggressive behavior before and after presentation
of a live female decoy and playback of female song. These behaviors were compared with a set of intrusions using a male decoy.
At the end of a trial, the birds were captured, and blood samples were analyzed for androstenedione, testosterone, estradiol
and corticosterone. During the pre-intrusion period, none of the females were observed. Females generally responded strongly
to the female decoy by increased flight rate, vocalizations, and by conspicuous perching. Nearly half of the males displayed
to the female decoy but never while the resident female was present. We suggest that resident female aggression in bluethroats
prevents courtship by her mate and signals her mating status to the female intruder. Female aggression could therefore prevent
additional females to settle on the territory and shape the mating system. Females that responded with song had higher levels
of estradiol. These findings suggest that estradiol may support aggression in breeding female birds. 相似文献
48.
Cremer S D'Ettorre P Drijfhout FP Sledge MF Turillazzi S Heinze J 《Die Naturwissenschaften》2008,95(11):1101-1105
Winged and wingless males coexist in the ant Cardiocondyla obscurior. Wingless (“ergatoid”) males never leave their maternal colony and fight remorselessly among each other for the access to
emerging females. The peaceful winged males disperse after about 10 days, but beforehand also mate in the nest. In the first
5 days of their life, winged males perform a chemical female mimicry that protects them against attack and even makes them
sexually attractive to ergatoid males. When older, the chemical profile of winged males no longer matches that of virgin females;
nevertheless, they are still tolerated, which so far has been puzzling. Contrasting this general pattern, we have identified
a single aberrant colony in which all winged males were attacked and killed by the ergatoid males. A comparative analysis
of the morphology and chemical profile of these untypical attacked winged males and the tolerated males from several normal
colonies revealed that normal old males are still performing some chemical mimicry to the virgin queens, though less perfect
than in their young ages. The anomalous attacked winged males, on the other hand, had a very different odour to the females.
Our study thus exemplifies that the analysis of rare malfunctioning can add valuable insight on functioning under normal conditions
and allows the conclusion that older winged males from normal colonies of the ant C. obscurior are guarded through an imperfect chemical female mimicry, still close enough to protect against attacks by the wingless fighters
yet dissimilar enough not to elicit their sexual interest. 相似文献