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271.
Stephen Nowicki Jeffrey Podos Frances Valdés 《Behavioral ecology and sociobiology》1994,34(5):329-335
In many songbird species, males sing a repertoire of distinct song types. Song sparrows typically are described as having repertoires of about a dozen song types, but these song types are themselves quite variable and some songs are produced that appear intermediate between two types. In this study we quantify the similarity between successive songs produced by song sparrows in order to determine if differences between song types are emphasized or deemphasized in bouts of continuous singing. In spite of the high degree of variation within song types and similarity between song types observed in this species, we show that transitions from one song type to the next are distinct as compared to transitions within sequences of the same type (Figs. 4 and 5). Variation does not accumulate across sequences of the same song type, and the average variation observed within a continuous sequence of the same song type is significantly less than is predicted from the total variation recorded for that type across many different bouts (Fig. 6). These results support the view that song sparrows include two levels of variation in their singing: differences between song types as is commonly observed in species with song repertoires, and an independent level of variation observed for songs of the same type. 相似文献
272.
Male mosquitofish are very persistent in their sexual activity and harass any female they encounter. Gravid females pay a
large tribute to this intense male sexual activity in terms of reduced foraging efficiency. Previous observations have demonstrated
that gravid females, when chased by a male, dilute male harassment by moving closer to other females to form shoals. They
also approach other males to promote male competition, and when males differ in size, they preferentially target large males,
whose harassment is less intense. In this study, we tested whether the modulation of females’ social preferences in response
to male harassment is innate or learned. We tested social preference in three groups of females that differed in experience
of sexual harassment and in the factors affecting it. Females of the first group were reared without any sexual experience,
and pregnancy was induced through artificial insemination. The second group was composed of naive females kept singly with
a male; these females experienced sexual harassment but were prevented from experiencing the effects of male–male competition
and shoaling on the amount of male sexual harassment. In the third group (controls), females were reared in multi-male, multi-female
groups and could experience the modulating effects of social interactions on sexual harassment. When exposed to a harassing
male, females of the three groups immediately reduced their distance from another female, approached a group of males or moved
toward the larger of two available males. Moreover, the results for these three groups of females were similar to those obtained
in wild-caught females that were tested in the same three tests in a previous study (Dadda et al. An. Behav., 70:463–471, 2005). This suggests that the strategies adopted by females in response to male sexual harassment do not need to be learned through
specific experience of the social contexts. 相似文献
273.
Sex linkage among genes controlling sexually selected traits 总被引:8,自引:0,他引:8
Klaus Reinhold 《Behavioral ecology and sociobiology》1998,44(1):1-7
Using literature data on reciprocal crosses I estimated the influence of sex-chromosomal genes on morphological and behavioral
traits. To determine a special role of the sex chromosomes for sexually selected traits, I compared the estimated influence
of X-chromosomal genes on sexually selected traits with their estimated influence on traits not under sexual selection. About
one-third of the phenotypic variation in sexually selected traits is caused by X-chromosomal genes. There was, in contrast,
no significant influence of X-chromosomal genes on traits that were classified as not sexually selected. Sexually selected
traits thus seem to be influenced significantly more by X-chromosomal genes than traits not under sexual selection. Though
this differential influence of X-chromosomal genes cannot readily be explained with current theoretical knowledge, it may
shed some light on X-linked hybrid sterility and on the discussion between arbitrary and good-gene models for the evolution
of female choice.
Received: 30 January 1998 / Accepted after revision: 20 June 1998 相似文献
274.
Masayo Soma Daichi S. Saito Toshikazu Hasegawa Kazuo Okanoya 《Behavioral ecology and sociobiology》2007,61(11):1695-1705
Maternal effects, such as investment in eggs, have profound effects on offspring fitness. Mothers are expected to skew their
investment depending on the laying order and sex when unequal sibling competition occurs within a brood because of sex-specific
vulnerability and age hierarchy caused by asynchronous hatching. The Bengalese finch hatches asynchronously and shows a moderate
reversed sexual size dimorphism. However, contrary to commonly accepted assumptions of size-dependent vulnerability, the smaller
sex (male) is more vulnerable to developmental stress caused by sibling competition. We investigated whether maternal investment
would be biased by the position in laying order and the sex of eggs, and also explored the possible differences in growth
patterns depending on sex, laying order, and age hierarchy by observing chicks fostered to experimentally manipulated broods
where brood composition was controlled and age hierarchy was more enhanced than in natural breeding conditions. We found that
overall patterns of maternal investment favored the disadvantageous sectors of sibling competition, i.e., eggs of later laying
order and sons over those of early laying order and daughters. We also examined the effect of laying order on adult body size
and sex differences in growth patterns. When reared in the subordinate age hierarchy, females could compensate for the deficit
of decreased growth rate by taking longer to mature, whereas males could not. We suggest that this sex-specific growth pattern
could be the cause of sex differences in vulnerability to early developmental stress. 相似文献
275.
Giuseppe Boncoraglio Roberta Martinelli Nicola Saino 《Behavioral ecology and sociobiology》2008,62(5):729-738
In diverse taxa, offspring solicit parental care using complex displays, which may evolve as reliable signals of condition
or as mechanisms to manipulate parental investment. Differential sex allocation may therefore result from adaptive parental
decisions or sex-related variation in competitive ability or because of sex-related asymmetries in kin selection. Under normal
food provisioning, female barn swallow (Hirundo rustica) nestlings begged more loudly but did not receive more food than male nestlings. After food deprivation, begging call loudness
of males but not females increased. Begging loudness positively predicted the number of feedings received by the nestlings,
and males gained more mass than females after food deprivation. Male nestlings are more severely affected by chronic food
reduction and may therefore accrue a larger benefit compared to females by increasing their food intake under short-term conditions
of food scarcity. These results suggest that either females do not increase begging intensity to favour male broodmates which
are more vulnerable to prolonged food stress, or that males prevail in scramble competition despite being similar in size
to females. 相似文献
276.
Although evidence is accumulating on the adaptive function of female ornamentation, very little is known about maternal allocation
decisions involving sexual signaling and other reproductive functions. Blue egg coloration has been suggested as a sexually
selected signal of female quality to males, and some recent studies are in accordance with this hypothesis. Blue eggshell
coloration results from the deposition of biliverdin pigment by laying females, which is a potent antioxidant. Thus, egg pigmentation
should be costly in terms of antioxidants, an assumption of the signaling hypothesis that has not been tested yet. We induced
increased reproductive effort in a set of female pied flycatchers Ficedula hypoleuca through nest removal and measured egg pigmentation and plasma antioxidant levels in relation with a control group. Experimental
females showed a negative association between egg color and plasma antioxidant levels, while there was no relationship for
control birds. This supports that egg pigmentation is costly in terms of general antioxidant defenses and suggests a tradeoff
between the allocations to both traits. Furthermore, experimental females with more colorful eggs raised more fledglings,
especially when breeding early. Controls did not show a relationship between egg color and reproductive success. Females laying
more colorful eggs could have shifted their allocation decisions towards current reproduction, at the expense of their own
antioxidant defenses. Our results highlight that blue egg coloration is a life-history trait, subject to tradeoffs with other
attributes, and seems to be especially informative under harsh breeding conditions. 相似文献
277.
Bushcricket males of Poecilimon zimmeri transfer large and protein-rich spermatophores during mating, which females directly ingest. There is correlational evidence
that heavier males transfer larger nuptial gifts. In no-choice mating trials, females mated randomly with respect to male’s
body weight. In contrast, in two-choice mating trials, female bushcrickets exhibit clear choice for the heavier male. This
heavier male advantage was also found in pre-mating choice during phonotaxis. With manipulated mute males, females mated at
random with regard to body weight of the competitors. The number of physical encounters between a female and males was low
in all tests with a single male (no choice) and greater in choice-tests with two competing males. The latencies to mate also
differed significantly between treatments. The time mating pairs spent in precopula was short in experiments where the males
could hear rivals and significantly longer in all other tests using either a single male or mute males. Thus, acoustic signalling
in male bushcrickets seems to signal male body weight. A preference for heavier males may reflect a female’s preference for
a larger spermatophore and therefore a greater direct benefit. 相似文献
278.
Parent–offspring conflict theory is well supported by theoretical arguments. However, empirical observations are often difficult to interpret and have contradicted one of its most appealing predictions that parent and offspring should disagree over killing of nest or littermates. We present the first examples of deadly conflict between siblings of different cohorts. In Galápagos fur seals (Arctocephalus galapagoensis) and sea lions (Zalophus wollebaeki), mothers often wean their single offspring at 2 years. This leads to a situation where up to 23% of all pups are born while the older sibling is still being nursed. Younger siblings are disadvantaged by being born lighter than neonates without older still dependent siblings. Pups born while an older sib is still dependent grow less in early life (fur seal) and suffer increased early mortality (both species) through direct aggression or scramble competition with the older sibling. This effect is much stronger in years of high sea surface temperature (El Niño) indicating low marine productivity and if the older offspring is a male. In both species, mothers interfere aggressively in this conflict by defending the younger offspring. In years of El Niño, intense resistance to maternal aggression by the older offspring happens frequently in the fur seal. Such resistance against weaning can induce maternal neglect of the newborn. Given substantial year to year variation in offspring growth, maternal aggression forces weaning in the older sibling only if it has reached sufficient size to support itself by foraging. In Galápagos fur seals, pups with older siblings can either represent insurance against loss of older offspring or extra reproductive value. 相似文献
279.
The social organization of gregarious lemurs significantly deviates from predictions of the socioecological model, as they
form small groups in which the number of males approximately equals the number of females. This study uses models of reproductive
skew theory as a new approach to explain this unusual group composition, in particular the high number of males, in a representative
of these lemurs, the redfronted lemur (Eulemur fulvus rufus). We tested two central predictions of “concession” models of reproductive skew theory, which assume that subordinates may
be allowed limited reproduction by dominant group members as an incentive to remain in the group, thereby increasing the group’s
overall productivity. Accordingly, relatives are predicted to receive less reproduction than non-relatives, and the overall
amount of reproductive concessions given to subordinates is predicted to increase as the number of subordinates increases.
In addition, we tested whether the number of females in a group, a variable not previously incorporated in reproductive skew
theory, affected reproductive skew among males. Using microsatellite analyses of tissue DNA, we determined paternities of
49 offspring born into our study population in Kirindy forest (western Madagascar) since 1996 to determine patterns of male
reproductive skew to test these predictions. Our analyses revealed remarkable reproductive skew, with 71% of all infants being
sired by dominant males, but both predictions of reproductive skew models could not be supported. Instead, the number of females
best predicted the apportionment of reproduction among the males in this species, suggesting that current reproductive skew
models need to incorporate this factor to predict reproductive partitioning among male primates and perhaps other group-living
mammals.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Both Peter M. Kappeler and Markus Port contributed equally to this paper. 相似文献
280.
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