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51.
Ectoparasites of house sparrows (Passer domesticus): an experimental test of the immunocompetence handicap hypothesis and a new model 总被引:2,自引:0,他引:2
Conspicuous secondary sexual traits may have evolved as handicap-revealing signals or as badges of status. We present results
of an experiment using males of the sexually dimorphic house sparrow (Passer domesticus), that support the idea that the male-specific bib can be both a handicap-revealing signal and a reliable badge indicating
the physical condition of the bird. In a test of the immunocompetence handicap hypothesis, wild-caught adult male house sparrows
were studied in captivity. Birds implanted with elevated doses of testosterone were more dominant, had higher circulating
levels of both testosterone and corticosterone and they also harboured relatively larger ectoparasite loads. Higher parasite
loads were also associated with individuals showing lower immunocompetence and larger changes in bib size. A new model for
immunocompetence effects in sexual selection is introduced, integrating actions that the hypothalamopituitary axis exerts
on gonads, adrenals and the thyroid gland. The ”integrated immunocompetence model” synthesizes both the ”handicap” (i.e. survival-decreasing)
and ”badge of status” (i.e. survival- enhancing) models for evolution of secondary sexual traits.
Received: 15 May 1999 / Received in revised form: 2 November 1999 / Accepted: 6 November 1999 相似文献
52.
Experimental evidence of a testosterone-induced shift from paternal to mating behaviour in a facultatively polygynous songbird 总被引:5,自引:2,他引:3
Previous studies have suggested that testosterone (T) profiles of male birds reflect a trade-off between mate attraction behaviours
(requiring high T levels) and parental care activities (requiring low T levels). In this study, we experimentally elevated
T levels of monogamous males in the facultatively polygynous European starling (Sturnus vulgaris), and compared mate attraction and paternal behaviour of T-treated males with those of controls (C-males). T-males significantly
reduced their participation in incubation and fed nestlings significantly less often than C-males. Females paired to T-treated
males did not compensate for their mate’s lower paternal effort. The observed reduction in a male’s investment in incubating
the eggs was accompanied by an increased investment in typical female-attracting behaviours: T-males spent a significantly
higher proportion of their time singing to attract additional females. They also occupied more additional nestboxes than C-males,
although the differences just failed to be significant, and carried significantly more green nesting materials into an additional
nestbox (a behaviour previously shown to serve a courtship function). T-males also behaved significantly more aggressively
than C-males. During the nestling period, the frequency of mate-attracting behaviours by T-treated and control males no longer
differed significantly. Despite the reduced paternal effort by T-males and the lack of compensation behaviour by females,
hatching and breeding success did not differ significantly between T- and C-pairs.
Received: 7 February 2000 / Revised: 10 August 2000 / Accepted: 3 September 2000 相似文献
53.
In many salmonid species, males exhibit morphological dimorphism associated with alternative mating behaviors. ”Precocious
males” have a small body size with little or no development of sexual characters and adopt sneaking to gain access to females,
while ”migratory males” of large body size and well-developed secondary sexual characters fight. We quantified selection on
precocious male parr of masu salmon (Oncorhynchus masou) under simulated natural conditions to examine the contribution of morphology to sneaking success. In contrast to the prediction
that sneaking behavior favors small body size, we detected selection favoring relatively large body size for sneaking success.
This selection pressure was caused by the dominance hierarchy within parr and may have been facilitated by indifference of
dominant migratory males to parr. Unlike the secondary sexual characters exhibited by migratory male salmon, such as the hooked
snout and humped back, no morphological characters other than body size contributed to the reproductive success of masu salmon
parr. This non-contribution may have been responsible for the lack of development of sexual characters in precocious males.
Received: 15 November 1999 / Accepted: 20 May 2000 相似文献
54.
Precopulatory sexual cannibalism (predation of a potential mate prior to copulation) offers an extreme example of intersexual conflict, a current focus in behavioral ecology. The aggressive-spillover hypothesis, posits that precopulatory sexual cannibalism may be a nonadaptive by-product of a general syndrome of voracity (aggression towards prey) that is expressed in multiple behavioral contexts. In this view, selection favoring high levels of voracity throughout ontogeny spills over to cause sexual cannibalism in adult females even when it is not necessarily beneficial. Using the North American fishing spider, Dolomedes triton, we present the first in depth test of this hypothesis. We found support for three aspects of the spillover hypothesis. First, voracity towards hetero-specific prey results in high feeding rates, large adult size, and increased fecundity. Second, juvenile and adult voracity are positively correlated (i.e., voracity is a consistent trait over ontogeny). Third, voracity towards hetero-specific prey is indeed positively correlated with precopulatory sexual cannibalism. Assays of antipredator behavior further revealed positive correlations between boldness towards predators, voracity and precopulatory sexual cannibalism. Overall, our results support the notion that precopulatory sexual cannibalism in D. triton is part of a behavioral syndrome spanning at least three major contexts: foraging, predator avoidance, and mating. 相似文献
55.
An unusual pollination strategy is pollination by sexual deception in which orchids sexually attract male insects as pollinators. One gap in knowledge concerns the pattern and extent of pollinator movement among these sexually deceptive flowers and how this translates to pollen and gene flow. Our aim was to use mark and recapture techniques to investigate the behavior and movement of male Colletes cunicularius, an important bee pollinator of Ophrys. Our study site was located in northern Switzerland where a large population of the bees was nesting. Within two plots, (10×40 m), we marked bees with different colors and numbered tags. Seventeen percent of the 577 marked bees were recaptured over a period of 1 to a maximum of 11 days. However, the number of recaptures dropped dramatically after 3–5 days, suggesting an average lifetime of less than 10 days. Mark-recapture distances varied from 0 to 50 m, with a mean of 5 m. Our findings show that individual male bees patrol a specific and restricted region of the nesting area in search of mates. This mark-recapture study provides the first clues about the potential movement of pollen within populations of Ophrys orchids. We predict that orchid-pollen movements mediated by bees will be similar to the mark-recapture distances in this study. Parallel studies within orchid populations, including direct studies of pollen movement, are now required to better understand how pollinator mate-searching behavior translates to pollination success and pollen movement within sexually deceptive orchid populations.Communicated by R.F.A. Moritz 相似文献
56.
Black spots and female association preferences in a sexual/asexual mating complex (Poecilia, Poeciliidae, Teleostei) 总被引:1,自引:0,他引:1
Michael Tobler Martin Plath Heike Burmeister Ingo Schlupp 《Behavioral ecology and sociobiology》2006,60(2):159-165
We investigated whether female association preferences for males are influenced by black spot disease (BSD), a parasite induced change of the host phenotype. We compared three different species of fish: a gynogenetic hybrid species, Poecilia formosa (amazon molly) and two sexual species (Poecilia latipinna and Poecilia mexicana), which were involved in the natural hybridisation leading to the amazon molly. Contrary to their sexual relatives, asexual amazon mollies significantly avoided images of males infected with black spot disease. We propose that amazon molly females have direct fitness benefits from choosing healthy males. The adaptive significance of the preference for BSD-uninfected males in the asexual amazon molly is yet unclear but may involve avoidance of predation or parasite infection as well as increased sperm availability. 相似文献
57.
Maria I. Sandell 《Behavioral ecology and sociobiology》2007,62(2):255-262
In the European starling, Sturnus vulgaris, optimal mating systems differ between males and females. Males gain from polygyny, whereas monogamy increases female fitness.
The cost of polygyny to females lead to intense female–female competition, and it has previously been shown that the intensity
of female aggression during the pre-breeding period can predict the realised mating system. The physiological regulation of
such female aggression in starlings is not yet known. This study examines the role of testosterone in mediating aggressive
behaviours involved in intra-specific reproductive competition in female starlings. Testosterone levels were experimentally
elevated with testosterone implants in females during the pre-laying period. To simulate a situation in which an additional
female tried to mate with the focal female’s mate, a caged female was presented close to a nest-site to which the male could
attract a secondary female. Testosterone was significantly related to several behaviours involved in female–female interactions.
Females with testosterone implants spent significantly more time close to the caged female and produced more song bouts than
control females. In contrast, male behaviour was unrelated to the experimental status of the mate. Females mated to males
that attracted a secondary female were less aggressive towards the caged female than those that remained monogamously mated.
The effect of exogenous testosterone in this study indicates that androgens may mediate social behaviours in female starlings
during the breeding season. 相似文献
58.
Sexual selection that results in the evolution of exaggerated secondary sexual characters has been hypothesized to impose production and maintenance costs of such traits on their bearers. Costs arising from sexual selection could increase the intensity of predator-mediated natural selection, leading to the prediction that species with exaggerated secondary sexual characters should be particularly susceptible to predation. We tested this prediction in a comparative analysis based on 31,745 prey individuals belonging to 66 species of birds collected from a total of 937 breeding events by 33 to 66 different pairs of European sparrowhawks Accipiter nisus annually during a period of 21 years. To assess vulnerability of different species we estimated a prey vulnerability index based on the difference in the logarithmically transformed absolute abundance of prey minus the logarithmically transformed expected abundance as determined by population density of breeding birds. The prey vulnerability index was predicted by sexual dichromatism, accounting for 23% of the variance in risk of predation among species, even when considering similarity in phenotype among species due to common descent (in the latter case explaining 12% of the variance). This finding suggests that sexual selection is an important evolutionary force-affecting predator–prey interactions.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
59.
Robert M. Gibson 《Behavioral ecology and sociobiology》1996,39(1):55-59
Previous studies of female choice in sage grouse Centrocercus urophasianus have implicated both the acoustic quality and repetition rate of the stereotyped strut display as putative cues for female
choice. Stages in the choice process at which specific components of male courtship display influence female decisions were
investigated using field observations of female pre-mating behavior. Females visited a subset of territorial males and then
actively chose one of these as a mate. The order in which males were visited suggested that females searched until an acceptable
mate was found, rather than employing a “best-of-n” tactic. Numbers of females visiting a male were related to differences
in an acoustical component of display (inter-pop interval) whereas the probability that a visiting female mated was related
to display rate (Table 3), indicating that initial attraction and active choice are influenced by different components of
display. In addition, inter-pop interval and display rate tended to covary inversely (Fig. 1), suggesting that attraction
and active choice may impose conflicting selection pressures on display performance.
Received: 11 November 1995/Accepted after revision: 16 March 1996 相似文献
60.
Determinants of paternity success in the spider Pholcus phalangioides (Pholcidae: Araneae): the role of male and female mating behaviour 总被引:1,自引:0,他引:1
In double mating experiments, we examined whether and to what extent various male and female behavioural traits influence
the course of mating and fertilization success in the cellar spider. In males, we focussed on pre-copulatory behaviour and
on the rhythmic twisting movements that the male performs with his pedipalps during copulation. In females, we investigated
remating decisions and the effect of female termination of copulation. Second males fertilized a high proportion of the eggs
(P
2: median 89%) despite much shorter second matings, with high variation in relative paternity success. The number of pedipalp
movements (PPMs) of either male was a better predictor of paternity than copulation duration. Our results suggest that in
second matings, PPMs help to remove sperm from previous males, whereas in first matings a high number of PPMs enhances fertilization
success, either due to numerical sperm competition or cryptic female choice. Furthermore, we found a negative male age effect
on paternity in second matings, implying that age-related deterioration of spermatozoa may promote variation in fertilization
success. Female receptivity decreased significantly in second matings; only 70% of the females remated. Females that accepted
a second copulation were found to terminate these much earlier and with higher probability than first matings. This suggests
that the intensity of conflict between the sexes is higher in second matings. Increased intensity of sexual conflict may be
responsible for stronger selection on male traits, as pre-copulatory behaviour and age only affected male copulatory performance
and paternity in second matings.
Electronic Publication 相似文献