摘要:

The common pheasant,Phasianus colchicus, is now considered a classic example of the difficulty of establishing a clear distinction between inter- and intrasexual selection since a role for male spurs as cues used by females in mate choice has been reported. Field and experimental studies on sexual selection in the ring-necked pheasant show that the dimorphic morphological (and behavioural) male traits have a dual function according to the armament-ornament model. They are weapons or reliable signals of male quality directed both to females and rivals, and the relative importance between them depends on a suite of factors affecting the decision-making processes of females, including the outcome of male-male encounters. Different mechanisms and models of sexual selection have been suggested in order to classify the overall competitive strategies found in nature; but the amount of empirical data on the evolution of epigamic traits suggests that what determines the reproductive success of males is a complex suite of characters producing differences between individuals, on which the effects of inter-sexual, intra-sexual and natural selection are difficult to define.

ISSN:0394-9370    

DOI:10.1080/08927014.1998.9522846

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In European quail, individual birds can be discriminated by using only three parameters describing the long-distance vocalizations used during pair bonding. In the male vibrato these parameters are: the total duration of the vibrato, the duration of the second syllable and the highest energy component of the fundamental. For the male triplet, the necessary parameters are: the interval between the highest frequency points of syllables 1 and 2, of syllables 2 and 3, and the frequency of the inflexion point of the third syllable. Individual females can usually be identified by three rally call parameters; these being the interval between syllables 1 and 2, the interval between the lowest frequency points, and the frequency of maximal amplitude in the second syllable of the rally call. Comparison based on these three parameters for each form of vocalization showed that more than 80% of individuals were correctly discriminated thus permitting fairly reliable counts of populations in the field. Intra-individual variations of parameters of male triplets linked with sexual development or age could permit sexual selection of singing males by females. Comparisons between the sexual calls of the European quail and the Grey partridge lead to evolutionary suggestions about the structure of vocalizations in these two related sympatric species.

ISSN:0394-9370    

DOI:10.1080/08927014.1998.9522847

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Worker reproduction and worker mating were compared between two temperate paper wasp speciesPolistes chinensisandP. snelleniin central Japan, by dissecting females. As a whole, potential egg-layers (worker reproductives) constituted 14.7% of 273 workers from queen-right colonies and 26.0% of 254 from orphaned colonies inP. chinensis. InP. snelleni, potential egg-layers constituted 8.1% of 307 workers from queen-right colonies and 11.6% of 337 from orphaned colonies. The numbers and proportions of potential egg-layers per colony were also larger inP. chinensisthan inP. snelleni. Despite the presence of more potential egg-layers, there were no inseminated workers inP. chinensiscolonies. By contrast, inP. snelleni8.5 and 18.1% of all workers were inseminated in queenright and orphaned colonies, respectively. The differences between the worker characteristics of the two species were investigated and were concluded to be mainly due to differences in the production schedules of new reproductive females (new queens) and males by the foundress queens.

ISSN:0394-9370    

DOI:10.1080/08927014.1998.9522848

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Starving adult beetles ofMenochilus sexmaculatusandCoccinella transversalisresorted to intra- and inter-specific predation in the absence of aphid prey. Particularly at high egg densities, predators consumed eggs of their own species much more readily than eggs of the other species. Between the two ladybird species, the eggs of the smaller species,M. sexmaculatus, were less vulnerable to predation from the larger species,C. transversalisthan vice versa. Results further indicate that adult female beetles are capable of discriminating eggs of their own species versus eggs of alien species on physical contact. The adaptive significance of this is discussed.

ISSN:0394-9370    

DOI:10.1080/08927014.1998.9522849

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The evolutionary effects of crowding on male courtship behavior were studied using wild and mass-reared medflies. Mass-reared strains had been raised under highly crowded conditions in mass-rearing facilities for approximately 75, 180, and 238 generations. Pre-mounting courtship was facultatively shortened in both wild and mass-reared males under conditions of greater crowding. The courtship behavior of males of mass-reared strains was also shorter than that of wild males under similar conditions of crowding. Shorter courtships are probably advantageous for males in crowded conditions because they reduce the likelihood of the courtship being interrupted by other flies. Several types of data indicated that males rather than females were responsible for shortened courtships. We conclude that heritable variation in male courtship behavior has persisted in a wild population despite its overall relatively low genetic variability, and that genetic changes in mass-reared strains have altered the range of facultative adjustments in courtship behavior.

ISSN:0394-9370    

DOI:10.1080/08927014.1998.9522850

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Vivivparus aterandV. contectusfrequently mate with each other in nature. We investigated mate preferences between the two species experimentally. Males were presented to females of either species and vice versa. Males of both species actively searched for mates and preferably mated with conspecific females. Females appeared passive and accepted matings from males of either species. Twenty-six per cent of heterosexual copulations were interspecific, suggesting either that the preference for conspecific mates, or that the ability to discriminate between partners of different species, is weak inViviparus. Male-male copulations occurred at a rate of 5.1%, but these copulations were of shorter duration suggesting that some discrimination against male partners occurred.V. contectusmales had a higher mating propensity thanV. atermales. In both species, the majority of first contacts was initiated by males. First contacts between conspecific individuals were more frequent than between species, suggesting that snails are already more attracted to conspecific individuals from a distance. The proportion of first contacts ending with a copulation was higher in conspecific pairs than in interspecific pairs. Thus choices are made before and after establishing contact with another individual.

ISSN:0394-9370    

DOI:10.1080/08927014.1998.9522851

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

New Zealand tree weta (Orthoptera Stenopelmatidae;Hemideinaspp.) have life-history traits that are typical of animals with female-defence mating systems. Individuals live for more than 1 year and single adult males fight to defend ha-rems of females from rival males in cavities in wood or under rock. The alpine weta,H. maori, inhabits schist outcrops (‘tors’) in the alpine zone of New Zealand's South Island. In this species (and otherHemideina) there is a large sexual dimorphism in cephalic weaponry; the mandibles used by males in fights are almost twice the size of those of females. In this paper we (i) document the sexual difference in head and mandible allometry forH. maoriand (ii) provide evidence for the hypothesis that sexual dimorphism is a result of sexual selection for male defence of a cavity that contains from one to seven adult females. Within two populations of this species inhabiting single tors there were significant positive correlations between harem size and both the head and mandible size of males. However, a third population failed to show a significant relationship, possibly because some of the large males were recently-moulted, young adults that had not yet acquired females.

ISSN:0394-9370    

DOI:10.1080/08927014.1998.9522852

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor