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131.
Females ofBlattella germanica andBlaberus craniifer produce a volatile sex pheromone attractive at a distance for conspecific males. During the emission of the pheromone, females ofB. craniifer adopt a typical calling posture; we never observe such a stance inB. germanica females. For both species, the glandular structures responsible for pheromonal production are located on the female pygidium. InB. germanica, the thickness of the glandular epithelium is clearly correlated with the attractiveness of females, being maximum for 13 day old females. The functions of the pygidial glands are discussed in both species. 相似文献
132.
Summary Adult male tree lizards, Urosaurus ornatus, practise alternative (territorial or sneaker/satellite) reproductive strategies that are correlated with differences in throat color and body size. In this study we raised tree lizards from hatching in the laboratory to examine the question of whether the phenotypic expression of secondary sex coloration and body size can be facultatively influenced by social or abiotic environmental factors. We compared males reared in the laboratory under different social and environmental conditions to males in the field and found no effect of different conditions on phenotypic differentiation (Figs. 2–4). Thus, phenotypic differences between morphs probably result largely from nonfacultative expression of different genotypes. This suggests that alternative male morphs practise a mixed evolutionary stable strategy (ESS) rather than one morph making the best of a bad situation. However, in the context of ESS theory it is difficult to explain our further result that the nonterritorial morph in this species grows faster and reaches a larger adult body size than the territorial morph (Fig. 5). 相似文献
133.
J. P. Kent 《Behavioral ecology and sociobiology》1995,36(2):101-104
The birth sex ratio of a commercial flock of Suffolk cross sheep, Ovis aries, was studied over nine consecutive lambing seasons. In all data from 2704 lambs were recorded and analysed. The overall (1985–1993) birth sex ratio was 49.96% male lambs. Ewes with single lambs produced significantly more males (53.04%) than ewes with triplets (45.54% male). A significant positive correlation was found between the flock age and the birth sex ratio (1985–1992). As the flock aged the birth sex ratio changed from female biased to male biased, remained male biased for a number of years, and then became female biased again. This pattern is evident first in single, then in twin and later in triplet births. Among like sex twins (males and females) (1985–1993) more males (53.88%) were born in the first half and more females (45.57% males) in the second half of the lambing season. The difference between the two halves is significant. 相似文献
134.
Raphaël Boulay Abraham Hefetz Xim Cerdá Séverine Devers Wittko Francke Robert Twele Alain Lenoir 《Behavioral ecology and sociobiology》2007,61(10):1531-1541
Models based on the kin selection theory predict that in social hymenopterans, queens may favor a lower investment in the
production of sexuals than workers. However, in perennial colonies, this conflict may be tuned down by colony-level selection
because of the trade off between colony survival and reproductive allocation. In this study, we present a survey of sexual
production in colonies of Aphaenogaster senilis, a common species of ant in the Iberian Peninsula. Similar to most species that reproduce by fission, males were found in
large excess compared to gynes (172:1). Sexuals were more likely to be found in queenless than in queenright (QR) field colonies.
However, we also found a few gynes and numerous males in very large QR colonies. We compared these data with those available
in the literature for A. rudis, a congeneric species from North America that has independent colony founding. The sex ratio in this species was only five
males for each female, and sexuals were mostly found in QR nests, irrespective of colony size. We confirmed queen inhibition
of sexual production in A. senilis in laboratory experiments and provide evidence that this inhibition is mediated by a nonvolatile pheromone. To seek the potential
source of such a queen pheromone, we analyzed the secretions of two conspicuous exocrine glands, the Dufour’s and postpharyngeal
glands (DG and PPG, respectively) in both queens and workers. Both secretions were composed of hydrocarbons, but that of DG
also contained small quantities of tetradecanal and hexadecanal. The hydrocarbon profile of the DG and PPG showed notable
caste specificity suggesting a role in caste-related behavior. The PPG secretions also differed between colonies suggesting
its role in colony-level recognition. We suggest that in A. senilis, there are two modes of colony fission: First, in very large colonies, gynes are produced, probably because of the dilution
of the queen pheromone, and consequently one or more gynes leave the mother colony with workers and brood to found a new nest.
This is beneficial at the colony level because it avoids the production of costly sexuals in small colonies. However, because
the queen and workers have different optima for sexual production, we hypothesize that queens tend to overproduce the pheromone
to delay their production. This in turn may drive workers to leave the mother colony during nest relocation and to produce
sexuals once they are away from the queen’s influence, creating a second mode of colony fission. 相似文献
135.
Abstract: When sex determination in a species is predominantly genetic but environmentally reversible, exposure to (anthropogenic) changes in the environment can lead to shifts in a population's sex ratio. Such scenarios may be common in many fishes and amphibians, yet their ramifications remain largely unexplored. We used a simple model to study the (short-term) population consequences of environmental sex reversal (ESR). We examined the effects on sex ratios, sex chromosome frequencies, and population growth and persistence after exposure to environmental forces with feminizing or masculinizing tendencies. When environmental feminization was strong, X chromosomes were driven to extinction. Analogously, extinction of normally male-linked genetic factors (e.g., Y chromosomes) was caused by continuous environmental masculinization. Although moderate feminization was beneficial for population growth in the absence of large viability effects, our results suggest that the consequences of ESR are generally negative in terms of population size and the persistence of sex chromosomes. Extreme sex ratios resulting from high rates of ESR also reduced effective population sizes considerably. This may limit any evolutionary response to the deleterious effects of ESR. Our findings suggest that ESR changes population growth and sex ratios in some counter-intuitive ways and can change the predominant factor in sex determination from genetic to fully environmental, often within only a few tens of generations. Populations that lose genetic sex determination may quickly go extinct if the environmental forces that cause sex reversal cease. 相似文献
136.
137.
Amy C. Dolan Michael T. Murphy Lucas J. Redmond Debbie Duffield 《Behavioral ecology and sociobiology》2009,63(10):1527-1537
Sex allocation theory predicts that if variance in reproductive success differs between the sexes, females who are able to
produce high-quality young should bias offspring sex ratio towards the sex with the higher potential reproductive success.
We tested the hypothesis that high-quality (i.e., heavy) female eastern kingbirds (Tyrannus tyrannus) that bred early in the breeding season would produce male-biased clutches. A significant opportunity for sexual selection
also exists in this socially monogamous but cryptically polygamous species, and we predicted that successful extra-pair (EP)
sires would be associated with an excess of male offspring. Although population brood sex ratio did not differ from parity,
it increased significantly with female body mass and declined with female breeding date, but was independent of the morphology
and display (song) behavior (correlates of reproductive success) of social males and EP sires. Male offspring were significantly
heavier than female offspring at fledging. Moreover, the probability that male offspring were resighted in subsequent years
declined with breeding date, and was greater in replacement clutches, but lower when clutch size was large. Probability of
resighting female offspring varied annually, but was independent of all other variables. Given that variance in reproductive
success of male kingbirds is much greater than that of females, and that male offspring are more expensive to produce and
have a higher probability of recruitment if fledged early in the season, our results support predictions of sex allocation
theory: high-quality (heavy) females breeding when conditions were optimal for male recruitment produced an excess of sons. 相似文献
138.
Apostolos Kapranas P. Pacheco L. D. Forster J. G. Morse R. F. Luck 《Behavioral ecology and sociobiology》2008,62(6):901-912
We examined whether several facultatively gregarious encyrtid (Hymenoptera: Encyrtidae) endoparasitoids of brown soft scale,
Coccus hesperidum L., manifest precise sex allocation under field conditions. Metaphycus luteolus (Timberlake), Metaphycus angustifrons (Compere), Metaphycus stanleyi (Compere), and Microterys nietneri (Motshulsky) evince brood sex ratios that are female-biased and extremely precise (low variance in the number of sons per
host). Typically, this sex allocation pattern is attributed to extreme local mate competition (LMC) in which only one foundress
exploits a patch of hosts and mating occurs mostly between her offspring. However, such a pattern of sex allocation was not
detected for Metaphycus helvolus (Compere). Also, a large proportion of the broods in all five species contained only daughters; thus, an excess of male-only
broods was expected if unmated females (i.e., females that can produce only sons) contribute offspring before mating. All-male
broods were rare in our samples. This finding coupled with the life history characteristics of these wasps, such as the exploitation
of aggregated hosts and the long life span and mobility of males, suggest that nonlocal mating is frequent. Our empirical
work suggests that it is advantageous to allocate precise sex ratios in cases in which mating opportunities for males are
not restricted to their natal host and/or when multiple foundresses exploit large patches of hosts. Limited theoretical work
also supports this prediction but more detailed studies of this taxon’s mating structure and other life history characteristics
are necessary to understand their sex allocation decisions. 相似文献
139.
A sex pheromone component novel to Ostrinia identified from Ostrinia latipennis (Lepidoptera: Crambidae) 总被引:1,自引:0,他引:1
Takuma Takanashi Suguru Ohno Yongping Huang Sadahiro Tatsuki Hiroshi Honda Yukio Ishikawa 《Chemoecology》2000,10(3):143-147
Summary. Extracts from the sex pheromone gland of Ostrinia latipennis (Lepidoptera: Crambidae) were analyzed by gas chromatography-electroantennographic detection (GC-EAD) and GC-mass spectrometry.
Only an EAD-active compound was detected in the extract, and it was identified as (E)-11-tetradecenol (E11-14:OH). In a wind-tunnel bioassay, E11-14:OH elicited a series of mate finding behaviors from males, although it was far less active than virgin females and crude
extract of the pheromone gland. The attractiveness of E11-14:OH to O. latipennis males was confirmed by field trapping experiments. Based on these findings, we concluded that E11-14:OH, which is novel to the genus Ostrinia, is a major component of the sex pheromone in O. latipennis. The significance of the use of alcohol in place of the usual acetates in Ostrinia is discussed in relation to the pheromone biosynthesis system.
Received 9 December 1999; accepted 14 March 2000 相似文献
140.
Erich Zeeck Carsten T. Müller Manfred Beckmann Jörg D. Hardege Ulrich Papke Volker Sinnwell Frank C. Schroeder Wittko Francke 《Chemoecology》1998,8(1):33-38
Summary. In the marine polychaete Nereis succinea (Frey & Leuckart 1847) a sex pheromone was isolated from the coelomic fluid of sexually mature females and identified by
NMR studies and independent synthesis. This pheromone is released by the females during reproduction together with eggs and
coelomic fluid into the free water column and induces sperm release of surrounding males. Its structure was ascertained as
L-cysteine-glutathione disulfide. It exhibited a response threshold of 0.6 · 10−7 M.
Received 15 July 1997; accepted 25 November 1997. 相似文献