scholarly journals Sex Ratio of Small Hive Beetles: The Role of Pupation and Adult Longevity

Insects ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 133 ◽  
Author(s):  
Anna Papach ◽  
Jérémy Gonthier ◽  
Geoffrey R. Williams ◽  
Peter Neumann
Keyword(s):  
Sex Ratio ◽  
Field Studies ◽  
Differential Mortality ◽  
Adult Longevity ◽  
Published Data ◽  
Larval Feeding ◽  
Intraspecific Interactions ◽  
Adult Sex Ratio ◽  
Biased Sex Ratio ◽  
Small Hive Beetles

The sex ratio of sexually reproducing animal species tends to be 1:1, which is known as Fisher’s principle. However, differential mortality and intraspecific competition during pupation can result in a biased adult sex ratio in insects. The female-biased sex ratio of small hive beetles (SHBs) is known from both laboratory and field studies, but the underlying reasons are not well understood. Here, we used laboratory mass and individual pupation to test if differential mortality between sexes and/or intraspecific interactions can explain this sex ratio. The data show a significant female-biased adult sex ratio in both mass and individual rearing, even when assuming that all dead individuals were males. Our results therefore suggest that neither differential mortality during pupation nor intraspecific interactions are likely to explain the female-biased sex ratio of freshly emerged adult SHBs. We regard it as more likely that either competition during the larval feeding stage or genetic mechanisms are involved. In addition, we compared our data with previously published data on the sex ratio of both freshly emerged and field-collected SHBs to investigate possible gender differences in adult longevity. The data show a significantly greater female bias in the sex ratio upon emergence, compared to field-collected SHBs, suggesting that adult females have a shorter longevity.

Effects of phytoseiid predators on the sex ratio of the spider mite Panonychus ulmi

1991 ◽  
Vol 69 (1) ◽  
pp. 208-212 ◽  
Author(s):  
Dan L. Johnson ◽  
Heather C. Proctor
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Spider Mite ◽  
Total Population ◽  
Panonychus Ulmi ◽  
Encounter Rate ◽  
Male Mortality ◽  
Adult Sex Ratio ◽  
Biased Sex Ratio ◽  
Male Activity

The effect of predator presence on the adult sex ratio of a spider mite (Panonychus ulmi) was examined in a field experiment. Phytoseiid predators (chiefly Typhlodromus occidentalis) were removed from 32 trees harboring P. ulmi populations, and allowed to remain at natural levels on 32 other trees. Both total population density and proportion of males in the prey population were significantly higher in predator-free trees. Mechanisms that could explain the increase in the proportion of males are examined. The most probable is that greater male activity results in a higher encounter rate between predator and prey, and that subsequent higher male mortality when predators are present exaggerates the female-biased sex ratio. The theoretical effects of sex-biased predation on diplo-diploid and haplo-diploid organisms are discussed.

Life history and feeding biology of the predatory thrips, Aleurodothrips fasciapennis (Thysanoptera: Phlaeothripidae)

1998 ◽  
Vol 88 (3) ◽  
pp. 351-357 ◽  
Author(s):  
D.M. Watson ◽  
T.Y. Du ◽  
M. Li ◽  
J.J. Xiong ◽  
D.G. Liu ◽  
...  
Keyword(s):  
Life History ◽  
Relative Humidity ◽  
Sex Ratio ◽  
Intrinsic Rate ◽  
Natural Increase ◽  
Adult Longevity ◽  
Female Fecundity ◽  
Adult Sex Ratio ◽  
Survival And Reproduction ◽  
Low Humidity

AbstractDetails of the life history, the effects of relative humidity and temperature on survival and reproduction, and the predatory ability of Aleurodothrips fasciapennis Franklin were examined under laboratory conditions. Stage-specific development and adult longevity were similar between sexes, and the adult sex ratio was 1:1. Females laid 23.3 ± 18.0 eggs of which 83% hatched. The survival rate of first instars to adulthood was 82%. The intrinsic rate of natural increase (rm) was 0.04, assuming a zero or 5.4 day pre-oviposition interval. Temperature did not affect the proportion of eggs that hatched, the proportion of first instars surviving to adulthood or adult sex ratios. However, female fecundity was dependent on temperature being highest at 24 ndash 28°C. Relative humidity did not affect adult sex ratio or female fecundity but the proportion of eggs hatched and the survival of first instars to adulthood increased as relative humidity increased. Few eggs hatched when relative humidity was <65%. Larval and adult female A. fasciapennis were voracious feeders but the number of prey killed per progeny was high, suggesting A. fasciapennis was inefficient at converting prey into progeny biomass. The potential value of A. fasciapennis as a biocontrol agent of Aonidiella aurantii (Maskell) on Australian citrus is discussed in terms of its rm, prey killing power and environmental adaptability. It is concluded that population growth of A. fasciapennis should exceed that of A. aurantii under field conditions but A. fasciapennis may be of little value against A. aurantii on citrus grown under conditions of high temperature and low humidity, or when prey densities are low.

Female-biased sex ratio in adults of the turtle Emys orbicularis at the northern limit of its distribution in France: a probable consequence of interaction of temperature with genotypic sex determination

1989 ◽  
Vol 67 (5) ◽  
pp. 1279-1284 ◽  
Author(s):  
J. Servan ◽  
P. Zaborski ◽  
M. Dorizzi ◽  
C. Pieau
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Emys Orbicularis ◽  
Gonad Differentiation ◽  
Adult Sex Ratio ◽  
Probable Consequence ◽  
Genotypic Sex Determination ◽  
Female Genotype ◽  
Biased Sex Ratio ◽  
Female Bias

Adult sex ratio in the turtle Emys orbicularis was determined in populations from seven ponds in Brenne (Indre, France). In all populations, the sex ratio was biased toward females. Among 290 captured animals, the male:female ratio was close to 0.5. Among different demographic factors that could affect the adult sex ratio, the most influential was probably the sex ratio of hatchlings. In Emys orbicularis, a ZZ male/ZW female system of genotypic sex determination has been postulated. Moreover, gonad differentiation is dependent on temperature and sex-reversed individuals can occur. To evaluate the importance of sex reversal among adult females, the blood of 78 animals was typed for the serologically detectable H-Y antigen, used as a tool to identify sexual genotype. In 73 of them, the H-Y phenotype was positive, conforming with female genotype, but in the other 5 females, it was negative (as in genotypic males), revealing that the sexual phenotype of these animals had been inverted. As the percentage of these sex-reversed genotypic males is low, the influence of temperature would appear not to be the sole cause of the observed unbalanced sex ratio. The female bias can be partly explained by the interaction of temperature with the ZZ/ZW system of genotypic sex determination. Indeed, in this system, sexual inversion under the influence of an epigenetic factor increases the ratio of genotypic females (ZW and WW) in the progeny.

Some Factors that Distort the Sex Ratio of the Gypsy Moth Porthetria dispar (L.) (Lepidoptera: Lymantriidae)

1963 ◽  
Vol 95 (5) ◽  
pp. 465-474 ◽  
Author(s):  
Robert W. Campbell
Keyword(s):  
New York ◽  
Sex Ratio ◽  
Gypsy Moth ◽  
Larval Density ◽  
Mortality Factor ◽  
Differential Mortality ◽  
Porthetria Dispar ◽  
Population Consequences ◽  
Adult Sex Ratio ◽  
The Town

AbstractDuring a study on the population dynamics of the gypsy moth, Porthetria dispar (L.), conducted in the Town of Glenville, New York, some factors were found to affect the sexes differentially. The importance of this differential mortality is indicated by the fact that 78 per cent of the variation in the logarithm of an index of population trend (the ratio of population density from year to year) was associated with the logarithm of adult sex ratio.Disease and desiccation during instars IV-VI and among pre-pupae were strongly selective against the female insects. This differential mortality caused a change in the pupal sex ratio from about 70 per cent females where no disease occurred to less than 25 per cent female pupae following an epizoötic. Ichneumonids, on the other hand, usually killed more male pupae than females, except when host size was reduced by excessive larval density and competition. The net result from this series of factors that distort the sex ratio has been to produce adult sex ratios varying from more than 80 per cent female moths to only 2 per cent females.In this host species, as in most other animals, it seems that the population consequences of a mortality factor that kills the host sexes in different proportions should be evaluated in terms of the more critical (female) sex destroyed.

Adult survival and recruitment and the explanation of an uneven sex ratio in a tortoise population

1990 ◽  
Vol 68 (3) ◽  
pp. 547-555 ◽  
Author(s):  
Adrian Hailey
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Adult Survival ◽  
Adult Longevity ◽  
Adult Males ◽  
Northern Greece ◽  
Female Population ◽  
Lower Survival Rate ◽  
Adult Sex Ratio ◽  
Testudo Hermanni

Survival, recruitment, and dynamics of adult Testudo hermanni at Alyki (northern Greece) were studied from 1980 to 1988. Recruitment of adult males was greater than that of females owing to their shorter time to maturity (9 vs. 11 years); recruitment of subadults (6 years old) was equal in males and females. Mean annual survival was slightly greater in males (0.914) than females (0.877), equivalent to mean adult longevity values of 11.6 and 8.1 years, respectively. Excluding tortoises that die before maturity, male and female T. hermanni are mature for about 56 and 42% of their life, respectively. Generation time was roughly twice the age at maturity, and three times the age at which secondary sexual characters develop, a pattern which may apply to other tortoises. The combination of adult survival and recruitment should lead to a stable sex ratio (males/females) of 2.1. The adult sex ratio was higher than this, but decreasing, from4.1 in 1982to3.0 in 1986, with an increase in the female population; the number of males was stable. The observed sex ratio showed a similar decline and a further fall to 2.4 in 1988. The cause of the lower survival rate of females compared with males is proposed to be damage during courtship attempts. The courtship behaviour and related anatomy of T. hermanni are compared with those of T. graeca, a species with even population sex ratios. The level of male-induced female mortality would depend on population density; the increasing number of females during the study follows the approximate halving of population density in 1980.

Male-biased adult sex ratios in a red squirrel population

1987 ◽  
Vol 65 (5) ◽  
pp. 1284-1286 ◽  
Author(s):  
T. Andrew Hurly
Keyword(s):  
Sex Ratio ◽  
Habitat Use ◽  
Sex Ratios ◽  
Sexual Differences ◽  
Differential Mortality ◽  
Red Squirrel ◽  
Red Squirrels ◽  
Male Mortality ◽  
Adult Sex Ratio ◽  
Sampling Biases

A 3-year study of a red squirrel population revealed that the adult sex ratio was biased towards males. There is no evidence that the skewed sex ratio was prejudiced by sampling biases due to sexual differences in mobility, observability, trappability, or habitat use. The tertiary juvenile sex ratio was even and therefore not the cause of the biased adult sex ratio. The data suggest that the skewed sex ratio may be the result of differential mortality. This is consistent with other reports of higher female than male mortality in red squirrels.

Demography, sex ratio, and sexual size dimorphism in a northern population of common musk turtles (Sternotherus odoratus)

1996 ◽  
Vol 74 (5) ◽  
pp. 918-925 ◽  
Author(s):  
Jonathan H. Edmonds ◽  
Ronald J. Brooks
Keyword(s):  
Sex Ratio ◽  
Sexual Size Dimorphism ◽  
Differential Mortality ◽  
Adult Males ◽  
Differential Growth ◽  
Size Dimorphism ◽  
Georgian Bay ◽  
Differential Movement ◽  
Sternotherus Odoratus ◽  
Biased Sex Ratio

A population of common musk turtles (Sternotherus odoratus) was studied in Georgian Bay, Ontario, near the northern limit of the species' range, during the summers of 1991–1994. A total of 314 (229 adult males, 68 adult females, and 17 juveniles) turtles were captured, marked, measured, and released. Over the geographic range of S. odoratus there was a positive relationship between body size and latitude, the musk turtles of the Georgian Bay population being significantly larger than those in any of the more southerly populations. The sex ratio was significantly male-biased, and the study population was unique in having sexual size dimorphism, with significantly larger males. We have hypothesized that this dimorphism has arisen through sexual selection that is being driven by the male-biased sex ratio. Male–male competition for mates is intensified and thereby selects for larger males. Proximately, biased sex ratios and sexual size dimorphism in turtles have been attributed to differential ages and sizes at sexual maturity. However, we found no support for this hypothesis in our population. We have attributed sexual size dimorphism to either differential growth rates after maturity or differential mortality of adults. The male-biased sex ratio may be due to differential movement patterns, differential mortality of the sexes, or the effects of ambient temperature on sex determination.

A natural population of the butterfly Eurema hecabe with Wolbachia-induced female-biased sex ratio not by feminization

Genome ◽  
2007 ◽  
Vol 50 (4) ◽  
pp. 365-372 ◽  
Author(s):  
Satoko Narita ◽  
Masashi Nomura ◽  
Daisuke Kageyama
Keyword(s):  
Sex Ratio ◽  
Underlying Mechanism ◽  
Single Nucleotide ◽  
Egg Hatch ◽  
Single Strain ◽  
Eurema Hecabe ◽  
Adult Sex Ratio ◽  
Ratio Distortion ◽  
Biased Sex Ratio ◽  
Sex Ratio Distortion

In butterflies, the adult sex ratio observed in the field is usually male-biased, although the sex ratio of their progeny is 1:1. This is due to the higher motility and larger behavioral range of males than females. As expected, the sex ratio of Eurema hecabe butterflies collected at 6 localities throughout Japan was male-biased. However, in Tsukuba, located in the central part of Japan, the sex ratio was found to be biased toward females. Their progeny reared in the laboratory also exhibited a female-biased sex ratio. A single strain of Wolbachia is considered to be the cause of the sex-ratio distortion, because antibiotic treatment reversed the sex ratio to 1:1, and only a single nucleotide sequence of wsp, a highly variable Wolbachia gene, was detected by molecular analysis. Cytogenetic analysis excluded the possibility of feminization as the underlying mechanism. In addition, when the wild-caught females that had already mated in nature were treated with antibiotics before oviposition, egg-hatch rates were extremely low, suggesting that the same Wolbachia strain also caused cytoplasmic incompatibility. Our findings suggest the possibility that a single strain of Wolbachia induces 2 distinct reproductive manipulations in the same host.

scholarly journals Adult sex ratio influences mate choice in Darwin’s finches

2019 ◽  
Vol 116 (25) ◽  
pp. 12373-12382 ◽  
Author(s):  
Peter R. Grant ◽  
B. Rosemary Grant
Keyword(s):  
Mate Choice ◽  
Sex Ratio ◽  
Phylogenetic Analyses ◽  
Sex Ratios ◽  
Differential Mortality ◽  
Sexual Imprinting ◽  
Darwin's Finches ◽  
Darwin’S Finches ◽  
Adult Sex Ratio ◽  
Geospiza Fortis

The adult sex ratio (ASR) is an important property of populations. Comparative phylogenetic analyses have shown that unequal sex ratios are associated with the frequency of changing mates, extrapair mating (EPM), mating system and parental care, sex-specific survival, and population dynamics. Comparative demographic analyses are needed to validate the inferences, and to identify the causes and consequences of sex ratio inequalities in changing environments. We tested expected consequences of biased sex ratios in two species of Darwin’s finches in the Galápagos, where annual variation in rainfall, food supply, and survival is pronounced. Environmental perturbations cause sex ratios to become strongly male-biased, and when this happens, females have increased opportunities to choose high-quality males. The choice of a mate is influenced by early experience of parental morphology (sexual imprinting), and since morphological traits are highly heritable, mate choice is expressed as a positive correlation between mates. The expected assortative mating was demonstrated when theGeospiza scandenspopulation was strongly male-biased, and not present in the contemporaryGeospiza fortispopulation with an equal sex ratio. Initial effects of parental imprinting were subsequently overridden by other factors when females changed mates, some repeatedly. Females of both species were more frequently polyandrous in male-biased populations, and fledged more offspring by changing mates. The ASR ratio indirectly affected the frequency of EPM (and hybridization), but this did not lead to social mate choice. The study provides a strong demonstration of how mating patterns change when environmental fluctuations lead to altered sex ratios through differential mortality.

scholarly journals Mortality of Fledgling Females Causes Male Bias in the Sex Ratio of Rufous Vangas (Schetba Rufa) in Madagascar

The Auk ◽  
2003 ◽  
Vol 120 (3) ◽  
pp. 700-705
Author(s):  
Shigeki Asai ◽  
Satoshi Yamagishi ◽  
Kazuhiro Eguchi
Keyword(s):  
Sex Ratio ◽  
Sex Chromosomes ◽  
Dna Analysis ◽  
Demographic Data ◽  
Differential Mortality ◽  
Male Bias ◽  
Young Males ◽  
Delayed Dispersal ◽  
Biased Sex Ratio

Abstract The Rufous Vanga (Schetba rufa) is a cooperative breeder. Although young males typically remain in natal territories, yearling females do not remain, but disperse to breed for themselves. The male-biased sex ratio likely restricts independent reproduction by young males. We analyzed demographic data from a seven-year study of the Rufous Vanga in Madagascar to estimate the mortality for each sex. We also examined the sex ratio at fledging and at hatching, sexing nestlings with DNA analysis on sex chromosomes. Analyses indicated that the biased sex ratio was due to differential mortality of fledglings rather than the bias at birth. We suggest that the delayed dispersal improved survival of auxiliary males.

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