Demographic Analysis of Sex Ratio on Population Growth ofBactrocera dorsalis(Diptera: Tephritidae) With Discussion of Control Efficacy Using Male Annihilation

2016 ◽  
Vol 109 (6) ◽  
pp. 2249-2258 ◽  
Author(s):  
Kevin Yu-Bing Huang ◽  
Remzi Atlihan ◽  
Ayhan Gökçe ◽  
Joyce Yu-Bing Huang ◽  
Hsin Chi
Keyword(s):  
Sex Ratio ◽  
Population Growth ◽  
Demographic Analysis ◽  
Control Efficacy ◽  
Male Annihilation

scholarly journals Sex Allocation, Diet, and Small Population Management of African Rhinoceros

2021 ◽  
Author(s):  
◽  
Elizabeth Victoria Berkeley
Keyword(s):  
Sex Ratio ◽  
Population Growth ◽  
Survival Probability ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Small Population ◽  
Ex Situ ◽  
Sex Bias ◽  
Theoretic Approach ◽  
Wet Season

<p>The application of sex allocation theory can provide useful insight into endangered rhinoceros biology to improve in situ and ex situ conservation efforts by understanding the factors that cause a female to produce one sex of calf. By decreasing the birth sex ratio (number of males born per number of females born) in a population it may be possible to increase population growth rates. The first aim was to determine if an environmentally cued sex allocation response occurred in black rhinos. By examining rainfall and calf sex records in a wild black rhino population, I identified that birth sex ratios increase in rainy seasons and rainy years. Mothers were more likely to be observed with male calves if they conceived during the wet season (57.3% male) than during the dry season (42.9% male). Mothers were more likely to raise male calves if they conceived during wet years (60.2% male) than during dry years (46.1% male). Next, I examined whether pulsatile or random variation in sex ratios of different magnitudes, as might occur under changes in climate patterns, would be detrimental to rhinoceros population growth. Results demonstrated that while random increases in the magnitude of birth sex ratio variation, in either direction, increased population survival probability up to 0.907, sequential pulsed years of birth sex ratio bias had the opposite effect on population performance down to a survival probability of 0.619. Furthermore, for both scenarios, populations of less than 50 animals are particularly vulnerable to extinction. Since the sex biases observed in the captive rhinoceros population were attributed to several factors, I used an information theoretic approach to evaluate the relative importance of different hypotheses for birth sex bias for predicting calf sex. The results demonstrated that none of the models tested were greatly predictive of calf sex. Suspecting that the mechanisms that were cueing calf sex occur close to the time of conception and were nutritionally cued, in the final experiment, I measured changes in blood glucose in white rhinos after they ate different meals. At 90 minutes, serum glucose levels in rhinos eating the 10 % lucerne hay diet were significantly lower than the 5% glucose and 10% glucose diets but not the 10% pellet nor 10% grass hay diets. This is the first time such an experiment has been published in a wildlife species and not only demonstrates the feasibility of training rhinos for successive blood draws but also that captive diets are low glycemic for white rhinos. Overall, my research confirmed that an environmentally cued sex allocation response does occur in African rhinos, and changes in the duration and magnitude of sex ratio patterns can decrease population growth and increase potential for extinction. Additionally, none of the previous hypotheses for the suspected male-sex bias in captive born rhinos were influential on calf sex, which shifts the focus of sex allocation research in rhinos to more acute signals around the time of conception, such as changes in diet and body condition.</p>

The effect of different diet on life history parameters and growth of Oppia denticulata (Acari: Oribatida: Oppiidae)

2017 ◽  
Vol 22 (5) ◽  
pp. 749 ◽  
Author(s):  
Anna Seniczak ◽  
Stanisław Seniczak ◽  
Mariola Słowikowska ◽  
Zbigniew Paluszak
Keyword(s):  
Life History ◽  
Sex Ratio ◽  
Population Growth ◽  
Laboratory Experiment ◽  
Green Algae ◽  
Penicillium Chrysogenum ◽  
Trichoderma Viride ◽  
Population Parameters ◽  
Good Population ◽  
Fungal Hyphae

The effect of different diet on Oppia denticulata was studied during a 4-month laboratory experiment, based on daily observations. This species is known as microphytophagous (i.e. feeding on bacteria and/or fungal hyphae and/or algae), like other species of Oppiidae, but our observations show its wider diet. We tested 11 types of food, including homogenous diet [green algae, lichens, fungi (dry yeasts, Trichoderma viride, Penicillium chrysogenum), nematodes], and combined diet [green algae and nematodes, lichens and nematodes, dry yeasts and nematodes, T. viride and nematodes, P. chrysogenum and nematodes]. The basic population parameters (fertility, mortality, sex ratio), time of development, population growth in four months and body length were compared between all groups. Observations on biology of O. denticulata were also made. The most favourable diet for O. denticulata was a combination of T. viride and nematodes, which allowed the highest population growth (about 50 times higher than the least favourable food, a combination of P. chrysogenum and nematodes), due to highest fertility and shortest development. Good population parameters and largest size were obtained on yeasts (served alone or with nematodes). This species did not do well on P. chrysogenum, probably because it produces penicillin.

Feral horse demography and population growth in the Kaimanawa Ranges, New Zealand

2004 ◽  
Vol 31 (2) ◽  
pp. 119 ◽  
Author(s):  
Wayne L. Linklater ◽  
Elissa Z. Cameron ◽  
Ed O. Minot ◽  
Kevin J. Stafford
Keyword(s):  
New Zealand ◽  
Sex Ratio ◽  
Population Growth ◽  
Management Problem ◽  
Feral Horses ◽  
Sex Structure ◽  
Young Males ◽  
Feral Horse ◽  
Adult Sex Ratio ◽  
Female Bias

Although feral horses are a common management problem in numerous countries, detailed and long-term demographic studies are rare. We measured the age and sex structure, and pregnancy, birth and death rates in a population of 413 feral horses in New Zealand during 1994–98 and used them to construct a model simulating population growth. Survivorship increased with age (0–1 years old = 86.8%, 1–2 = 92.3%, 2–4 = 92.4%, ≥�4 years old = females 94%, males 97% per annum). Birth sex ratio parity, a slight female bias in the adult sex ratio (92 males per 100 females) and higher adult male survivorship indicated lower average survivorship for young males than females that was not detectable in mortality statistics. Pregnancy and foaling rates for mares ≥�2 years old averaged 79 and 49%, respectively. Foaling rates increased as mares matured (2–3-year-old mares = 1.9%, 3–4 = 20.0%, 4–5 = 42.1%, ≥�5 = 61.5% per annum). Young mares had higher rates of foetal and neonatal mortality (95% of pregnancies failed and/or were lost as neonatal foals in 2–3-year-old mares, 70.6% in 3–4, 43.2% in 4–5, and 31% in mares ≥�5 years old). Population growth was 9.6% per annum (9.5–9.8, 95% CI) without human-induced mortalities (i.e. r = 0.092). Our model, standardised aerial counts, and historical estimates of annual reproduction suggest that the historical sequence of counts since 1979 has overestimated growth by ~50% probably because of improvements in count effort and technique.

scholarly journals Evolution of sex ratio through gene loss

2019 ◽  
Vol 116 (26) ◽  
pp. 12919-12924 ◽  
Author(s):  
Da Yin ◽  
Eric S. Haag
Keyword(s):  
Sex Ratio ◽  
Population Growth ◽  
Mating System ◽  
Mating Success ◽  
Population Subdivision ◽  
Male Mating ◽  
Mixed Mating ◽  
Male Mating Success ◽  
Caenorhabditis Briggsae ◽  
Male Frequency

The maintenance of males at intermediate frequencies is an important evolutionary problem. Several species ofCaenorhabditisnematodes have evolved a mating system in which selfing hermaphrodites and males coexist. While selfing produces XX hermaphrodites, cross-fertilization produces 50% XO male progeny. Thus, male mating success dictates the sex ratio. Here, we focus on the contribution of themale secreted short(mss) gene family to male mating success, sex ratio, and population growth. Themssfamily is essential for sperm competitiveness in gonochoristic species, but has been lost in parallel in androdioecious species. Using a transgene to restoremssfunction to the androdioeciousCaenorhabditis briggsae,we examined how mating system and population subdivision influence the fitness of themss+genotype. Consistent with theoretical expectations, whenmss+andmss-null (i.e., wild type) genotypes compete,mss+is positively selected in both mixed-mating and strictly outcrossing situations, though more strongly in the latter. Thus, while sexual mode alone affects the fitness ofmss+, it is insufficient to explain its parallel loss. However, in genetically homogenous androdioecious populations,mss+both increases male frequency and depresses population growth. We propose that the lack of inbreeding depression and the strong subdivision that characterize naturalCaenorhabditispopulations impose selection on sex ratio that makes loss ofmssadaptive after self-fertility evolves.

scholarly journals Sex Selection and Gender Balance

2011 ◽  
Vol 3 (1) ◽  
pp. 214-244 ◽  
Author(s):  
V Bhaskar
Keyword(s):  
Sex Ratio ◽  
Population Growth ◽  
Marriage Market ◽  
Sex Selection ◽  
Son Preference ◽  
Market Selection ◽  
Excess Supply ◽  
Gender Balance ◽  
Biased Sex Ratio ◽  
And Gender

We model the equilibrium sex ratio when parents can choose the sex of their child. With intrinsic son preference, sex selection results in a male-biased sex ratio. This is inefficient due to a marriage market congestion externality. Medical innovations that facilitate selection aggravate the inefficiency. If son preference arises endogenously, due to population growth causing an excess supply of women on the marriage market, selection may improve welfare. Empirically, sex selection causes an excess of males and reduces welfare in China. In most parts of India, cohort sizes are growing, implying an excess supply of women. (JEL J12, J13, J16, O15, P23)

Relationship between body size and population growth rate in two opportunistic polychaetes

2002 ◽  
Vol 82 (3) ◽  
pp. 403-408 ◽  
Author(s):  
D. Prevedelli ◽  
R. Simonini
Keyword(s):  
Growth Rate ◽  
Body Size ◽  
Sex Ratio ◽  
Population Growth ◽  
Growth Rates ◽  
Life Histories ◽  
Population Growth Rate ◽  
Population Growth Rates ◽  
The Relationship ◽  
Dinophilus Gyrociliatus

The relationship between body size and population growth rate λ has been studied in two species of opportunistic polychaetes, Dinophilus gyrociliatus and Ophryotrocha labronica, which colonize harbour environments. These species exhibit a semi-continuous iteroparous reproductive strategy, are phylogenetically closely-related but differ in body size and in some aspects of their sexuality. Ophryotrocha labronica is about 4 mm in body length, displays only slight sexual dimorphism and its sex ratio is biased towards the female sex in the ratio 2:1. Dinophilus gyrociliatus is about 1 mm in length, the males are extremely small and the sex ratio is strongly biased (3:1) in favour of the females. In spite of the considerable differences in all traits of their life histories and in many demographic parameters, the growth rates of the two populations are very similar. The analyses carried out have shown that the rapid attainment of sexual maturity of D. gyrociliatus gives it an advantage that offsets the greater fecundity of O. labronica. It is very likely that the reproductive peculiarities of D. gyrociliatus help to raise the population growth rates. The ‘saving’ on the male sex achieved both by the shift of the sex ratio in favour of the females and by the reduction in the males' body size would appear to enable D. gyrociliatus to grow at the same rate as O. labronica, a larger and more fecund species.

Pairing Success of Kirtland's Warblers in Marginal vs. Suitable Habitat

The Auk ◽  
1987 ◽  
Vol 104 (2) ◽  
pp. 234-241 ◽  
Author(s):  
John R. Probst ◽  
Jack P. Hayes
Keyword(s):  
Sex Ratio ◽  
Population Growth ◽  
Nest Success ◽  
Breeding Population ◽  
Lower Proportion ◽  
Control Measures ◽  
Suitable Habitat ◽  
Annual Productivity ◽  
Adult Sex Ratio ◽  
Marginal Habitat

Abstract We compared pairing success of male Kirtland's Warblers (Dendroica kirtlandii) in different habitats to test the hypothesis that a lower proportion of males in marginal habitat are mated. Fewer than 60% of the males in marginal habitat were paired, but 95% of the males in suitable habitat were paired. We estimated the overall pairing success of the known breeding population at 85%. We could not estimate the number of females because the adult sex ratio is unknown, and an unknown proportion of Kirtland's Warblers are polygynous. The Kirtland's Warbler population was fairly constant from 1971 to 1983, despite markedly improved nest success resulting from cowbird control measures. If there are more males than females, or if many females fail to breed or must accept mated males or marginal habitat, population growth could be impeded. We combined reduced pairing success with an estimate of fledgling mortality, and revised the estimated number of fall immatures to between 369 and 471 birds-about 36% lower than the uncorrected estimate. Lower annual productivity of a static population implies higher annual survivorship of adults, yearlings, or both.

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