Sex ratios in natural populations ofAphelinus mali (Hym.: Aphelinidae) in relation to host size and host density

Entomophaga ◽  
1993 ◽  
Vol 38 (3) ◽  
pp. 391-403 ◽  
Author(s):  
S. K. Asante ◽  
W. Danthanarayana
Keyword(s):  
Sex Ratios ◽  
Natural Populations ◽  
Host Density ◽  
Host Size

Sex ratio and life history traits at reaching sexual maturity in the dioecious shrub Fuchsia parviflora: field and common garden experiments

2021 ◽  
pp. 1-6
Author(s):  
Jessica S. Ambriz ◽  
Clementina González ◽  
Eduardo Cuevas
Keyword(s):  
Natural Population ◽  
Sexual Maturity ◽  
Sex Ratios ◽  
Natural Populations ◽  
Common Garden ◽  
Common Garden Experiment ◽  
Trade Offs ◽  
Reproductive Biomass ◽  
Common Garden Experiments ◽  
Growth And Reproduction

Abstract Fuchsia parviflora is a dioecious shrub that depends on biotic pollination for reproduction. Previous studies suggest that the male plants produce more flowers, and male-biased sex ratios have been found in some natural populations. To assess whether the biased sex ratios found between genders in natural populations are present at the point at which plants reach sexual maturity, and to identify possible trade-offs between growth and reproduction, we performed a common garden experiment. Finally, to complement the information of the common garden experiment, we estimated the reproductive biomass allocation between genders in one natural population. Sex ratios at reaching sexual maturity in F. parviflora did not differ from 0.5, except in one population, which was the smallest seedling population. We found no differences between genders in terms of the probability of germination or flowering. When flowering began, female plants were taller than males and the tallest plants of both genders required more time to reach sexual maturity. Males produced significantly more flowers than females, and the number of flowers increased with plant height in both genders. Finally, in the natural population studied, the investment in reproductive biomass was seven-fold greater in female plants than in male plants. Our results showed no evidence of possible trade-offs between growth and reproduction. Despite the fact that female plants invest more in reproductive biomass, they were taller than the males after flowering, possibly at the expense of herbivory defence.

scholarly journals Sex Chromosome Meiotic Drive in Stalk-Eyed Flies

Genetics ◽  
1997 ◽  
Vol 147 (3) ◽  
pp. 1169-1180 ◽  
Author(s):  
Daven C Presgraves ◽  
Emily Severance ◽  
Gerald S Willrinson
Keyword(s):  
Sex Ratio ◽  
Sex Chromosome ◽  
Sex Ratios ◽  
Natural Populations ◽  
Meiotic Drive ◽  
Operational Sex Ratio ◽  
Genetic Modifiers ◽  
Ratio Distortion ◽  
The Impact ◽  
Sex Ratio Distortion

Meiotically driven sex chromosomes can quickly spread to fixation and cause population extinction unless balanced by selection or suppressed by genetic modifiers. We report results of genetic analyses that demonstrate that extreme female-biased sex ratios in two sister species of stalk-eyed flies, Cyrtodiopsis dalmanni and C. whitei, are due to a meiotic drive element on the X chromosome (Xd). Relatively high frequencies of Xd in C. dalmanni and C. whitei (13–17% and 29%, respectively) cause female-biased sex ratios in natural populations of both species. Sex ratio distortion is associated with spermatid degeneration in male carriers of Xd. Variation in sex ratios is caused by Y-linked and autosomal factors that decrease the intensity of meiotic drive. Y-linked polymorphism for resistance to drive exists in C. dalmanni in which a resistant Y chromosome reduces the intensity and reverses the direction of meiotic drive. When paired with Xd, modifying Y chromosomes (Ym) cause the transmission of predominantly Y-bearing sperm, and on average, production of 63% male progeny. The absence of sex ratio distortion in closely related monomorphic outgroup species suggests that this meiotic drive system may predate the origin of C. whitei and C. dalmanni. We discuss factors likely to be involved in the persistence of these sex-linked polymorphisms and consider the impact of Xd on the operational sex ratio and the intensity of sexual selection in these extremely sexually dimorphic flies.

STUDIES OF LATHROMEROIDEA SP.NOV. (HYMENOPTERA: TRICHOGRAMMATIDAE), A PARASITOID OF GERRID EGGS

1993 ◽  
Vol 125 (4) ◽  
pp. 693-702 ◽  
Author(s):  
Nidia Priscila Henriquez ◽  
John R. Spence
Keyword(s):  
Body Length ◽  
Sex Ratios ◽  
Reproductive Behaviour ◽  
Egg Parasitoid ◽  
Host Size

AbstractUse of gerrids (Hemiptera: Gerridae) as primary hosts by the solitary egg parasitoid Lathromeroidea sp.nov. is established and parasitoid reproductive behaviour is described. Four species of Limnoporus (L. dissortis Drake and Harris, L. notabilis Drake and Hottes, L. rufoscutellatus Latreille, and L. esakii Miyamoto) and two of Gerris (G. buenoi Kirkaldy and G. pingreensis Drake and Hottes) were successfully parasitized in the laboratory. A greater proportion of wasps eclosed successfully from eggs of Gerris than from Limnoporus. Host size was directly proportional to both weight and body length of adult parasitoids. Sex ratios were female-biased, with males emerging before females.

Host size-dependent sex allocation behaviour in a parasitoid: implications forCatolaccus grandis(Hymenoptera: Pteromalidae) mass rearing programmes

1998 ◽  
Vol 88 (1) ◽  
pp. 37-45 ◽  
Author(s):  
K.M. Heinz
Keyword(s):  
Biological Control ◽  
Sex Ratio ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Boll Weevil ◽  
Mass Rearing ◽  
Host Size ◽  
Offspring Sex Ratio ◽  
Offspring Sex ◽  
Control Programmes

AbstractAn often encountered problem associated with augmentative and inundative biological control programmes is the high cost of producing sufficient numbers of natural enemies necessary to suppress pest populations within the time constraints imposed by ephemeral agroecosystems. In many arrhenotokous parasitoids, overproduction of males in mass-rearing cultures inflates costs (per female) and thus limits the economic feasibility of these biological control programmes. Within the context of existing production technologies, experiments were conducted to determine if the sex ratio ofCatolaccus grandis(Burks), an ectoparasitoid of the boll weevilAnthonomous grandisBoheman, varied as a function of boll weevil larval size. Results from natural and manipulative experiments demonstrate the following behavioural characteristics associated with C.grandissex allocation behaviour: (i) femaleC. grandisoffspring are produced on large size hosts and male offspring are produced on small hosts; (ii) whether a host is considered large or small depends upon the overall distribution of host sizes encountered by a female parasitoid; and (iii) female parasitoids exhibit a greater rate of increase in body size with host size than do male parasitoids. The observed patterns cannot be explained by sex-specific mortality of immature parasitoids developing on the different host size categories. In subsequent experiments, laboratory cultures ofC. grandisexposed daily to successively larger sizes ofA. grandislarvae produced successively greater female biased offspring sex ratios, cultures exposed daily to successively smaller sizes of host larvae produced successively greater male biased offspring sex ratios, and cultures exposed daily to equivalent host size distributions over time maintained a uniform offspring sex ratio. By increasing the average size ofA. grandislarval hosts exposed toC. grandisby 2.5 mg per day in mass rearing cultures, the percentage of male progeny can be reduced from 33% to 23% over a period of four consecutive exposure days.

scholarly journals Dwarf Mistletoe-Host Interactions in Mixed-Conifer Forests in the Sierra Nevada

2002 ◽  
Vol 92 (6) ◽  
pp. 597-602 ◽  
Author(s):  
Patricia E. Maloney ◽  
David M. Rizzo
Keyword(s):  
Sierra Nevada ◽  
Bark Beetles ◽  
Spatial Dynamics ◽  
Host Density ◽  
Lake Tahoe ◽  
Host Size ◽  
Lake Tahoe Basin ◽  
Dwarf Mistletoe ◽  
Jeffrey Pine ◽  
White Fir

We determined the spatial pattern of dwarf mistletoe (Arceuthobium spp.) associated with two different conifer hosts, white fir (Abies concolor) and Jeffrey pine (Pinus jeffreyi), in forests around the Lake Tahoe Basin and at the Teakettle Experimental Forest, both located in the Sierra Nevada. We also examined a number of host variables and bark beetle incidence to determine how these factors might be involved in the Arceuthobium—conifer interaction. There was no significant relationship between dwarf mistletoe-infected trees and associated bark beetles. We found the highest incidence of dwarf mistletoe on Jeffrey pine in Lake Tahoe (87%), followed by dwarf mistletoe on white fir in Lake Tahoe (30%), with the lowest incidence on white fir at Teakettle (27%). Dwarf mistletoe incidence on white fir in our Lake Tahoe grid was not correlated to density but the dwarf mistletoe rating (DMR) was positively correlated to host size. At the Teakettle Forest, dwarf mistletoe incidence on white fir was not correlated with host density but the DMR was correlated with host size. Dwarf mistletoe incidence and DMR on Jeffrey pine were correlated with host density. Individuals, of both conifer species, in all diameter size classes were susceptible to dwarf mistletoe, with the lowest infection rate in the seedling-10-cm-diameter class. Arceuthobium on white fir in Lake Tahoe showed spatial dependence to a range of 20 m. However, Arceuthobium on Jeffrey pine in Lake Tahoe and on white fir at Teakettle showed no clear pattern of spatial structuring. The degree of infection and stand history appear to be important in the spatial dynamics of Arceuthobium spp.

Development of Cotesia orobenae Forbes (Hymenoptera: Braconidae) in its Host, Evergestis rimosalis (Guenée) (Lepidoptera: Pyralidae)

2001 ◽  
Vol 36 (1) ◽  
pp. 9-16
Author(s):  
L. T. Kok ◽  
J. A. Acosta-Martinez
Keyword(s):  
Sex Ratios ◽  
Host Density ◽  
Female Offspring ◽  
Developmental Time ◽  
The Other ◽  
Optimal Temperature ◽  
Density Effects ◽  
Adult Parasitoid ◽  
Early Instar ◽  
Lepidoptera Pyralidae

Temperature and host density effects on the development of Cotesia orobenae Forbes (Hymenoptera: Braconidae), and its parasitism of the cross-striped cabbageworm, Evergestis rimosalis (Guenée) (Lepidoptera: Pyralidae), were investigated. Time for adult parasitoid emergence from cocoon masses of C. orobenae maintained at 15, 20, 25, 30 and 35°C and a photoperiod of 15:9 (L: D) was inversely related to temperature. Parasitoid emergence exceeded 86% for all temperatures except that at 35°C. Development of C. orobenae on early-instar hosts was best at 20 and 25°C. Although the shortest developmental time was observed at 35°C, survival of both parasitoid and host was low at this temperature. At 15°C, the parasitoid was not very active, and developmental time was the longest among the temperatures tested. Percent of host larvae parasitized was significantly higher at 20 and 25°C than the other temperatures tested. Females were short-lived and oviposited an average of 118 and 136 eggs at 20 and 25°C, respectively. Females died after 24 h of being placed in the oviposition chamber at 30 and 35°C. At 15°C they lived longer, but did not parasitize host larvae provided. Virgin females produced only male progeny. Mated females produced slightly more female offspring than males. Sex ratios of progeny from females paired with single or multiple males were not different. Percentage parasitization of host larvae between treatments differed for the first day, but not the second day. Fecundity of C. orobenae exposed to five host densities (5, 10, 15, 20, and 25 per parasitoid) showed significant differences in percent parasitization among the treatments. Percentage parasitization was highest with five and 10 hosts per parasitoid. The highest number of parasitoid cocoons recovered per cocoon mass was obtained with 10 hosts. The data indicate that optimal temperature for C. orobenae oviposition, development, and parasitism of its host is between 20 to 25°C.

Sex ratios and survival in fluctuating populations of the deer mouse, Peromyscus mamculatus borealis

1970 ◽  
Vol 48 (4) ◽  
pp. 809-811 ◽  
Author(s):  
Raymond P. Canham
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Deer Mouse ◽  
Sex Ratios ◽  
Natural Populations ◽  
In Captivity ◽  
Males And Females ◽  
Young Of The Year ◽  
Fluctuating Populations ◽  
Number Of Males

In litters of the deer mouse, Peromyscus mamculatus borealis, born in captivity there was a significantly greater number of males than females. In natural populations of the same subspecies, an excess of males caused the sex ratio in captured young of the year to differ significantly from 1:1 only in those summers in which population density increased considerably. The sex ratio did not change appreciably during a winter in which density remained stable, but in winters of low survival the proportion of males declined. A difference between males and females in the amplitude of the fluctuations in postnatal survival thus appeared responsible for variations in the sex ratio.

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