Offspring Sex Ratio Research Articles

Effect of feeding male mice with palm, fish, and sunflower oils on sperm characteristics and sex ratio of offspring.

Several studies have indicated that feeding female animal with fatty acids could result in alteration of offspring sex ratio; however, there is little information available regarding the effect of feeding male animal with fatty acids on sex ratio of offspring. The aim of current study was to investigate the effect of paternal feeding with n-3 and n-6 polyunsaturated fatty acids (PUFAs) on sperm characteristics and sex ratio of offspring in mice. Male mice received 2.50% of palm oil (control), fish oil (n-3 PUFAs) or sunflower oil (n-6 PUFAs) for two months. Sperm kinematics and viability were assessed using computer-assisted sperm analyzer and eosin-Y staining, respectively. Additionally, female mice were randomly introduced to males of three experimental groups to determine reproductive parameters including litter size, conception rate and sex ratio. Fish oil enhanced sperm concentration, motility and viability, whereas sunflower oil decreased sperm concentration. Nevertheless, progressive motility, velocity, linearity and straightness of sperms were not affected by source of fatty acids. Although supplementation with fish oil resulted in male-biased sex ratio, palm and sunflower oils did not impact sex ratio. Besides, source of fatty acids failed to influence conception rate and litter size. In conclusion, the present study provided evidence for the impact of paternal fish oil consumption on sex ratio of offspring for the first time. Moreover, it showed beneficial effect of n-3 PUFAs and adverse effects of n-6 PUFAs on seminal parameters.

Egg load is a cue for offspring sex ratio adjustment in a fig-pollinating wasp with male-eggs-first sex allocation.

Fig-pollinating wasps (Agaonidae) only reproduce within fig treeinflorescences (figs). Agaonid offspring sex ratios are usually female-biased and often concur with local mate competition theory (LMC). LMC predicts less female-bias when several foundresses reproduce in a fig due to reduced relatedness among intra-sexually competing male offspring. Clutch size, the offspring produced by each foundress, is a strong predictor of agaonid sex ratios and correlates negatively with foundress number. However, clutch size variation can result from several processes including egg load (eggs within a foundress), competition among foundresses and oviposition site limitation, each of which can be used as a sex allocation cue. We introduced into individual Ficus racemosa figs single Ceratosolen fusciceps foundresses and allowed each to oviposit from zero to five hours thus variably reducing their eggs-loads and then introduced each wasp individually into a second fig. Offspring sex ratio (proportion males) in second figs correlated negatively with clutch size, with males produced even in very small clutches. Ceratosolen fusciceps lay mainly male eggs first and then female eggs. Our results demonstrate that foundresses do not generally lay or attempt to lay a 'fixed' number of males, but do 'reset to zero' their sex allocation strategy on entering a second fig. With decreasing clutch size, gall failure increased, probably due to reduced pollen. We conclude that C.fusciceps foundresses can use their own egg loads as a cue to facultatively adjust their offspring sex ratios and that foundresses may also produce more 'insurance' males when they can predict increasing rates of offspring mortality.

PSI-30 Identification of fetal microchimerism in older ewes using qPCR

Abstract The presence of a male co-twin during pregnancy has been found to impact lifetime reproductive performance in the sibling ewe. XY chimerism, thought to originate from a male co-twin, has been observed in ewes, and may be associated with the rare development of freemartins. Fetal ram DNA has been observed in the maternal circulation during pregnancy, but it is unknown if this chimerism persists after parturition. The objective of this study was to determine if fetal male cells were present in soft tissues of older ewes and if so, does the occurrence differ with lifetime offspring sex ratio. Eight ewes approximately 7-years-old and having given birth to at least 71% female (n = 4) or 82% males (n = 4) were tested. DNA was extracted from 10 different tissues from each ewe (n = 80). In triplicate, real-time PCR (qPCR) was used to identify the presence of the SRY gene in each sample. Using the SRY primer pair, male DNA was identified in the brain (between 1.25 ng / µL and 125 pg / µL) and liver (between 125 and 12.5 pg / µL) from a ewe that had given birth to two males during her lifetime. If any additional male fetal DNA was present, it was below the detectable limits. In addition to giving birth to two males, this ewe was also born with two male co-siblings, thus the origin (sibling or offspring) of the male DNA is not known. These data suggest fetal cell transfer in sheep is possible and the frequency of fetal microchimerism is not associated with sex ratio of lifetime offspring.

Androgen and mineralocorticoid receptors are present on the germinal disc region in laying hens: Potential mediators of sex ratio adjustment in birds?

Female birds skew offspring sex ratios based on environmental and social stimuli; however, the mechanism mediating this phenomenon remains unknown. Growing evidence suggests that testosterone and corticosterone may influence meiosis, as they skew sex ratios when given immediately before chromosomal segregation. It is unclear if these hormones act on the germinal disc (GD) or through a downstream mediator. It is also unknown whether the GD contains receptors for these hormones. If testosterone and/or corticosterone act on the GD to skew sex ratios, then the GD should have receptors for them and that receptor levels should be higher in the GD regions compared to other follicular regions. Furthermore, fluctuations of receptor levels should occur near meiotic segregation. We collected ovarian follicles at 5 h pre-ovulation (just before meiotic segregation) and 20 h pre-ovulation (when sex chromosomes are arrested), and measured androgen receptor (AR) and mineralocorticoid receptor (MR) protein levels via Western blot. ARs and MRs were on the follicle in the GD and non-GD regions, and at 5 h and 20 h pre-ovulation. Both AR and MR protein levels were higher in the GD region than the non-GD region at both time points, but did not differ between time points. These results suggest that hen ovarian follicles have receptors for testosterone and corticosterone, and that the ability for testosterone to respond may be specifically higher in the GD-region, providing further support for the role of testosterone in the alteration of meiotic segregation.

Potential of Two Trichogrammatidae species for Helicoverpa armigera control.

Helicoverpa armigera (Hübner) has attacked several economically important crops since it was first reported in Brazil in 2013. Because insecticides have been used intensively to control H. armigera, resistant populations have been detected more frequently. One alternative to insecticides is the use of biological control with egg parasitoids from the family Trichogrammatidae (Hymenoptera). The present study evaluated the use of different species and strains of these parasitoids to control H. armigera in soybean. Five strains of Trichogramma pretiosum (Riley): RV (Rio Verde, Goiás, Brazil), SO (Sorriso, Mato Grosso, Brazil), 47A (Irvine, CA, USA), PR (Colombo, Paraná, Brazil), and AN (Anhumas, São Paulo, Brazil), and Trichogrammatoidea annulata (De Santis) denominated TR, from Anhumas, were used. The following parasitoid biological parameters were evaluated: parasitism rates (%), offspring viability (%) number of parasitoids emerged per egg, egg-adult duration (days), female longevity, and offspring sex ratio. Strain RV of T. pretiosum from central Brazil performed best.

Fitness consequences of the selfish supergene Segregation Distorter.

Segregation distorters are selfish genetic elements that subvert Mendelian inheritance, often by destroying gametes that do not carry the distorter. Simple theoretical models predict that distorter alleles will either spread to fixation or stabilize at some high intermediate frequency. However, many distorters have substantially lower allele frequencies than predicted by simple models, suggesting that key sources of selection remain to be discovered. Here, we measured the fitness of Drosophila melanogaster adults and juveniles carrying zero, one or two copies of three different variants of the naturally occurring supergene Segregation Distorter (SD), in order to investigate why SD alleles remain relatively rare within populations despite being preferentially inherited. First, we show that the three SD variants differ in the severity and dominance of the fitness costs they impose on individuals carrying them. Second, SD-carrying parents produced less fit offspring in some crosses, independent of offspring genotype, indicating that SD alleles can have nongenetic, transgenerational costs in addition to their direct costs. Third, we found that SD carriers sometimes produce a biased offspring sex ratio, perhaps due to off-target effects of SD on the sex chromosomes. Finally, we used a theoretical model to investigate how sex ratio and transgenerational effects alter the population genetics of distorter alleles; accounting for these additional costs helps to explain why real-world segregation distorter alleles are rarer than predicted.

Pelvic Radiation-Induced Testicular Damage: An Experimental Study at 1 Gray

ABSTRACTTherapeutic radiation of the pelvic region has been shown to cause damage to testicular germ cells. In this study we aimed to evaluate the effects of a low therapeutic dose of 1 Gy on the induction of cellular and histological damage in early-stage testicular germ cells and the impact of this radiation on offspring sex ratio. Unirradiated and irradiated male rats were mated with unirradiated female rats. Female rats were followed and the sex of the offspring was determined. The male rats were sacrificed at the end of the second week, and the testicular germ cells were subjected to genetic analysis along with cytological and histopathological examination. Sperm DNA was amplified with primers specific to testis-specific Y-linked protein, rat actin beta and testis-specific X-linked genes. The resulting products were separated by capillary electrophoresis. Histopathological changes were investigated by light microscopy along with the TUNEL assay and immunohistochemical staining for caspase-3. There was no significant difference between the two groups for sex ratio and size of offspring. The number of sperm cells bearing X or Y chromosomes’ did not differ significantly between these two groups. However, a 1 Gy dose of radiation caused significant cytopathological and histopathological changes in the testicular tissue. In the irradiated group, edematous regions were evident. The number of caspase-3 positive cells in the germinal epithelium of the seminiferous tubules was also significantly higher in the irradiated group. Our results showed that low-dose radiation induced apoptosis and caused significant cyto- and histopathological changes in the testicular tissue. Further research is required to fully elucidate their contribution to apoptosis and if low-dose radiation may potentially lead to long-term effects in the offspring. These results may also lead us to develop a new technique using the caspase-3 staining to monitor the susceptibility to low dose radiation.

Relationships amongst sex ratio of progeny in Anastatus disparis (Hymenoptera: Eupelmidae), sperm depletion and decreased fecundity

Sex allocation in haplodiploid arthropods has implications for fitness and has received much attention with regard to parasitoid wasps. In addition to environmental variables, maternal characteristics (such as age) are important factors that shape sex allocation. Despite this, maternal characteristics have received less research attention. Older females may experience an increase, a decrease, or no change in the sex ratio [male/(female + male)] of their offspring compared with younger females. Using mated Anastatus disparis (Ruschka) (Hymenoptera: Eupelmidae), a quasi-gregarious parasitoid, we determined experimentally the sex of offspring in relation to the age of their mother. As most studies predicted, the result showed that, as maternal A. disparis grew older, the sex ratio of offspring increased. However, most females continued to produce offspring of both sexes until their death. Sperm depletion was a likely reason for the increase in numbers of male offspring in response to maternal age. However, both fecundity and the number of male offspring declined overall in the whole colony, suggesting that the increase in sex ratio amongst offspring was mainly due to decreased fecundity in older maternal A. disparis. Overall, both sperm depletion and decreased fecundity played a role in determining the sex ratio of progeny from older mothers.

Differential Sperm Motility Mediates the Sex Ratio Drive Shaping Mouse Sex Chromosome Evolution.

SummaryThe mouse sex chromosomes exhibit an extraordinary level of copy number amplification of postmeiotically expressed genes [1, 2], driven by an “arms race” (genomic conflict) between the X and Y chromosomes over the control of offspring sex ratio. The sex-linked ampliconic transcriptional regulators Slx and Sly [3, 4, 5, 6, 7] have opposing effects on global transcription levels of the sex chromosomes in haploid spermatids via regulation of postmeiotic sex chromatin (PMSC) [8, 9, 10, 11] and opposing effects on offspring sex ratio. Partial deletions of the Y chromosome (Yq) that reduce Sly copy number lead to global overexpression of sex-linked genes in spermatids and either a distorted sex ratio in favor of females (smaller deletions) or sterility (larger deletions) [12, 13, 14, 15, 16]. Despite a large body of work studying the role of the sex chromosomes in regulating spermatogenesis (recent reviews [17, 18, 19, 20]), most studies do not address differential fertility effects on X- and Y-bearing cells. Hence, in this study, we concentrate on identifying physiological differences between X- and Y-bearing sperm from Yq-deleted males that affect their relative fertilizing ability and consequently lead to sex ratio skewing. We show that X- and Y-bearing sperm in these males have differential motility and morphology but are equally able to penetrate the cumulus and fertilize the egg once at the site of fertilization. The altered motility is thus deduced to be the proximate cause of the skew. This represents the first demonstration of a specific difference in sperm function associated with sex ratio skewing.

Shared reproduction and sex ratio adjustment to clutch size in a socially polymorphic orchid bee

AbstractNests of the primitively eusocial orchid beeEuglossa viridissimaare generally founded by a solitary female but can be reactivated by female offspring, in the presence or absence of the mother. The population therefore exists of solitary and social nests that co‐occur in an area. A female can stay as a subordinate helper under a dominant female or disperse to become a solitary foundress. Yet, the costs and benefits of the different social phenotypes are so far little understood. Here, we compared solitary and social nests of orchid bees. We used offspring of solitary and social nests to calculate offspring sex ratio, and applied molecular markers to calculate intranidal relatedness, infer maternity and test whether sociality may have a genetic component. We found that social nests had on average more brood than solitary nests. The overall sex ratio in the population did not differ from 1:1. However, social nests tended to produce a split sex ratio with some nests producing mainly males and others mainly female offspring. Regardless of social phenotype, the number of offspring was correlated with the sex ratio, with smaller nests having a more female‐biased offspring. In social nests, not all offspring resulted from a single‐mated mother, which was also the case for some solitary nests. This suggests shared reproduction in social nests and may be an indication that intraspecific parasitism and nest takeover are not uncommon. Structure analyses did not reveal different genetic background of the two social phenotypes. Our results suggest that there is no clear benefit that favours one of the two social phenotypes over the other and that the population is kept at balance in terms of sex ratio.

Queen–worker conflict can drive the evolution of social polymorphism and split sex ratios in facultatively eusocial life cycles*

Hamilton's idea that haplodiploidy favors the evolution of altruism-the haplodiploidy hypothesis-relies on the relatedness asymmetry between the sexes caused by the sex-specific ploidies. Theoretical work on the consequences of relatedness asymmetries has significantly improved our understanding of sex allocation and intracolony conflicts, but the importance of haplodiploidy for the evolution of altruism came to be seen as minor. However, recently it was shown that haplodiploidy can strongly favor the evolution of eusociality, provided additional "preadaptations" are also present, such as the production of multiple broods per season and maternal ability to bias offspring sex ratios. These results were obtained assuming no influence of workers on the sex ratio, even though worker control of the sex ratio is known to occur. Here, we model the evolution of sex-specific fratricide as a mechanism of worker control over the sex ratio. We show that fratricide can facilitate the initial evolution of helping. However, fratricide can also hamper the evolution of unconditional help. Instead, social polymorphism evolves a mixture of helping and dispersing offspring. Finally, we show that the co-evolution of sex-allocation strategies of workers (fratricide) and queens leads to a split production of the sexes, with some colonies specializing in males and others in females. Thus, the model predicts that fratricide spawns a diversity of co-existing life cycles that strongly vary in degree of sociality and sex ratios.

Biological and demographic parameters of Tegolophus brunneus (Acari: Eriophyidae) in citrus.

The brown citrus rust mite, Tegolophus brunneus Flechtmann (Acari: Eriophyidae), causes citrus rust, as does Phyllocoptruta oleivora (Ashmead) (Acari: Eriophyidae). As the citrus rust damage has intensified in recent years and T. brunneus has been reported in high population levels in several regions of Brazil, this mite has caused concern to growers and technicians. Because T. brunneus has been little studied and its bioecological characteristics are unknown, this study investigated the biological and demographic parameters of T. brunneus on citrus fruits under laboratory conditions. Our results showed that the egg incubation period and viability were 3.0 and 94.5%, respectively. The larval and nymphal stage durations were 1.1 and 2.8days, respectively. The development time of the immature stage was 6.9days, with 92.3% survival. When females and males were maintained together, the sex ratio of offspring was 0.7; virgin females produced only males. The pre-oviposition (from adult emergence to the first egg) and total pre-oviposition (egg-to-egg) periods were 1.6 and 8.5days, respectively. Fecundity was 8.5 eggs, and female and male longevities were 13.2 and 11.4days, respectively. The estimate of demographic parameters indicated that the Ro and T of T. brunneus were 6.45 offspring and 13.0days, and r and λ were 0.142 and 1.153day-1, respectively. These results suggest that T. brunneus has high growth potential on citrus trees. Therefore, management strategies may be required to reduce the population levels and damage caused by T. brunneus in citrus groves.

Activation of Toll-like receptor 7/8 encoded by the X chromosome alters sperm motility and provides a novel simple technology for sexing sperm.

In most mammals, the male to female sex ratio of offspring is about 50% because half of the sperm contain either the Y chromosome or X chromosome. In mice, the Y chromosome encodes fewer than 700 genes, whereas the X chromosome encodes over 3,000 genes. Although overall gene expression is lower in sperm than in somatic cells, transcription is activated selectively in round spermatids. By regulating the expression of specific genes, we hypothesized that the X chromosome might exert functional differences in sperm that are usually masked during fertilization. In this study, we found that Toll-like receptors 7/8 (TLR7/8) coding the X chromosome were expressed by approximately 50% of the round spermatids in testis and in approximately 50% of the epididymal sperm. Especially, TLR7 was localized to the tail, and TLR8 was localized to the midpiece. Ligand activation of TLR7/8 selectively suppressed the mobility of the X chromosome–bearing sperm (X-sperm) but not the Y-sperm without altering sperm viability or acrosome formation. The difference in sperm motility allowed for the separation of Y-sperm from X-sperm. Following in vitro fertilization using the ligand-selected high-mobility sperm, 90% of the embryos were XY male. Likewise, 83% of the pups obtained following embryo transfer were XY males. Conversely, the TLR7/8-activated, slow mobility sperm produced embryos and pups that were 81% XX females. Therefore, the functional differences between Y-sperm and X-sperm motility were revealed and related to different gene expression patterns, specifically TLR7/8 on X-sperm.

The Embryos of Turtles Can Influence Their Own Sexual Destinies

Sessile organisms with thermally sensitive developmental trajectories are at high risk from climate change. For example, oviparous reptiles with temperature-dependent sex determination (TSD) may experience strong (potentially disastrous) shifts in offspring sex ratio if reproducing females are unable to predict incubation conditions at the time of oviposition. How then have TSD reptile taxa persisted over previous periods of extreme climatic conditions? An ability of embryos to move within the egg to select optimal thermal regimes could buffer ambient extremes, but the feasibility of behavioral thermoregulation by embryos has come under strong challenge. To test this idea, we measured thermal gradients within eggs in semi-natural nests of a freshwater turtle species with TSD, manipulated embryonic thermoregulatory ability, and modeled the effects of embryonic thermoregulation on offspring sex ratios. Behavioral thermoregulation by embryos accelerated development and influenced offspring sex ratio, expanding the range of ambient conditions under which nests produce equal numbers of male and female offspring. Model projections suggest that sex ratio shifts induced by global warming will be buffered by the ability of embryos to influence their sexual destiny via behavioral thermoregulation.

RNAi mediated knockdown of RpL11, RpS2, and tra-2 led to reduced reproduction of Phytoseiulus persimilis.

Phytoseiulus persimilis is one of the most important biological control agents of spider mites. Multiple studies have been conducted on factors affecting its reproduction, but limited research on related molecular mechanisms has been carried out. In this study, RNA interference of three genes, ribosomal protein L11 (RpL11), ribosomal protein S2 (RpS2), and transformer-2 (tra-2), to newly emerged females were performed through oral delivery of double-stranded RNA, and knockdown of target genes was verified using qRT-PCR analysis. When RpL11 or RpS2 was interfered, 42 and 30% P. persimilis individuals either laid no eggor had no egg hatched, whereas the remaining females had their oviposition duration reduced by 31.8 and 49.9%, fecundity reduced by 48.1 and 67.8%, and egg hatching rate reduced by 20.4 and 22.4%, respectively. In addition, offspring sex ratios were significantly male biased especially at low fecundities. When tra-2 was interfered, no significant difference in fecundity was detected, but egg hatching rate reduced by 30.6%. This study verified the possibility of RNA interference in Phytoseiidae through oral delivery, and indicated that RpL11 and RpS2 are involved in egg formation, whereas tra-2 is involved in embryo development in P. persimilis. Phytoseiid mites have different sex determination pathways compared to insects. The present study provides data and evidence at molecular biological level for future research on reproduction and sex determination of phytoseiid mites.

Effects of Extrinsic, Intraspecific Competition and Host Deprivation on the Biology of Trichopria anastrephae (Hymenoptera: Diapriidae) Reared on Drosophila suzukii (Diptera: Drosophilidae).

The pupal parasitoid Trichopria anastrephae Lima (Hymenoptera: Diapriidae) shows potential to control Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), and understanding the behavior of this parasitoid in challenging environments is important to obtain a higher efficiency in mass rearing and in biological control programs. This study aimed to verify the effects of extrinsic intraspecific competition and the absence of host on the parasitism of T. anastrephae in D. suzukii pupae. Therefore, to evaluate the parasitism of T. anastrephae under intraspecific competition, groups of 20 pupae (24h old) of D. suzukii were offered for different densities of parasitoids (1, 3, 5, or 10 couples) during a 7-day period. Whereas to evaluate the effects of host deprivation on parasitism of T. anastrephae, we tested different treatments: T1-no deprivation, T2-complete deprivation, T3-deprivation every other day, T4-deprivation for 3days, and T5-deprivation for 7days. The increase of density of parasitoids resulted in an increase of oviposition scars on pupae and a longer biological cycle, suggesting the occurrence of superparasitism. Increased density also resulted in a higher percentage of attacked pupae, but did not affect parasitoids emergence nor sex ratio. Host deprivation affected number of parasitized pupae, number and sex ratio of offspring, and the longevity of females. Based on our findings, competition among females do not impair offspring viability, and host deprivation for a period up to 7days do not influence parasitism capacity, indicating that it can be used as a pre-release strategy.

Insecticidal activity of isolated essential oils from three medicinal plants on the biological control agent, Habrobracon hebetor Say (Hymenoptera: Braconidae)

The effects of Allium sativum L. (Alliaceae), Piper nigrum L. (Piperaceae) and Glycyrrhiza glabra L. (Fabaceae) essential oils were investigated on the biological control agent, Habrobracon hebetor Say. The female wasps of H. hebetor were treated by LC30 concentrations of the tested essential oils for 24 h and their demography was investigated. Results indicated that the adult longevity, survival, fecundity, fertility, hatch rate, offspring sex ratio and the other demographic parameters negatively were affected by these essential oils. At the same time, our findings indicated that G. glabra essential oil has the less severe effect on H. hebetor. Accordingly, G. glabra essential oil seems to be a compatible botanical compound with H. hebetor for applying in integrated pest management programs.

Southern Lapwing Vanellus chilensis cooperative helpers at nests are older siblings

Cooperative breeding is rare in shorebirds, and when found it is thought to be due to polygamous mating (cooperative polygamy). Here we describe the social structure of cooperatively breeding groups in Southern Lapwing Vanellus chilensis and test the prediction that offspring sex ratio is skewed towards the sex that helps. The social groups consisted of a breeding pair with one or two young (mostly males, 68%) from the previous breeding season, and offspring sex ratio was not skewed. Cooperative breeding in the Southern Lapwing is not the consequence of cooperative polygamy, but rather groups were formed by a mated pair and some of their offspring from previous nests as helpers.

Effect of male age structure on reproduction in white‐tailed deer

ABSTRACTSelective harvest regimes that create female‐biased sex ratios can potentially lead to delayed breeding, reduced breeding synchrony, reduced productivity, and a female‐biased sex ratio of offspring. These resulting changes in breeding behavior and population dynamics have potential to adversely affect population growth. In 2002, Pennsylvania implemented harvest regulation changes that reduced deer density (increased harvest of antlerless deer) and increased the number and age of antlered deer (implemented antler point restriction regulations) that resulted in a less female‐biased sex ratio. We monitored date of conception, productivity (embryos/female), and sex ratio of embryos during 1999–2006 to test if timing of breeding occurred earlier and with greater synchrony, if productivity of females increased, and if the sex ratio of offspring would shift towards more males. Deer density decreased 23% and the adult (≥1.5 yr old) sex ratio declined from 2.30 to 1.95 females/male. The ratio of ≥2.5‐year‐old to 1.5‐year‐old males shifted towards more older males (1:3.7 in 2002 to 1:1.59 in 2006) and the ≥2.5‐year‐old male population increased from 41,853 during 1999–2001 to 54,064 by 2006. We found no evidence of any change in the timing or variability of date of conception, productivity, or offspring sex ratio. We conclude that harvest regulation changes implemented in Pennsylvania, USA, were insufficient to affect timing of breeding or population dynamics and that efforts by managers to identify a desired sex ratio or manipulate sex ratios to achieve management goals on a statewide scale will be challenging. © 2019 The Wildlife Society.

Parental effects of male alternative reproductive tactics (ARTs) on ARTs of haploid sons

Abstract Alternative reproductive tactics (ARTs) represent distinct behavioural phenotypes to maximize reproductive success within the same sex, primarily males, and may be genetically and/or conditionally determined. Across animals, intragenerational determinants of conditional ARTs are relatively well understood but transgenerational (non‐genetic) effects of parental ARTs on filial ARTs are largely unknown. Here, we assessed parental effects of conditional male ARTs on sons' ARTs in arrhenotokous spider mites Tetranychus urticae. Arrhenotoky, that is, males arising from unfertilized and females from fertilized eggs, sets the stage for sexual and transgenerational conflicts between male mates and females and their sons. Male ARTs of T. urticae are dichotomous, fighting and sneaking, and apparent in male–male combat and pre‐copulatory guarding behaviour. Due to haplodiploidy, male ARTs can only exert non‐genetic effects on sons of their mates. We hypothesized that parental ART effects are likely to occur in T. urticae because maternal ART mating status (unmated, sneaker‐ or fighter‐mated) is indicative of the offspring' social environment and ART flexibility rather prevails in younger than older males. Fighter‐mated mothers produced more offspring than unmated mothers and had a more daughter‐biased offspring sex ratio than unmated and sneaker‐mated mothers. Sons of fighter‐mated mothers were more likely to guard and did so earlier than sons of unmated and sneaker‐mated mothers. Unmated and sneaker‐mated, but not fighter‐mated, mothers produced sneaker sons that were quicker to start guarding than were fighter sons. Proximately, parental ART effects on sons' ARTs were most likely mediated by differences in seminal fluids. Ultimately, observed alterations of sons' ARTs represent adaptive maternal responses to ART phenotypes rather than manipulation by male mates. Fighter‐mated mothers tuned filial ARTs to male‐competitive environments whereas unmated and sneaker‐mated mothers tuned them to benign environments. Observed alterations in reproductive traits of fighter‐mated mothers suggest adaptive manipulation by the fighter phenotype or aligned male and female interests. Overall, our study documents previously unknown transgenerational ART effects on haploid sons' ARTs. A free Plain Language Summary can be found within the Supporting Information of this article.