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opencc-zeroJun 2020View details →

Data from: Sibling rivalry vs mother's curse: can kin competition facilitate a response to selection on male mitochondria?

Assuming that fathers never transmit mitochondrial DNA (mtDNA) to their offspring, mitochondrial mutations that affect male fitness are invisible to direct selection on males, leading to an accumulation of male-harming alleles in the mitochondrial genome (mother's curse). However, male phenotypes encoded by mtDNA can still undergo adaptation via kin selection provided that males interact with females carrying related mtDNA, such as their sisters. Here, using experiments with Drosophila melanogaster carrying standardised nuclear DNA but distinct mitochondrial DNA, we test whether the mitochondrial haplotype carried by interacting pairs of larvae affects survival to adulthood, as well as the fitness of the adults. Although mtDNA had no detectable direct or indirect genetic effect on larva-to-adult survival, the fitness of male and female adults was significantly affected by their own mtDNA and the mtDNA carried by their social partner in the larval stage. Thus, mtDNA mutations that alter the effect of male larvae on nearby female larvae (which often carry the same mutation, due to kinship) could theoretically respond to kin selection. We discuss the implications of our findings for the evolution of mitochondria and other maternally inherited endosymbionts.

opencc-zeroAug 2020View details →

Males adjust their manipulation of female remating in response to sperm competition risk

To reduce the potential for sperm competition, male insects are thought to inhibit the post-mating reproductive behaviour of females through receptivity inhibiting compounds transferred in the ejaculate. Selection is expected to favour phenotypic plasticity in male post-copulatory expenditure, with males investing strategically in response to their perceived risk of sperm competition. However, the impact that socially cued strategic allocation might have on female post-mating behaviour has rarely been assessed. Here, we varied male perception of sperm competition risk, both prior to and during mating, to determine if a male's competitive environment impacts the extent to which he manipulates female remating behaviour. We found that female Australian field crickets (Teleogryllus oceanicus) mated to males that were reared under sperm competition risk emerged from a shelter in search of male song sooner than did females mated to males reared without risk, but only when mating occured in a risk free environment. We also found that females reared in a silent environment where potential mates were scarce displayed greater post-mating mate searching behaviour than females exposed to male calls during development. Collectively, our findings suggest complex interacting effects of male and female sociosexual environments on female post-mating sexual receptivity.

Figure 1 from: Dai X, Zhou L-Y, Xu T-T, Wang Q-Y, Luo B, Li Y-Y, Gu C, Li S-P, Wang A-Q, Wei W-H, Yang S-M (2020) Reproductive responses of the male Brandt's vole, Lasiopodomys brandtii (Rodentia: Cricetidae) to tannic acid. Zoologia 37: 1-11. https://doi.org/10.3897/zoologia.37.e52232

Figure 1 The effect of TA on body weight. The body weight of male Lasiopodomys brandtii provided low dose (3 mg/mL) and high dose (6 mg/mL) tannic acid (TA) from four weeks of age to eight weeks of age. Error bars indicate standard error (n = 6).

Figure 13 from: Dai X, Zhou L-Y, Xu T-T, Wang Q-Y, Luo B, Li Y-Y, Gu C, Li S-P, Wang A-Q, Wei W-H, Yang S-M (2020) Reproductive responses of the male Brandt's vole, Lasiopodomys brandtii (Rodentia: Cricetidae) to tannic acid. Zoologia 37: 1-11. https://doi.org/10.3897/zoologia.37.e52232

Figure 13 The effect of TA on the expression of autophagy-related genes. Relative mRNA expression levels of LC3A and Beclin1 in the testes of male Lasiopodomys brandtii provided low dose (3 mg/mL) and high dose (6 mg/mL) tannic acid (TA). Error bars indicate standard error. Same letters connect bars with no significant differences at p < 0.05 (n = 6).

Figure 10-12 from: Dai X, Zhou L-Y, Xu T-T, Wang Q-Y, Luo B, Li Y-Y, Gu C, Li S-P, Wang A-Q, Wei W-H, Yang S-M (2020) Reproductive responses of the male Brandt's vole, Lasiopodomys brandtii (Rodentia: Cricetidae) to tannic acid. Zoologia 37: 1-11. https://doi.org/10.3897/zoologia.37.e52232

Figure 10-12 The effect of TA on the content of anti-oxidative enzymes in serum. GSH-Px (10), CAT (11), and SOD (12) level in the serum of male Lasiopodomys brandtii provided low dose (3 mg/mL) and high dose (6 mg/mL) tannic acid (TA). Error bars indicate standard error. Same letters connect bars with no significant differences at p < 0.05 (n = 6).

Figure 6-9 from: Dai X, Zhou L-Y, Xu T-T, Wang Q-Y, Luo B, Li Y-Y, Gu C, Li S-P, Wang A-Q, Wei W-H, Yang S-M (2020) Reproductive responses of the male Brandt's vole, Lasiopodomys brandtii (Rodentia: Cricetidae) to tannic acid. Zoologia 37: 1-11. https://doi.org/10.3897/zoologia.37.e52232

Figure 6-9 The effect of TA on the reproduction-related hormones concentration and StAR expression. Concentrations of luteinizing hormone (LH) (6), follicle-stimulating hormone (FSH) (7), and testosterone (T) (8) in the serum and relative mRNA expression levels of steroidogenic acute regulatory protein (StAR) (9) in the testes of male Lasiopodomys brandtii provided low dose (3 mg/mL) and high dose (6 mg/mL) tannic acid (TA). Error bars indicate standard error. Same letters connect bars with no significant differences at p < 0.05 (n = 6).

Figure 4-5 from: Dai X, Zhou L-Y, Xu T-T, Wang Q-Y, Luo B, Li Y-Y, Gu C, Li S-P, Wang A-Q, Wei W-H, Yang S-M (2020) Reproductive responses of the male Brandt's vole, Lasiopodomys brandtii (Rodentia: Cricetidae) to tannic acid. Zoologia 37: 1-11. https://doi.org/10.3897/zoologia.37.e52232

Figure 4-5 The effect of TA on the sperm quality. Sperm density (4), Sperm abnormality rate (5), and Sperm mortality rate (5) in the epididymis of male Lasiopodomys brandtii provided low dose (3 mg/mL) and high dose (6 mg/mL) tannic acid (TA). Error bars indicate standard error. Same letters connect bars with no significant differences at p < 0.05 (n = 6).

Figures 2-3 from: Dai X, Zhou L-Y, Xu T-T, Wang Q-Y, Luo B, Li Y-Y, Gu C, Li S-P, Wang A-Q, Wei W-H, Yang S-M (2020) Reproductive responses of the male Brandt's vole, Lasiopodomys brandtii (Rodentia: Cricetidae) to tannic acid. Zoologia 37: 1-11. https://doi.org/10.3897/zoologia.37.e52232

Figures 2-3 The effect of TA on the reproductive organ weight. Relative testis weight (2) and relative epididymis weight (3) of male Lasiopodomys brandtii provided low dose (3 mg/mL) and high dose (6 mg/mL) tannic acid (TA). Error bars indicate standard error. Same letters connect bars with no significant differences at p < 0.05 (n = 6). Note: Relative testis and epididymis weight were calculated as paired testes and epididymis weight (g) divided by body weight (g).

opencc-zeroDec 2015View details →

Data from: Resource limitation and responses to rivals in males of the fruit fly Drosophila melanogaster

Diet has a profound direct and indirect effect on reproductive success in both sexes. Variation in diet quality and quantity can significantly alter the capacity of females to lay eggs and of males to deliver courtship. Here, we tested the effect of dietary resource limitation on the ability of male Drosophila melanogaster to respond adaptively to rivals by extending their mating duration. Previous work carried out under ad libitum diet conditions showed that males exposed to rivals prior to mating significantly extend mating duration, transfer more ejaculate proteins and achieve higher reproductive success. Such adaptive responses are predicted to occur because male ejaculate production may be limited. Hence, ejaculate resources require allocation across different reproductive bouts, to balance current vs. future reproductive success. However, when males suffer dietary limitation, and potentially have fewer reproductive resources to apportion, we expect adaptive allocation of responses to rivals to be minimized. We tested this prediction and found that males held on agar-only diets for 5–7 days lost the ability to extend mating following exposure to rivals. Interestingly, extended mating was retained in males held on low yeast/sugar: no sugar/yeast diet treatments, but was mostly lost when males were maintained on 'imbalanced' diets in which there was high yeast: no sugar and vice versa. Overall, the results show that males exhibit adaptive responses to rivals according to the degree of dietary resource limitation and to the ratio of individual diet components.

opencc-zeroDec 2016View details →

Data from: Precopulatory but not postcopulatory male reproductive traits diverge in response to mating system manipulation in Drosophila melanogaster

Competition between males creates potential for pre- and postcopulatory sexual selection and conflict. Theory predicts that males facing risk of sperm competition should evolve traits to secure their reproductive success. If those traits are costly to females, the evolution of such traits may also increase conflict between the sexes. Conversely, under the absence of sperm competition, one expectation is for selection on male competitive traits to relax thereby also relaxing sexual conflict. Experimental evolution studies are a powerful tool to test this expectation. Studies in multiple insect species have yielded mixed and partially conflicting results. In this study, we evaluated male competitive traits and male effects on female costs of mating in Drosophila melanogaster after replicate lines evolved for more than 50 generations either under enforced monogamy or sustained polygamy, thus manipulating the extent of intrasexual competition between males. We found that in a setting where males competed directly with a rival male for access to a female and fertilization of her ova polygamous males had superior reproductive success compared to monogamous males. When comparing reproductive success solely in double mating standard sperm competition assays, however, we found no difference in male sperm defense competitiveness between the different selection regimes. Instead, we found monogamous males to be inferior in precopulatory competition, which indicates that in our system, enforced monogamy relaxed selection on traits important in precopulatory rather than postcopulatory competition. We discuss our findings in the context of findings from previous experimental evolution studies in Drosophila ssp. and other invertebrate species.

opencc-zeroDec 2017View details →

Data from: Developmental plasticity of the stress response in female but not male guppies

To survive, animals must respond appropriately to stress. Stress responses are costly, so early-life experiences with potential stressors could adaptively tailor adult stress responses to local conditions. However, how multiple stressors influence the development of the stress response remains unclear, as is the role of sex. Trinidadian guppies (Poecilia reticulata) are small fish with extensive life history differences between the sexes and population variation in predation pressure and social density. We investigated how sex and early-life experience influence hormonal stress responses by manipulating conspecific density and perceived predation risk during development. In adults, we sampled cortisol twice to measure initial release and change over time in response to a recurring stressor. The sexes differed considerably in their physiological stress response. Males released more cortisol for their body mass than females and did not reduce cortisol release over time. By contrast, all females, except those reared at high density with predation cues, reduced cortisol release over time. Cortisol responses of males were less dynamic in response to current circumstances and early-life experiences than females, consistent with life history differences between the sexes. Our study underscores the importance of early-life experiences, interacting ecological factors, and sex differences in the organization of the stress response.

opencc-zeroDec 2018View details →

Data from: Male responses to sperm competition risk when rivals vary in their number and familiarity

Males of many species adjust their reproductive investment to the number of rivals present simultaneously. However, few studies have investigated whether males sum previous encounters with rivals, and the total level of competition has never been explicitly separated from social familiarity. Social familiarity can be an important component of kin recognition and has been suggested as a cue that males use to avoid harming females when competing with relatives. Previous work has succeeded in independently manipulating social familiarity and relatedness among rivals, but experimental manipulations of familiarity are confounded with manipulations of the total number of rivals that males encounter. Using the seed beetle Callosobruchus maculatus we manipulated three factors: familiarity among rival males, the number of rivals encountered simultaneously, and the total number of rivals encountered over a 48-hour period. Males produced smaller ejaculates when exposed to more rivals in total, regardless of the maximum number of rivals they encountered simultaneously. Males did not respond to familiarity. Our results demonstrate that males of this species can sum the number of rivals encountered over separate days, and therefore the confounding of familiarity with the total level of competition in previous studies should not be ignored.

opencc-zeroDec 2012View details →

Data from: Age-dependent female responses to a male ejaculate signal alter demographic opportunities for selection

A central tenet of evolutionary explanations for ageing is that the strength of selection wanes with age. However, data on age-specific expression and benefits of sexually selected traits are lacking—particularly for traits subject to sexual conflict. We addressed this by using as a model the responses of Drosophila melanogaster females of different ages to receipt of sex peptide (SP), a seminal fluid protein transferred with sperm during mating. SP can mediate sexual conflict, benefitting males while causing fitness costs in females. Virgin and mated females of all ages showed significantly reduced receptivity in response to SP. However, only young virgin females also showed increased egg laying; hence, there was a narrow demographic window of maximal responses to SP. Males gained significant 'per mating' fitness benefits only when mating with young females. The pattern completely reversed in matings with older females, where SP transfer was costly. The overall benefits of SP transfer (hence opportunity for selection) therefore reversed with female age. The data reveal a new example of demographic variation in the strength of selection, with convergence and conflicts of interest between males and ageing females occurring over different facets of responses to a sexually antagonistic trait.

opencc-zeroJul 2019View details →

Data from: Flexible polyandry in female flies is an adaptive response to infertile males

Infertility is common in nature despite its obvious cost to individual fitness. Rising global temperatures are predicted to decrease fertility, and male sterility is frequently used in attempts to regulate pest or disease vector populations. When males are infertile, females may mate with multiple males to ensure fertilisation, and changes in female mating behaviour in turn could intensify selection on male fertility. Fertility assurance is a potentially wide-spread explanation for polyandry, but whether and how it actually contributes to the evolution of polyandry is not clear. Moreover, whether a drop in male fertility would lead to a genetic increase in polyandry depends on whether females respond genetically or through behavioural plasticity to male infertility. Here, we experimentally manipulate male fertility through heat-exposure in Drosophila pseudoobscura, and test female discrimination against infertile males before and after mating. Using isogenic lines, we compare the roles of behaviourally plastic versus genetically fixed polyandry. We find that heat-exposed males are less active and attractive, and that females are more likely to remate after mating with these males. Remating rate increases with reduced reproductive output, indicating that females use current sperm storage threshold to make dynamic remating decisions. After remating with fertile males, females restore normal fecundity levels. Our results suggest that male infertility could explain the evolution of adaptively flexible polyandry, but is less likely to cause an increase in genetic polyandry.

opencc-zeroDec 2014View details →

Data from: Mating with an allopatric male triggers immune response and decreases longevity of ant queens

In species with lifelong pair bonding, the reproductive interests of the mating partners are aligned, and males and females are expected to jointly maximize their reproductive success. Mating increases both longevity and fecundity of female reproductives (queens) of the ant Cardiocondyla obscurior, indicating a tight co-evolution of mating partners. Here, we show that mating with a male from their own population increases lifespan and reproductive success of queens more than mating with a male from a different population, with whom they could not co-evolve. A comparison of transcriptomes revealed an increased expression of genes involved in immunity processes in queens, which mated with males from a different population. Increased immune response might be proximately associated with decreased lifespan. Our study suggests a synergistic co-evolution between the sexes and sheds light on the proximate mechanisms underlying the decreased fitness of allopatrically mated queens.

opencc-zeroDec 2016View details →

Data from: The role of species-specific sensory cues in male responses to mating rivals in Drosophila melanogaster fruitflies

Complex sets of cues can be important in recognising and responding to conspecific mating competitors and avoiding potentially costly heterospecific competitive interactions. Within Drosophila. melanogaster, males can detect sensory inputs from conspecifics to assess the level of competition. They respond to rivals by significantly extending mating duration and gain significant fitness benefits from doing so. Here, we tested the idea that the multiple sensory cues used by D. melanogaster males to detect conspecifics also function to minimise 'off-target' responses to heterospecific males that they might encounter (D. simulans, D. yakuba. D. pseudoobscura or D. virilis). Focal D. melanogaster males exposed to D. simulans or D. pseudoobscura subsequently increased mating duration, but to a lesser extent than following exposure to conspecific rivals. The magnitude of rivals responses expressed by D. melanogaster males did not align with genetic distance between species and none of the sensory manipulations caused D. melanogaster to respond to males of all other species tested. However, when we removed or provided 'false' sensory cues, D. melanogaster males became more likely to show increased mating duration responses to heterospecific males. We suggest that benefits of avoiding inaccurate assessment of the competitive environment may shape the evolution of recognition cues.