Search

Abstract Multiple mating by avian females may increase hatching and overall brood success; however, reproductive effort and parental investment are costly, and females may be gradually depleted, with lowered outputs over time. Thus, males in social polyandry systems may differ greatly in their reproductive gains. In the present study, we investigated the reproductive outputs of social polyandrous and sex-role-reversed pheasant-tailed jacanas, Hydrophasianus chirurgus, to assess the effects of polyandry, seasonality, and male mating order on breeding success. Female jacanas produced multiple clutches, either by leaving two or more clutches with an individual male (22%), or by mating with two or more males (78%). The polyandrous females laid both the first and second clutches earlier and showed a breeding period more than twice as long as that of monandrous females. Both polyandry and seasonality affected the fate of a clutch, where clutches from polyandrous females and the early season had higher hatching and brood success rates, but the number of polyandrous females declined over the season. Polyandrous females not only laid more clutches and eggs, and gained more hatchlings and fledglings, but also achieved higher per-clutch outputs and hatching rates than monandrous females. In polyandry groups, males gained higher total hatchlings and fledglings, although not total clutches or eggs, than males in monandry or bi-andry groups. Moreover, males in polyandry groups achieved higher hatchlings and fledglings per clutch and higher hatching and brood success rates. In polyandry groups, the first-mating males obtained more clutches, eggs, and hatchlings; however, they did not have higher success rates, nor total fledglings and per-clutch outputs, than males who mated later. Overall, the results indicate a selective advantage of polyandry for the jacanas studied, particularly in the early breeding season. This advantage, however, differs both between the sexes and intra-sexually, suggesting strong connections with certain ecological/environmental conditions in addition to the jacanas’ own quality.

Multiple mating by avian females may increase hatching and overall brood success; however, reproductive effort and parental investment are costly, and females may be gradually depleted, with lowered outputs over time. Thus, males in social polyandry systems may differ greatly in their reproductive gains. In the present study, we investigated the reproductive outputs of social polyandrous and sex-role-reversed pheasant-tailed jacanas, Hydrophasianus chirurgus, to assess the effects of polyandry, seasonality, and male mating order on breeding success. Female jacanas produced multiple clutches, either by leaving two or more clutches with an individual male (22%), or by mating with two or more males (78%). The polyandrous females laid both the first and second clutches earlier and showed a breeding period more than twice as long as that of monandrous females. Both polyandry and seasonality affected the fate of a clutch, where clutches from polyandrous females and the early season had higher hatching and brood success rates, but the number of polyandrous females declined over the season. Polyandrous females not only laid more clutches and eggs, and gained more hatchlings and fledglings, but also achieved higher per-clutch outputs and hatching rates than monandrous females. In polyandry groups, males gained higher total hatchlings and fledglings, although not total clutches or eggs, than males in monandry or bi-andry groups. Moreover, males in polyandry groups achieved higher hatchlings and fledglings per clutch and higher hatching and brood success rates. In polyandry groups, the first-mating males obtained more clutches, eggs, and hatchlings; however, they did not have higher success rates, nor total fledglings and per-clutch outputs, than males who mated later. Overall, the results indicate a selective advantage of polyandry for the jacanas studied, particularly in the early breeding season. This advantage, however, differs both between the sexes and intra-sexually, suggesting strong connections with certain ecological/environmental conditions in addition to the jacanas' own quality. [ABSTRACT FROM AUTHOR]

Sperm competition drives traits that enhance fertilization success. The amount of sperm transferred relative to competitors is key for attaining paternity. Female reproductive morphology and male mating order may also influence fertilization, however the outcome for sperm precedence under intense sperm competition remains poorly understood. In the polyandrous spider Pisaura mirabilis, males offer nuptial gifts which prolong copulation and increase sperm transfer, factors proposed to alter sperm precedence patterns under strong sperm competition. First, we assessed the degree of female polyandry by genotyping wild broods. A conservative analysis identified up to four sires, with a mean of two sires per brood, consistent with an optimal mating female rate. Then we asked whether intense sperm competition shifts sperm precedence patterns from first male priority, as expected from female morphology, to last male advantage. We varied sexual selection intensity experimentally and determined competitive fertilization outcome by genotyping broods. In double matings, one male monopolised paternity regardless of mating order. A mating order effect with first male priority was revealed when females were mated to four males, however this effect disappeared when females were mated to six males, probably due to increased sperm mixing. The proportion of males that successfully sired offspring drastically decreased with the number of competitors. Longer copulations translated into higher paternity shares independently of mating order, reinforcing the advantage of traits that prolong copulation duration under intense competition, such as the nuptial gift. Sperm competition intensity enhances the impact of competitive sexual traits and imposes multiple effects on paternity. [ABSTRACT FROM AUTHOR]

Studies of birds have made a fundamental contribution to elucidating sperm competition processes, experimentally demonstrating the role of individual mechanisms in competitive fertilization. However, the relative importance of these mechanisms and the way in which they interact under natural conditions remain largely unexplored. Here, we conduct a detailed behavioural study of freely mating replicate groups of red junglefowl, Gallus gallus, to predict the probability that competing males fertilize individual eggs over the course of 10-day trials. Remating frequently with a female and mating last increased a male's probability of fertilization, but only for eggs ovulated in the last days of a trial. Conversely, older males, and those mating with more polyandrous females, had consistently lower fertilization success. Similarly, resistance to a male's mating attempts, particularly by younger females, reduced fertilization probability. After considering these factors, male social status, partner relatedness and the estimated state of male extragonadal sperm reserves did not predict sperm competition outcomes. These results shed new light on sperm competition dynamics in taxa such as birds, with prolonged female sperm storage and staggered fertilizations. [ABSTRACT FROM AUTHOR]

Multiple matings result in varying paternity share based on mating interval and order. Thus, assessing the effect of mating interval and order on patterns of sperm usage and paternity is crucial. We designed consecutive and delayed double-mating experiments to investigate paternity variation in ladybird, Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae), using two distinct morphs of the species as phenotypic markers of paternity. The time to commence mating, copulation duration and reproductive output were recorded. The morphs of the offspring from the two setups were taken as a measure of paternity accumulated by the males. The time to commence mating decreased for the second mating in the consecutive mating treatment, while the reverse was observed in the delayed mating treatment. Consecutive double matings reduced the mating duration. Fecundity increased when second mating occurred after a few days, though percent egg viability remained unaffected. The second male accrued higher paternity (P2 = 0.61) than the first male (P1 = 0.39) in the consecutive mating treatment, while in the delayed mating treatment, the overall paternity share of the first 0.49 (P1) and last male was equal 0.51 (P2). Thus, our study revealed that both mating order and the time interval between successive matings regulate the male paternity share. This finding is reported for the first time in this ladybird species. [ABSTRACT FROM AUTHOR]

Studies of the effects of mating order on fertilization success, classically analyzed as the proportional paternity of the second male, have advanced our understanding of the relative influences of postcopulatory male-male competition and female choice on sexual selection. However, results from these studies are often difficult to analyze because (1) distributions of offspring per dam rarely follow a normal distribution and (2) proportional paternities are never normally distributed. Previous studies partially account for these limitations by using nonparametric statistics. However, behavioral studies are often plagued by relatively small sample sizes and require a more powerful analytical approach. Here, we develop a new analytical framework for studying fertilization bias. Our Approximate Bayesian Computational (ABC) model overcomes many of the limitations of currently employed methods. We apply our model to analyze the effects of male mating order on paternity success in the brown anole lizard, Anolis sagrei. Using our ABC simulation, we find a marked first-male advantage: first males sired approximately 80 % of the offspring in our study. Next, based on re-analysis of four previously published datasets, we show that traditional statistical methods often over- or underestimate biases related to mating order. Moreover, by comparing our model to more traditional statistical tests, we show that the ABC method is robust to relatively small samples sizes and should therefore be useful for studying mating-order effects in a variety of systems. Our model is implemented as an R package, ABCp2, and is freely available for use. [ABSTRACT FROM AUTHOR]

In polyandrous and polygynandrous species where females mate with multiple partners, males are expected to maximize their fitness by exhibiting an array of reproductive behaviors to ensure fertilization success, such as competing for the best mating order within a mating sequence, optimizing their investment in copulation, and mate guarding. Though there is genetic evidence of a first-male precedence in siring success for many mammalian species, the causes of this effect are poorly understood. We studied influences on first-male precedence in Columbian ground squirrels ( Urocitellus columbianus). We found that the time a male spent consorting and mate guarding declined with his mating order (both the highest for the first male to mate). Mate guarding by the first male significantly reduced, but did not exclude, the number of additional males a female accepted. Later mating males reduced the time spent consorting, suggesting a perceived decreased chance of fertilization success. Consortship and mate guarding durations were positively related to the male's siring success and to each other, suggesting that males adjusted these behaviors strategically to increase their chances of fertilization success. Our results suggest that besides being the first male to consort, first-male sperm precedence is further enhanced through longer mating bouts and by suppressing the chances and/or efforts of later mating males. [ABSTRACT FROM AUTHOR]

Sperm competition, as the last form of male competition prior to fertilization, is an important component in the reproductive and evolutionary biology of polyandrous species. Golden cuttlefish (Sepia esculenta) is a commercially important annual cephalopod, in which females often mate with multiple males during their mating season and maintain viable sperm in their sperm storage organs for a long time. This multiple-mating system leads to male competition and ultimately sperm competition. To explore the mechanisms of sperm competition in cuttlefish, a laboratory study was conducted using three experimental approaches. First, two similar-sized males were introduced to sequentially mate with a single female (experiment 1), to investigate mating order effects on paternity. Thereafter, a four-male experiment was run (experiment 2), which again tested for mating sequence on paternal contribution. Finally, to test whether male size is a factor affecting paternity, we compared the paternity of two different-sized males that were sequentially mated with a single female (experiment 3). The paternity of the offspring was analyzed using six microsatellite DNA markers on fertilized eggs. The results revealed last-male sperm precedence in all experiments, and no effect of male size was detected. For the two-male experiment, the last male to mate had a progeny share (P 2) of 42.86%–61.90%. For the four-male experiment, the last mated male had the highest progeny share (P 4) with a proportion of 35.56%–43.75%. Even with differential male sizes in the two-male experiment, the last mated male retained the highest progeny share (P 2 , 58.33%–91.67%). This study shows a consistent pattern of last-sperm advantage across different experiments and contributes to growing research on cephalopod mating systems. Proper mating schemes should be considered during seedling production for S. esculenta to ascertain efficient resource use and genetic diversity in produced offspring. • Mating order is a factor affecting sperm competition in cuttlefish Sepia esculenta. • A general pattern of last male sperm precedence was demonstrated in S. esculenta. • Proper sex ratio set should be considered during the practice of breeding of S. esculenta. [ABSTRACT FROM AUTHOR]