Male Reproductive Output Research Articles

Assessing Variance in Male Reproductive Skew Based on Long-Term Data in Free-Ranging Rhesus Macaques.

The unequal share in male reproduction (male reproductive skew) has been reported across primate species. To explain the distribution of male reproduction within groups various skew models have been applied to primates, however the "dynamic tug-of-war" model first accounted for the specifics of primate sociality. This model assumes that an increase in the number of competing males, a high degree of female cycle synchrony and their interaction will result in a lower degree of male reproductive skew. Here, we first tested the predictors of this model in rhesus macaques (Macaca mulatta) using long-term demographic and genetic data (up to 9 groups over 22 seasons) of the Cayo Santiago population (Puerto Rico). We also tested an extended version including group size and sex ratio and their interaction with female cycle synchrony. Finally, we investigated which male attributes determine the probability to become a top sire (highest paternity share per group and season). Confirming studies, male rhesus macaques exhibited low to medium degrees of reproductive skew based on the multinomial index, M. Unlike predicted, reproductive skew was higher in groups with more males. The extended analysis suggested that reproductive skew increased with group size in more male-biased groups, but decreased with group size in female-biased groups indicating that the numbers of male and female group members matter. We detected no effect of female cycle synchrony on the variance of reproductive skew. Finally, only maternal rank predicted the probability to become a top sire as long as males resided in their natal group. Together, our results did not support predictions by the dynamic skew model in rhesus macaques, but strengthen studies suggesting that other factors in addition to male-male competition predict male reproductive output in rhesus macaques. Future skew studies should consider female choice and alternative male mating strategies.

Adaptation and carry over effects of extreme sporadic heat stress in Culex mosquitoes

Mosquitoes, as temperature-sensitive ectothermic vectors, exhibit temperature-dependence. This study investigates Culex pipiens pallens (Cx. pallens) responses to abrupt temperature increases and their implications on mosquito physiology.First instar larvae (24hr post hatching) and newly enclosed adults (24hr post emergence) were separately exposed to heat shock regimes of 33 °C, 37 °C, and 42 °C for 3 days alongside a control temperature of 27 °C. Results showed that mortality was triggered at 42 °C within a day. Adult male mosquitoes were less tolerant to all temperatures than larvae and adult females (p < 0.05). Exposing larvae to constant temperatures for 3 days significantly decreased larvae's development time, growth rate and adult emergence (p < 0.05). Reproductive fitness was significantly reduced (p < 0.05) in males emerging from larvae exposed to 37 °C. Life table parameters showed significant increased mortality rate, kill power and decreased life expectancy at the embryonic stage (p < 0.05). Furthermore, heatwaves deactivated the Transient receptor protein ankyrin 1 at 37 °C (p < 0.05) in larvae but not adults. Calmodium, Heat shock protein 90, and small heat shock protein expression were significantly decreased in larvae at 37 °C (p < 0.05) as compared to larvae raised at 33 °C and 27 °C.In conclusion, we classified the heat waves into three categories: adaptable (33 °C), critical (37 °C), and fatal (42 °C). Prolonged exposure of Culex pallens larvae to extreme heat affects the male reproductive output. These findings may serve as an important reference for forecasting vector and pest dynamics and used to tailor mosquito prevention and control measures.

Male reproductive output and sperm competition as indicated by gonadosomatic index in Paddlefish stocks

AbstractObjectiveWe investigated if large Paddlefish Polyodon spathula invest in testis weight disproportionately more than smaller males, as expressed by the gonadosomatic index (GSI). The approach was to assess the relation between testis weight F (i.e., the combined weight of both testes) and fish weight W in the expression F = aWb. The hypothesis was that sperm competition in Paddlefish would be expected (with b &gt; 1) based on observations of several male fish attending a female spawner in a past study in the Osage River, Missouri.MethodsWe used a large, three‐state data set from three fisheries (Montana, North Dakota, and Oklahoma) to evaluate isometry and allometry in the power function relationship between fish weight and testis weight.ResultAll three data sets showed hyperallometric increases in testis weight with fish weight (i.e., b &gt; 1). For Montana males, hyperallometry was greatest (b = 1.56; n = 8798), followed by North Dakota (b = 1.36; n = 8209) and Oklahoma (b = 1.22; n = 9571). Paddlefish from Montana and North Dakota had much lower testis weights through age 18 and much lower fish weights through age 25 than Oklahoma Paddlefish. By ages 17–25, mean male GSI in Oklahoma declined, whereas it remained level at about 1.5 for combined Montana and North Dakota Paddlefish. Throughout their lives, at each age, Montana and North Dakota Paddlefish allocated a higher percentage of their total weight to testis weight and reached a higher asymptotic GSI (GSI∞) than did Oklahoma Paddlefish; GSI∞ was 1.50 for Montana fish, 1.44 for North Dakota fish, and 1.26 for Oklahoma fish.ConclusionResults provide evidence supporting the occurrence sperm competition (i.e., b &gt; 1), as would occur when two or more males compete to fertilize the eggs of a female spawning Paddlefish. Comparisons among species and stocks are made but were limited by an acute shortage of data on male testis weights and other testis characteristics (e.g., sperm size, energy content), and reproductive investment in Paddlefish and most other fishes in other localities.

Incidence and frequency of desynapsis in Eremurus persicus (Jaub. &amp; Spach) Boiss.(Asphodelaceae) – A native and important medicinal plant species of Western Himalaya

Eremurus persicus (Jaub. &amp; Spach) Boiss. (Asphodelaceae); a little known species of genus Eremurus grows in arid and semi-arid regions, on rocky mountains in Central Asia and Middle East. The species is native and an important medicinal plant used to treat various diseases. In the current study, we examined male meiosis, karyotypic variability, pollen viability and reproductive output of three populations of the target species. All the studied populations have diploid chromosome count of 2n = 2x =14. Meiotic course in majority of the pollen mother cells (PMCs) in all the three populations is not normal due to the presence of desynapsis at diplotene and metaphase-I. Instead of 7IIs most of the PMCs examined reveal varying number of bivalents and univalents. Anaphasic segregation is also affected in few PMCs. Present study also revealed that the species has asymmetric karyotype of 10 long and 4 short chromosomes. Species exhibits fruit abortion that results in extremely low fruit/seed set. The meiotic abnormalities and low fruit/seed set may be attributed to restricted distribution of this important plant species. Present study may prove helpful in devising the conservation and management strategies for this prized plant species.

An integrative measure of cognitive performance, but not individual task performance, is linked to male reproductive output in budgerigars

Cognitive abilities such as learning and memory are key for survival and reproduction. Individuals with high cognitive abilities may be more successful at attracting mates and producing offspring. However, empirical tests of and evidence supporting this hypothesis remain scarce. We measured cognitive performance of male budgerigars in four tasks: problem solving, detour reaching, seed discrimination, and spatial memory. We then tested female choice for male cognition at three stages of the mating choice process: social pairing, extra-pair mating, and continued reproductive investment with a social mate. We also measured female reproductive output. We used an integrative measure of male cognitive performance that encapsulates performance across all tasks, the ‘composite cognitive score’ by summing performance on the four tasks. In the first stage, females did not choose their social mates based on any of the measures of male cognitive performance. In the second stage, however, males with higher composite cognitive scores sired and raised more offspring. In the third stage, females increased their reproductive investment after the first breeding attempt when paired with males with higher detour-reaching scores. These results suggest that female reproductive decisions may shape overall male cognitive performance.

Calling activity determines male mating success in a territorial frog with parental care

AbstractA contentious aspect in dendrobatoid frog behaviour is the recognition of the predominant factor—if any—driving male mating success. This is probably related to an extensive correlation among different male quality predictors. Here, we investigated the diurnal and territorial nurse frog Allobates subfolionidificans by means of a field study during one entire breeding season in Brazilian Amazonia. We tested the roles of two intrinsic male properties (body size and calling activity) and five territory‐related variables (territory size, vegetation cover, nesting site, perch height and food availability) on male reproductive output. A multiple regression analysis revealed calling activity as the only variable predicting male mating success in A. subfolionidificans. Vocalisation probably represents the most energetically expensive activity that a male frog undertakes during his lifetime, thus calling activity may be used by A. subfolionidificans females as a cue to mate choice that indicates competitive potential and male quality. Alternatively, non‐choosy females also should be more likely to encounter and mate with males that advertise more often throughout the breeding season.

Anthropogenic noise reduces male reproductive investment in an acoustically signaling insect

Rapidly changing environments impose novel selection pressures on organisms, and sometimes adaptive phenotypic plasticity allows organisms to survive and reproduce in the face of environmental change. However, plastic responses can also be maladaptive. In this study, we investigate whether male reproductive investment responds plastically to varied experience with traffic noise. We exposed male crickets chronically to one of three noise treatments from the 2nd-3rd instar until their natural death: masking traffic noise (including noise that overlaps in frequency with the male crickets’ mating calls), non-masking traffic noise (an identical traffic noise track from which we digitally removed the frequencies that mask the crickets’ mating call), and silence. We dissected and weighed their testes and spermatophore molds. Controlling for body mass, we found that the spermatophore molds of crickets reared in masking and non-masking noise were 29% and 24% lighter, respectively, than those of crickets reared in silence. There were no differences in body mass-adjusted testes mass among treatments. If spermatophore mold mass is positively associated with male reproductive output, this reduction in size could have negative fitness consequences for animals exposed to traffic noise. We encourage future work to investigate impacts of noise on reproductive investment in other study systems that are likely sensitive to anthropogenic noise (e.g., birds, frogs, singing insects). Anthropogenic noise is a pervasive pollutant and chronic noise can negatively affect fitness. How does anthropogenic noise influence reproductive investment? Phenotypically plastic responses to noise may increase survival and reproduction in noisy environments. Traffic noise masks the sounds crickets make, potentially changing conspecifics’ perception of population density, mate availability, and the risk of sperm competition. We found that male crickets reared in silence developed significantly larger spermatophore molds (a reproductive structure that delivers the sperm containing packet to the female) than those reared in traffic noise. If the spermatophore mold influences male reproductive output, this reduction in size may have negative impacts on reproductive success of animals exposed to masking traffic noise.

Fluctuations in nutrient composition affect male reproductive output in Drosophila melanogaster

Insects are known to selectively balance their intake of protein and carbohydrate to optimize reproduction and survival. For insects who feed on decomposing fruit, fluctuations in macronutrient composition occur as fruits ripe and decomposition progresses which may challenge optimal resource allocation. Using Drosophila melanogaster, we tested the effect of macronutrient fluctuations and the variability of these fluctuations on starvation resistance and components of reproductive output; traits known to be sensitive to different protein to carbohydrate (P:C) ratios in the diet. For 8 days, flies were fed the same protein to carbohydrate (P:C) ratio (constant feeding), or fed diets with fluctuations in P:C ratio on each day; these fluctuations being regular (predictably fluctuating) or irregular (unpredictably fluctuating). The three feeding regimes yielded the same average P:C ratio across the duration of the experiment. We found no difference in starvation resistance across the feeding regimes. Interestingly, there was a sexual dimorphism in the effect on reproductive output with males performing worst in the unpredictable feeding regime, and with no effect of feeding regime on female performance. Our study provides evidence for means of adapting to fluctuating macronutrient composition and suggests females are more tactful than males in storing and allocating resources for reproduction.

Genetic Quality Affects the Rate of Male and Female Reproductive Aging Differently in Drosophila melanogaster.

Males and females often maximize fitness by pursuing different reproductive strategies, with males commonly assumed to benefit more from increased resource allocation into current reproduction. Such investment should trade off with somatic maintenance and may explain why males frequently live shorter than females. It also predicts that males should experience faster reproductive aging. Here we investigate whether reproductive aging and life span respond to condition differently in male and female Drosophila melanogaster, as predicted if sexual selection has shaped male and female resource-allocation patterns. We manipulate condition through genetic quality by comparing individuals inbred or outbred for a major autosome. While genetic quality had a similar effect on condition in both sexes, condition had a much larger general effect on male reproductive output than on female reproductive output, as expected when sexual selection on vigor acts more strongly on males. We find no differences in reproductive aging between the sexes in low condition, but in high condition reproductive aging is relatively faster in males. No corresponding sex-specific change was found for life span. The sex difference in reproductive aging appearing in high condition was specifically due to a decreased aging rate in females rather than any change in males. Our results suggest that females age slower than males in high condition primarily because sexual selection has favored sex differences in resource allocation under high condition, with females allocating relatively more toward somatic maintenance than males.

Consequences for conservation: population density and genetic effects on reproduction of an endangered lagomorph.

Understanding reproduction and mating systems is important for managers tasked with conserving vulnerable species. Genetic tools allow biologists to investigate reproduction and mating systems with high resolution and are particularly useful for species that are otherwise difficult to study in their natural environments. We conducted parentage analyses using 19 nuclear DNA microsatellite loci to assess the influence of population density, genetic diversity, and ancestry on reproduction, and to examine the mating system of pygmy rabbits (Brachylagus idahoensis) bred in large naturalized enclosures for the reintroduction and recovery of the endangered distinct population in central Washington, USA. Reproductive output for females and males decreased as population density and individual homozygosity increased. We identified an interaction indicating that male reproductive output decreased as genetic diversity declined at high population densities, but there was no effect at low densities. Males with high amounts (> 50%) of Washington ancestry had higher reproductive output than the other ancestry groups, while reproductive output was decreased for males with high northern Utah/Wyoming ancestry and females with high Oregon/Nevada ancestry. Females and males bred with an average of 3.8 and 3.6 mates per year, respectively, and we found no evidence of positive or negative assortative mating with regards to ancestry. Multiple paternity was confirmed in 81% of litters, and we report the first documented cases of juvenile breeding by pygmy rabbits. This study demonstrates how variation in population density, genetic diversity, and ancestry impact fitness for an endangered species being bred for conservation. Our results advance understanding of basic life history characteristics for a cryptic species that is difficult to study in the wild and provide lessons for managing populations of vulnerable species in captive and free-ranging populations.

Male pursuit of higher reproductive success drives female polyandry in the Omei treefrog

Female polyandry and corresponding multiple paternity have been detected in many species. Several hypotheses, such as the fertility guarantee hypothesis, the good gene hypothesis, the genetic compatibility hypothesis and the genetic diversity hypothesis, have been proposed to explain the evolution of female polyandry. Anuran amphibians are widely observed to breed in polyandrous spawning groups; however, few studies have evaluated multiple paternity in these species or the evolutionary mechanisms underlying polyandry. In this study, we addressed these questions pertaining to polyandry in the Omei treefrog, Rhacophorus omeimontis. Eight microsatellite markers of R. omeimontis were used to determine the patterns of paternity. Paternity analyses revealed that offspring were multiply sired in a majority (79.07%) of the polyandrous spawning groups. A male's reproductive output during a breeding season was greatly affected by the mating rate, revealing that male fitness benefited from multiple copulations. By contrast, no evidence supported the fertility guarantee hypothesis that polyandry increases the fertility rate of females or the compatible/good gene hypotheses that polyandrous females produce more compatible or superior offspring. The increased allelic diversity observed in polyandrous clutches is probably a nonadaptive by-product of multiple mating. In conclusion, males join as many copulations as possible to increase their reproductive success, regardless of whether their mate has already been in amplexus with other males. Females may gain no benefits from polyandry but are incapable of preventing superfluous males from joining the mating group due to the physical characteristics and breeding behaviour of anurans. Thus, in R. omeimontis, male pursuit of higher reproductive success is the primary explanation for female polyandry.

Contaminants reduce male contribution to reproduction at the population scale

In many populations, males compete for mates and contribute to genetic diversity, but are assumed to have little impact on population growth rates and density, because one father is all that is necessary to fertilize a large number of eggs and sire a potential cohort. A factor affecting male reproductive output is exposure to contaminants that either disrupt endocrine function or mimic hormones. Polychlorinated biphenyls (PCBs) persist in aquatic ecosystems and may interfere with the reproductive contribution of male fish to populations. We quantified 28 PCB congeners in adult male bluegills across eight Illinois lakes. In spring 2011 and 2012, mature male bluegills from lakes with conspecifics with PCB whole‐body residues ranging from undetectable to high (2,000 ng/g dry mass total PCBs) were placed in experimental ponds with mature females containing no detectable PCB body residues and allowed to reproduce in spring under natural conditions. The presence of PCBs in fish had no effect on the presence of intersex or other gonadal deformities in adult males nor was gonad size, lipid concentration, and survival affected. Males with high PCBs were heavier than those from lakes with low PCB concentrations. The relative density of juvenile bluegills produced in ponds by fall, a fitness endpoint in this species, was negatively related to contaminant concentration in fathers. Contaminant exposure and other factors that affect male reproduction may not only suppress the relative contribution of males to genetic diversity, but also the overall density of cohorts within populations.

Female and male moths display different reproductive behavior when facing new versus previous mates.

Multiple mating allows females to obtain material (more sperm and nutrient) and/or genetic benefits. The genetic benefit models require sperm from different males to fertilize eggs competitively or the offspring be fathered by multiple males. To maximize genetic benefits from multiple mating, females have evolved strategies to prefer novel versus previous mates in their subsequent matings. However, the reproductive behavior during mate encounter, mate choice and egg laying in relation to discrimination and preference between sexes has been largely neglected. In the present study, we used novel and previous mate treatments and studied male and female behavior and reproductive output in Spodoptera litura. The results of this study do not support the sperm and nutrient replenishment hypotheses because neither the number of mates nor the number of copulations achieved by females significantly increased female fecundity, fertility and longevity. However, females showed different oviposition patterns when facing new versus previous mates by slowing down oviposition, which allows the last male has opportunities to fertilize her eggs and the female to promote offspring diversity. Moreover, females that have novel males present called earlier and more than females that have their previous mates present, whereas no significant differences were found on male courtship between treatments. These results suggest that S. litura females can distinguish novel from previous mates and prefer the former, whereas males generally remate regardless of whether the female is a previous mate or not. In S. litura, eggs are laid in large clusters and offspring competition, inbreeding and disease transfer risks are thus increased. Therefore, offspring diversity should be valuable for S. litura, and genetic benefits should be the main force behind the evolution of female behavioral strategies found in the present study.

Sex‐Biased Inbreeding Effects on Reproductive Success and Home Range Size of the Critically Endangered Black Rhinoceros

A central premise of conservation biology is that small populations suffer reduced viability through loss of genetic diversity and inbreeding. However, there is little evidence that variation in inbreeding impacts individual reproductive success within remnant populations of threatened taxa, largely due to problems associated with obtaining comprehensive pedigree information to estimate inbreeding. In the critically endangered black rhinoceros, a species that experienced severe demographic reductions, we used model selection to identify factors associated with variation in reproductive success (number of offspring). Factors examined as predictors of reproductive success were age, home range size, number of nearby mates, reserve location, and multilocus heterozygosity (a proxy for inbreeding). Multilocus heterozygosity predicted male reproductive success (p< 0.001, explained deviance >58%) and correlated with male home range size (p < 0.01, r(2) > 44%). Such effects were not apparent in females, where reproductive success was determined by age (p < 0.01, explained deviance 34%) as females raise calves alone and choose between, rather than compete for, mates. This first report of a 3-way association between an individual male's heterozygosity, reproductive output, and territory size in a large vertebrate is consistent with an asymmetry in the level of intrasexual competition and highlights the relevance of sex-biased inbreeding for the management of many conservation-priority species. Our results contrast with the idea that wild populations of threatened taxa may possess some inherent difference from most nonthreatened populations that necessitates the use of detailed pedigrees to study inbreeding effects. Despite substantial variance in male reproductive success, the increased fitness of more heterozygous males limits the loss of heterozygosity. Understanding how individual differences in genetic diversity mediate the outcome of intrasexual competition will be essential for effective management, particularly in enclosed populations, where individuals have restricted choice about home range location and where the reproductive impact of translocated animals will depend upon the background distribution in individual heterozygosity.

Increase in Male Reproductive Success and Female Reproductive Investment in Invasive Populations of the Harlequin Ladybird Harmonia axyridis

Reproductive strategy affects population dynamics and genetic parameters that can, in turn, affect evolutionary processes during the course of biological invasion. Life-history traits associated with reproductive strategy are therefore potentially good candidates for rapid evolutionary shifts during invasions. In a series of mating trials, we examined mixed groups of four males from invasive and native populations of the harlequin ladybird Harmonia axyridis mating freely during 48 hours with one female of either type. We recorded the identity of the first male to copulate and after the 48 h-period, we examined female fecundity and share of paternity, using molecular markers. We found that invasive populations have a different profile of male and female reproductive output. Males from invasive populations are more likely to mate first and gain a higher proportion of offspring with both invasive and native females. Females from invasive populations reproduce sooner, lay more eggs, and have offspring sired by a larger number of fathers than females from native populations. We found no evidence of direct inbreeding avoidance behaviour in both invasive and native females. This study highlights the importance of investigating evolutionary changes in reproductive strategy and associated traits during biological invasions.

Effects of Population Size on Synchronous Display of Female and Male Flowers and Reproductive Output in Two Monoecious Sagittaria Species

BackgroundFlowering synchrony and floral sex ratio have the potential to influence the mating opportunities and reproductive success through female function. Here, we examine the variances in synchronous display of female and male function, ratio of male to female flowers per day and subsequently reproductive output in small populations of two monoecious plants, Sagittaria trifolia and Sagittaria graminea. Methodology/Principal FindingWe created plant populations of size 2, 4, 10 and 20 and recorded the daily number of blooming male and female flowers per plant to determine daily floral display, flowering synchrony index and ratio of male to female flowers per day. We also harvested the fruits, counted the seeds and calculated the number of fruits and seeds per flower to measure reproductive success through female function. There is less overlap in flowering time of female and male function in smaller populations than in larger populations. Most importantly, we found that male-biased floral sex ratio and imbalanced display period of female and male function for individual plant can lead to a population-size-dependent ratio of male to female flowers per day. Increasing ratio of male to female flowers per day was generally associated with a greater percentage of fruit production.Conclusions/SignificanceOur results highlight the importance of flowering synchrony of female and male function and population-size-dependent ratio of male to female flowers per day for female reproductive success. This finding improves our understanding of a mechanism that reduces reproductive success in small populations.

Male fertility versus sterility, cytotype, and DNA quantitative variation in seed production in diploid and tetraploid sea lavenders (Limonium sp., Plumbaginaceae) reveal diversity in reproduction modes

The genus Limonium Miller, a complex taxonomic group, comprises annuals and perennials that can produce sexual and/or asexual seeds (apomixis). In this study, we used diverse cytogenetic and cytometric approaches to analyze male sporogenesis and gametogenesis for characterizing male reproductive output on seed production in Limonium ovalifolium and Limonium multiflorum. We showed here that the first species is mostly composed of diploid cytotypes with 2n = 16 chromosomes and the latter species by tetraploid cytotypes with 2n = 32, 34, 35, 36 chromosomes and had a genome roughly twice as big as the former one. In both species, euploid and aneuploid cytotypes with large metacentric chromosomes having decondensed interstitial sites were found within and among populations, possibly involved in chromosomal reconstructions. L. ovalifolium diploids showed regular meiosis resulting in normal tetrads, while diverse chromosome pairing and segregation irregularities leading to the formation of abnormal meiotic products are found in balanced and non-balanced L. multiflorum tetraploids. Before anther dehiscence, the characteristic unicellular, bicellular, or tricellular pollen grains showing the typical Limonium micro- or macro-reticulate exine ornamentation patterns were observed in L. ovalifolium using scanning electron microscopy. Most of these grains were viable and able to produce pollen tubes in vitro. In both balanced and unbalanced L. multiflorum tetraploids, microspores only developed until the “ring-vacuolate stage” with a collapsed morphology without the typical exine patterns, pointing to a sporophytic defect. These microspores were unviable and therefore never germinated in vitro. L. ovalifolium individuals presented larger pollen grains than those of L. multiflorum, indicating that pollen size and ploidy levels are not correlated in the Limonium system. Cytohistological studies in mature seeds from both species revealed that an embryo and a residual endosperm were present in each seed. Flow cytometric seed screens using such mature seeds showed quantitative variations in seeds ploidy level. It is concluded that male function seems to play an important role in the reproduction modes of Limonium diploids and tetraploids.Electronic supplementary materialThe online version of this article (doi:10.1007/s00497-012-0199-y) contains supplementary material, which is available to authorized users.

Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird

Postcopulatory sexual selection is an important force in the evolution of reproductive traits, including sperm morphology. In birds, sperm morphology is known to be highly heritable and largely condition-independent. Theory predicts, and recent comparative work corroborates, that strong selection in such traits reduces intraspecific phenotypic variation. Here we show that some variation can be maintained despite extreme promiscuity, as a result of opposing, copulation-role-specific selection forces. After controlling for known correlates of siring success in the superb fairy-wren (Malurus cyaneus), we found that (a) lifetime extra-pair paternity success was associated with sperm with a shorter flagellum and relatively large head, and (b) males whose sperm had a longer flagellum and a relatively smaller head achieved higher within-pair paternity. In this species extrapair copulations occur in the same morning, but preceding, pair copulations during a female's fertile period, suggesting that shorter and relatively larger-headed sperm are most successful in securing storage (defense), whereas the opposite phenotype might be better at outcompeting stored sperm (offense). Furthermore, since cuckolding ability is a major contributor to differential male reproductive output, stronger selection on defense sperm competition traits might explain the short sperm of malurids relative to other promiscuous passerines.

Closing the lifecycle for the sustainable aquaculture of the bath sponge Coscinoderma matthewsi

Aquaculture of the bath sponge Coscinoderma matthewsi relies on collection of seed stock from the wild. This study investigated the potential of larval culture as a sustainable source of seed stock by quantifying reproduction, larval metamorphosis, and juvenile survival and growth of C. matthewsi. The accuracy of using surface area (2-dimensional) measurements as a proxy for juvenile growth was also assessed against volumetric (3-dimensional) data. Coscinoderma matthewsi is gonochoric and releases parenchymellae larvae over several weeks, corresponding with increasing sea surface temperatures, over the Austral summer (26.6 °C in November and 29.1 °C in January). Sexual maturity is size dependent and smaller individuals (1267.78 cm 3 ± 405.66) were non-reproductive. There were no size differences between males and females and both sexes occur in equal proportions. Male reproductive output (ROI) (4.33% ± 0.75) was higher than females (1.62% ± 0.15). Larval metamorphic success was 98.0% ± 2 after 72 h post-release. Juvenile survival over seven months was independent of settlement density and ranged between 18% and 30%. Using surface area underestimated growth of juvenile sponges by approximately half in comparison to volume estimates. This study demonstrates larval culture as a sustainable source of seed stock to support large scale aquaculture operations.

Patterns of interventions and the effect of coalitions and sociality on male fitness.

In group living animals, especially among primates, there is consistent evidence that high-ranking males gain a higher reproductive output than low-ranking males. Primate studies have shown that male coalitions and sociality can impact male fitness; however, it remains unclear whether males could potentially increase their fitness by preferentially supporting and socializing with females. Here we investigate patterns of male interventions and the effect of coalitions and sociality on male fitness in rhesus macaques (Macaca mulatta) with particular focus on male-female interactions. We combined behavioural observations collected on Cayo Santiago with genetic data analysed for male reproductive output and relatedness. Our results revealed that the ten top-ranking males provided the majority of all male support observed. In contrast to other primates, male rhesus macaques mainly formed all-down coalitions suggesting that coalitions are less likely used to enhance male dominance. Males supporting females during and before their likely conception were not more likely to fertilize those females. We also found no evidence that males preferably support their offspring or other close kin. Interestingly, the most important predictor of male support was sociality, since opponents sharing a higher sociality index with a given male were more likely to be supported. Furthermore, a high sociality index of a given male-female dyad resulted in a higher probability of paternity. Overall, our results strengthen the evidence that sociality affects fitness in male primates, but also suggest that in species in which males queue for dominance, it is less likely that males derive fitness benefits from coalitions.