Male tactics and reproductive success in the harem polygynous bat Saccopteryx bilineata

Alternative tactics in reproductive behavior enable individualsto maximize their fitness in relation to competitors in thesame population. In many taxa, territoriality is a common tacticof males to increase their reproductive success. In the batSaccopteryx bilineata, territorial males defend roosting areasfor females against other males and court females throughout the year. Peripheral males in the same colonies do not defendterritories but compete with territorial males for reproductionwith females. In this study, we monitored the behavior of themales in a natural colony over three reproductive seasons.We compared morphological and age data and measured the reproductiveoutput of males adopting the territorial or peripheral tactic.No differences in body size or weight were detected betweenmale types, but the probability of adopting a tactic seemedto be age dependent. Peripherals were often young males andreplaced territorials in several cases, whereas the oppositecase was not observed. Peripherals were not excluded from reproduction,but territorials were more likely to reproduce. Variation in reproductive success was high within both male tactics, andthe reproductive success of some peripherals was comparableto territorials, but, on average, the reproductive successof territorials was more than twice as high. Therefore, behavioraltactics do not seem to be equally profitable in general butmay represent different phases in the reproductive life of manyS. bilineata males.     

Ten novel dinucleotide microsatellite loci cloned from the Galápagos sea lion (Zalophus californianus wollebaeki) are polymorphic in other pinniped species

We isolated and characterized 10 novel dinucleotide microsatellite loci from the Galápagos sea lion (Zalophus californianus wollebaeki) and tested their amplification utility in four further otariid species (Zalophus californianus californianus, Arctocephalus gazella, Arctocephalus australis and Eumetopias jubatus) and three phocid species (Hydrurga leptonyx, Halichoerus grypus and Phoca vitulina). All of the loci amplified polymorphic polymerase chain reaction (PCR) products in at least three species other than the Galápagos sea lion. These markers will be useful for studies of pinniped mating systems, genetic structure and genetic diversity.     

Age-related changes in hematocrit in the Galápagos sea lion (Zalophus wollebaeki) and the Weddell seal (Leptonychotes weddellii)

In mammals, hematocrit (Hct) is optimized between the divergent requirements of blood flow characteristics and oxygen transport and storage capacity. This trade‐off plays a particularly major role in marine mammals, in which oxygen demand during sustained diving requires high Hct levels. Galápagos sea lions (Zalophus wollebaeki) need a long time after birth to develop from terrestrial life to the state of an independent forager at sea. We here show that pups were born with high Hct of 45%, then reduced Hct during the first 40 d of life to 31% while they remain constantly ashore, and increased Hct again until the adult level (57%) is reached at 1 yr of age when they begin to dive for foraging at sea. A similar, but much more rapidly changing pattern is seen in Weddell seal pups, but not in northern elephant seals, where no reduction in Hct is seen after birth. These and similarly changing patterns in terrestrial mammals likely reflect species specific functional adjustments during development due to a trade‐off between the costs of circulation and the changing need to store and transport oxygen.     

The outcome of sperm competition is affected by behavioural and anatomical reproductive traits in a simultaneously hermaphroditic land snail

Sperm competition is important in species with reproductive strategies that involve multiple mating and prolonged sperm storage such as the simultaneously hermaphroditic land snail Cornu aspersum. Double mating trials in this species have revealed that mating order and courtship behaviour affect paternity success. We investigated the effect of behavioural and anatomical reproductive traits on paternity success from triple mating trials. Triple mating resulted in triple fertilization in 58% of the cases whereas zero paternity was observed in 16% of sperm donors. Third sperm donors achieved higher paternity followed by first and second sperm donors. Snails with a longer epiphallus, the spermatophore forming organ, sired more offspring regardless of their mating order. Genetic compatibility between sperm donor and recipient did not influence paternity success. The results of the present study identified mating order and epiphallus length, as traits affecting the outcome of sperm competition in this species.     

Male mating success, reproductive success and multiple paternity in a natural population of sand lizards: behavioural and molecular genetics data

Sand lizard Lacerta agilis females characteristically mate with several males which, in staged mating experiments, results in multiple paternity of the offspring. In order to investigate multiple paternity in a natural population and interpret male reproductive behaviours in terms of sired young, we sampled the blood of females, potential fathers and hatchlings, and determined paternity using multilocus DNA fingerprinting as well as the variation at a single locus detected by the probe (TC) _n . The paternity analyses were preceded by a laboratory experiment in which we established that the parental alleles identified by the single locus probe were inherited in a Mendelian way. Our molecular data demonstrated that 12 out of 13 males (92%) that sired offspring were correctly identified from the 56 sexually mature males in the population. Also smaller males were accepted as sexual partners by the females, but sired fewer young in competition with larger males and were less able to maintain prolonged post-copulatory mate guarding. This may result in that some sexually successful males are only observed inside a female's home range, but never in pair-association with the female.     

Male reproductive strategies in black and gold howler monkeys (Alouatta caraya)

Behavioral and demographic factors such as group size, social structure, dispersal patterns, and mating systems affect male reproductive success. In the present study, we analyze the relationship between social structure, genetic relatedness of adult males and offspring paternity in one population of Alouatta caraya inhabiting a continuous forest in Northern Argentina. After 14 months of behavioral studies and genotyping 11 microsatellites, we found that dominant or central males achieved greater mating success and fathered all the offspring conceived during our study in two multimale–multifemale groups (both including three adult males). Although skewed toward the dominant males, females copulated with almost all resident males and with extra group males. We found significantly fewer agonistic interactions between adult males in the group with fewer females and where males were more genetically related to each other (average relatedness r = 0.237; 0.015 int/ind/hr vs. r = 0.02; 0.029 int/ind/hr). Paternity was also analyzed in two other neighboring groups which also showed strong skew to one male over a 2‐year period. These results reveal that even though female black and gold howlers mate with many males, infants are typically fathered by one dominant male. Am. J. Primatol. 76:43–55, 2014. © 2013 The Authors. American Journal of Primatology Published by Wiley Periodicals, Inc.     

Male dominance and genetically determined reproductive success in the mandrill (Mandrillus sphinx)

Darwin referred to the adult male mandrill (Mandrillus sphinx) as the most brightly coloured of all mammals, citing the brilliant red and blue pigmentation of the face, rump, and genitalia as extreme examples of evolution by sexual selection. Considerable controversy exists concerning possible effects of sexually selected phenotypes via intermale competition on reproductive success. Behavioural and genetic studies of a large, semi-free ranging mandrill colony in Gabon have now demonstrated that clear-cut relationships exist between male secondary sexual development, social dominance, copulatory behaviour, and reproductive success in this primate species. Two morphological variants of adult male were identified; “fatted” males, with maximum secondary sexual coloration, which occupied dominant positions in the social group, and “non-fatted” males, with muted secondary sexual adornments, smaller testes and lower plasma testosterone levels, which lived as peripheral/solitary individuals. DNA fingerprinting analyses on infants born over five successive years showed that only the two most dominant, fatted males in the group had fathered offspring. Throughout the annual mating season these males attempted to mate-guard and copulate with females during periods of maximal sexual skin tumescence. Male rank and mating success were strongly positively related and the alpha male sired 80 – 100% of the resulting offspring during three consecutive years. Non-fatted adult males and group associated subadult males engaged in infrequent, opportunistic matings and did not guard females. Loss of alpha status resulted in a fall in reproductive success, but the effect was gradual; the deposed alpha male continued to father 67% and 25% of infants born during the next two years. Thus, whilst claims that male dominance determines mating success and paternity in primates have caused considerable debate, these results on mandrills provide unequivocal evidence for the existence of such effects.     

Influence of male courtship intensity and male–male competition on paternity distribution in Hermann's tortoise,Testudo hermanni hermanni (Chelonia: Testudinidae)

Honest‐advertisement models of sexual selection suggest that condition‐dependent male secondary sexual characters could function as reliable signals of male quality, enabling females to discriminate among potential partners, both in the pre‐ and post‐copulatory phases. In this context, many studies have revealed the importance of promiscuous mating systems and female sperm storage in determining the occurrence of such a model of sexual selection. By contrast, few studies have investigated the presence and extent of post‐copulatory female choice in chelonian species. The present study aimed to investigate the effect of male size, male–male competition, and courtship intensity on paternity distribution in Testudo hermanni hermanni, combining behavioural and genetic data. We created experimental groups composed of two males of different sizes and three or four randomly selected females. Observations conducted during social interactions between males revealed that a hierarchy, unrelated to male size, was soon established: Alpha males were more aggressive towards competitors and courted females more intensively. Alpha males also achieved a higher mounting success than Beta males. Paternity analysis performed on hatchlings produced from experimental females revealed that male reproductive success was not correlated with male–female size ratio. Finally, despite the higher mounting success of Alpha males, paternity analysis revealed that male reproductive success did not differ between Alpha and Beta males. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 656–667.     

Genetic variation,multiple paternity,and measures of reproductive success in the critically endangered hawksbill turtle (Eretmochelys imbricata)

The Yucatán Peninsula in Mexico contains some of the largest breeding groups of the globally distributed and critically endangered hawksbill turtle (Eretmochelys imbricata). An improved understanding of the breeding system of this species and how its genetic variation is structured among nesting areas is required before the threats to its survival can be properly evaluated. Here, we genotype 1195 hatchlings and 41 nesting females at 12 microsatellite loci to assess levels of multiple paternity, genetic variation and whether individual levels of homozygosity are associated with reproductive success. Of the 50 clutches analyzed, only 6% have multiple paternity. The distribution of pairwise relatedness among nesting localities (rookeries) was not random with elevated within‐rookery relatedness, and declining relatedness with geographic distance indicating some natal philopatry. Although there was no strong evidence that particular rookeries had lost allelic variation via drift, younger turtles had significantly lower levels of genetic variation than older turtles, suggesting some loss of genetic variation. At present there is no indication that levels of genetic variation are associated with measures of reproductive success such as clutch size, hatching success, and frequency of infertile eggs.     

Multiple mating and its effect on the reproductive success of female Epiphyas postvittana (Lepidoptera: Tortricidae)

Abstract.

• 1 Multiple mating and its effect on reproductive performance of female Epiphyas postvittana (Walker) moths were studied under controlled conditions.
• 2 The age at which the moths mated for the first time ranged from the first to the tenth day after emergence, but 71% of first matings were during the first 3 days.
• 3 The majority (63%) of females had one or two spermatophores in the bursa copulatrix. Some (24%) were found with three to five spermatophores, whereas no successful mating occurred among 13% of individuals. The number of matings was partly dependent on the number of mates available to the female. Between the range of sex ratios of one male to one female and four males to one female maximal mating success occurred at the ratio of three males to one female.
• 4 Virgin females were capable of egg-laying, but mating stimulated and accelerated oviposition. Mated individuals laid twice as many eggs as unmated ones.
• 5 The level of copulatory activity did not influence the longevity of females irrespective of the number of males available to them.
• 6 Sex ratios with greater than one male to a female improved the reproductive success by marginally increasing fecundity and fertility.
• 7 It is concluded that multiple mating would enhance population growth, and is of particular benefit to populations with a preponderance of females, as is known to occur naturally in this species.

     

Male Dominance Rank,Female Mate Choice and Male Mating and Reproductive Success in Captive Chimpanzees

Mating and consequently reproductive success in male vertebrates are predominantly determined by intermale competition and female mate choice. Their relative importance however, is still poorly understood. We investigated the interrelationship between male dominance rank — a formal indicator of male competitive ability — female mate choice, and male mating success in a multimale-multifemale group of captive chimpanzees. In addition, we examined the relationship between male dominance rank and reproductive success determined by genetic paternity analysis over a 13-yr period in the same captive population. We related the frequencies of sociosexual behaviors to the female anogenital swelling stage and female fertile phase as determined by urinary and fecal progestogen analysis. Rates of behaviors in both sexes increased with increasing intensity of female swelling, but they were not influenced by the timing of the fertile phase. Male mating success was clearly related to male dominance rank, with high-ranking males performing the overwhelming majority of copulations. This was mainly due to both rank-related rates of male soliciting behavior and intermale aggressiveness during the period of well-developed female anogenital swelling. Although females solicited copulations mainly from the high-ranking males and thus expressed a mate choice based on rank, their overall contribution in initiating copulations and thus influencing male mating success was low. The data on paternity from the population, which always contained 4 adult males, revealed that -males sired the majority (65%) of offspring. We conclude, that male dominance rank is an important determinant of male mating and reproductive success in captive (and presumably wild) chimpanzees and that female mate choice is of minor importance in modulating male reproductive outcome.     

Alternative reproductive tactics and reproductive success in male Carollia perspicillata (Seba's short‐tailed bat)

The use of alternative reproductive tactics (ARTs) is widespread in animals. Males of some species may change tactics depending on age, body condition and social environment. Many bat species are polygynous where a fraction of males only have access to fertile females. For polygynous bats, knowledge of the reproductive success of males using different ARTs is scarce, and it remains unclear how age of males is related to switching decisions between social statuses. We studied a large captive population of Carollia perspicillata, where males are either harem holders, bachelors or peripheral males. Using a multistate procedure, we modelled the age‐related switches in reproductive tactics and in survival probability. From the model, we calculated the reproductive success and the frequencies of males displaying different reproductive tactics. As in mammals, the switch between social statuses is often related to age, we predicted that the transition probability of bachelor and peripheral males to harem status would increase with age. We show, however, that social status transition towards a harem holding position was not related to age. Reproductive success changed with age and social status. Harem males had a significantly higher reproductive success than bachelor males except between a short period from 3.8 to 4.4 years of age where success was similar, and a significantly higher reproductive success than peripheral males between 2.6 and 4.4 years of age. Harem males showed a clear decrease in the probability of maintaining social status with age, which suggests that senescence reduces resource holding potential.     

Gamete traits influence the variance in reproductive success, the intensity of sexual selection, and the outcome of sexual conflict among congeneric sea urchins

Sea-urchin species differ in susceptibility to sperm limitation and polyspermy, but the influences of gamete traits on reproductive variance, sexual selection, and sexual conflict are unknown. I compared male and female reproductive success of two congeners at natural densities in the sea. The eggs of the species occurring at higher densities, Strongylocentrotus purpuratus, require higher sperm concentrations for fertilization but are more resistant to polyspermy compared to S. franciscanus. Both species show high variance in male fertilization success at all densities and high variance in female success at low densities, but they differ in female variance at high densities, where only S. franciscanus shows high female variance. The intensity of sexual selection based on Bateman gradients is high in males of both species, variable in S. franciscanus females, and low in S. purpuratus females. Strongylocentrotus franciscanus females experience sexual selection at low densities and sexual conflict at high densities. Strongylocentrotus purpuratus may rarely experience sperm limitation and may have evolved to ameliorate sexual conflict. This reduces the variance in female fertilization, providing females with more control over fertilization. Sperm availability influences sexual selection directly by determining sperm-egg encounter probabilities and indirectly through selection on gamete traits that alter reproductive variances.     

Male reproductive success in plateau pikas (Ochotona curzoniae): A microsatellite analysis

In many social species, competition and cooperation between group members may lead to a large variance in reproductive success among individuals, especially for adult male. From April to August 2002, we studied the adult male reproductive success of plateau pikas in Haibei Alpine Meadow Ecosystem Research Station, Chinese Academy of Science, using microsatellite analysis of paternity, mark-recapture and behavioral observations. Our result indicated that the reproductive success of adult males had a large variance. Its average was 6 individuals and range was from 0 to 13 individuals. One-third of males sired 63.22% offspring. There was a hierarchy system in polygynandrous families. Although the reproductive success of dominant males was higher than that of subordinate males, subordinate males still play an important role in the reproductive success of the population.     

Seasonal reproductive cycle of the Galápagos tortoise (Geochelone nigra) in captivity

The reproductive physiology of nine Galápagos tortoises (Geochelone nigra) was studied from February 1988 to May 1989. The study encompassed the annual reproductive cycle to include complete mating and nesting sequences. Male (n = 4) and female (n = 5) seasonal reproductive changes were determined throughout the study with endocrine analysis and ultrasonographic examinations. Males displayed a prenuptial rise in serum testosterone (x― ±SE = 6.62 ± 0.92 ng/ml in August) during which gonadal maturation and spermatogenesis are thought to occur. The male reproductive cycle appears consistent with the prenuptial spermatogenic pattern exhibited by other tropical turtles. In the females, testosterone rose during the mating period (x― ± SE = 499.3 ± 124.6 pg/ml in October) prior to ovulation and is probably related to receptivity in the females. Progesterone was more variable, but also peaked during the mating period (x― ± SE = 1,017.2 ± 220.6 pg/ml in October) and appears related to ovulation. Estradiol rose several months prior to mating (x― ± SE = 75.5 ± 11.9 pg/ml in July) and was correlated with increased serum calcium levels. This increase in estradiol is thought to stimulate vitellogenesis several months prior to mating. Nesting occurred from November 1988 to April 1989, during which six clutches were laid. Clutch size ranged from eight to 17 eggs. Both male and female Galápagos tortoises display seasonal physiological changes that function to regulate annual reproductive patterns. Zoo Biol 17:505–517, 1998. © 1998 Wiley-Liss, Inc.     

Microsatellite determination of male reproductive success in a natural population of the territorial ornate dragon lizard, Ctenophorus ornatus

It is now evident that the genetic mating system can be very different to the observed mating system. However, it is less well known what makes particular individuals more (or less) successful than expected from the observed system. In this study the observed territorial structure of a field population of the agamid lizard, Ctenophorus ornatus, was compared with the mating system as evidenced by microsatellite parentage assignment. This study also investigated whether any male traits predicted reproductive success. Sixty-five per cent of clutches were sired at least partially by a male other than the main territory-holding male and 35% of clutches were sired by a male with no overlap of the female's territory. Multiple paternity was moderately frequent at 25% of clutches. Male chest patch size predicted territory size and the number of females in the territory, but did not predict reproductive success. Instead, male head depth and body size were independently related to the number of offspring sired. As male head depth also predicted the number of females in a territory, these males are likely to be gaining increased reproductive success as a consequence of the higher number of females in their territories. Larger body size males, however, did not have a greater number of females in their territory and instead had more extra-territorial copulations. Whether these extra-territorial copulations are due to female choice or success in male competition is unknown.     

Male reproductive competition in spawning aggregations of cod (Gadus morhua, L.)

Reproductive competition may lead to a large skew in reproductive success among individuals. Very few studies have analysed the paternity contribution of individual males in spawning aggregations of fish species with huge census population sizes. We quantified the variance in male reproductive success in spawning aggregations of cod under experimental conditions over an entire spawning season. Male reproductive success was estimated by microsatellite-based parentage analysis of offspring produced in six separate groups of spawning cod. In total, 1340 offspring and 102 spawnings distributed across a spawning season were analysed. Our results show that multiple males contributed sperm to most spawnings but that paternity frequencies were highly skewed among males, with larger males on average siring higher proportions of offspring. It was further indicated that male reproductive success was dependent on the magnitude of the size difference between a female and a male. We discuss our results in relation to the cod mating system. Finally, we suggest that the highly skewed distribution of paternity success observed in cod may be a factor contributing to the low effective population size/census population size ratios observed in many marine organisms.