Factors influencing paternity success in Antechinus agilis: last‐male sperm precedence,timing of mating and genetic compatibility

We describe the patterns of paternity success from laboratory mating experiments conducted in Antechinus agilis, a small size dimorphic carnivorous marsupial (males are larger than females). A previous study found last‐male sperm precedence in this species, but they were unable to sample complete litters, and did not take male size and relatedness into account. We tested whether last‐male sperm precedence regardless of male size still holds for complete litters. We explored the relationship between male mating order, male size, timing of mating and relatedness on paternity success. Females were mated with two males of different size with either the large or the small male first, with 1 day rest between the matings. Matings continued for 6 h. In these controlled conditions male size did not have a strong effect on paternity success, but mating order did. Males mating second sired 69.5% of the offspring. Within first mated males, males that mated closer to ovulation sired more offspring. To a lesser degree, variation appeared also to be caused by differences in genetic compatibility of the female and the male, where high levels of allele‐sharing resulted in lower paternity success.     

High frequency of multiple paternity in the largest rookery of Mediterranean loggerhead sea turtles

Mating systems are a central component in the evolution of animal life histories and in conservation genetics. The patterns of male reproductive skew and of paternal shares in batches of offspring, for example, affect genetic effective population size. A prominent characteristic of mating systems of sea turtles seem to be a considerable intra- and interspecific variability in the degree of polyandry. Because of the difficulty of observing the mating behaviour of sea turtles directly in the open sea, genetic paternity analysis is particularly useful for gaining insights into this aspect of their reproductive behaviour. We investigated patterns of multiple paternity in clutches of loggerhead sea turtles in the largest Mediterranean rookery using four highly variable microsatellite loci. Furthermore, we tested for a relationship between the number of fathers detected in clutches and body size of females. More than one father was detected in the clutches of 14 out of 15 females, with two clutches revealing the contribution of at least five males. In more than half the cases, the contributions of different fathers to a clutch did not depart from equality. The number of detected fathers significantly increased with increasing female body size. This relationship indicates that males may prefer to mate with large, and therefore productive, females. Our results suggest that polyandry is likely to increase effective population size compared to a population in which females would mate with only one male; male reproductive contributions being equal.     

Noninvasive paternity assignment in Gombe chimpanzees

The relative success of chimpanzee male mating strategies, the role of male dominance rank and the success of inbreeding avoidance behaviour can only be assessed when paternities are known. We report the probable paternities of 14 chimpanzees included in a long‐term behavioural study of chimpanzees (Pan troglodytes schweinfurthii) at Gombe National Park, Tanzania. DNA samples were collected noninvasively from shed hair and faeces and genotyped using 13–16 microsatellite loci characterized in humans. All 14 offspring could be assigned to fathers within the community. While there is a positive relationship between male rank and reproductive success, we demonstrate that a range of male mating strategies (possessiveness, opportunistic mating and consortships) can lead to paternity across all male ranks. Several adult females were at risk of breeding with close male relatives. Most successfully avoided close inbreeding but in one case a high‐ranking male in the community mated with his mother and produced an offspring. In contrast to recent data on chimpanzees (P. t. verus) from the Taï forest, Côte d’Ivoire, no evidence of extra‐group paternity was observed in our study. Reanalysis of Taï data using a likelihood approach casts doubt on the occurrence of extra‐group paternity in that community as well.     

Genetic analysis of the mating system and opportunity for sexual selection in northern water snakes (Nerodia sipedon)

We used data collected over 3 years at two study sites to quantifythe rates and consequences of multiple paternity and to determinethe opportunity for selection on male and female northern watersnakes (Nerodia sipedon). We sampled litters from 45 femalesthat gave birth to 811 offspring. Using eight microsatelliteDNA loci (probability of exclusion of nonparental males >0.99), we assigned paternity to 93% of neonates from one studypopulation and 69% of neonates from the other population. Observationsof participation in mating aggregations predicted individual reproductive success poorly for two reasons. First, males regularlycourted nonreproductive females. Second, more than half ofall sexually mature males obtained no reproductive successeach year, despite the fact that many of them participatedin mating aggregations. The number of sires per litter ranged from one to five, with 58% of all litters sired by more thanone male. Multiple paternity increased with female size, apparentlyboth because bigger females mated with more males and becausethe larger litters of big females provide paternity opportunitiesto more males. Multiple paternity was also more prevalent inyears with shorter mating seasons. We detected no advantage to multiple paternity in reducing either the number of unfertilizedovules or stillborn young. Despite the majority of males siringno young each year, some males fathered young with as manyas three different females in one year. Male reproductive successincreased by more than 10 offspring for each additional mate,whereas female success increased by fewer than 2 offspring foreach additional mate. The opportunity for sexual selectionwas more than five times higher in males than females.     

Multiple paternity occurs with low frequency in the territorial roe deer, Capreolus capreolus

An explanation for female multiple mating when males offer no material benefits but sperm remains elusive, largely because of a lack of empirical support for the genetic benefits hypothesis. We used 21 microsatellite markers to test for multiple paternities among 88 litters of roe deer, Capreolus capreolus , and to investigate the inbreeding avoidance hypothesis as a potential mechanism for the evolution of female multiple mating. From paternity analyses, we found that 13.5% of polytocous litters were sired by more than one male. We also found that a half-sib relationship was more likely than a full-sib relationship for 20.5% of all litters. This is the first report of multiple paternities in a territorial ungulate species. In support of the inbreeding avoidance hypothesis, we found that parents who were strongly related produced offspring with lower individual heterozygosity that survived less well during their first summer than fawns with unrelated parents. In addition, fawns from multiple paternity litters survived their first summer better than fawns from single paternity litters. However, it remains unclear whether all female multiple paternity events in this species are provoked by an initial consanguineous mating.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society 2009, 97 , 128–139.     

Hierarchical polygyny in multiparous lesser flat-headed bats

How males gain access to mates and the potential for female choice will determine whether polygyny can operate at several levels, from within litters and groups to the wider population. Female lesser flat-headed bats (Tylonycteris pachypus) form maternity groups in bamboo stems. Unusually for bats, they are multiparous, providing the opportunity to test whether multi-level polygyny differs among males depending on whether they roost with females, with males or are solitary. We genotyped 662 individuals from 54 internodes and analysed parentage of 165 litters. Our results revealed 170 sets of paternal twins/triplets, of which 96 were full-sibs and 74 were half-sibs. We found that males captured roosting with females typically sired more offspring overall than did other males and also showed a greater tendency to monopolize paternity within both litters and roosting groups. In comparison, males that sired fewer full-sibs were assigned more maternal half-sibs. These latter individuals, which included solitary males and those from all-male groups, might gain copulations either via roaming with furtive mating or during visits by females. Indeed, female lesser flat-headed bats store sperm, so could benefit from multiple mating to reduce genetic incompatibilities. At the same time, however, we found no evidence of outbreeding. Finally, relatedness and mtDNA analyses revealed that polygyny also operated within matrilineal kin, suggesting a system that might promote social cohesiveness. Future studies of individual movements will help to determine the extent to which mixed paternities in litters, matrilines and groups are driven by male or female behaviour.     

Predominance of single paternity in the black spiny-tailed iguana: conservation genetic concerns for female-biased hunting

Because of female-biased illegal harvesting, knowledge about the genetic mating system of the black spiny-tailed iguana Ctenosaura pectinata is of primary interest for the conservation of this threatened species. Based on the high levels of multiple paternity found in clutches of many other reptiles, particularly in lizards, it is hypothesised that multiple paternity may also be common in black iguanas. This was investigated by using microsatellite DNA to estimate the number of males siring nine litters (9 mothers, 121 offspring genotyped at ten polymorphic loci) of black iguanas. Contrary to expectations, only 11% of sampled black iguana females produced litters consistent with being sired by multiple males. These data are the first evidence for the predominance of single paternity within an iguanid lizard, and suggest that black iguana may be more susceptible to loss of genetic variation in the face of gender-biased over-hunting pressure than previously thought.     

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.     

保加利亚北部地区匈牙利小家鼠的空间组织结构

本文研究了保加利亚北部地区的匈牙利小家鼠在繁殖期的空间关系和分布。这种动物最普遍的空间关系是一雄一雌,也观察到两个或三个雄鼠与一个雌鼠、一个雄鼠与两个或三个雌鼠的组织形式。很少观察到雌性的社群小组。雌鼠之间的巢区没有发现重叠。一般雄鼠的巢区大于雌鼠。有一半雄鼠的巢区与一个雌鼠的巢区相重叠,其他的雄鼠与两个成年雌鼠的巢区相重叠。这些结果表明,匈牙利小家鼠具有多变的社群繁殖婚配体制,即单配制和多配制共存。比较普遍的一雄一雌的配对形式和雌性的独居特性,以及雌性之间巢区的相对独立性,表明单配制是该物种的主要婚配体制。     

Conflict over multiple-partner mating between males and females of the polygynandrous common lizards

The optimal number of mate partners for females rarely coincides with that for males, leading to a potential sexual conflict over multiple-partner mating. This suggests that the population sex ratio may affect multiple-partner mating and thus multiple paternity. We investigate the relationship between multiple paternity and the population sex ratio in the polygynandrous common lizard (Lacerta vivipara). In six populations the adult sex ratio was biased toward males, and in another six populations the adult sex ratio was biased toward females, the latter corresponding to the average adult sex ratio encountered in natural populations. In males the frequency and the degree of polygyny were lower in male-biased populations, as expected if competition among males determines polygyny. In females the frequency of polyandry was not different between treatments, and polyandrous females produced larger clutches, suggesting that polyandry might be adaptive. However, in male-biased populations females suffered from reduced reproductive success compared to female-biased populations, and the number of mate partners increased with female body size in polyandrous females. Polyandrous females of male-biased populations showed disproportionately more mating scars, indicating that polyandrous females of male-biased populations had more interactions with males and suggesting that the degree of multiple paternity is controlled by male sexual harassment. Our results thus imply that polyandry may be hierarchically controlled, with females controlling when to mate with multiple partners and male sexual harassment being a proximate determinant of the degree of multiple paternity. The results are also consistent with a sexual conflict in which male behaviors are harmful to females.     

Spacing pattern in a social group of stray cats: effects on male reproductive success

Reproductive consequences of male spacing patterns have received relatively little attention in nonterritorial mammals, in particular in group-living species, where most studies have focused on the relation between social rank and reproductive success. We investigated the effects of spacing pattern on male reproductive success within a social, nonterritorial, promiscuous population of stray cats, Felis catus. Male home ranges overlapped home ranges of many females, consistent with a promiscuous mating system. Furthermore, males with the largest home ranges included the most female home ranges; they successfully reproduced with these females and had the highest reproductive success. Home range size predicted male reproductive success even when controlling for the effect of social rank. However, males also reproduced with females whose home range did not overlap their home range, suggesting that males can make quick excursions outside their home range to find new mating opportunities. We conclude that, in group-living situations, a male's ability to maintain a large home range may be one of the principal causes of variation in mating success in the stray cat.     

Male reproductive success and sexual selection in northern water snakes determined by microsatellite DNA analysis

Male northern water snakes (Nerodia sipedon) have high variancein reproductive success relative to females. We used DNA-basedpaternity analyses from a 3-year study of two marsh populationsof water snakes to investigate the factors that contributeto variation in male success. Male traits investigated includedbody size, condition, tail length, home range size, activityduring the mating season, and genetic profile (genetic similarityto females, heterozygosity, and genetic variability [d²]).We successfully assigned > 80% of offspring to sires froma sample of 811 offspring from 45 litters. Male reproductivesuccess did not vary significantly with body size, tail length,condition, home range size, or the number of microsatelliteloci at which males were heterozygous, nor with other featuresof their genetic profiles. However, we found evidence of positive assortative mating by size in the marsh in which receptive femaleswere not spatially clumped. Also, males that were most activeduring the mating season were more successful, particularlywhere females were not clumped. We failed to find evidenceof selection acting on male size through variance in reproductivesuccess, indicating that sexual selection does not have an important influence on sexual size dimorphism in this species(males are smaller than females). We propose that males aresmaller than females because the lack of advantage to largesize allows males to adopt a low-energy, low-growth strategythat reduces their risk of predation outside the mating season.     

Paternity success and the direction of sexual selection in a field population of a semelparous marsupial,Antechinus agilis

Antechinus agilis is a small sexually size dimorphic marsupial with a brief annual mating period of 2-3 weeks. All males die after this period, and females give birth to up to 10 young. Mating is thought to be promiscuous, however, there is no field data to confirm this. Using microsatellites, we investigated paternity patterns over two seasons in a wild population. Male weight was significantly positively related to the number of females fertilized and with the number of offspring sired, in both years. Furthermore, selection gradients indicated selection for larger males. Both results suggest that size dimorphism in A. agilis can be explained by sexual selection for larger males. The proportion of offspring sired within litters, did not relate to male size. Therefore, larger males are more successful through higher mating access, not through their sperm outcompeting that of smaller males. As expected from their known ranging behaviour, the number of offspring within litters left unassigned to a father did not depend on the grid location of the mother. Female size did not differ between successful reproducing and unsuccessful females. However, females that weaned offspring had larger heads than females that did not wean offspring. Males did not 'prefer' mating with larger females, nor did assortative mating occur. From our results, the mating system of A. agilis is clearly promiscuous. Selection for larger males occurred in both years, even though in one year the operational sex ratio was highly female biased, suggesting that the potential reproductive rate is a better predictor of the direction of sexual selection in A. agilis.     

Space use in the root vole: basic patterns and variability

Home range characteristics and spatial organization of the root vole Microtus oeconomus were assessed by radio-tracking The aim of this paper is to test the assumption that each microtine species employs a certain modal spatial system around which there is considerable flexibility In the studied population the basic modes of spatial organization were female territoriality and male use of overlapping home ranges Female territories were significantly smaller and less diversified in size than male ranges The size of male home ranges was positively correlated with body mass Each female territory was overlapped by several male ranges, larger male ranges usually overlapped more female territories The above spatial organization suggests that the prevailing mating system in the root vole is promiscuity, and larger males have an access to more receptive females than have small-sized males
Departures from these basic modes were found among young mature females from summer cohort, forming clusters even at low density, and occasionally among females in locally crowded habitat patches, where they held overlapping home ranges A single male usually monopolized such a cluster, excluding other males from the area used by the females     

Restrictive mating by females on black grouse leks

In bird species with pair bonds, extra-pair matings could allow females to choose genetically superior males. This is not needed in lekking species because female choice is not constrained by pairing opportunities. However, polyandry has been reported in most lekking species studied so far. Using 12 microsatellite loci, we determined the paternity of 135 broods of black grouse sampled between 2001 and 2005 (970 hatchlings and 811 adult birds genotyped). The paternity assignments were combined to lek observations to investigate the mating behaviour of black grouse females. About 10% of the matings seemed to take place with males displaying solitarily. Forty per cent of the copulations between males displaying on the studied leks and radio-tagged females were not recorded. This was due to difficulties in identifying the females and because our observations did not cover all the possible time for matings. However, females of the undetected copulations had chosen males that were already known to be successful on the leks. There was a strong consistency between the observations and true paternity, even when the copulation was disturbed by a neighbouring male. Multiple mating and multiple paternities were rare. We can now confidently ascertain that most females mate only once with one male for the whole clutch. This mating behaviour requires that a single insemination is sufficient to fertilize a clutch and that females can determine whether the sperm has been successfully transferred. Grouse Tetraoninae with many lekking species may be the only bird taxon that has evolved these traits.     

Polyandry and multiple paternities in the threatened Agassiz’s desert tortoise, <Emphasis Type="Italic">Gopherus agassizii</Emphasis>

We used data from 17 to 20 microsatellite markers to investigate the incidence of multiple paternities in wild Agassiz’s desert tortoises, Gopherus agassizii. Neonates were sampled from clutches of eggs laid by wild mothers in nesting enclosures at Edwards Air Force Base and at the Marine Corps Air Ground Combat Center, California. We genotyped 28 clutches from 26 females sampling an average of six neonates per clutch. The number of paternal alleles was used to determine the minimum number of sires for each clutch. Based on conservative criteria requiring evidence from at least two loci to determine multiple paternity, a minimum of 64% of females were polyandrous, while a minimum of 57% of clutches were sired by multiple males. This formed one of the highest incidences of multiple paternities recorded to date in any species of tortoise. The high number of microsatellite loci involved in the analyses allowed detection of multiple paternities in clutches where this may have been missed if fewer loci were used. Our results highlighted the potential pitfalls of quantitatively comparing paternity studies based on differing sampling strategies. Finally, we summarized the conservation implications of the high rate of multiple paternities in this threatened species.     

Size and overlap of home range inCalomys musculinus (Muridae: Sigmodontinae)

Home range size and overlap ofCalomys musculinus (Thomas, 1913) was examined in relation to sex and breeding periods. The study was carried out in four 0.25 ha enclosures, in a natural pasture, between October 2002 and July 2003. The four enclosures functioned as independent populations and each was considered a replicate. The capture, mark and recapture method was used. Home range size and overlap inC. musculinus depended on sex and period. Home range size of males was always larger than that of females. Females showed a small degree of intra-sexual home range overlap during the breeding period. In general, male home ranges overlapped with females. We conclude that differences in home range size inC. musculinus is determined by sex and breeding period. Moreover, the degree of inter- and intra-sexual home range overlap during the breeding period suggests that both males and females ofC. musculinus use space differently. Females did not share their home range with other females, while males fully shared it with both sexes, and male spacing is influenced by the distribution of females. A promiscuous-polygynous mating system is suggested forC. musculinus.     

In hot pursuit: fluctuating mating system and sexual selection in sand lizards

A changing climate is expected to have profound effects on many aspects of ectotherm biology. We report on a decade-long study of free-ranging sand lizards (Lacerta agilis), exposed to an increasing mean mating season temperature and with known operational sex ratios. We assessed year-to-year variation in sexual selection on body size and postcopulatory sperm competition and cryptic female choice. Higher temperature was not linked to strength of sexual selection on body mass, but operational sex ratio (more males) did increase the strength of sexual selection on body size. Elevated temperature increased mating rate and number of sires per clutch with positive effects on offspring fitness. In years when the "quality" of a female's partners was more variable (in standard errors of a male sexual ornament), clutches showed less multiple paternity. This agrees with prior laboratory trials in which females exercised stronger cryptic female choice when male quality varied more. An increased number of sires contributing to within-clutch paternity decreased the risk of having malformed offspring. Ultimately, such variation may contribute to highly dynamic and shifting selection mosaics in the wild, with potential implications for the evolutionary ecology of mating systems and population responses to rapidly changing environmental conditions.     

Female American mink, Mustela vison, mate multiply in a free-choice environment

Like most solitary carnivores, the home ranges of male American mink overlap with those of several females, but each female typically shares its range with only a single male. Nevertheless, female mink produce multiply sired litters. Unusually among mammals, the physiological characteristics of female American mink make them highly suited to multiple paternity, suggesting that polyandry in the species may result from female behaviour rather than from coercion by males. In a free-choice experiment on captive-bred animals, all female mink mated multiply, with seven of the eight mating with all three available partners. Since females sometimes resisted copulations, multiple mating in this species may result from their behaviour rather than male coercion. Females visited males nonrandomly, but visiting patterns did not predict mating patterns, suggesting disparate social and mating preferences. There was no evidence for precopulatory female choice, since the allocation of copulations among available males did not deviate significantly from the expected distribution. Females mated multiply only around the predicted times of ovulation, contrary to the expectation that they should be more selective at times of peak fertility. Larger males copulated for longer in total: copulation duration is probably under male control, suggesting that larger males could influence mating duration, perhaps increasing their share of paternity by greater sperm transfer. Our observations suggest that in wild populations, mating patterns could be influenced by female preference for multiple partners.