scholarly journals Allee effect in polar bears: a potential consequence of polychlorinated biphenyl contamination

2016 ◽  
Vol 283 (1843) ◽  
pp. 20161883 ◽  
Author(s):  
Viola Pavlova ◽  
Jacob Nabe-Nielsen ◽  
Rune Dietz ◽  
Christian Sonne ◽  
Volker Grimm
Keyword(s):  
Reproductive Success ◽  
Population Growth ◽  
Polar Bear ◽  
Allee Effect ◽  
Polychlorinated Biphenyl ◽  
Sperm Quality ◽  
Male Competition ◽  
Male Reproductive Success ◽  
Male Mating ◽  
Polar Bears

Polar bears ( Ursus maritimus ) from East Greenland and Svalbard exhibited very high concentrations of polychlorinated biphenyls (PCBs) in the 1980s and 1990s. In Svalbard, slow population growth during that period was suspected to be linked to PCB contamination. In this case study, we explored how PCBs could have impacted polar bear population growth and/or male reproductive success in Svalbard during the mid-1990s by reducing the fertility of contaminated males. A dose–response relationship linking the effects of PCBs to male polar bear fertility was extrapolated from studies of the effects of PCBs on sperm quality in rodents. Based on this relationship, an individual-based model of bear interactions during the breeding season predicted fertilization success under alternative assumptions regarding male–male competition for females. Contamination reduced pregnancy rates by decreasing the availability of fertile males, thus triggering a mate-finding Allee effect, particularly when male–male competition for females was limited or when infertile males were able to compete with fertile males for females. Comparisons of our model predictions on age-dependent reproductive success of males with published empirical observations revealed that the low representation of 10–14-year-old males among breeding males documented in Svalbard in mid-1990s could have resulted from PCB contamination. We conclude that contamination-related male infertility may lead to a reduction in population growth via an Allee effect. The magnitude of the effect is largely dependent on the population-specific mating system. In eco-toxicological risk assessments, appropriate consideration should therefore be given to negative effects of contaminants on male fertility and male mating behaviour.

scholarly journals Male–male competition leads to less abundant but more attractive sperm

2013 ◽  
Vol 9 (6) ◽  
pp. 20130762 ◽  
Author(s):  
Z. Valentina Zizzari ◽  
Nico M. van Straalen ◽  
Jacintha Ellers
Keyword(s):  
Reproductive Success ◽  
Adaptive Response ◽  
Mating Systems ◽  
Male Competition ◽  
Male Reproductive Success ◽  
Optimization Strategy ◽  
Relative Contribution ◽  
Female Quality ◽  
Rival Male ◽  
Spermatophore Production

Males employ complex strategies to optimize their reproductive success when faced with male–male competition; for instance, they can adjust the ejaculate characteristics. In copulating species, a male may also strategically adjust his ejaculate expenditure according to female quality. Quantifying the relative contribution of ejaculate plasticity in male reproductive success is often difficult, especially when females exert postcopulatory cryptic choice. One way to quantify the functional significance of ejaculate plasticity is offered by mating systems in which the reproductive partners do not meet each other during insemination. In the collembolan Orchesella cincta , males deposit their ejaculates (spermatophores) irrespective of the presence of females. We tested whether Orchesella males adjust spermatophore number when exposed to the presence of another male and whether changes in spermatophore production influence female choice. We found that Orchesella males display plasticity in spermatophore allocation. Males decreased the spermatophore number when exposed to a rival male. Moreover, females preferentially took up spermatophores of males that were exposed to a competitor. The reduction in spermatophore number suggests, besides an adaptive response to the risk of ejaculate removal by rival males, an optimization strategy owing to the costs of more attractive spermatophores.

The Relationships Among Population Density, Individual Size, Mating Tactics, and Reproductive Success in a Hermaphroditic Fish, Serranus Fasciatus

Behaviour ◽  
1990 ◽  
Vol 113 (1-2) ◽  
pp. 57-80 ◽  
Author(s):  
Christopher W. Petersen
Keyword(s):  
Reproductive Success ◽  
Social Group ◽  
Local Density ◽  
Social Systems ◽  
Male Reproductive Success ◽  
Male Mating ◽  
Mating Tactics ◽  
Intermediate Group ◽  
Female Function ◽  
Mating Opportunities

AbstractThe hermaphroditic reef fish Serranus fasciatus exhibits three types of social systems. The size of a social group is correlated with the local density of conspecifics. At very low densities, isolated pairs of individuals reciprocally spawn with each other, achieving equal current reproductive success. At intermediate group sizes, harems form, with the largest individual typically losing all of its female function and becoming a functional male. In harems, subordinate hermaphrodites obtain little male reproductive success through streaking, an alternative male mating tactic. The lone pure male maintains almost total monopolization of male reproductive success in harems, apparently due to aggressive domination of subordinates. At high group sizes, the ability of the male to monopolize all of the matings in a social group decreases, and some of the larger hermaphrodites obtain some male-role reproductive success by pair spawning with smaller subordinate hermaphrodites while continuing to spawn as females with the male. Mating partners stay relatively constant through time, resulting in a pattern of small 'sub-harems' within harems. These mating tactics are consistent with the hypothesis that dominant individuals increase their current reproductive success in this species by restricting male mating opportunities of conspecifics. Subordinate individuals spawn as males when the dominant is unable to restrict interactions between hermaphrodites that are potential mates, or when they successfully streak. The increased male reproductive success of hermaphrodites in isolated pairs and complex harems compared with hermaphrodites in harems appears to be important in maintaining a hermaphroditic subordinate phenotype in this largely non-reciprocating species.

scholarly journals A Comparative Study of Mating Strategies in Two Species of Philanthus (Hymenoptera: Sphecidae)

1980 ◽  
Vol 4 ◽  
pp. 48-52
Author(s):  
Howard Evans ◽  
Kevin O'Neill
Keyword(s):  
Reproductive Success ◽  
Activity Patterns ◽  
Important Variable ◽  
Mating Strategies ◽  
Male Reproductive Success ◽  
Male Mating ◽  
Male Mating Strategies ◽  
Jackson Hole ◽  
Male Activity

Our work on the reproductive biology of Philanthus pulcher and P. zebratus in Jackson Hole in 1980 was a continuation of a study which had three major objectives. The first was to determine the relationship between female and male activity patterns. As in other species with extensive female-contributed and no male-contributed parental investment, females are a resource necessary for reproductive success of males. Thus, the activity of females in time and space should be an important parameter affecting the evolution of male mating strategies. Our work in this area is being combined with data we have gathered elsewhere on other species of Philanthus (O'Neill and Evans, unpublished). The second objective was to determine what characteristic of males was important in determining reproductive success and the form of the mating strategy. Since our preliminary data on Philanthus indicated that body size may be the most important variable affecting male reproductive success, we concentrated on this aspect of male biology. This report will focus on our results in this area. The third objective was to determine the role of male-produced sex pheromones in the mating system. (* Erratum: pp. 56 and 57 should be 51 and 52 )

scholarly journals Sperm Numbers as a Paternity Guard in a Wild Bird

Cells ◽  
2022 ◽  
Vol 11 (2) ◽  
pp. 231
Author(s):  
Melissah Rowe ◽  
Annabel van Oort ◽  
Lyanne Brouwer ◽  
Jan T. Lifjeld ◽  
Michael S. Webster ◽  
...  
Keyword(s):  
Reproductive Success ◽  
Sperm Competition ◽  
Ecological Factors ◽  
Fertilization Success ◽  
Male Reproductive Success ◽  
Male Mating ◽  
Sexually Selected Traits ◽  
Paternity Success ◽  
Mating Conditions ◽  
Sperm Traits

Sperm competition is thought to impose strong selection on males to produce competitive ejaculates to outcompete rival males under competitive mating conditions. Our understanding of how different sperm traits influence fertilization success, however, remains limited, especially in wild populations. Recent literature highlights the importance of incorporating multiple ejaculate traits and pre-copulatory sexually selected traits in analyses aimed at understanding how selection acts on sperm traits. However, variation in a male’s ability to gain fertilization success may also depend upon a range of social and ecological factors that determine the opportunity for mating events both within and outside of the social pair-bond. Here, we test for an effect of sperm quantity and sperm size on male reproductive success in the red-back fairy-wren (Malurus melanocephalus) while simultaneously accounting for pre-copulatory sexual selection and potential socio-ecological correlates of male mating success. We found that sperm number (i.e., cloacal protuberance volume), but not sperm morphology, was associated with reproductive success in male red-backed fairy-wrens. Most notably, males with large numbers of sperm available for copulation achieved greater within-pair paternity success. Our results suggest that males use large sperm numbers as a defensive strategy to guard within-pair paternity success in a system where there is a high risk of sperm competition and female control of copulation. Finally, our work highlights the importance of accounting for socio-ecological factors that may influence male mating opportunities when examining the role of sperm traits in determining male reproductive success.

scholarly journals Variance in lifetime reproductive success of male polar bears

2020 ◽  
Vol 31 (5) ◽  
pp. 1224-1232 ◽  
Author(s):  
Evan S Richardson ◽  
Corey Davis ◽  
Ian Stirling ◽  
Andrew E Derocher ◽  
Nicholas J Lunn ◽  
...  
Keyword(s):  
Reproductive Success ◽  
Polar Bear ◽  
Mating Systems ◽  
Male Reproduction ◽  
Lifetime Reproductive Success ◽  
Male Mating ◽  
Sexually Dimorphic ◽  
Size Dimorphism ◽  
Opportunity For Selection ◽  
Solitary Species

Abstract Despite the important role that population density plays in ecological and evolutionary processes, studies of solitary species that occur at low densities remain scarce. In the context of mating systems, density is expected to influence the ability of males to find and monopolize mates, in turn, influencing variance in lifetime mating/reproductive success and the opportunity for selection. Herein, we investigate variance in male lifetime mating success (LMS), lifetime reproductive success (LRS), and the mating system of a sexually dimorphic carnivore that occurs at low densities, the polar bear (Ursus maritimus). Across 17 cohorts, born from 1975 to 1991, male LMS ranged from 0 to10 mates and LRS from 0 to 14 cubs; 40% of known-age males were not known to have reproduced. The opportunity for sexual selection (Is = 1.66, range = 0.60–4.99) and selection (I = 1.76, range: 0.65–4.89) were low compared to species with similar levels of sexual size dimorphism. Skew in male LRS was also low but significant for most cohorts indicating nonrandom reproductive success. Age-specific reproductive success was biased toward males from 11 to 17 years of age, with variation in fecundity (54%) but not longevity (10%) playing an important role in male reproduction. Our results support a growing body of evidence that suggests that male-biased size dimorphism and polygynous mating systems need not be associated with high variance in male mating and/or reproductive success.

Sexual Selection in Dung Beetles .2. Female Fecundity as an Estimate of Male Reproductive Success in Relation to Horn Size, and Alternative Behavioral Strategies in Onthophagus-Binodis Thunberg (Scarabaeidae, Onthophagini)

1988 ◽  
Vol 36 (5) ◽  
pp. 521 ◽  
Author(s):  
D Cook
Keyword(s):  
Body Size ◽  
Reproductive Success ◽  
Mate Guarding ◽  
Mating Strategies ◽  
Male Reproductive Success ◽  
Male Mating ◽  
Behavioral Strategies ◽  
Alternative Tactics ◽  
Female Fecundity ◽  
Similar Body

One component of the reproductive success (fitness) of Onthophagus binodis Thunberg males was estimated by the number of offspring their mate produced relative to male horn and body size. O. binodis males consist of large horned and small hornless morphs. Female fecundity was significantly increased when reproducing with: (1) large horned males compared with small hornless males; (2) the horned morph compared with the hornless morph of males with similar body size. Horned males cooperating with females invest a considerable effort in providing each egg with dung. Hornless males do not appear to assist females after mating. Alternative male mating strategies are predicted under intense intrasexual competition. As hornless O. binodis males persist in large numbers alongside cooperative, mate guarding horned males, selection should favour alternative tactics by hornless males to gain reproductive opportunities.

Male lake sturgeon (Acipenser fulvescens) migratory and spawning behaviors are associated with sperm quality and reproductive success

2020 ◽  
Vol 77 (12) ◽  
pp. 1943-1959
Author(s):  
Douglas L. Larson ◽  
Jacob G. Kimmel ◽  
Joseph J. Riedy ◽  
Jonathan Hegna ◽  
Edward A. Baker ◽  
...  
Keyword(s):  
Reproductive Success ◽  
Reproductive Effort ◽  
Sperm Quality ◽  
Lake Sturgeon ◽  
Operational Sex Ratio ◽  
Computer Assisted ◽  
Acipenser Fulvescens ◽  
Male Reproductive Success ◽  
Upstream Migration ◽  
Sperm Depletion

Intra-annual reproductive investments may not be predictive of male reproductive success because of the effects of intra- and intersexual interactions on sperm depletion. For long-lived iteroparous fish species such as lake sturgeon (Acipenser fulvescens), reproductive effort may affect lifetime reproductive success. Radio frequency identification antennas were placed at the mouth of the Upper Black River, Michigan, and downstream of spawning locations to quantify male migratory and mating behaviors, including upstream migration time (UT), river residence time (RT), number of intra-annual spawning migrations (IM), interannual spawning interval, and operational sex ratio during 2017–2018. Computer assisted sperm analysis was used to quantify sperm quality. RT had a strong negative influence on sperm concentration and with measures of sperm quality. RT and the number of females encountered were positively associated with male reproductive success (number of offspring sired) across years. RT, IM, and UT were negatively associated with sperm quality, indicating sperm depletion is a reliable measure of sexual activity. Results demonstrate trade-offs between benefits and costs associated with current reproductive effort on future reproduction.

047. SPERM COMPETITION, INBREEDING AND THE EVOLUTION OF SUPERIOR EJACULATES

2009 ◽  
Vol 21 (9) ◽  
pp. 12 ◽  
Author(s):  
J. Fitzpatrick
Keyword(s):  
Reproductive Success ◽  
Sperm Competition ◽  
Sperm Morphology ◽  
Sperm Quality ◽  
Male Reproductive Success ◽  
High Quality ◽  
Genetic Quality ◽  
Viable Sperm ◽  
And Performance ◽  
Reproductive Consequences

The production of viable sperm is essential for male reproductive success. However, because females in many species mate with several males during a single reproductive episode, leading to sperm competition, a male's reproductive success also depends critically on the ability of his sperm to compete efficiently with those from rival males for fertilizations. Therefore, males who regularly encounter sperm competition are expected to produce high quality ejaculates. Here, I will provide an overview of how sperm morphology and performance are influenced by sperm competition, both within and between species, using recent empirical examples. Having established the importance of producing high quality ejaculates in males experiencing sperm competition, I will then examine the reproductive consequences of producing sub-optimal sperm. Given the well known role that inbreeding plays in reducing genetic quality and reproductive success, I will focus in particular on how inbreeding acts to reduce sperm quality. Finally, I will examine the consequences of inbreeding for male reproductive success in species where sperm competition is rampant. Together, these results highlight the evolutionary importance of sperm competition and inbreeding in shaping ejaculate traits.

The steroid pheromone 4-pregnen-17,20ss-diol-3-one increases fertility and paternity in goldfish.

1997 ◽  
Vol 200 (22) ◽  
pp. 2833-2840
Author(s):  
W Zheng ◽  
C Strobeck ◽  
N Stacey
Keyword(s):  
Reproductive Success ◽  
Seminal Fluid ◽  
Sperm Quality ◽  
Paternity Analysis ◽  
Male Reproductive Success ◽  
Spawning Activity ◽  
Control Male ◽  
Goldfish Carassius Auratus ◽  
Serum Gonadotropin

Previous studies in goldfish (Carassius auratus) showed that the oocyte maturation-inducing steroid 4-pregnen-17,20ss-diol-3-one (17,20ssP) functions after release as a pheromone that increases male serum gonadotropin II (GtH II) concentration, milt (sperm and seminal fluid) volume and sexual activity, effects hypothesized to increase male reproductive success in the sperm competition of multi-male spawnings. The present study tested this hypothesis by determining whether overnight exposure to 17,20ssP increases fertility. In pair spawnings, 17,20ssP-exposed males fertilized a greater percentage of eggs than did control males, apparently because 17,20ssP-exposed males had more releasable sperm at the onset of spawning. Microsatellite DNA paternity analysis showed that 17,20ssP-exposed males also fertilized more eggs in competitive spawnings involving one control male and one 17,20ssP-exposed male. This effect of 17,20ssP on competitive fertility could be due to demonstrated increases in spawning activity, milt volume, duration of sperm motility and proportion of motile sperm. However, it appears that a change in sperm quality is a major component of the pheromonal effect because, in competitive in vitro fertilizations, sperm from 17,20ssP-exposed males fertilized more eggs than did sperm from control males. The results indicate that the response to pheromonal 17,20ssP is a major determinant of reproductive success in male goldfish.

scholarly journals Dynamic resource allocation between pre- and postcopulatory episodes of sexual selection determines competitive fertilization success

2015 ◽  
Vol 282 (1817) ◽  
pp. 20151279 ◽  
Author(s):  
Marion Mehlis ◽  
Ingolf P. Rick ◽  
Theo C. M. Bakker
Keyword(s):  
Reproductive Success ◽  
Gasterosteus Aculeatus ◽  
Sperm Quality ◽  
Fertilization Success ◽  
Carotenoid Content ◽  
Male Reproductive Success ◽  
Reduced Body ◽  
Food Quantity ◽  
Sexual Ornamentation ◽  
Breeding Coloration

In polyandrous mating systems, male reproductive success depends on both mate-acquisition traits (precopulatory) and sperm competitive abilities (postcopulatory). Empirical data on the interaction between these traits are inconsistent; revealing positive, negative or no relationships. It is generally expected that the investment in pre- and postcopulatory traits is mediated by environmental conditions. To test how dietary resource availability affects sexual ornamentation, sperm quality and their interrelationship in three-spined sticklebacks ( Gasterosteus aculeatus ), full-sibling groups were raised under three conditions differing in food quantity and/or quality (i.e. carotenoid content): (i) high-quantity/high-quality, (ii) high-quantity/low-quality or (iii) low-quantity/low-quality. After 1 year of feeding, food-restricted males developed a more intense breeding coloration and faster sperm compared with their well-fed brothers, indicating that they allocated relatively more in pre- and postcopulatory traits. Moreover, they outcompeted their well-fed, carotenoid-supplemented brothers in sperm competition trials with equal numbers of competing sperm, suggesting that food-restricted males maximize their present reproductive success. This may result in reduced future reproductive opportunities as food-restricted males suffered from a higher mortality, had an overall reduced body size, and sperm number available for fertilization. In accordance with theory, a trade-off between the investment in pre- and postcopulatory traits was observed in food-restricted males, whereas well-fed males were able to allocate to both traits resulting in a significantly positive relationship.

Sign in / Sign up

Export Citation Format

Share Document