Variation in reproductive success of male and female Columbian ground squirrels (Urocitellus columbianus)

2012 ◽  
Vol 90 (6) ◽  
pp. 736-743 ◽  
Author(s):  
Philip H. Jones ◽  
Jeffrey L. Van Zant ◽  
F. Stephen Dobson
Keyword(s):  
Reproductive Success ◽  
Mating System ◽  
Multiple Paternity ◽  
Ground Squirrels ◽  
Male Reproductive Success ◽  
Offspring Production ◽  
Bateman Gradient ◽  
Coefficients Of Variation ◽  
Males And Females ◽  
Columbian Ground Squirrels

The imbalanced reproductive success of polygynous mammals results in sexual selection on male traits like body size. Males and females might have more balanced reproductive success under polygynandry, where both sexes mate multiply. Using 4 years of microsatellite DNA analyses of paternity and known maternity, we investigated variation in reproductive success of Columbian ground squirrels, Urocitellus columbianus (Ord, 1815); a species with multiple mating by both sexes and multiple paternity of litters. We asked whether male reproductive success was more variable than that of females under this mating system. The overall percentage of confirmed paternity was 61.4% of 339 offspring. The mean rate of multiple paternity in litters with known fathers was 72.4% (n = 29 litters). Estimated mean reproductive success of males (10.27 offspring) was about thrice that of females (3.11 offspring). Even after this difference was taken into account statistically, males were about three times as variable in reproductive success as females (coefficients of variation = 77.84% and 26.74%, respectively). The Bateman gradient (regression slope of offspring production on number of successful mates) was significantly greater for males (βM = 1.44) than females (βF = 0.28). Thus, under a polygynandrous mating system, males exhibited greater variation in reproductive success than females.

POLYGYNY, REPRODUCTIVE SUCCESS AND CHILD HEALTH IN RURAL ETHIOPIA: WHY MARRY A MARRIED MAN?

2006 ◽  
Vol 39 (2) ◽  
pp. 287-300 ◽  
Author(s):  
MHAIRI A. GIBSON ◽  
RUTH MACE
Keyword(s):  
Reproductive Success ◽  
Male Reproductive Success ◽  
Family Status ◽  
Rural Ethiopia ◽  
Younger Age ◽  
Married Individuals ◽  
Males And Females ◽  
Child Nutritional Status ◽  
And Child Health ◽  
Better Than

Summary.This study examines the reproductive success of men and women in rural Ethiopia as a function of their marital status, specifically by comparing polygamously and monogamously married individuals. In line with predictions from evolutionary theory, polygamy is beneficial to male reproductive success (i.e. producing larger numbers of surviving offspring). The success of polygamously married females depends on wife rank: the first wives of polygamous husbands do better than monogamously married women and much better than second or third wives. These effects are mirrored in child nutritional status: the children of second and third wives have lower weight for height. Due to potential, largely unmeasurable differences in marriageability (quality) between individuals, it was not possible to support a model of either resource-holding polygyny combined with female choice or female coercion into unwanted marriages. First wives of polygamously married men marry at a younger age and attract a higher brideprice, suggesting that both the males and females in the marriage are likely to be of higher quality (due to wealth, family status or some other factor such as beauty). Unions that end up monogamous are likely to be between slightly lower quality individuals; and second and third wives, who marry at the oldest ages and attract the lowest brideprice, may be ‘making the best of a bad job’. The relatively long gap between first and second marriages may mean that first wives of highly marriageable males can enjoy considerable reproductive success before their husbands marry again.

scholarly journals The measure and significance of Bateman's principles

2014 ◽  
Vol 281 (1782) ◽  
pp. 20132973 ◽  
Author(s):  
Julie M. Collet ◽  
Rebecca F. Dean ◽  
Kirsty Worley ◽  
David S. Richardson ◽  
Tommaso Pizzari
Keyword(s):  
Reproductive Success ◽  
Mating Success ◽  
Male Reproductive Success ◽  
Female Fecundity ◽  
Male Preference ◽  
Bateman Gradient ◽  
Red Junglefowl ◽  
Experimental Approaches ◽  
Empirical Tests ◽  
Paternity Share

Bateman's principles explain sex roles and sexual dimorphism through sex-specific variance in mating success, reproductive success and their relationships within sexes (Bateman gradients). Empirical tests of these principles, however, have come under intense scrutiny. Here, we experimentally show that in replicate groups of red junglefowl, Gallus gallus , mating and reproductive successes were more variable in males than in females, resulting in a steeper male Bateman gradient, consistent with Bateman's principles. However, we use novel quantitative techniques to reveal that current methods typically overestimate Bateman's principles because they (i) infer mating success indirectly from offspring parentage, and thus miss matings that fail to result in fertilization, and (ii) measure Bateman gradients through the univariate regression of reproductive over mating success, without considering the substantial influence of other components of male reproductive success, namely female fecundity and paternity share. We also find a significant female Bateman gradient but show that this likely emerges as spurious consequences of male preference for fecund females, emphasizing the need for experimental approaches to establish the causal relationship between reproductive and mating success. While providing qualitative support for Bateman's principles, our study demonstrates how current approaches can generate a misleading view of sex differences and roles.

The genetic mating system, male reproductive success and lack of selection on male traits in the greater bilby

2010 ◽  
Vol 58 (2) ◽  
pp. 113 ◽  
Author(s):  
Emily J. Miller ◽  
Mark D. B. Eldridge ◽  
Neil Thomas ◽  
Nicola Marlow ◽  
Catherine A. Herbert
Keyword(s):  
Reproductive Success ◽  
Mating System ◽  
Morphological Traits ◽  
Life History Traits ◽  
Male Reproductive Success ◽  
Home Ranges ◽  
Captive Population ◽  
Genetic Mating System ◽  
Free Ranging ◽  
Conservation And Management

The greater bilby (Macrotis lagotis) is the sole remaining species of desert bandicoot on the Australian mainland. The mating system of this species remains poorly understood, due to the bilby’s cryptic nature. We investigated the genetic mating system of the greater bilby in a five-year study of a semi-free-ranging captive population that simulated their wild environment. Morphological traits were examined to determine whether these influenced patterns of male reproductive success and whether selection was acting on them. In any given year more than half the males (59.2 ± 9.3%) failed to sire any offspring. Approximately 70% of sires fathered one offspring, and 30% two or three offspring. Since paternity was not dominated by few males, and given the species’ solitary nature, lack of territoriality and large home ranges, it is likely that males adopt a roving strategy to find receptive females. These results are consistent with an overlap promiscuous mating system. Sires and non-sires could not be distinguished by their morphological traits, and there was no evidence for strong linear or non-linear selection on male traits. These data increase our understanding of bandicoot life-history traits and will assist conservation and management efforts.

scholarly journals Ectoparasites and fitness of female Columbian ground squirrels

2015 ◽  
Vol 370 (1669) ◽  
pp. 20140113 ◽  
Author(s):  
Shirley Raveh ◽  
Peter Neuhaus ◽  
F. Stephen Dobson
Keyword(s):  
Natural Selection ◽  
Reproductive Success ◽  
Ground Squirrels ◽  
Fitness Costs ◽  
Treatment Control ◽  
Free Living ◽  
Sham Treatment ◽  
Adult Females ◽  
And Control ◽  
Columbian Ground Squirrels

Parasites play an important role in the evolution of host traits via natural selection, coevolution and sexually selected ornaments used in mate choice. These evolutionary scenarios assume fitness costs for hosts. To test this assumption, we conducted an ectoparasite removal experiment in free-living Columbian ground squirrels ( Urocittelus columbianus ) in four populations over three years. Adult females were randomly chosen to be either experimentally treated with anti-parasite treatments (spot-on solution and flea powder, N = 61) or a sham treatment (control, N = 44). We expected that experimental females would show better body condition, increased reproductive success and enhanced survival. Contrary to our expectations, body mass was not significantly different between treatments at mating, birth of litter or weaning of young. Further, neither number nor size of young at weaning differed significantly between the two treatments. Survival to the next spring for adult females and juveniles was not significantly different between experimental and control treatments. Finally, annual fitness was not affected by the treatments. We concluded that females and their offspring were able compensate for the presence of ectoparasites, suggesting little or no fitness costs of parasites for females in the different colonies and during the years of our experiments.

Detection of multiple paternity and sperm storage in a captive colony of the central Asian tortoise, Testudo horsfieldii

2006 ◽  
Vol 84 (4) ◽  
pp. 520-526 ◽  
Author(s):  
Emily E. Johnston ◽  
Matthew S. Rand ◽  
Stephan G. Zweifel
Keyword(s):  
Reproductive Success ◽  
Microsatellite Markers ◽  
Sperm Competition ◽  
Genomic Library ◽  
Multiple Paternity ◽  
Female Mate Choice ◽  
Sperm Storage ◽  
Male Reproductive Success ◽  
Critical Measure ◽  
Central Asian

Reproductive success is a critical measure of an organism’s fitness. Determining reproductive success in vertebrates is confounded by the concealed mechanism and timing of fertilization (e.g., sperm competition and storage). To assess the relationship between observed mating behavior and reproductive success in the central Asian tortoise, Testudo horsfieldii Gray, 1844, we determined individual genotypes from a captive colony of adults and their offspring. We constructed a size-selected genomic library from T. horsfieldii and screened for polymorphic microsatellite markers. The screen resulted in identification of two novel microsatellite regions. Cross-species amplification of microsatellite markers using primers developed for the bog turtle, Glyptemys muhlenbergii (Schoepff, 1801), resulted in isolation of three additional polymorphic microsatellites for T. horsfieldii. The five loci, which have between 5 and 17 alleles and observed heterozygosities between 0.44 and 0.90, were used to determine the frequency of multiple paternity in the captive colony. We found evidence for multiple paternity in 27% of the clutches examined, as well as evidence for overwinter sperm storage and variance in adult male reproductive success. These data indicate that ample opportunity exists for sperm competition and female mate choice in T. horsfieldii.

scholarly journals Paternity and male mating strategies of a ground squirrel ( Ictidomys parvidens ) with an extended mating season

2016 ◽  
Vol 97 (2) ◽  
pp. 576-588 ◽  
Author(s):  
Lisa E. Schwanz ◽  
William B. Sherwin ◽  
Katherine Ognenovska ◽  
Eileen A. Lacey
Keyword(s):  
Mating System ◽  
Reproductive Strategy ◽  
Ground Squirrel ◽  
Multiple Paternity ◽  
Rio Grande ◽  
Mating Strategies ◽  
Ground Squirrels ◽  
Male Mating ◽  
Mating Season ◽  
Temporal And Spatial Distribution

Abstract Animal mating systems are driven by the temporal and spatial distribution of sexually receptive females. In mammals, ground-dwelling squirrels represent an ideal clade for testing predictions regarding the effects of these parameters on male reproductive strategies. While the majority of ground squirrel species have a short, highly synchronous annual breeding season that occurs immediately after females emerge from hibernation, the Mexican or Rio Grande ground squirrel ( Ictidomys parvidens ) differs markedly in having an extended mating season (2 months) and a long delay between emergence from hibernation and female receptivity (1–2 months). Both traits are expected to favor polygyny by increasing the chances that a male can secure matings with multiple females (e.g., females that come into estrus on different days). To test this prediction, we used microsatellite markers to characterize the mating system of a population of Rio Grande ground squirrels from Carlsbad, New Mexico. Our analyses indicated a high frequency of multiple paternity of litters in this population. Paternity was not related to spatial overlap between known mothers and assigned fathers, suggesting that territory defense is unlikely to be an effective male reproductive strategy in the study population. Dominance interactions among males were frequent, with heavier males typically winning dyadic interactions. Surprisingly, however, males with lower dominance scores appeared to have higher reproductive success, as did males that were active over a greater extent of the study site. Collectively, these results suggest that the mating system of the Rio Grande ground squirrel is best described as scramble competition polygyny, with the primary male reproductive strategy consisting of searching for estrous females. Similar patterns of male–male competition have been reported for a few other ground squirrel species, providing potentially important opportunities for comparative studies of the factors favoring this form of male reproductive strategy.

scholarly journals Comparing fitness measures and the influence of age of first reproduction in Columbian ground squirrels

2020 ◽  
Vol 101 (5) ◽  
pp. 1302-1312
Author(s):  
Kristin K Rubach ◽  
F Stephen Dobson ◽  
Bertram Zinner ◽  
Jan O Murie ◽  
Vincent A Viblanc
Keyword(s):  
Reproductive Success ◽  
Population Growth ◽  
Life Cycles ◽  
Ground Squirrels ◽  
Relative Fitness ◽  
Age At First Reproduction ◽  
Individual Fitness ◽  
First Reproduction ◽  
Fitness Measures ◽  
Columbian Ground Squirrels

Abstract The timing of life-history traits may have strong influences on the evolution of life cycles and on population demography. This is especially true of the age at which females first reproduce (Cole’s principle). We examined whether the age at which females first reproduce influences fitness in Columbian ground squirrels (Urocitellus columbianus), for which females varied in the age at which they initially produce weaned offspring, from ages 1 through 5 years. With 148 females with complete known life spans in a 28-year data set, we examined four fitness measures: individual fitness (λ ind), individual fitness relative to the pattern of growth of the population (λ rel), lifetime reproductive success (LRS), and LRS relative to the total LRS for each female’s cohort (LRSrel). These metrics were calculated for offspring produced at the time of weaning and offspring that survived to emerge after their first hibernation period. Individual fitness (λ ind) was significantly associated with population growth during a female’s lifetime (λ Leslie; R2 = 0.523, P < 0.0001), indicating the need to adjust individual fitness for demonstrated changes in population growth and thus producing a relative individual fitness index (λ rel). We regressed λ rel on age at first reproduction, and found significant selection favoring earlier reproductive success (β ± SE = −0.20 ± 0.06; R2 = 0.306, P < 0.0001). When using an earlier (offspring at weaning) versus later (those that survived their first hibernation) measure of fecundity, we found that the latter introduced considerable variation, likely environmental, into the estimate of selection. This greatly weakened the regression of relative fitness on the age at first successful reproduction. LRS and LRSrel exhibited nonsignificant changes with age at first reproduction. Finally, those females that reproduced successfully at younger ages had similar litter sizes but significantly shorter life spans than females that matured when older, perhaps reflecting costs to early reproduction.

Determinants of reproductive success in female Columbian ground squirrels

Oecologia ◽  
1991 ◽  
Vol 86 (4) ◽  
pp. 528-534 ◽  
Author(s):  
Wendy J. King ◽  
Marco Festa-Bianchet ◽  
Susan E. Hatfield
Keyword(s):  
Reproductive Success ◽  
Ground Squirrels ◽  
Columbian Ground Squirrels
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