Determinant Of Reproductive Success Research Articles

Reproductive consequences of bilateral asymmetry for individual male red-winged blackbirds

We used morphological and breeding data from a 2-year field study of red-winged blackbirds (Agelaius phoeniceus) to test the hypothesis that males characterized by low levels of bilateral asymmetry (i.e., high developmental competence) realize a reproductive advantage. Specifically, we evaluated each of several distinct components of male reproductive success relative to asymmetry measures made on five bilaterally paired characters. Results of a male removal experiment generally failed to support die prediction that symmetry would be associated with success in competition for access to breeding territories: established territory owners and nonterritorial replacement males were effectively indistinguishable in this regard. Similarly, there was no indication that symmetrical males were more likely to establish territories in high-quality marsh habitat than in marginal upland field habitat. Finally, monitoring of breeding activity in high-quality habitat revealed that male symmetry was generally unrelated to recruitment of social mates (i.e., harem size), the productivity of those mates (average female reproductive success), widiinpair paternity (assessed using DNA-based analysis of parentage), or extrapair mating success. Collectively, these results indicate that symmetry is not an important determinant of reproductive success among individual male red-winged blackbirds. This observation, in combination with the results of several other recent investigations, suggests that the fitness consequences of subtle departures from perfect symmetry may be less significant and/or less ubiquitous than initially suggested.

Behavioral and environmental determinants of reproductive success in traditional Moroccan Berber groups

Behavioral and environmental determinants of reproductive success in traditional Moroccan Berber groups

Does reproductive success increase with age or with size in species with indeterminate growth? A case study using sand lizards (Lacerta agilis).

Most data on determinants of reproductive success (RS) and reproductive "tactics" are correlational in nature, and hence cannot be used to infer causation. Consistent patterns-such as an increase in RS with age, as seen in many types of organisms-may result from diverse underlying mechanisms. Ontogenetic increases in RS in mammals and birds may be due largely to direct effects of age (via learning, etc.) but our analyses show that apparently analogous ontogenetic shifts in reproductive tactics and increases in RS in sand lizards (Lacerta agilis) are actually due to ontogenetic changes in body size. When size effects are removed, age exerts very little effect on either reproductive behaviour or RS in either sex. In many taxa, both age and body size may exert important effects on reproductive biology, and disentangling these effects should be a focus of further research.

Light or Pollen--Seasonal Limitations on Female Reproductive Success in the Understory Shrub Lindera Benzoin

Light, pollen, and leaf area were manipulated to examine the role of each of these as determinants of reproductive success in the understory shrub Lindera benzoin. Fruit set was significantly greater in the sun than in the shade, and was reduced in both habitats by shading branches. Supplemental pollination added significantly more viable pollen to stigmas, but plants never responded with increased fruit set, even under conditions of high light availability. Treatments had no effect on fruit and seed mass, but there was a significant maternal effect on these variables. Treatments did result in a significant reduction in per branch flower production in the following year, especially on fruit-bearing branches in shaded sites and on artificially shaded branches (...)

Peahens lay more eggs for peacocks with larger trains

Reproduction is costly and individual decisions about when and how much to invest in reproduction will relate to potential benefits in terms of offspring survivorship or mating success. For those organisms that can reproduce more than once, individuals should invest relatively more in reproduction when the potential benefits are high. If females gain directly or indirectly from choosing attractive, highly ornamented males, then it could be predicted that females mated to these males should invest more in reproduction. Here we report the first test of this prediction for a lekking species, peafowl (Pavo cristatus), in which males do not provide resources for offspring, and females prefer to mate with those males that possess the most elaborate trains. We find that peahens randomly mated to males that vary in the degree of ornament produce more eggs for those peacocks with more elaborate trains. We could find no evidence to support the possibility that this difference arises as a result of difference between males in their ability to fertilize eggs.

Determinants of reproductive success in female adders, Vipera berus.

Female lifetime reproductive success in a small population of individually-marked adders in southern Sweden was studied over a period of seven years. Reproductive characteristics varied little from year to year and were consistent through time in individual females. Most females mature at four years of age and reproduce every two years. The total number of offspring produced by a female depends on her adult body size (and thus, litter size) and longevity (and thus, number of litters per lifetime). Adult body size in females is influenced mainly by subadult growth rates. Offspring size depends on maternal body size and a tradeoff between offspring size and offspring number. Maternal age does not affect litter sizes and offspring sizes except through ontogenetic changes in maternal body size.Survival of females after parturition is low because of the high energy costs of reproduction, compounded by low feeding rates of gravid females because of their sedentary behaviour at this time. About one-half of females produce only a single litter during their lifetimes, although some females live to produce four or five litters. On a proximate basis, rates of energy accumulation for growth (in subadults) and reproduction (in adults) may be the most important determinants of fitness in female adders.

Social stratification, social strategies, and reproductive success in primates

Social stratification characterizes primate societies, and the conventional assumption is that high rank should enable one to produce more offspring. But the data from primate studies offers conflicting evidence with respect to the actual reproductive consequences of high social status. Nonhuman primates are tactical opportunists who use multiple means for improving reproductive success. Social skills can circumvent social status as determinants of reproductive success. Social stratification probably evolved as a mechanism for reducing the probability of escalated aggressive encounters by providing a reasonable degree of predictability and stability to social relationships. Social cognition may have evolved as a mechanism enabling individuals to adopt alternative reproductive tactics for improving their reproductive success. The frequent nonassociation between rank and reproduction in primates can be attributed to the diversity of reproductive tactics used by primate in attempting to maximize their individual fitness.

Determinants of reproductive success in female Columbian ground squirrels.

We studied the reproductive success of female Columbian ground squirrels (Spermophilus columbianus) in southwestern Alberta for nine years. We defined reproductive success as the number of offspring surviving their first hibernation, classified as yearlings. The number of weaned juveniles explained one third of the variance in number of yearlings at emergence from their first hibernation the following spring, and much of the variance in individual reproductive success originated after weaning. Weight of adult females at emergence from hibernation was correlated with annual reproductive success. The mother's survival beyond weaning and the subsequent winter's snow accumulation had positive effects on annual reproductive success, whereas population density and summer temperature had negative effects. We found no effects on annual reproductive success of date of litter emergence, weight at emergence as a yearling, presence or absence of adult kin, distance from the natal site, location within the study area, winter temperature or summer precipitation. Age of first breeding did not affect lifetime reproductive success, which ranged from 0 to 19 yearlings produced over a lifetime. The greatest source of variation in lifetime reproductive success for females surviving to breeding age was offspring survival, followed by reproductive lifespan.

Body Size, Sperm Competition, and Determinants of Reproductive Success in Male Savanna Baboons

Body Size, Sperm Competition, and Determinants of Reproductive Success in Male Savanna Baboons

Determinants of Reproductive Success of Male Sticklebacks in the Field and in the Laboratory

Several determinants of reproductive success of male three-spined sticklebacks, Gasterosteus aculeatus L., have been identified in the laboratory under semi-natural conditions. The impact of these determinants in natural populations is largely unknown. Here we analyse some determinants of reproductive success in natural Dutch stickleback populations and compare them with those obtained in a laboratory study of VAN DEN ASSEN (1967). Although we fail to affirm a positive correlation between territory size and aggression, the determinants of reproductive success revealed in VAN DEN ASSEM'S study are shown also to be of importance under natural conditions. Superior reproductive success is associated with large territory size and males with large territories suffer less egg raiding. An enhanced likelihood of nest entering by ripe females occurs right after creeping through and this male behaviour is observed more frequently in males with relatively large territories. Further, ripe females are more apt to enter a nest that already contains eggs, and this is not a result of changes in the male's courtship through the presence of eggs in its nest. The functional significance of some behavioural patterns like creeping through, sneaking and egg-raiding is discussed.