Heliconia acuminata reproductive success is independent of local floral density

Reproductive plants in tropical forests are patchily distributed, with some in large aggregations of reproductive consepecifics while others are relatively isolated. This variation in floral density is hypothesized to have a major effect on plant reproductive success, since individuals in higher density neighborhoods can attract more or higher quality pollinators. We experimentally tested this hypothesis with populations of the understory herb Heliconia acuminata in central Amazonia. We created replicated plots in which reproductive plant density spanned the range of naturally occurring floral neighborhood size, then measured three surrogates of plant fitness in focal plants in each array. There was no significant difference between any of the three floral neighborhood treatments in total seed production, fruit set, or the number of seeds produced per fruit. Pollinator visitation rates to plants in all treatments were extremely low, with many plants not visited at all during the observation period. This could be because H. acuminata's hummingbird pollinators are unable to find the widely scattered reproductive plants, however this hypothesis appears unlikely. Instead, natural flowering plant densities may simply be below the threshold value at which neighborhood effects become important, even in "high-density" aggregations. Nutrient limitation, selective fruit abortion, and reproduction via male rather than female function may also be playing a role. We argue the absence of neighborhood effects may be a general phenomenon in central Amazonian forests, though additional experiments with other plant-pollinator systems are needed to determine the extent to which this hypothesis is supported.

Individual reproductive success and effective population size in the greater white-toothed shrew Crocidura russula.

In order to investigate the determinants of effective population size in the socially monogamous Crocidura russula, the reproductive output of 44 individuals was estimated through genetic assignment methods. The individual variance in breeding success turned out to be surprisingly high, mostly because the males were markedly less monogamous than expected from previous behavioural data. Males paired simultaneously with up to four females and polygynous males had significantly more offspring than monogamous ones. The variance in female reproductive success also exceeded that of a Poisson distribution (though to a lesser extent), partly because females paired with multiply mated males weaned significantly more offspring. Polyandry also occurred occasionally, but only sequentially (i.e. without multiple paternity of litters). Estimates of the effective to census size ratio were ca. 0.60, which excluded the mating system as a potential explanation for the high genetic variance found in this shrew's populations. Our data suggest that gene flow from the neighbourhood (up to one-third of the total recruitment) is the most likely cause of the high levels of genetic diversity observed in this shrew's subpopulations.

Male reproductive success and multiple paternity in wild, low-density populations of the adder (Vipera berus).

We studied for the first time the occurrence of multiple paternity, male reproductive success, and neonate survival in wild, low-density adder (Vipera berus) populations using 13 microsatellite loci. Paternity was assigned for 15 clutches, collected during 3 years. Our data demonstrated that multiple paternity can occur at a high level (69%) in natural populations of V. berus, even if the density of adults is low. The high proportion of multiple sired clutches was comparable to the proportion observed in captive populations. Male reproductive success significantly increased with body length, and only the largest males successfully sired entire clutches. Finally, no relationship was detected between the number of fathers per clutch and neonate survival. These results suggest that multiple matings could be beneficial in populations with high level of inbreeding or low male fecundity.

Age and multiple mating effects on reproductive success of Grapholita molesta (Busck) (Lepidoptera, Tortricidae)

The reproductive success of the oriental peach moth was evaluated in four experiments: 1) assessment of the mating duration, fecundity, fertility and longevity of females paired with virgin and immediately mated males; 2) mating duration, spermatophore size, fecundity, fertility and longevity in females paired with virgin and up to four times mated males; 3) receptivity of females to additional copulations after mating with virgin or mated males, and the effects of this behavior in female fecundity, fertility and longevity; 4) influence of insects age in the reproductive output. Males (33%) could copulate immediately after a previous copula. They were fertile until the fourth mating, but only in the first copula they transferred the longest (1.43 ± 0.10 mm) and widest (0.83 ± 0.11 mm) spermatophore, presenting the fastest mating duration (34.8 ± 2.62 min). A high proportion of females copulated by non-virgin males (84%) was receptive to other copulas, in comparison to those copulated by virgin males (32.4%). However, the fecundity, fertility, and longevity were similar among females that copulate once or more. The age was the most important factor affecting reproductive variables, where one and three day old insects had a significant higher fecundity, fertility and presented a shorter mating duration in comparison with older individuals. Results pointed out that the reproductive capacity of Grapholita molesta changes a little with respect to the analyzed factors, highlighting the elevated biotic potential of the species.

Male body size and breeding tubercles are both linked to intra-sexual dominance and reproductive success in the minnow

Male dominance hierarchies are usually linked to relative body size and to weapon size, that is, to determinants of fighting ability. Secondary sexual characters that are not directly used as weapons could still be linked to dominance if they reveal determination or overall health and vigour and hence, indirectly, fighting ability. We studied the mating behaviour of the minnow, Phoxinus phoxinus, a cyprinid fish in which males develop breeding tubercles during the spawning season. The function of these breeding tubercles is still not clear. Using microsatellite markers, we determined male reproductive success under controlled conditions. The minnows were territorial and quickly established a dominance hierarchy at the beginning of the spawning season. Dominance was strongly and positively linked to fertilization success. Although body size and number of breeding tubercles were not significantly correlated in our sample, both large males and males with many breeding tubercles were more dominant and achieved higher fertilization success than small males or males with few tubercles. We found multimale fertilization in most clutches, suggesting that sperm competition is important in this species. Females showed behaviour that may be linked to spawning decision, that is, male dominance might not be the only determinant of male reproductive success in minnows

Male reproductive success: paternity contribution to queens and workers in Formica ants

The relative number of workers and female sexuals fathered by two males mated with a queen were directly assessed using microsatellite and allozyme markers in field colonies of the ants Formica exsecta and F. truncorum. In both species one of the two males consistently fathered more offspring than the other. There was, however, no evidence that one male might be particularly successful in fathering a disproportionally high proportion of female sexuals relative to the proportion of workers. Moreover, in F. exsecta, the proportions of worker pupae and worker adults fathered by each male did not differ significantly between cohorts. The most likely explanation for this pattern is that females store different amounts of sperm from the two males they mated with.

The assessment of reproductive success of queens in ants and other social insects

Recently considerable research has focused on the causes of evolution of multiple-queen (polygynous) colonies. In order to better understand the factors which may have led to these polygynous associations it is vital to compare the reproductive success of queens in monogynous (one queen per colony) and polygynous colonies as well as the relative fitness of queens in polygynous colonies. This paper addresses the difficulties arising from such comparisons and their implications with regard to the methods commonly used to assess reproductive success in queens. The relative reproductive success of queens in monogynous and polygynous colonies is commonly assessed by comparing the relative number of reproductives they produce during a single reproductive season. However, shift in queen number seems to be only one aspect of a profound shift in social structure and reproductive strategy that constitutes, in effect, a ''polygyny syndrome''. For example, female reproductives produced in polygynous colonies frequently use a different mode of colony founding, which in turn affects the probability of their survival. Furthermore, queens from monogynous and polygynous colonies frequently differ in their life-span and the number of sexual broods they produce. As a result, the reproductive success of queens in monogynous and polygynous colonies may not be directly related to the relative number of sexuals they produce during a single reproductive season.

Relationship between diet and reproductive success in the Israeli barn owl

The effect of diet on barn owl (Tyto alba) breeding biology has been well studied in the temperate regions but not in the more arid Middle East. In temperate regions, barn owls are darker colored and mainly prey upon Cricetidae rodents, whereas in arid regions, they are lighter colored and prey to a larger degree upon Muridae rodents. In this study we analyzed the diet and breeding success of 261 barn owl pairs nesting in Israel. The reproductive success of barn owls declined from March to August, and fledged more young when they consumed a larger proportion of social voles (Microtus socialis guentheri). Although the diet of the lighter colored barn owls in Israel comprises more Muridae than that of the darker morphs in temperate regions, in both regions the number of barn owl young increases with an increased proportion of voles in the diet.

An investigative study on the effects of black fly (diptera: simuliidae) sugar meals on reproductive success and parasite transmission /

Black flies are opportunistic sugar-feeders. They take sugar meals from Homopteran honeydew secretions or plant nectars, depending on availability. Homopteran honeydew secretions contain both simple and complex carbohydrates while plant nectars contain primarily simple carbohydrates. In order to determine whether honeydew secretions offer more energy than plant nectars to their insect visitors a study of wild-caught black flies was undertaken in Algonquin Provincial Park, Canada during the spring of 1 998 and 1 999. It was hypothesized that female black flies maintained on honeydew sugars will survive longer, produce more eggs and have a greater parasite vectoring potential than those maintained on artificial nectar or distilled water. Results demonstrated that: (1) host-seeking female Prosimulimfuscum/mixtum and Simulium venustum maintained on artificial honeydew did not survive longer than those maintained on artificial nectar when fed ad libitum; (2) fiiUy engorged S. venustum and Simulium rugglesi maintained on artificial honeydew did not produce more eggs than those maintained on artificial nectar when fed ad libitum; and (3) S. rugglesi did not have a greater vectoring potential of Leucocytozoon simondi when maintained on artificial honeydew as opposed to artificial nectar when fed ad libitum. However, all flies maintained on the two sugars (artificial honeydew and artificial nectar) survived longer, produce more eggs and had greater vectoring potential than those maintained on distilled water alone.

Predator Exclosures Enhance Reproductive Success but Increase Adult Mortality of Piping Plovers (Charadrius melodus)

Piping Plovers (Charadrius melodus) are listed as endangered throughout Canada and the United States Great Lakes region. Most attempts to increase their numbers have focused on enhancing reproductive success. Using 22 years of data collected by Parks Canada in Prince Edward Island National Park of Canada, we examined whether predator exclosures installed around Piping Plover nests increased nest success and hatching and fledging success when compared to nests without exclosures. Nests with exclosures were significantly more likely to hatch at least one egg than nests without exclosures, and they hatched a significantly greater number of young. The greater reproductive success observed in exclosed nests is likely due to the increased protection from predators that the exclosures conferred; significantly fewer exclosed nests were depredated than nonexclosed nests. However, significantly more exclosed than nonexclosed nests were abandoned by adults, and they had significantly greater adult mortality. Whether benefits of increased reproductive success from exclosures outweigh costs of increased abandonment and adult mortality remains unknown, but must be considered.

Some factors affecting reproductive success in crossbred dairy cows on smallholder farms in coastal north-east Tanzania

A 2-year longitudinal survey was carried out to investigate factors affecting reproduction in crossbred cows on smallholder farms in and around an urban centre. Sixty farms were visited at approximately 2-week intervals and details of reproductive traits and body condition score (BCS) were collected. Fifteen farms were within the town (U), 23 farms were approximately 5 km from town (SU), and 22 farms approximately 10 km from town (PU). Sources of variation in reproductive traits were investigated using a general linear model (GLM) by a stepwise forward selection and backward elimination approach to judge important independent variables. Factors considered for the first step of formulation of the model included location (PU, SU and U), type of insemination, calving season, BCS at calving, at 3 months postpartum and at 6 months postpartum, calving year, herd size category, source of labour (hired and family labour), calf rearing method (bucket and partial suckling) and parity number of the cow. The effects of the independent variables identified were then investigated using a non-parametric survival technique. The number of days to first oestrus was increased on the U site (p = 0.045) and when family labour was used (p = 0.02). The non-parametric test confirmed the effect of site (p = 0.059), but effect of labour was not significant. The number of days from calving to conception was reduced by hiring labour (p = 0.003) and using natural service (p = 0.028). The non-parametric test confirmed the effects of type of insemination (p = 0.0001) while also identifying extended calving intervals on U and SU sites (p = 0.014). Labour source was again non-significant. Calving interval was prolonged on U and SU sites (p = 0.021), by the use of AI (p = 0.031) and by the use of family labour (p = 0.001). The non-parametric test confirmed the effect of site (p = 0.008) and insemination type (p > 0.0001) but not of labour source. It was concluded that under favourable conditions (PU site, hired labour and natural service) calving intervals of around 440 days could be achieved.

Measuring the discrepancy between fecundity and lifetime reproductive success in a pollinating fig wasp

Lifetime reproductive success in female insects is often egg- or time-limited. For instance in pro-ovigenic species, when oviposition sites are abundant, females may quickly become devoid of eggs. Conversely, in the absence of suitable oviposition sites, females may die before laying all of their eggs. In pollinating fig wasps (Hymenoptera: Agaonidae), each species has an obligate mutualism with its host fig tree species [Ficus spp. (Moraceae)]. These pro-ovigenic wasps oviposit in individual ovaries within the inflorescences of monoecious Ficus (syconia, or ‘figs’), which contain many flowers. Each female flower can thus become a seed or be converted into a wasp gall. The mystery is that the wasps never oviposit in all fig ovaries, even when a fig contains enough wasp females with enough eggs to do so. The failure of all wasps to translate all of their eggs into offspring clearly contributes to mutualism persistence, but the underlying causal mechanisms are unclear. We found in an undescribed Brazilian Pegoscapus wasp population that the lifetime reproductive success of lone foundresses was relatively unaffected by constraints on oviposition. The number of offspring produced by lone foundresses experimentally introduced into receptive figs was generally lower than the numbers of eggs carried, despite the fact that the wasps were able to lay all or most of their eggs. Because we excluded any effects of intraspecific competitors and parasitic non-pollinating wasps, our data suggest that some pollinators produce few offspring because some of their eggs or larvae are unviable or are victims of plant defences.