Improvement In Reproductive Success Research Articles

Effect of Crown Layers on Reproductive Effort and Success in Andromonoecious Aesculus indica (Wall. ex Camb.) Hook (Sapindaceae) in a Temperate Forest of Garhwal Himalaya.

The andromonoecy is an unusual sex expression in trees in which an individual plant bears both functionally staminate and hermaphrodite flowers on the inflorescences. This study aims to investigate the effect of crown layers on the floral biology and reproductive effort of Aesculus indica (Wall. ex Camb.) Hook. The results revealed that the peak period of anthesis was between 06:00 and 08:00 h of the day. Male flower production was predominantly higher as compared to the perfect flowers on the inflorescences. There was no significant variation between total pollen production in staminate and perfect flowers. Features like protogyny and inter-level asynchrony promote xenogamy; however, intra-level asynchrony results in geitonogamy. Controlled pollination treatments revealed the existence of self-incompatibility in flowers. Pollination syndromes in flowers support ambophily. A trend of consistent improvement in reproductive success from lower canopy layers to upper crown layers in the analyzed trees was recorded. The crown layers have a significant impact on flower production, fruit, and seed set. An increase in male flower production due to the increment in the crown is a mechanism of reproductive assurance as a pollen donor and pollinator recipient and also due to the differential cost of expenditure of reproduction in crown layers. Andromonoecy in A. indica promotes self-incompatibility, and there was a tapering trend of reproductive success in the crown layers.

‘Self‐fumigation’ of nests by an endangered avian host using insecticide‐treated feathers increases reproductive success more than tenfold

AbstractParasites can cause great fitness cost to their hosts, however, their impact on host populations is often unknown. In healthy populations, parasites are not expected to cause declines, but they can be devastating to small and/or declining populations. Nest ectoparasites can have detrimental impacts on the breeding output of their hosts and are emerging as a threat to several endangered bird species. Therefore, finding cost‐effect ways to reduce the impact of parasites on endangered hosts is crucial. Although ‘close‐order’ management techniques available to manage nest parasites are effective, they are often expensive and might not be suitable for species that are intolerant of intensive manipulation. We tested a low cost, ‘close‐order’ management technique to control parasites and boost nest productivity in an endangered passerine. The endangered forty‐spotted pardalote Pardalotus quadragintus is exploited by an ectoparasitic fly Passeromyia longicornis, an obligate subcutaneous parasite of nestling birds. We offered adult pardalotes the opportunity to ‘self‐fumigate’ their nests by supplying feathers treated with insecticide with which to line their nests and tested whether this boosted nest productivity. Pardalotes readily incorporated the experimental feathers in nest building, and survival of hatchlings was significantly higher in nests lined with treated feathers (95%) compared to nests lined with control feathers (8%). This represents a substantially greater improvement in reproductive success than in previous experimental studies, offering the strongest evidence yet that self‐fumigation is a highly effective, simple and low cost ‘close‐order’ management technique for defending endangered birds against ectoparasites.

Reproduction during lactation of dairy cattle: Integrating nutritional aspects of reproductive control in a systems research approach

Reproductive success in any mammalian species, including highly selected dairy cattle, is a result of dynamic, interacting genetic and environmental factors. These include the genetic background or genome of the animal and the nutrient composition, and intake; a complex of interaction between hormonal and neural processes; and environmental factors such housing, temperature, and season of year. Although few would argue with this generic summary, it is a primary premise of this review that to improve dairy cattle reproductive success, the research and application communities including university scientists, breeding organizations, bull studs, nutrition companies, and pharmaceutical firms must fully accept the complexity of the process and adapt accordingly. That said, we have had a tremendous increase in both basic and applied, “on-farm” knowledge about reproductive management. Because of the increase in basic knowledge and improved method to apply it practically, attitudes about research funding and practical management are changing rapidly. There is in the past few years a significant increase in more complex (systems biology) approaches to reproductive improvement and recognition that this is truly the only way to move forward. We hope to encapsulate recent research findings that demonstrate the complexity of the situation and provide one or two examples of how the dairy science research and application communities are moving forward, which should speed improvement in reproductive success. The primary goal is to stimulate an increase in coordinated, systems-based research and analysis in the animal agriculture community worldwide. This is meant to be a general review, not an in-depth reiteration of detail, which can be found in the references. In addition, the primary goal is to stimulate discussion and thought from, perhaps, a little different perspective compared with traditional approaches and also to encourage the audience of younger scientists and students to pursue new approaches in their careers. As an example of a systems approach in describing complex biological relationships, in the decision process for a title of this paper, the phrase “how lactation competes with resources for subsequent reproduction” was suggested. Additionally, phrases such as “negative energy balance reduces reproduction” or “high-producing cows are less fertile,” or “genetics does not affect reproduction” have been used many times in teaching and in research reviews. However, in fact, these are all simplifications that can be misleading, especially to students. Thus, in this review we hope to encapsulate recent research findings that demonstrate the complexity of the situation and provide one or two examples of how the dairy science research communities, both basic and applied, are moving forward and can speed improvement in reproductive success. Hopefully, we can seize opportunities to solve what in effect is actually a quite simple problem: how to feed everyone in the world a highly nutritious diet that includes animal products. Our call and challenge as animal scientists is no less than this: how do we ensure a safe and sustainable high quality protein food supply worldwide for future generations?

Differential expression microarrays reveal candidate genes potentially associated with reproductive dysfunction of captive-reared prawn Penaeus monodon

The Black tiger prawn Penaeus monodon is an internationally significant aquaculture species. However, partial dependence on wild-caught broodstock, due to compromised fecundity in most captive-reared animals, remains a major constraint to industry development. Reproductive performance of captive-reared females is often characterised by longer latency period, lower egg production, egg hatch rates and post-larval survivorship compared with their wild-caught counterparts. Improved understanding of the cellular and associated molecular events occurring during penaeid ovarian maturation could therefore be fundamental to improving reproductive success of captive-reared animals. In support of other studies (Brady et al., 2012) that focussed on non-ovarian tissues, this present study considered both gene expression and histological analyses of ovarian tissue (i.e. developing oocytes) and revealed differences between wild-caught and captive-reared P. monodon, including reduced lipid accumulation in oocytes of captive-reared animals. We have employed oligonucleotide microarray analysis to compare expression profiles of genes involved in ovarian maturation among wild-caught and captive-reared animals. Custom oligonucleotide microarrays were constructed and screened with transcripts derived from the ovary, cephalothorax and eyestalk from animals of all ovarian maturation stages. Ovarian maturation-related differential expression patterns were observed for 111 transcripts, with 53 transcripts displaying differential expression between wild-caught and captive-reared animals. Notably transcripts encoding vitellogenin — the major egg yolk protein precursor, and a lipid storage droplet protein (which we named pmLSD) which is involved in lipid accumulation, were found to have higher expression in wild-caught animals. pmLSD transcripts localise to pre-vitellogenic oocytes of wild-caught animals and the pmLSD protein is exclusively localised to the surface of lipid droplets of oocytes at vitellogenic and cortical rod stages. Our identification of differentially expressed genes, and in particular those encoding a PAT-family lipid storage droplet protein, pmLSD, may provide the molecular tools for further functional characterisation in prawns and improvement of reproductive success among captive-reared animals.

Nest positioning by male Daito White‐eyes Zosterops japonicus daitoensis improves with age to reduce nest predation risk

Age‐related improvement in reproductive success is widely observed in birds, and the mechanisms by which productivity is enhanced have received considerable attention. However, little is known about how parental age affects the loss of eggs or nestlings despite the fact that age effects on nesting success are often reported. We examined parental age effects on reproductive success in relation to the avoidance of nest predation in an island subspecies of the Japanese White‐eye, the Daito White‐eye Zosterops japonicus daitoensis. Clutch size and annual number of breeding attempts did not differ between parental age classes. Reproductive success was affected only by male age through an increase in nesting success. Nest failure was attributed only to predation in this species and nest concealment and nest height were important nest characteristics promoting successful fledging. Older males built their nests in more concealed and higher positions than first‐year birds, regardless of vegetation status around the nest. Analysis of individual birds suggested that by shifting the nest to a safer position, male White‐eyes achieved higher nesting success than in the previous year. Of three hypotheses of age‐related improvement in reproductive success considered, our data favoured the hypothesis that as individuals grow older, their breeding competence improves.

Improvement in chick provisioning with parental experience in a seabird

Age-related differences in the reproductive success of birds may be the result of experience-dependent changes in foraging and parental skills. We tested this hypothesis in a long-lived seabird, the common tern, Sterna hirundo. Transponder-marked birds were observed while feeding their young (1) as first-time breeders (recruits) and (2) as experienced breeders in 2 consecutive years in a breeding colony at Port Wilhelmshaven, Lower Saxony, Germany. The influence of individual breeding experience on feeding rate, feeding success and food composition was investigated, including potential year effects, using multivariate statistics. In addition, we compared the breeding success of experienced and inexperienced breeders. Feeding rate was not linked to experience, whereas experienced breeders had a higher feeding success than recruits. Both experienced breeders and recruits fed their young with the same prey species, but in recruits the proportion of prey items with low energy content was higher. The latter was linked to a lower breeding success of recruits. Our study is, to our knowledge, the first to document an individual improvement in breeding performance as a reason for age-dependent improvement in reproductive success in birds after recruitment.

Microsatellite markers for the analysis of genetic variability and relatedness in red-legged partridge ( Alectoris rufa) farms in Spain

The usefulness of several microsatellites in the management of Alectoris rufa restocking farms is evaluated in the present report. We analysed seven microsatellite loci in 147 randomly chosen individuals from four Spanish farms. Global F IS values were not significant. Slight genetic differentiation was only found between Farms 1 and 4. The global first and second parent exclusionary powers were 0.742 and 0.930, respectively. Microsatellite analysis can estimate the genetic relatedness between pairs of individuals by means of the Identity index. Since genealogies are unknown in most farms, pairwise Identity index values proved to be helpful in the management of matings, and the improvement of reproductive success and fitness of the descendants. Mean Identity index values showed that individuals within farms were not genetically more related than expected under random mating. Variance of the Identity index values suggest the absence of closed familial groups in these farms.

Age‐related patterns of reproductive success in house sparrows Passer domesticus

A common life history pattern in many organisms is that reproductive success increases with age. We report a similar pattern in house sparrows Passer domesticus, older individuals performed better than yearlings for most measures of reproductive success. Older males and females began breeding earlier in a given season and fledged more young than their yearling counterparts. Individual males also fledged more young in their second breeding season than they did in their first, but individual females did not show consistent improvement in reproductive success from year one to two. A path analysis indicated that age in both sexes acted primarily through the timing of breeding; earlier nesters laid more eggs and hence fledged more young but did not have more nesting attempts. We tested whether the increased reproductive success with age arose from high quality individuals surviving to be older (selection hypothesis). In contrast to the main prediction of this hypothesis that reproductive success and survival should be positively related, we found that survival from one year of age to two years of age was negatively related to reproductive success in the first year for males and females combined. Additionally, individuals that survived to breed as two‐year‐olds did not differ in total young fledged in their first year from those that did not survive to their second season of breeding. Our results indicate that fledgling production increases with age due to improvements in timing of breeding, particularly in females, and not because of the loss of poor breeders or increased output. Mechanisms producing age‐related differences in timing of breeding warrant further study.

Is Divorce in Young Common Terns,Sterna hirundo, after Recruitment just a Question of Timing?

AbstractThe probability of divorce in birds has been linked with age, breeding experience, reproductive output and synchrony in return. Here, we investigate the consequences of first breeding attempts in common terns for mating in the subsequent season. Nearly 20% of all first‐time breeders disappeared or skipped at least one season after recruitment. In 84 pairs, which consisted of at least one recruit and of which both partners returned to the colony, the divorce rate was 45%. We compared reproductive success, arrival dates, and asynchrony in arrival dates of pairs of the first breeding season against the second season, for both reunited and divorced pairs and males and females separately. First, in pairs of which both members came back to the colony, we found an increase of reproductive success most pronounced in males. In the second season reproductive success of divorced compared with reunited pairs was higher, as only divorced pairs significantly improved the number of fledglings, and again this relation was stronger in males. Secondly, females of reunited pairs arrived significantly earlier from the first to the second season and by far more days than their males. However, in divorced pairs former mates did not differ in the number of days they advance their arrivals. Finally, divorced males arrived on average 4 d earlier than their former mates, whereas divorced females arrived 5 d later compared with their former mates of the recruitment season. Contradictory to nearly all other divorce studies in birds so far, we found a clear fitness gain in divorced males. We suggest that the improvement in reproductive success of young males stems from a side‐effect of the birds’ quality and ability to reach the breeding site in appropriate time and earlier as potential competitors. In long‐lived bird species the heterogeneity among young individuals in the timing of arrival at the colony seems to explain why former recruit‐pairs reunite or split. For young males we suggest as best explanation of divorce that they profit from ‘pushing for an empty chair’, while females seem to profit from their choosiness and may actively decide between former and other mates.

Age-related improvement of reproductive success in Bluethroats Luscinia svecica

Capsule Young birds are less likely to have high reproductive success compared with older ones because of a lack of several skills influencing breeding performance. Aims To test the ‘constraint’ hypothesis by investigating the effect of male and female age on reproductive performance of a Bluethroat Luscinia svecica population. Methods We compared two age-classes (yearling versus old), breeding for the first time at Guérande salt-pans, France, by evaluating arrival dates on breeding site, territory quality, laying dates, clutch size and egg size, delay before re-nesting, breeding performance, feeding rate at two different nestling periods (on days 4–5 and 10–11 after hatching) and nestling body condition. Results Our results clearly demonstrated an age effect on reproductive performance for both males and females: young breeders were less likely to fledge young. In older males, improvement of reproductive success was related to feeding rate during the first nestling period. For females, timing of breeding (laying date) and reproductive investment (such as clutch size, feeding rate in the whole nestling period, brood condition) were the main determinants. The presence of a yearling in a pair strongly decreased the number of young produced per breeding season. Conclusion Bluethroat supported the ‘constraint’ hypothesis, i.e. that behavioural and physiological maturation is needed for young breeders to enhance reproductive performance.

Do "helpers at the nest" increase their parents' reproductive success?

"Helpers at the nest," usually offspring of a preceding litter who contribute by feeding the young to increase the reproductive success of a breeding pair, are known in many species of birds and mammals. Although similar behaviors were described by ethnological observations in several human societies, there is a lack of data on their existence and role. This study of 794 reproductive life histories of post-menopausal Berber women of Southern Morocco aims to provide such information. Results show that the presence of "probable helpers" in the household is related to higher fertility scores and is associated with improved survival of offspring to sexual maturity. In contrast to sparse observations from other human societies, there is no indication that child caretaking would be specific to eldest daughters. Although the association between offspring survival and helping patterns seems highly probable, there is no confirmation that child caretaking per se is the relevant variable. Contrary to nonhuman helpers at the nest, workloads of children range from housekeeping to light agricultural tasks, and are not focused on assisting younger siblings. The improvement of reproductive success is probably the result of multiple interactions, among which the network of kinship would play a role at both the levels of economy and reciprocal assistance.