The impact of Fishers Reproductive Compensation on raising equilibrium frequencies of semi-dominant, non-lethal mutations under mutation/selection balance.

Fishers reproductive compensation (fRC) occurs when a species demography means the death of an individual allows increased survival of his/her relatives, usually assumed to be full sibs. This likely occurs in many species, including humans. Several important recessive human genetic diseases cause early foetal/infant death allowing fRC to act on these mutations. The impact of fRC on these genetic conditions has been calculated and shown to be substantial as quantified by w, the fold increase in equilibrium frequencies of the mutation under fRC compared to its absence i.e. w=1.22 and w =1.33 for autosomal and sex-linked loci, respectively. However, the impact of fRC on the frequency of the much large class of semi-dominant, non-lethal mutations is unknown. This is calculated here by a mixture of simulation and algebra and shown that w is approximately 2-h*s and 2-0.19s-0.85h*s for autosomal and sex-linked loci respectively where h is dominance (varied between 0.05 and 0.95) and s is selection coefficient (varied between 0.05 and 0.9). These results show that the actions of fRC can almost double equilibrium frequency of mutations with low values of h and/or s. The dynamics of fRC acting on this type of mutation are also identified and discussed.

Reproductive Profile and Evidence of Reproductive Compensation among the Miju Mishmi of Indo-Myanmar-China Border

ABSTRACT Understanding the reproductive profile of a population is required for making and implementing various health policies. A plethora of studies on the behaviour of fertility and mortality across the globe have been reported. Very few studies have been reported from the population of Arunachal Pradesh, one of the states in northeast India. The present study aims to examine the reproductive profile of a small tribe of Arunachal Pradesh, namely, Miju Mishmi, inhabiting the Indo-Myanmar-China border area. Two hundred and ten households were surveyed to collect the information regarding fertility, mortality, and associated factors using a pretested schedule. Miju Mishmi is experiencing considerably high fertility and mortality. Many social and biological factors for fertility and mortality prevailing in this population were identified. The existence of reproductive compensation is also found in this population. However, unlike in many Indian societies, Miju Mishmi has no preference for a son and hence no impact on fertility.

Arranged Marriage, Partner Traits and Parental Investment

Both sexes choose mates based on qualities that will enhance offspring viability and quality. In some cases individuals are forced to reproduce with less desirable mates which has been shown to result in lower quality offspring. The Reproductive Compensation Hypothesis (RCH) predicts that parents who mate under constraint will increase their reproductive effort and investment in offspring to compensate for lowered offspring viability. Evidence for the RCH has been found in several animal species; however it has not been examined in humans. One possible type of mate choice constraint in humans is that of arranged marriage in which parents or others choose mates for individuals. In order to test the RCH, I examine whether there are differences in both partner traits between women in arranged marriages and those in self-choice marriages, and differences in parental investment between women in arranged and self-choice marriages using data from the Indonesian Family Life Survey. Except for husband’s education level, no differences were found in mate characteristics between the husbands of women in self-choice marriages and those in arranged marriages. Marriage type did not significantly correlate with parental investment except for number of live births. This correlation, however, was not in the predicated direction. Results show that women in self-choice marriages had more offspring (controlling for marriage duration) than woman in arranged marriages. It is possible that arranged marriage is not a true constraint on mate choice or that parental investment measures used in this study need to be more refined.

Reproductive compensation and embryo competition drive the evolution of polyembryony

Simple polyembryony – where a single gametophyte produces multiple embryos with different sires but the same maternal haplotype – is common in conifers, ferns, horsetails and other vascular plants. Polyembryony could be favored as a mechanism of reproductive compensation, providing a backup for inviable embryos, or as a mechanism of embryo competition and eliminating plants with low fitness, perhaps acting as a mechanism of Self-Incompatibility (SI). However as the evolution of polyembryony from monoembryony has not been modeled these long standing verbal models have not been evaluated. We develop an infinite-site, forward population genetics model to test how these factors can favor the evolution of polyembryony, and how these underlying benefits of polyembryony shape the genetic load under a range of selfing rates, dominance, and selection coefficients. We find that the benefit of reproductive compensation strongly favors the evolution of polyembryony, while the benefits of embryo competition are much weaker. Importantly, when embryo competition favors the evolution of polyembryony it increases embryo competitiveness, but does not act as an SI mechanism, as it does not effectively trade low-fitness selfed offspring for high fitness outcrossed offspring. We find that the impact of polyembryony on the genetic load depends on its function – increasing the embryo load when acting as a mechanism of embryo compensation and decreasing the embryo load when acting as a mechanism of competition.

Reproductive compensation in female Palaemonetes argentinus (Decapoda: Natantia) due to Microphallus szidati (Trematoda) infection

Parasites may affect host demographic characteristics because they can directly or indirectly cause the death of their hosts and/or influence their reproduction. Parasitism is therefore recognized as a factor that influences the composition and structure of populations and communities. One of these behaviours is the compensatory response: the host can compensate for the parasite losses effect, modifying the reproductive effort to enhance fitness. Ovigerus female Palaemonetes argentinus was collected and sorted into two groups according to the degree of development of their embryos: newly spawned embryos and embryos ready to hatch. The number of embryos and their dry weight for each female were determined. All parts of the female body were checked for parasites. The females of P. argentinus were parasitized by Microphalus szidati. We found that parasitized females produce more embryos but had more egg loss during development and the percentage of embryonic loss was higher in the parasitized females than in non-parasitized. Parasitized females produced lighter eggs than those from uninfected females. This supports the compensatory reproduction hypothesis suggested for this species. Parasitism can change life history traits in a way that fecundity can be compensated; this co-evolution between host and parasites will be population or context dependent. Parasites are a functional part of any ecosystem and as our results show, deleting parasites in life history traits and reproduction studies in free living organisms could lead to an incomplete picture of the true processes that happen in nature.

Females allocate differentially to offspring size and number in response to male effects on female and offspring fitness

Female investment in offspring size and number has been observed to vary with the phenotype of their mate across diverse taxa. Recent theory motivated by these intriguing empirical patterns predicted both positive (differential allocation) and negative (reproductive compensation) effects of mating with a preferred male on female investment. These predictions, however, focused on total reproductive effort and did not distinguish between a response in offspring size and clutch size. Here, we model how specific paternal effects on fitness affect maternal allocation to offspring size and number. The specific mechanism by which males affect the fitness of females or their offspring determines whether and how females allocated differentially. Offspring size is predicted to increase when males benefit offspring survival, but decrease when males increase offspring growth rate. Clutch size is predicted to increase when males contribute to female resources (e.g. with a nuptial gift) and when males increase offspring growth rate. The predicted direction and magnitude of female responses vary with female age, but only when per-offspring paternal benefits decline with clutch size. We conclude that considering specific paternal effects on fitness in the context of maternal life-history trade-offs can help explain mixed empirical patterns of differential allocation and reproductive compensation.

Evidence for tolerance of parasitism in a tropical cavity-nesting bird, planalto woodcreeper (Dendrocolaptes platyrostris), in northern Argentina

Avian hosts may either resist the negative effects of nestling ectoparasites by minimizing the number of parasites, or tolerate parasitism by increasing their fecundity via the reproductive compensation hypothesis. Little is known about the interactions between ectoparasites and their avian hosts in the tropics. We (1) examined nestling development rates, and tested whether (2) parasitism by a subcutaneous ectoparasitic botfly (Philornissp.) had negative effects on the condition of nestlings, and (3) these negative effects were minimized in larger broods in a tropical cavity-nesting bird, the planalto woodcreeper (Dendrocolaptes platyrostris), in primary and secondary Atlantic forests in the northern province of Misiones, Argentina. Nestling mass and ectoparasite load per nestling reached maxima when nestlings (n = 50) were between 10 and 14 d old. General linear mixed models predicted that mass at fledging declined with increasing nestling parasite load, suggesting that botflies had a negative influence on fledging condition. Parasite load per nestling declined with increasing brood size indicating that woodcreepers that increase their reproductive output minimize the negative effects of parasitism. Overall we found evidence to support the tolerance via reproductive compensation hypothesis. Future tests of the reproductive compensation hypothesis may help determine the underlying mechanism of the observed negative correlation between parasite load of nestlings and brood size.