Genetic Benefits Research Articles

Female Choice for Males with Greater Fertilization Success in the Swedish Moor Frog, Rana arvalis

BackgroundStudies of mate choice in anuran amphibians have shown female preference for a wide range of male traits despite females gaining no direct resources from males (i.e. non-resource based mating system). Nevertheless, theoretical and empirical studies have shown that females may still gain indirect genetic benefits from choosing males of higher genetic quality and thereby increase their reproductive success.Methodology/Principal FindingsWe investigated two components of sexual selection in the Moor frog (Rana arvalis), pre-copulatory female choice between two males of different size (‘large’ vs. ‘small’), and their fertilization success in sperm competition and in isolation. Females' showed no significant preference for male size (13 small and six large male preferences) but associated preferentially with the male that subsequently was the most successful at fertilizing her eggs in isolation. Siring success of males in competitive fertilizations was unrelated to genetic similarity with the female and we detected no effect of sperm viability on fertilization success. There was, however, a strong positive association between a male's innate fertilization ability with a female and his siring success in sperm competition. We also detected a strong negative effect of a male's thumb length on his competitive siring success.Conclusions/SignificanceOur results show that females show no preference for male size but are still able to choose males which have greater fertilization success. Genetic similarity and differences in the proportion of viable sperm within a males ejaculate do not appear to affect siring success. These results could be explained through pre- and/or postcopulatory choice for genetic benefits and suggest that females are able to perceive the genetic quality of males, possibly basing their choice on multiple phenotypic male traits.

The benefits of pre-release population genetics: A case study using Ceutorhynchus scrobicollis, a candidate agent of garlic mustard, Alliaria petiolata

Incorporating population genetics into research on candidate biological control agents can help improve the safety and success rates of biological control of weeds. As a case in point, the population structure of Ceutorhynchus scrobicollis, a candidate agent for garlic mustard ( Alliaria petiolata) in North America, was evaluated using mitochondrial sequence data and amplified fragment length polymorphisms (AFLPs). The region surrounding Berlin, Germany, from which individuals have been collected for host-specificity tests, was examined to determine whether individuals from this area constitute one or more populations, to estimate numbers of individuals required to capture 90–99% of the diversity in AFLPs within the region, and to evaluate dispersal capabilities. Significant differentiation of C. scrobicollis between sites was observed, however most (94%) of the genetic diversity was found within sites. The area around Berlin appears to be a network of connected subpopulations. Estimates for the number of individuals needed from the focal area to capture 90% and 99% of the diversity present in AFLP loci were 10 and 27. Assignment tests indicated that while few individuals disperse, some move up to 65 km. Inclusion of more distant samples from Romania and Georgia revealed substantial genetic differentiation between them and German samples. These areas might therefore be useful to explore further should populations with different ecological characteristics be sought. These findings increase confidence in host-specificity tests, which incorporated more than 4000 individual weevils from the Berlin area, provide guidance for eventual release strategies, and illustrate how basic population genetic data can be incorporated into biological control programs to increase safety and efficacy.

Phytosequestration: Carbon Biosequestration by Plants and the Prospects of Genetic Engineering

Photosynthetic assimilation of atmospheric carbon dioxide by land plants offers the underpinnings for terrestrial carbon (C) sequestration. A proportion of the C captured in plant biomass is partitioned to roots, where it enters the pools of soil organic C and soil inorganic C and can be sequestered for millennia. Bioenergy crops serve the dual role of providing biofuel that offsets fossil-fuel greenhouse gas (GHG) emissions and sequestering C in the soil through extensive root systems. Carbon captured in plant biomass can also contribute to C sequestration through the deliberate addition of biochar to soil, wood burial, or the use of durable plant products. Increasing our understanding of plant, microbial, and soil biology, and harnessing the benefits of traditional genetics and genetic engineering, will help us fully realize the GHG mitigation potential of phytosequestration.

Realising the benefits of genetics for health

In the future, whole-genome sequencing will become a clinical reality for both germline and somatic genomes,1,2 but we should also consider how genetics can be used to improve health now. Since the advent of single-nucleotide polymorphism genotyping arrays, the proliferation of genome-wide association studies has led to the identification of hundreds of common variants. These variants are associated with complex diseases and traits, and provide valuable insights into underlying causation and potential drug targets.

Patterns of ancestry and genetic diversity in reintroduced populations of the slimy sculpin: implications for conservation

Reintroductions are a common approach for preserving intraspecific biodiversity in fragmented landscapes. However, they may exacerbate the reduction in genetic diversity initially caused by population fragmentation because the effective population size of reintroduced populations is often smaller and reintroduced populations also tend to be more geographically isolated than native populations. Mixing genetically divergent sources for reintroduction purposes is a practice intended to increase genetic diversity. We documented the outcome of reintroductions from three mixed sources on the ancestral composition and genetic variation of a North American fish, the slimy sculpin (Cottus cognatus). We used microsatellite markers to evaluate allelic richness and heterozygosity in the reintroduced populations relative to computer simulated expectations. Sculpins in reintroduced populations exhibited higher levels of heterozygosity and allelic richness than any single source, but only slightly higher than the single most genetically diverse source population. Simulations intended to mimic an ideal scenario for maximizing genetic variation in the reintroduced populations also predicted increases, but they were only moderately greater than the most variable source population. We found that a single source contributed more than the other two sources at most reintroduction sites. We urge caution when choosing whether to mix source populations in reintroduction programs. Genetic characteristics of candidate source populations should be evaluated prior to reintroduction if feasible. When combined with knowledge of the degree of genetic distinction among sources, simulations may allow the genetic diversity benefits of mixing populations to be weighed against the risks of outbreeding depression in reintroduced and nearby populations.

Findings from a community education needs assessment to facilitate the integration of genomic medicine into primary care

PurposeTo assess the lay public's knowledge of, and beliefs about, genetics and genetic testing to create an educational initiative that promotes acceptance and utilization of genomic medicine in primary health care. MethodsA telephone survey of English-speaking adults in Guilford County, North Carolina was conducted in 2006 to identify community members' educational needs regarding genetics and genetic testing. ResultsMost respondents recognized the connection between family history and disease risk. A majority did not appear to know about: (1) basic principles of inheritance, (2) laws prohibiting genetic discrimination, and (3) the availability and limitations of genetic tests. About 25% thought that they could not reduce their risk if they have a genetic predisposition for disease. Knowledge level was affected by education, experience, age, and race. ConclusionIf primary care providers use family history as a risk assessment tool, community education programs must address (1) the collection of family health history, (2) legislation regarding genetic nondiscrimination, (3) benefits and limitations of existing genetic tests, and (4) genetic determinism. Programs emphasizing practical, “how to” information can be targeted to individuals likely to collect family history information and address misperceptions about discrimination, testing, and determinism.

Testing the fisherian mechanism: examining the genetic correlation between male song and female response in waxmoths

Models of indirect (genetic) benefits sexual selection predict linkage disequilibria between genes that influence male traits and female preferences, owing to either non-random mate choice or physical linkage. Such linkage disequilibria, a genetic correlation, can accelerate the evolution of male traits and female preferences to exaggerated levels. But relatively few empirical studies have measured the genetic correlation between male traits and female responses in natural populations, and the findings of those few are mixed: often, genetic correlations are not found. We tested the above prediction in an acoustic pyralid moth, Achroia grisella, in which males attract females with a rhythmic train of sound pulses, and females respond only to song that exceeds a minimum pulse rhythm. Both male song rhythm and female threshold response are repeatable and heritable characters. Because female choice in A. grisella is based largely on male song, and males do not appear to provide direct benefits at mating, genetic correlation between male song rhythm and female response is expected. We studied 2 A. grisella populations, bred them according to a full-sib/half-sib design, split the progeny among 4 different environmental conditions, and measured the male song/female response genetic correlation in each of the 8 resulting groups. While song rhythm and response threshold were generally heritable, we found no evidence of significant genetic correlation between these traits. We suggest that the complexity of the various male song characters, of female response to male song, and of correlations between male song characters and between aspects of female response have mitigated the evolution of strong genetic correlation between song and response. Thus, exaggerated levels of trait development may be tempered.

Male‐induced costs of mating for females compensated by offspring viability benefits in an insect

Sexual conflict facilitates the evolution of traits that increase the reproductive success of males at the expense of components of female fitness. Theory suggests that indirect benefits are unlikely to offset the direct costs to females from antagonistic male adaptations, but empirical studies examining the net fitness pay-offs of the interaction between the sexes are scarce. Here, we investigate whether matings with males that invest intrinsically more into accessory gland tissue undermine female lifetime reproductive success (LRS) in the cricket Teleogryllus oceanicus. We found that females incur a longevity cost of mating that is proportional to the partner's absolute investment into the production of accessory gland products. However, male accessory gland weight positively influences embryo survival, and harmful ejaculate-induced effects are cancelled out when these are put in the context of female LRS. The direct costs of mating with males that sire offspring with higher viability are thus compensated by direct and possibly indirect genetic benefits in this species.

MHC-dependent survival in a wild population: evidence for hidden genetic benefits gained through extra-pair fertilizations

Females should prefer to be fertilized by males that increase the genetic quality of their offspring. In vertebrates, genes of the major histocompatibility complex (MHC) play a key role in the acquired immune response and have been shown to affect mating preferences. They are therefore important candidates for the link between mate choice and indirect genetic benefits. Higher MHC diversity may be advantageous because this allows a wider range of pathogens to be detected and combated. Furthermore, individuals harbouring rare MHC alleles might better resist pathogen variants that have evolved to evade common MHC alleles. In the Seychelles warbler, females paired with low MHC-diversity males elevate the MHC diversity of their offspring to levels comparable to the population mean by gaining extra-pair fertilizations. Here, we investigate whether increased MHC diversity results in higher life expectancy and whether there are any additional benefits of extra-pair fertilizations. Our 10-year study found a positive association between MHC diversity and juvenile survival, but no additional survival advantage of extra-pair fertilizations. In addition, offspring with a specific allele (Ase-ua4) had a fivefold longer life expectancy than offspring without this allele. Consequently, the interacting effects of sexual selection and pathogen-mediated viability selection appear to be important for maintaining MHC variation in the Seychelles warbler. Our study supports the prediction that MHC-dependent extra-pair fertilizations result in genetic benefits for offspring in natural populations. However, such genetic benefits might be hidden and not necessarily apparent in the widely used fitness comparison of extra- and within-pair offspring.

No preference for novel mating partners in the polyandrous nuptial-feeding spider Pisaura mirabilis (Araneae: Pisauridae)

Polyandrous females may gain genetic benefits for their offspring through postmating sexual selection. To facilitate postcopulatory choice for males of superior genetic quality females are expected to bias precopulatory mate choice towards novel males (i.e. genetically novel sources). Preference for novel partners is also expected to maximize male lifetime reproductive success by allowing males to increase the number of mates. We investigated male and female preference for novel or former mating partners in the spider Pisaura mirabilis by offering females novel males (polyandry) or the same male (monogamy). Precopulatory (mate acceptance) and prefertilization (latency to copulation, mating interruption and copulation duration) behaviours were compared between the two treatments. Males provide females with a nuptial prey gift during courtship. Because of the direct benefit associated with nuptial feeding, females should accept males indiscriminately and exert preference only at the prefertilization level. We found that monogamous females remated more readily than polyandrous females, suggesting less resistance to remating with the same male than with novel mates. No differences in female prefertilization responses were found. Lack of preference for novel mates may suggest that direct selection exerted by the nuptial gift rather than indirect selection for genetic benefits is a more likely driver of female remating propensity. Females were nevertheless resistant to remating, suggesting a trade-off between direct benefits and costs of remating. We found no effect of mate novelty on male mating behaviour, indicating either lack of discriminatory ability or that risk of sperm competition creates paternity benefits from remating with the same female.

Combined effect of longevity-associated mitochondrial DNA 5178 C/A polymorphism and coffee consumption on the risk of hyper-LDL cholesterolemia in middle-aged Japanese men

The objective of this study was to investigate whether the mitochondrial DNA 5178 cytosine/adenine (Mt5178 C/A) polymorphism modifies the effects of coffee consumption on serum lipid levels and the risk of dyslipidemia in middle-aged Japanese men. A total of 397 male subjects (age, 53.9±7.8 years; mean±s.d.) were selected from among individuals visiting the hospital for regular medical check-ups. After adjustment for age, body mass index, habitual alcohol consumption, habitual smoking and use of antihypertensive medication, among subjects who consumed <1 cup of coffee per day, the odds ratio (OR) for hyper-low-density lipoprotein (LDL) cholesterolemia (serum LDL cholesterol > or =140 mg per 100 ml) was significantly lower in those with Mt5178A than in those with Mt5178C (OR=0.378, 95% confidence interval: 0.153-0.919). After adjustment, the association between the Mt5178A genotype and hyper-LDL cholesterolemia depended on coffee consumption (P for trend=0.018). Coffee consumption was positively associated with serum LDL cholesterol levels only in subjects with Mt5178A. However, in subjects with Mt5178C, serum LDL cholesterol level or risk of hyper-LDL cholesterolemia did not seem to depend on coffee consumption. These results suggest that for men with Mt5178A, coffee consumption negates the genetic benefit of lower risk for hyper-LDL cholesterolemia.

Genic Capture, Sex Linkage, and the Heritability of Fitness

Several sexual selection models predict that females will obtain indirect genetic benefits by preferentially mating with males that transmit high-quality genes to their offspring. However, despite widespread observations of additive population genetic variation for fitness as well as for male sexually selected traits, estimated fitness associations between fathers and offspring are often weak. Perhaps more puzzling, the strength of these associations differs drastically between species, leading many researchers to question the relevance of genetic benefits for processes of sexual selection. Here, I show that a species' sex chromosome system can strongly influence the genetic architecture of male and female fitness variation and, consequently, the heritability of fitness between fathers and their offspring. Indirect genetic benefits are reduced, and sexually antagonistic costs are pronounced, in species with X chromosomes relative to species with homomorphic sex chromosomes, environmental sex determination, or Z chromosomes. Data from the sexual selection literature are consistent with predictions of the models, though additional studies will be required to circumvent phylogenetic nonindependence between sex determination systems. This study strongly suggests that inferences about genetic benefits of female choice must be considered within a species-specific genomic context, and it has several implications for the evolution of female preferences as well as the genomic consequences of sex and sexual selection.

Incorporating Traditional Knowledge in an International Regime on Access to Genetic Resources and Benefit Sharing: Problems and Prospects

The Seventh Meeting of the Conference of the Parties (2004) of the Convention on Biological Diversity established a mandate for the negotiation of an international regime on Access to Genetic Resources and Benefit Sharing arising from their utilization. Negotiations have been proceeding and have entered the final phase. Seven working group meetings have been held to date and there is expectation that an instrument will emerge by the final deadline � the Tenth Meeting of the Conference of the Parties in Nagoya, Japan in October 2010. A key component singled out for inclusion in the international regime relates to the recognition and protection of the rights of indigenous and local communities (ILCs) over their traditional knowledge (TK) associated with genetic resources. The Ninth Meeting of the Conference of the Parties (2008) established a Group of Technical and Legal Experts to assist the Working Group to deal with this issue. The Group met in India in June 2009 and has submitted a report. This article reflects on the key outcomes of this Expert Group report. In particular, it identifies the key issues that need to be considered and resolved for TK associated to genetic resources to form an integral and viable component of the proposed international regime.

Oestrous red deer hinds prefer male roars with higher fundamental frequencies

Across vertebrates, the observation that lower-pitched vocalizations are typically associated with larger and/or higher quality males has lead to the widespread belief that inter- and intra-sexual selection will produce male calls with low fundamental frequencies (F0). Here we investigated the response of oestrous red deer hinds to playback of re-synthesized male roars characterized by either higher than average or lower than average F0. We found that hinds prefer higher rather than lower 'pitched' roars, providing, to our knowledge, the first evidence of such a bias in nonhuman mammals. Our findings can be interpreted in relation to previous observations that the minimum F0 of roars is positively correlated with male reproductive success in free-ranging red deer stags, and that across Cervids the F0 of male mating calls shows extreme variability. Females showing preferences for higher-pitched roars might derive genetic benefits through more competitive male offspring. Our results emphasize the need for further investigations of female preferences in mammals in order to better understand the extreme variation of F0 values observed in male sexual calls.

Fitness benefits of polyandry for experienced females

Females often mate with several different males, which may promote sperm competition and increase offspring viability. However, the potential benefits of polyandry remain controversial, particularly in birds where recent reviews have suggested that females gain few genetic benefits from extra-pair mating. In tree swallows (Tachycineta bicolor), we found that females with prior breeding experience had more sires per brood when paired to genetically similar social mates, and, among experienced females, broods with more sires had higher hatching success. Individual females breeding in two consecutive years also produced broods with more sires when they were more genetically similar to their mate. Thus, experienced females were able to avoid the costs of mating with a genetically similar social mate and realize fitness benefits from mating with a relatively large number of males. This is one of the first studies to show that female breeding experience influences polyandry and female fitness in a natural population of vertebrates. Our results suggest that the benefits of polyandry may only be clear when considering both the number of mates females acquire and their ability to modify the outcome of sexual conflict.

The Sexually Antagonistic Genes of Drosophila melanogaster

Author SummaryMales and females of many species are different: many of these differences are thought to have evolved because the sexes often have needs and strategies that do not coincide. For example, in fruit-flies, females may do best by concentrating their efforts in acquiring resources to be able to lay more eggs, while males would benefit most from increasing their mating and fertilization success. Such differences generate a sexual “conflict of interests”, and since as a general rule each behavioural, morphological or physiological characteristic is regulated by the same set of genes in the two sexes, this conflict takes place ultimately at the genetic level. In our study, we combined data on the reproductive success of different lines of fruit-flies with their gene expression profiles. We show that a large proportion of genes that contribute to male fertilization success are detrimental for female fecundity, and vice-versa. These results indicate that an optimal genotype for both sexes does not exist: many genes maintain different variants because they have opposite effects in males and females, perhaps helping to explain how genetic diversity is maintained in the face of selection.

Cryptic Sex-Ratio Bias Provides Indirect Genetic Benefits Despite Sexual Conflict

When selection favors sexual dimorphism, high-fitness parents often produce low-fitness progeny of the opposite sex. This sexual conflict is thought to overwhelm the genetic benefits of mate choice because preferred males incur a cost through the production of low-fitness daughters. We provide a counterpoint in a lizard (Anolis sagrei) that exhibits sexual conflict over body size. By using mate-choice experiments, we show that female brown anoles produce more sons than daughters via large sires but more daughters than sons via small sires. Measures of progeny fitness in the wild suggest that maximal fitness payoffs can be achieved by shifting offspring production from daughters to sons as sire size increases. These results illustrate how the resolution of sexual conflict can restore the genetic benefits of mate choice.

MATE CHOICE FOR NONADDITIVE GENETIC BENEFITS CORRELATE WITH MHC DISSIMILARITY IN THE ROSE BITTERLING (RHODEUS OCELLATUS)

Good genes models of mate choice predict additive genetic benefits of choice whereas the compatibility hypothesis predicts nonadditive fitness benefits. Here the Chinese rose bitterling, Rhodeus ocellatus, a freshwater fish with a resource-based mating system, was used to separate additive and nonadditive genetic benefits of female mate choice. A sequential blocked mating design was used to test female mate preferences, and a cross-classified breeding design coupled with in vitro fertilizations for fitness benefits of mate choice. In addition, the offspring produced by the pairing of preferred and nonpreferred males were reared to maturity and their fitness traits were compared. Finally, the MHC DAB1 gene was typed and male MHC genotypes were correlated with female mate choice. Females showed significant mate preferences but preferences were not congruent among females. There was a significant interaction of male and female genotype on offspring survival, rate of development, growth rate, and body size. No significant male additive effects on offspring fitness were observed. Female mate preferences corresponded with male genetic compatibility, which correlated with MHC dissimilarity. It is proposed that in the rose bitterling genetic compatibility is the mechanism by which females obtain a fitness benefit through mate choice and that male MHC dissimilarity, likely mediated by odor cues, indicates genetic compatibility.

Benefits of polyandry in Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae)

The influence of polyandry on the reproductive performance of females and on offspring fitness in Zygogramma bicolorata Pallister was investigated using four experimental treatments, viz. (A) monandrous, limited mating, (B) monandrous, unlimited mating, (C) polyandrous, no-choice limited mating, and (D) polyandrous, mate choice unlimited mating. Polyandrous females had higher reproductive performance than monandrous ones. Monandrous females subjected to unlimited matings had higher egg viability than those subjected to limited matings, but fecundity did not differ significantly. In polyandrous females, the freedom to choose mates did not affect reproductive performance. However, offspring of polyandrous females allowed mate choice developed fastest and had the highest survival at 25, 27, and 30 °C. Thus, polyandry in Z. bicolorata appears to provide both direct (material) and indirect (genetic) benefits resulting in better reproductive performance and increased adaptability of the offspring to counter environmental stresses. The present study not only adds to the knowledge of reproductive biology of Z. bicolorata but it could also be of economic value as it may help in the mass rearing of Z. bicolorata and in the management of Parthenium hysterophorus.

Genetic and potential non-genetic benefits increase offspring fitness of polyandrous females in non-resource based mating system

BackgroundThe adaptive significance of female polyandry is currently under considerable debate. In non-resource based mating systems, indirect, i.e. genetic benefits have been proposed to be responsible for the fitness gain from polyandry. We studied the benefits of polyandry in the Arctic charr (Salvelinus alpinus) using an experimental design in which the material investments by the sires and maternal environmental effects were controlled.ResultsEmbryonic mortality showed a strong paternal genetic component, and it was lower in polyandrously fertilized offspring (sperm competition of two males) than in monandrous fertilizations. We also found that high sperm velocity was associated with low offspring mortality, but not with the size of the offspring or their yolk volume. Although no male effect was found on the size of the offspring yolk reserves, yolk volume was higher in offspring from polyandrous matings than offspring of the either of the two males when mated monandrously.ConclusionsIn support of the "good sperm hypothesis, we found that sperm velocity was positively associated with offspring fitness. In addition, our results suggest that polyandrous females gain genetic advantage (higher offspring survival) from this behavior, but that some benefits of polyandry (larger yolk volume) may not be explained solely by the additive genetic effects. This suggests that sperm competition environment may intensify the selection on genetically superior sperm which in turn may produce offspring that have superior yolk reserves. However, as high sperm velocity was not associated with larger yolk volume, it is possible that also some other non-genetic effects may contribute to offspring fitness. The potential role of polyandrous mating in inbreeding avoidance is discussed.