Brother-sister Mating Research Articles

Recombination fraction in pre-recombinant inbred lines (PRERIL) - revisiting a century old problem in genetics

BackgroundTraditional recombinant inbred lines (RILs) are generated from repeated self-fertilization or brother-sister mating from the F1 hybrid of two inbred parents. Compared with the F2 population, RILs cumulate more crossovers between loci and thus increase the number of recombinants, resulting in an increased resolution of genetic mapping. Since they are inbred to the isogenic stage, another consequence of the heterozygosity reduction is the increased genetic variance and thus the increased power of QTL detection. Self-fertilization is the primary form of developing RILs in plants. Brother-sister mating is another way to develop RILs but in small laboratory animals. To ensure that the RILs have at least 98% of homozygosity, we need about seven generations of self-fertilization or 20 generations of brother-sister mating. Prior to homozygosity, these lines are called pre-recombinant inbred lines (PRERIL). Phenotypic values of traits in PRERILs are often collected but not used in QTL mapping. To perform QTL mapping in PRERILs, we need the recombination fraction between two markers at generation t for t < 7 (selfing) or t < 20 (brother-sister mating) so that the genotypes of QTL flanked by the markers can be inferred.ResultsIn this study, we developed formulas to calculate the recombination fractions of PRERILs at generation t in self-fertilization, brother-sister mating, and random mating. In contrast to existing works in this topic, we used computer code to construct the transition matrix to form the Markov chain of genotype array between consecutive generations, the so-called recurrent equations.ConclusionsWe provide R functions to calculate the recombination fraction using the newly developed recurrent equations of ordered genotype array. With the recurrent equations and the R code, users can perform QTL mapping in PRERILs. Substantial time and effort can be saved compared with QTL mapping in RILs.

Variation in the Spectrum of New Mutations among Inbred Strains of Mice.

The mouse serves as a mammalian model for understanding the nature of variation from new mutations, a question that has both evolutionary and medical significance. Previous studies suggest that the rate of single-nucleotide mutations (SNMs) in mice is ∼50% of that in humans. However, information largely comes from studies involving the C57BL/6 strain, and there is little information from other mouse strains. Here, we study the mutations that accumulated in 59 mouse lines derived from four inbred strains that are commonly used in genetics and clinical research (BALB/cAnNRj, C57BL/6JRj, C3H/HeNRj, and FVB/NRj), maintained for eight to nine generations by brother-sister mating. By analyzing Illumina whole-genome sequencing data, we estimate that the average rate of new SNMs in mice is ∼μ = 6.7 × 10-9. However, there is substantial variation in the spectrum of SNMs among strains, so the burden from new mutations also varies among strains. For example, the FVB strain has a spectrum that is markedly skewed toward C→A transversions and is likely to experience a higher deleterious load than other strains, due to an increased frequency of nonsense mutations in glutamic acid codons. Finally, we observe substantial variation in the rate of new SNMs among DNA sequence contexts, CpG sites, and their adjacent nucleotides playing an important role.

Together inbreeding and reproductive compensation favor lethal t-haplotypes.

Male mice who are heterozygous for distorting and non-distorting alleles at the t-haplotype transmit the driving t-haplotype around 90% of the time-a drastic departure from Mendelian expectations. This selfish act comes at a cost. The mechanism underlying transmission distortion in this system causes severe sterility in males homozygous for the drive alleles, ultimately preventing its fixation. Curiously, many driving t-haplotypes also induce embryonic lethality in both sexes when homozygous; however, this is neither universal nor a necessity for this distortion mechanism. Charlesworth provided an adaptive explanation for the evolution of lethal t-haplotypes in a population segregating for distorting and non-distorting t alleles-if mothers compensate by replacing dead embryos with new offspring (or by transferring energy to surviving offspring), a recessive lethal can be favored because it effectively allows mothers the opportunity to trade in infertile males for potentially fertile offspring. This model, however, requires near complete reproductive compensation for the invasion of the lethal t-haplotype and produces an equilibrium frequency of lethal drivers well below what is observed in nature. We show that low levels of systemic inbreeding, which we model as brother-sister mating, allow lethal t-haplotypes to invade with much lower levels of reproductive compensation. Furthermore, inbreeding allows these lethal haplotypes to largely displace the ancestral male-sterile haplotypes. Our results show that together inbreeding and reproductive compensation move expected equilibria closer to observed haplotype frequencies in natural populations and occur under lower, potentially more reasonable, parameters.

Environmental dependence of mutational (co)variances of adaptive traits.

Standing genetic variation, and capacity to adapt to environment change, will ultimately depend on the fitness effects of mutations across the range of environments experienced by contemporary, panmictic, populations. We investigated how mild perturbations in diet and temperature affect mutational (co)variances of traits that evolve under climatic adaptation, and contribute to individual fitness in Drosophila serrata. We assessed egg-to-adult viability, development time and wing size of 64 lines that had diverged from one another via spontaneous mutation over 30 generations of brother-sister mating. Our results suggested most mutations have directionally concordant (i.e., synergistic) effects in all environments and both sexes. However, elevated mutational variance under reduced macronutrient conditions suggested environment-dependent variation in mutational effect sizes for development time. We also observed evidence for antagonistic effects under standard versus reduced macronutrient conditions, where these effects were further contingent on temperature (for development time) or sex (for size). Diet also influenced the magnitude and sign of mutational correlations between traits, although this result was largely due to a single genotype (line), which may reflect a rare, large effect mutation. Overall, our results suggest environmental heterogeneity and environment-dependency of mutational effects could contribute to the maintenance of genetic variance.

A natural mutator allele shapes mutation spectrum variation in mice.

Although germline mutation rates and spectra can vary within and between species, commongenetic modifiers of themutation rate have not been identifiedin nature1. Here we searched for loci that influence germline mutagenesis using a uniquely powerful resource: a panel of recombinant inbred mouse lines known as theBXD, descended from the laboratory strains C57BL/6J (B haplotype) and DBA/2J (D haplotype). Each BXD lineage has been maintained by brother-sister mating in the near absence of natural selection, accumulating de novo mutations for up to 50 years on a known genetic background that is a unique linear mosaic of B and D haplotypes2. We show that mice inheriting D haplotypes at a quantitative trait locus on chromosome 4 accumulate C>A germline mutations at a 50% higher rate than those inheriting B haplotypes, primarily owing to the activity of a C>A-dominated mutational signature known as SBS18. The B and D quantitative trait locus haplotypes encode different alleles of Mutyh, a DNA repair gene that underlies the heritable cancer predisposition syndromethat causes colorectal tumors with a high SBS18 mutation load3,4. Both B and D Mutyh alleles are present in wild populations of Mus musculus domesticus, providing evidence that common genetic variation modulates germline mutagenesis in a model mammalian species.

HODOWLA ZWIERZ ˛AT GOSPODARSKICH Z ZASOBÓW GENETYCZNYCH DLA MŁODYCH ROLNIKÓW NA TAJWANIE

The agricultural employed population of the year 2020 in Taiwan were 548,000 persons with 74.1% male and 24.9% female. Only 10.9% of those were young farmers with age of 15 to 34 years old. According to the survey of animal industry in 2020, there were about 10,300 livestock farms and 9,900 poultry farms in Taiwan. For those of producing milk, meat and egg in different sectors, the average annual incomes per farm is more than 20 million Taiwan dollar in dairy cattle farms and broiler chicken farms with number of rearing animals per farm were 210 cows and 27,618 birds, respectively. Farm animal genetic resources of 117 breeds in Taiwan updated to 2021, including 20 native breeds, 43 imported breeds, 39 registered new breeds, and 15 ongoing selection breeds, serve as a gene bank for the study of genetic diversity. In Taiwan experience, mule duck production with two species crossbreeding via artificial insemination of laying duck sired with mixed semen from Muscovy duck, it is an essential application of multiple-sires instrumental breeding. In free range production, females of native chicken and laying duck can be multiple-sire natural mating to ensure a higher fertility rate of ovulated eggs. Application of frozen semen and embryo may perform sire-daughter mating, brother-sister mating, or son-dam mating for increasing genetic homogeneity without inbreeding depression of reproduction performance. Inbreeding quickly brings to the surface any detrimental genes that are in a population. With the facility of paternal DNA test, single-sire breeding can be used with extended semen and intra-uterine insemination to test the allele effect of sire genome on their economic traits of pig, cattle, goat, and poultry breeds in a small-scale farming system. Advanced breeding efforts are undertaken to broaden the genetic base of conserved animals and create new breeds that meet the manifold demands in relation to quality, resilience, and sustainability in small-scale farms.

Slow Recovery from Inbreeding Depression Generated by the Complex Genetic Architecture of Segregating Deleterious Mutations.

The deleterious effects of inbreeding have been of extreme importance to evolutionary biology, but it has been difficult to characterize the complex interactions between genetic constraints and selection that lead to fitness loss and recovery after inbreeding. Haploid organisms and selfing organisms like the nematode Caenorhabditis elegans are capable of rapid recovery from the fixation of novel deleterious mutation; however, the potential for recovery and genomic consequences of inbreeding in diploid, outcrossing organisms are not well understood. We sought to answer two questions: 1) Can a diploid, outcrossing population recover from inbreeding via standing genetic variation and new mutation? and 2) How does allelic diversity change during recovery? We inbred C. remanei, an outcrossing relative of C. elegans, through brother-sister mating for 30 generations followed by recovery at large population size. Inbreeding reduced fitness but, surprisingly, recovery from inbreeding at large populations sizes generated only very moderate fitness recovery after 300 generations. We found that 65% of ancestral single nucleotide polymorphisms (SNPs) were fixed in the inbred population, far fewer than the theoretical expectation of ∼99%. Under recovery, 36 SNPs across 30 genes involved in alimentary, muscular, nervous, and reproductive systems changed reproducibly across replicates, indicating that strong selection for fitness recovery does exist. Our results indicate that recovery from inbreeding depression via standing genetic variation and mutation is likely to be constrained by the large number of segregating deleterious variants present in natural populations, limiting the capacity for recovery of small populations.

Reproductive Strategies That May Facilitate Invasion Success: Evidence From a Spider Mite.

With significant surge of international trade in recent decades, increasingly more arthropod species have become established outside their natural range of distribution, causing enormous damage in their novel habitats. However, whether a species can colonize its new environment depends on its ability to overcome various barriers which may result in establishment failure, such as inbreeding depression and difficulty to find mates. Here, we used a haplodiploid pest, Tetranychus ludeni Zacher (Acari: Tetranychidae), which is native to Europe but now cosmopolitan, to investigate whether its reproductive strategies have facilitated its invasion success, providing knowledge to develop programs for prediction and management of biological invasions. We show that inbreeding had no negative influence on female reproductive outputs and longevity over 11 successive generations, allowing mother-son and brother-sister mating to occur at the invasion front without adverse consequences in fitness. Virgin females produced maximum number of sons in their early life to ensure subsequent mother-son mating but later saved resources to prolong longevity for potential future mating. Females maximized their resource allocation to egg production immediately after mating to secure production of maximum number of both daughters and sons as early as possible. Furthermore, mated females with mating delay increased proportion of daughters in offspring produced to compensate the loss of production of daughters during their virgin life. We suggest that the lack of inbreeding depression in successive generations and the ability to adjust resource allocations depending whether and when mating occurs may be the key features that have facilitated its invasion success.

Statistical properties of model kinship networks

We report on the statistical characterization of a class of networks representing kinship in a model for a human population of men and women who form heterosexual monogamous married couples. Specifically, networks are built from blood and in-law sibling connections within the same generation, for either gender. The distribution of the number of blood siblings of each individual is controlled by a randomness parameter, and the only condition imposed on marriages is avoidance of brother-sister mating. By means of numerical simulations of the population, we analyze the statistics of the number and size of connected components, properties of the degree distribution, clustering, assortativity, and distances inside the giant component. To emphasize structural peculiarities of kinship networks, in all cases, we compare with random networks with the same degree distribution. Kinship networks exhibit a nontrivial coexistence of distinctive traits—such as high clustering and assortativity—and features which are typical of random networks.

Haldane, Waddington and recombinant inbred lines: extension of their work to any number of genes.

In the early 1930s, J. B. S. Haldane and C. H. Waddington collaborated on the consequences of genetic linkage and inbreeding. One elegant mathematical genetics problem solved by them concerns recombinant inbred lines (RILs) produced via repeated self or brother-sister mating. In this classic contribution, Haldane and Waddington derived an analytical formula for the probabilities of 2-locus and 3-locus RIL genotypes. Specifically, the Haldane-Waddington formula gives the recombination rate R in such lines as a simple function of the per generation recombination rate r. Interestingly, for more than 80 years, an extension of this result to four or more loci remained elusive. In 2015, we generalized the Haldane-Waddington self-mating result to any number of loci. Our solution used self-consistent equations of the multi-locus probabilities 'for an infinite number of generations' and solved these by simple algebraic operations. In practice, our approach provides a quantum leap in the systems that can be handled: the cases of up to six loci can be solved by hand while a computer program implementing our mathematical formalism tackles up to 20 loci on standard desktop computers.

Fine scale population genetic structure of Varroa destructor, an ectoparasitic mite of the honey bee (Apis mellifera).

Varroa destructor is an obligate ectoparasitic mite and the most important biotic threat currently facing honey bees (Apis mellifera). We used neutral microsatellites to analyze previously unreported fine scale population structure of V. destructor, a species characterized by extreme lack of genetic diversity owing to multiple bottleneck events, haplodiploidy, and primarily brother-sister matings. Our results surprisingly indicate that detectable hierarchical genetic variation exists between apiaries, between colonies within an apiary, and even within colonies. This finding of within-colony parasite diversity provides empirical evidence that the spread of V. destructor is not accomplished solely by vertical transmission but that horizontal transmission (natural or human-mediated) must occur regularly.

Some principles of causal analysis in genetics

The science of genetics is concerned with differences between organisms belonging to the same species, or to species which can be crossed. It is not concerned with all such differences. If we have two dogs, one with straight legs, the other with bent legs, the difference may be due to the fact that the bent-legged dog had a diet insufficient in vitamin D, or that his father was a dachshund. The geneticist is concerned with the latter case. The difference may also turn out to be inexplicable in terms of our present knowledge. Now if an observed quantity or quality varies as the result of a number of conditions, we shall try to analyse the variation by keeping all but one of these conditions constant, and varying the remaining one. Thus if we wish to analyse the variation in the volume of a gas we shall first keep its temperature constant, and obtain Boyle’s law; then keep its pressure constant, and obtain Charle’s law. It is obvious that if we are studying the genetics of a character which varies appreciably in response to environment we shall try to keep the environment constant. We shall see that all our dogs receive the same amount of vitamins, sunlight, and so on, so far as possible. This is an ideal which we cannot even approach asymptotically. For it turns out that high frequency radiation and particles of high velocity are very important components of the environment, causing heritable changes by a process called mutation. Even if we could conduct our experiments behind 30 metres of lead the fact that mutation has a temperature coefficient is enough to show that it depends in part on energy fluctuations which are uncontrollable. Secondly we do not know a priori how long our constant environment must operate. In mammals it is no use to stabilise it after birth. For example in the guinea-pig the children of young mothers are more likely than those of old mothers to have extra toes. The question as to how long the environment must remain uniform to eliminate variation due tu [sic] its diversity it [sic] is an empirical question. The affirmation or denial of Lamarckism depends on how it is answered. In a sufficiently constant environment variation still occurs, and it is found that the children of different parents differ. The difference may or may not be an example of heredity in the ordinary sense of that word, namely resemblance between parents and offspring. Thus in Matthiola a yellow flowered plant will give all yellow offspring, and a red plant will give all, or at any rate many, red offspring. Also some parents will give all normal flowered offspring, others a majority with double flowers, in which the presumptive reproductive organs are represented by petals. We cannot however say that doubleness is inherited (I discuss later the meaning of this distressingly vague word), because double-flowered plants are always completely sterile. How are we to minimise the difference between the progeny of different parents? In other words, how are we to approximate to a genetically homogeneous population? The answer to this question is given by experiment, and rests on well-verified theory. There are three main methods. We may obtain a clone, that is to say a group of individuals related only by mitotic, and not meiotic, nuclear divisions. Such are a group of tulips of a named variety derived by vegetative reproduction from a single individual, or a pair of human monozygotic twins. We may obtain a pure line by prolonged inbreeding or by brother sister mating (though here of course we really have a pure line of females and another of males in bisexual organisms). Such are the named varieties of wheat, and a few lines of mice and rats. Finally we may use the first generation of hybrids between two pure lines. It can be shown theoretically that the variance in a population is reduced to a millionth after 10 generations of self-fertilisation or 30 of brother-sister mating. 1 Haldane, JBS. Some Principles of Causal Analysis in Genetics. Erkenntnis 1936; 6: 346-357. Reprinted with the kind permission of Mrs Lois Godfrey.

Sexually antagonistic zygotic drive: a new form of genetic conflict between the sex chromosomes.

Sisters and brothers are completely unrelated with respect to the sex chromosomes they inherit from their heterogametic parent. This has the potential to result in a previously unappreciated form of genetic conflict between the sex chromosomes, called sexually antagonistic zygotic drive (SA-ZD). SA-ZD can arise whenever brothers and sisters compete over limited resources or there is brother-sister mating coupled with inbreeding depression. Although theory predicts that SA-ZD should be common and influence important evolutionary processes, there is little empirical evidence for its existence. Here we discuss the current understanding of SA-ZD, why it would be expected to elude empirical detection when present, and how it relates to other forms of genetic conflict.

Abstract 568: Congenic Mapping of Hypertension in the Nephrectomy Model of Chronic Kidney Disease.

Introduction: We previously reported a locus on mouse chromosome 11 (chrom 11) linked to development of hypertension (HTN) after sub-total nephrectomy (Nx). To begin fine mapping, we used the 129S6 (129) susceptible strain and the C57BL/6 (B6) resistant strain to generate 4 reciprocal congenic lines carrying ~ 2-LOD intervals of the linked locus for recombinant progeny testing. The intervals are defined by microsatellite markers 1-5 and markers 1-6, corresponding to regions defined by markers D11Mit2 and D11Mit177, and D11Mit2 and D11Mit285, respectively. Through brother-sister matings, the 4 lines are as follows: 1) 129 background, homozygous for B6 segment defined by markers 1-5 (129 Chrom11:1-5ofB6 ), 2) 129 background, homozygous for 129 segment defined by markers 1-5 (129 Chrom11:1-5of129 ), 3) B6 background, homozygous for 129 segment defined by markers 1-6 (B6 Chrom11:1-6of129 ) and 4) B6 background, homozygous for B6 segment defined by markers 1-6 (B6 Chrom11:1-6ofB6 ). Methods: Sub-total Nx was performed on male and female congenic mice at ~ 8 weeks of age. Beginning 4 weeks after surgery, using tail cuff manometer, mice were trained for 2 weeks, after which systolic blood pressure (SBP) was recorded daily for 2 weeks. Results: Table 1 summarizes the average SBP of the congenic lines. Conclusion: These findings confirm the effect of this chrom 11 region is dependent on the 129 genetic background, and suggest that interactions between this 129 locus and other loci in the 129 genome are necessary for the development of HTN after nephron mass reduction. Moreover, the influence of this region on chrom 11 appears to be dependent on sex.

Inbreeding and thermal adaptation inDrosophila subobscura

Using a well-adapted Drosophila subobscura population (Avala, Serbia), a drastic experiment of inbreeding was carried out to assess whether the expected level of homozygosity could be reached or if other evolutionary forces affected the process. In general, no significant changes of inversion (or arrangement) frequencies were detected after 12 brother-sister mating generations. Furthermore, no significant differences were obtained between observed and expected (under the inbreeding model) karyotypic frequencies. Thus, these results seemed to indicate that the main evolutionary factor in the experiment was inbreeding. However, in the G12 generation, complete chromosomal fixation was reached only in two out of the eight final inbred lines. In these lines, the chromosomal compositions were difficult to interpret, but they could be likely a consequence of adaptation to particular laboratory conditions (constant 18 °C, food, light period, etc.). Finally, in a second experiment, the inbred lines presented higher fertility at 18 °C than at 13 °C. Also, there was a significant line effect on fertility: inbred line number 6 (A1, J1, U1+2; U1+2+6, E8, and O3+4+7) presented the highest values, which maybe the result of an adaptation to laboratory conditions. Thus, the results obtained in our experiments reflect the adaptive potential of D. subobscura inversions.

Fine-mapping QTLs in advanced intercross lines and other outbred populations.

Quantitative genetic studies in model organisms, particularly in mice, have been extremely successful in identifying chromosomal regions that are associated with a wide variety of behavioral and other traits. However, it is now widely understood that identification of the underlying genes will be far more challenging. In the last few years, a variety of populations have been utilized in an effort to more finely map these chromosomal regions with the goal of identifying specific genes. The common property of these newer populations is that linkage disequilibrium spans relatively short distances, which permits fine-scale mapping resolution. This review focuses on advanced intercross lines (AILs) which are the simplest such population. As originally proposed in 1995 by Darvasi and Soller, an AIL is the product of intercrossing two inbred strains beyond the F2 generation. Unlike recombinant inbred strains, AILs are maintained as outbred populations; brother-sister matings are specifically avoided. Each generation of intercrossing beyond the F2 further degrades linkage disequilibrium between adjacent makers, which allows for fine-scale mapping of quantitative trait loci (QTLs). Advances in genotyping technology and techniques for the statistical analysis of AILs have permitted rapid advances in the application of AILs. We review some of the analytical issues and available software, including QTLRel, EMMA, EMMAX, GEMMA, TASSEL, GRAMMAR, WOMBAT, Mendel, and others.

Heteroplasmy of Mouse mtDNA Is Genetically Unstable and Results in Altered Behavior and Cognition

Maternal inheritance of mtDNA is the rule in most animals, but the reasons for this pattern remain unclear. To investigate the consequence of overriding uniparental inheritance, we generated mice containing an admixture (heteroplasmy) of NZB and 129S6 mtDNAs in the presence of a congenic C57BL/6J nuclear background. Analysis of the segregation of the two mtDNAs across subsequent maternal generations revealed that proportion of NZB mtDNA was preferentially reduced. Ultimately, this segregation process produced NZB-129 heteroplasmic mice and their NZB or 129 mtDNA homoplasmic counterparts. Phenotypic comparison of these three mtDNA lines demonstrated that the NZB-129 heteroplasmic mice, but neither homoplasmic counterpart, had reduced activity, food intake, respiratory exchange ratio; accentuated stress response; and cognitive impairment. Therefore, admixture of two normal but different mouse mtDNAs can be genetically unstable and can produce adverse physiological effects, factors that may explain the advantage of uniparental inheritance of mtDNA.

Inbreeding in three-spined sticklebacks (Gasterosteus aculeatusL.): effects on testis and sperm traits

Mating between relatives often results in inbreeding depression, and is assumed to have a strong effect on fitness traits such as fertility and gonad/gamete quality. However, data concerning this topic are contradictory and particularly scarce in fishes. Three-spined sticklebacks (Gasterosteus aculeatus L.) show inbreeding depression in fertilization and hatching success, survival rates, body symmetry and behavioural traits. To date, any knowledge of the impact of inbreeding on males' gonads and gametes is lacking in this species. In the present study, testis and sperm traits were quantified in outbred and inbred males. Overall, these traits were not generally impaired by inbreeding, and this result was not changed by a second/third generation of brother–sister matings. However, testes brightness, a potential measure of oxidative stress, was negatively correlated with sperm number. Additionally, inbred males with higher body condition had significantly brighter testes, whereas their sperm number was significantly negatively correlated with sperm quality (as estimated by head volume). Such a trade-off did not appear in outbred males. The comparatively small impact of inbreeding on testis and sperm traits might be explained by the low number of inbred individuals that reached the reproductive phase. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 107, 510–520.

Healing quantitative trait loci in a combined cross analysis using related mouse strain crosses

Inbred mouse strains MRL and LG share the ability to fully heal ear hole punches with the full range of appropriate tissues without scarring. They also share a common ancestry, MRL being formed from a multi-strain cross with two final backcrosses to LG before being inbred by brother-sister mating. Many gene-mapping studies for healing ability have been performed using these two strains, resulting in the location of about 20 quantitative trait loci (QTLs). Here, we combine two of these crosses (N = 638), MRL/lpr × C57BL/6NTac and LG/J × SM/J, in a single combined cross analysis to increase the mapping power, decrease QTL support intervals, separate multiple QTLs and establish allelic states at individual QTL. The combined cross analysis located 11 QTLs, 6 affecting only one cross (5 LG × SM and 1 MRL × B6) and 5 affecting both crosses, approximately the number of common QTLs expected given strain SNP similarity. Amongst the five QTLs mapped in both crosses, three had significantly different genetic effects, additive in one cross and over or underdominant in the other. It is possible that allelic states at these three loci are different in SM and B6 because they lead to differences in dominance interactions with the LG and MRL alleles. QTL support intervals are 40% smaller in the combined cross analysis than in either of the single crosses. Combined cross analysis was successful in enhancing the interpretation of earlier QTL results for these strains.

Effects of inbreeding on potential and realized immune responses inTenebrio molitor

Although numerous studies on vertebrates suggest that inbreeding reduces their resistance against parasites and pathogens, studies in insects have found contradictory evidence. In this study we tested the effect of 1 generation of brother-sister mating (inbreeding) on potential and realized immune responses and other life-history traits in Tenebrio molitor. We found that inbreeding reduced adult mass, pre-adult survival and increased development time, suggesting that inbreeding reduced the condition of the adults and thus potentially made them more susceptible to physiological stress. However, we found no significant effect of inbreeding on the potential immune response (encapsulation response), but inbreeding reduced the realized immune response (resistance against the entomopathogenic fungi, Beauveria bassiana). There was a significant family effect on encapsulation response, but no family effect on the resistance against the entomopathogenic fungi. Given that this latter trait showed significant inbreeding depression and that the sample size for the family-effect analysis was small it is likely that the lack of a significant family effect is due to reduced statistical power, rather than the lack of a heritable basis to the trait. Our study highlights the importance of using pathogens and parasites in immunoecological studies.