Intergenotypic Competition Research Articles

A novel strategy to predict clonal composites by jointly modeling spatial variation and genetic competition

Biotic and abiotic stresses have been making it difficult to maintain the rates of genetic gains in forest tree breeding. Planting a mixture of genotypes or clonal composites can be an alternative to increase the security of forest plantations. The formation of clonal composites is complex due to inter-genotypic competition and indirect genotypic effects that can affect the efficiency of genetic selection. This study aims to understand how indirect genotypic effects can impact the response to selection and how the stand composition can be used to explore these effects and enhance forest yield. We used two clonal trials of eucalyptus hybrids implanted in a randomized complete block design with 24 replications, containing a single tree per plot evaluated for mean annual increment at 3 and 6 years. We focused on partitioning the genotypic variation into direct and indirect genotypic effects based on competition intensity factors. We identified aggressive, homeostatic, and sensitive clones based on the magnitude of indirect genotypic effects. Considering indirect genotypic effects, for mean annual increment, the total heritability decreased from 0.25 to 0.10 for 3 years and from 0.30 to 0.14 for 6 years, respectively. We proposed a workflow that uses the direct and indirect genotypic effects to predict the mean values for clonal composite combinations and to select the one with the highest yield. Our methodology considered spatial variation and interplot competition that can affect the total heritable estimates and response to selection in forest trials. The clones were classified as aggressive, homeostatic, and sensitive, according to their deviation from the indirect genotypic effects means. Our methodology enabled the extraction of useful information and predict many clonal composites' performance, which can be used in recommending genotypes to be planted in mixtures.

Single and Multiple High-Risk Human Papillomavirus Infections in Histopathologically Confirmed Cervical Squamous Lesions: Incidences, Distribution, and Associated Detection Rates for Precancerous and Cancerous Lesions

Coinfection with multiple high-risk human papillomavirus (hrHPV) is frequently observed in cervical specimens; however, the clinical significance of concomitant multiple hrHPV infections is poorly understood, and the published results remain inconsistent. A retrospective study at a tertiary care institution was performed, evaluating Tellgenplex human papillomavirus (HPV) 27 genotyping or YanengBio HPV 23 genotyping results and immediate cervical histologic diagnosis (within 6 months after HPV genotyping), between November 2015 and October 2022. Among 49,299 cases with hrHPV genotyping and histologic diagnosis, 24,361 cases were diagnosed as cervical intraepithelial neoplasia (CIN) and squamous cell carcinoma. Among women with cervical squamous lesions, 86.5% (21,070/24,361) had hrHPV infections, and concomitant multiple hrHPV infections accounted for 24.7% of hrHPV-positive cases (5210/21,070). The hrHPV-positive rates in these cervical squamous lesions increased progressively with disease severity; however, the percentages of concomitant multiple hrHPV infection rates among hrHPV-positive cases decreased significantly with increasing degree of squamous abnormalities. There was no increased detection rate of CIN3+ (CIN3 and squamous cell carcinoma) in cases with concomitant 2 or 3 hrHPV genotype infections when compared with those with corresponding single hrHPV infections. Conversely, some combinations of multiple hrHPV infections demonstrated a decrease in the detection rates of CIN3+ lesions. In this large cohort, our results demonstrated that multiple hrHPV infections do not carry an increased risk for developing CIN3+ lesions when compared to the corresponding single-genotype infection. The reduced risk of CIN3+ in women infected with some combinations of hrHPV genotypes compared to those with single-genotype infections supports the concept of intergenotypic competition of hrHPV genotypes in cervical squamous lesions.

Crop resilience via inter-plant spacing brings to the fore the productive ideotype.

Natural selection favors the competitive ideotype, enabling native plants to survive in the face of intense competition. The productive ideotype is the goal of artificial selection to achieve high crop yields via the efficient use of resources in a self-competition regime. When breeding is established under inter-genotypic competition, the competitive ideotype dominates and may fictitiously become selectable. The productive ideotype becomes selectable at the nil-competition regime, where widely spaced individuals prevent plant-to-plant interference for any input. Principal reasons bring to the fore the productive ideotype that combines low competitiveness and improved plant yield efficiency. Crop spacing via the productive ideotype is mandated to alleviate the varying optimum density and ensure efficient use of resources inter-seasonally, cope with intra-field variation and optimize resource use, compensate for missing plants and promote stability, counteract unpredictable stresses and offer a buffer against environmental diversity, and adopt low-input agriculture to conserve natural resources and the environment. For breeding toward the productive ideotype, nil-competition is the due condition to overcome the confounding effects of competition, maximize phenotypic differentiation and facilitate selection from an early segregating generation, optimize heritability due to moderated environmental variance and experimental designs that sample spatial heterogeneity, apply high selection pressure focusing exclusively on the targeted genotype, and avoid the risk of bias selection or loss of desired genotypes due to proximity to empty hills. The view of a modern crop variety composed of genotype(s) belonging to the productive ideotype is a viable option to reach crop resilience serving sustainability in enormously fluctuating agroecosystems.

Intra-and intergenotypic competition among commercial eucalyptus clones

Abstract Plantations made up of clones carry genetic uniformity that can compromise production. The use of multiclonal plantations is a possible solution. The objective of this study was to identify effects of competition on silvicultural performance of Eucalyptus spp. commercial clones. The experiment was carried out in a randomized block design with 12 eucalyptus clones, three replicates, and five plants per plot. Clones were evaluated for two competition types, intra- and intergenotypic, at 3 and 5 years of age. Competition parameters were estimated based on the analyses performed. Differences were found between the types of competition at both ages for mean annual increment and wood volume. Clones 8 and 9 stood out from the others in both intra- and intergenotypic competition. At 5 years of age, intergenotypic competition produced productivity gains of 13% in clones 8 and 9 and 4% overall considering wood volume and mean annual increment.

Fitness Cost and Competitive Ability to Different Ploidy Levels in Ryegrass Genotypes

ABSTRACT: The intergenotypic competition of tetraploid ryegrass with natural diploid population may be a tool to reduce the frequency of resistant individuals in an area. This study aimed to identify and compare the phenological development, fitness cost, and competitive ability between diploid and tetraploid ryegrass genotypes. Genotypes were grown in pots, and the morphological variables of genotype growth were assessed every 15 days up to 120 days after emergence to evaluate the fitness cost. Phenological development and seed yield components were measured in a single time together with the fitness cost. Competitive ability was determined in a replacement-series experiment with proportions of tetraploid and diploid ryegrass, in which the number of tillers, plant height, leaf area, and shoot dry weight were assessed at 50 days after emergence. The results of fitness cost showed that the number of tillers, leaf area, root dry weight, and the number of seeds were higher for tetraploid ryegrass, which presented a higher competitive ability than the diploid genotype regardless of the tested proportions. Tetraploid ryegrass may be useful for reducing the frequency of herbicide-resistant diploid ryegrass because of its higher competitive potential.

ЭФФЕКТИВНОСТЬ ОТБОРА В РАННИХ ПОКОЛЕНИЯХ ГИБРИДОВ CЕЛЬСКОХОЗЯЙСТВЕННЫХ КУЛЬТУР ПО УРОЖАЙНОСТИ И ПРИЗНАКАМ ПРОДУКТИВНОСТИ (обзор)

Despite the success of molecular genetics, overwhelming majority of Russian breeders still rely on selection based on plant phenotype. The most common way of identifying traits for such selection is calculation of their correlation with yield. However, the world science has accumulated extensive experience in direct selection among early generations of hybrid populations for different traits with the purpose to increase yield. The aim of this study was to inform Russian scientific community about the results of such experiments and analyze them in order to find the most efficient selection criteria. Sixty-seven scientific papers on direct or indirect selection in early generations have been analyzed. Thirty-three papers have reported positive results. The highest ratio of positive research results to negative ones refers to 1000 kernel weight and biological yield (aboveground biomass), and the lowest ratio of positive research results to negative ones is found in harvest index and yield. Taking into account high heritability of 100 kernel weight and simplicity of measuring, this trait is recommended for use in breeding practice. This result contradicts some reports on the evolution of productivity traits in plant breeding. Five efficiency-reducing factors have been identified for early generation selection: genotype-environment interaction, heterozygosity, low heritability of quantitative traits, intergenotype competition, and polygenic nature of productivity traits. The main conclusion of the study is that promising plants often emerge in the process of breeding, but many of them cannot be identified due to imperfect selection techniques. A still unresolved fundamental problem is making prognoses for hybrid populations where selection according to a definite selection criterion may lead to the appearance of a promising line.

Ecological interactions shape the adaptive value of plant defence: Herbivore attack versus competition for light.

Plants defend themselves against diverse communities of herbivorous insects. This requires an investment of limited resources, for which plants also compete with neighbours. The consequences of an investment in defence are determined by the metabolic costs of defence as well as indirect or ecological costs through interactions with other organisms. These ecological costs have a potentially strong impact on the evolution of defensive traits, but have proven to be difficult to quantify.We aimed to quantify the relative impact of the direct and indirect or ecological costs and benefits of an investment in plant defence in relation to herbivory and intergenotypic competition for light. Additionally, we evaluated how the benefits of plant defence balance its costs in the context of herbivory and intergenotypic competition.To this end, we utilised a functional‐structural plant (FSP) model of Brassica nigra that simulates plant growth and development, morphogenesis, herbivory and plant defence. In the model, a simulated investment in defences affected plant growth by competing with other plant organs for resources and affected the level and distribution of herbivore damage.Our results show that the ecological costs of intergenotypic competition for light are highly detrimental to the fitness of defended plants, as it amplifies the size difference between defended and undefended plants. This leads to herbivore damage counteracting the effects of intergenotypic competition under the assumption that herbivore damage scales with plant size. Additionally, we show that plant defence relies on reducing herbivore damage rather than the dispersion of herbivore damage, which is only beneficial under high levels of herbivore damage.We conclude that the adaptive value of plant defence is highly dependent on ecological interactions and is predominantly determined by the outcome of competition for light. plain language summary is available for this article.

Influence of intergenotypic competition on multigenerational persistence of abiotic stress resistance transgenes in populations of Arabidopsis thaliana.

Reducing crop losses due to abiotic stresses is a major target of agricultural biotechnology that will increase with climate change and global population growth. Concerns, however, have been raised about potential ecological impacts if transgenes become established in wild populations and cause increased competitiveness of weedy or invasive species. Potential risks will be a function of transgene movement, population sizes, and fitness effects on the recipient population. While key components influencing gene flow have been extensively investigated, there have been few studies on factors subsequent to transgene movement that can influence persistence and competitiveness. Here, we performed multiyear, multigenerational, assessment to examine fitness effects and persistence of three mechanistically different abiotic stress tolerance genes: C‐repeat binding factor 3/drought responsive element binding factor 1a (CBF3/DREB1a); Salt overly sensitive 1 (SOS1); and Mannose‐6‐phosphate reductase (M6PR). Transgenic Arabidopsis thaliana overexpressing these genes were grown in pure populations and in competition with wild‐type (WT) parents for six generations spanning a range of field environment conditions. Growth, development, biomass, seed production, and transgene frequency were measured at each generation. Seed planted for each generation was obtained from the previous generation as would occur during establishment of a new genotype in the environment. The three transgenes exhibited different fitness effects and followed different establishment trajectories. In comparison with pure populations, CBF3 lines exhibited reduced dry weight, seed yield, and viable seed yield, relative to WT background. In contrast, overexpression of SOS1 and M6PR did not significantly impact productivity measures in pure populations. In competition with WT, negative fitness effects were magnified. Transgene frequencies were significantly reduced for CBF3 and SOS1 while frequencies of M6PR appeared to be subject to genetic drift. These studies demonstrate the importance of fitness effects and intergenotype competition in influencing persistence of transgenes conferring complex traits.

Indirect selection for potential yield in early-generation, spaced plantings of wheat and other small-grain cereals: a review

Early-generation (e.g. F2–F4) selection for grain yield itself is frustrated in particular by the small amounts of seed available. However, there has long been an interest in traits related to yield and reasonably faithfully expressed in spaced planting arrangements using little seed; these are potentially useful as indirect selection criteria for yield, with the view to increasing genetic progress per unit cost. This subject is revisited in this review, targeting potential yield (yield in the absence of abiotic and biotic stresses) of small-grain cereals. A brief assessment of current breeding systems for self-pollinated crops such as wheat reveals that all have some stage during which selection among visually acceptable spaced plants has to, or could, be practiced. The relative performance of different genotypes in such spaced plantings is then explored, highlighting interactions arising from intergenotypic competition as well as from the extra space itself. The theory of indirect selection is presented, along with some practical examples. After a brief survey of possible selection traits and developments in high-throughput measurement, harvest index, fruiting efficiency and stomatal conductance (and its surrogates) are chosen for in-depth review. All three traits show promise, especially in the light of possible new ways of reducing the cost of their measurement in early generations. Remote sensing of foliage temperature for the detection of genotypic differences in stomatal conductance makes this clearly the most promising trait for thorough testing in commercial breeding populations. Such traits could be used directly or they could complement genomic selection in early generations.

Multiple Human Papilloma Virus Infections and Their Impact on the Development of High-Risk Cervical Lesions

Objective: Individuals are often infected with multiple genotypes of human papillomavirus (HPV) simultaneously, but the role these infections play in the development of cervical disease is not well established. This study aimed to determine the association of multiple HPV infections with high-risk cervical lesions (hrCLs). Study Design: HPV genotyping was performed on 798 SurePath specimens collected between December 1, 2009, and April 30, 2011. The cases were classified as hrCL (n = 90) or non-hrCL (n = 708) based on cytology diagnoses. The association between hrCL and HPV infection patterns was analyzed. Results: Multiple HPV infections were frequently encountered (38.2%) in the cohort. Increased frequency of hrCLs was associated with a single high-risk HPV (hrHPV) infection. An additive or synergistic effect was not observed for hrCL in multiple HPV infections. The hrCL rates appeared to decrease in various patterns of multiple HPV infections, but the reduction was not statistically significant. Conclusions: Multiple HPV infections are common with no additive or synergistic effect on the development of hrCL. Conversely, reduced hrCL rates were observed in various patterns of multiple HPV infections compared to their single-genotype infection counterparts, suggestive of possible intergenotypic competition or more effective immune response triggered by multiple infections. Further studies in larger cohorts are needed.

Impact of disease on diversity and productivity of plant populations.

Summary Experiments were conducted on the role of intra‐ and inter‐genotypic competition in ecological processes operating at the population scale in diseased plant populations.Combinations of Arabidopsis thaliana genotypes showing variation for phenotypic traits relating to competitive ability and pathogen compatibility were infected with the oomycete Hyaloperonospora arabidopsidis and Turnip yellows virus in separate experiments. Plant fitness and competitive ability were estimated from phenotypic measurements.Pathogen‐induced reduction in competitive ability for susceptible genotypes increased the competitive ability of resistant genotypes, resulting in maintenance of yield via competitive release. The two diseases had different effects on competitive interactions between plants. In experiments involving the oomycete, the highest yields were produced by mixtures of two weakly competing genotypes.The Arabidopsis model system has elucidated the ecological processes by which compensatory competitive interactions can increase the buffering capacity of plant populations under pathogen attack. Highly competitive genotypes may not maximize the productivity of the population as a whole, as they may over‐yield at the expense of less competitive, more productive genotypes. The specific outcomes of competitive interactions cannot be generalized because they depend on the disease and the host genotypes.

Early selection in open-pollinated Eucalyptus families based on competition covariates

The objetive of this work was to evaluate the influence of intergenotypic competition in open-pollinated families of Eucalyptus and its effects on early selection efficiency. Two experiments were carried out, in which the timber volume was evaluated at three ages, in a randomized complete block design. Data from the three years of evaluation (experiment 1, at 2, 4, and 7 years; and experiment 2, at 2, 5, and 7 years) were analyzed using mixed models. The following were estimated: variance components, genetic parameters, selection gains, effective number, early selection efficiency, selection gain per unit time, and coincidence of selection with and without the use of competition covariates. Competition effect was nonsignificant for ages under three years, and adjustment using competition covariates was unnecessary. Early selection for families is effective; families that have a late growth spurt are more vulnerable to competition, which markedly impairs ranking at the end of the cycle. Early selection is efficient according to all adopted criteria, and the age of around three years is the most recommended, given the high efficiency and accuracy rate in the indication of trees and families. The addition of competition covariates at the end of the cycle improves early selection efficiency for almost all studied criteria.

Resource availability modulates above‐ and below‐ground competitive interactions between genotypes of a dominantC4grass

SummaryThe well‐described pattern of a few common and many rare species in plant communities (dominance‐diversity curves) also has been documented within populations of dominant plant species. Understanding how these common genotypes coexist has implications for how genotype richness of a dominant species may impact community and ecosystem processes. Some studies have shown that increased genotype richness of a dominant species leads to an increase in above‐ground productivity, suggesting niche complementarity between genotypes. However, mechanistic understanding of how genotypes may complement one another is lacking.We conducted a pairwise competition experiment between four common and naturally co‐occurring genotypes of a dominantC4grass species,Andropogon gerardii, in tallgrass prairie of the centralUnitedStates. The genotypes were grown under both intra‐ and intergenotypic competition with different combinations of resources (low and high light, water, and nitrogen) in the greenhouse.We determined that there were above‐ and below‐ground phenotypic differences between genotypes which results in altered competitive interactions depending on resource conditions. Different genotypes were competitively dominant under low‐ and high‐light conditions and low and highNand water availability. Moreover, relative yield total values (RYT) for each genotype pairwise combination indicated that all four genotypes make demands on different resources, providing evidence for niche complementarity.Finally, we found that differential success in resource acquisition, biomass accumulation, and subsequent competitive ability translated to variation in vegetative reproductive success of the genotypes, which has implications for the population dynamics of this primarily asexually reproducing perennial grass.Our results suggest that naturally co‐occurring genotypes coexist because they are competitively dominant under different environmental conditions, providing insight into how genetic diversity within dominant plant species is maintained and may potentially affect important ecosystem processes.

Plot size matters: interference from intergenotypic competition in plant phenotyping studies.

Genetic and physiological studies often comprise genotypes diverse in vigour, size and flowering time. This can make the phenotyping of complex traits challenging, particularly those associated with canopy development, biomass and yield, as the environment of one genotype can be influenced by a neighbouring genotype. Limited seed and space may encourage field assessment in single, spaced rows or in small, unbordered plots, whereas the convenience of a controlled environment or greenhouse makes pot studies tempting. However, the relevance of such growing conditions to commercial field-grown crops is unclear and often doubtful. Competition for water, light and nutrients necessary for canopy growth will be variable where immediate neighbours are genetically different, particularly under stress conditions, where competition for resources and influence on productivity is greatest. Small hills and rod-rows maximise the potential for intergenotypic competition that is not relevant to a crop's performance in monocultures. Response to resource availability will typically vary among diverse genotypes to alter genotype ranking and reduce heritability for all growth-related traits, with the possible exception of harvest index. Validation of pot experiments to performance in canopies in the field is essential, whereas the planting of multirow plots and the simple exclusion of plot borders at harvest will increase experimental precision and confidence in genotype performance in target environments.

Efeito competicional em testes de progênies de eucalipto

http://dx.doi.org/10.5902/198050986612Muitos estudos têm recomendado o uso de parcelas pequenas na experimentação florestal, porém, não consideram o aumento da competição intergenotípica que isto acarreta e que pode resultar na seleção incorreta dos materiais genéticos. O objetivo deste trabalho foi o de avaliar sete covariáveis de competição sobre o caráter volume de madeira em dois testes de progênies de Eucalyptus spp. O delineamento utilizado foi de blocos casualizados, com seis repetições de 10 plantas. As sete covariáveis analisadas foram índice de competição de Hegyi (IC), autocompetição (AT), alocompetição (AL), média da autocompetição (MAT), média da alocompetição (MAL) e média aritmética dos quatro (M4) e oito vizinhos mais próximos (M8). Essas covariáveis foram avaliadas individualmente bem com em todas as suas possíveis combinações, obtendo-se estimativas de componentes de variâncias e suas alterações com o emprego das mesmas. A competição influenciou os resultados de análises de testes de progênies de eucalipto, em que, autocompetição e alocompetição interferem de forma diferenciada. As covariáveis mais influentes são a MAT, a MAL e o IC. A rotina de análise que apresentou melhores resultados foi a que incluiu as covariáveis IC/MAT, sendo eficiente na redução do efeito competicional em testes de progênies de eucalipto.

Minimizing inter-genotypic competition effects to predict genetic values and selection in forestry genetic tests

The effect of competition is an important source of variation in breeding experiments. This study aimed to compare the selection of plants of open-pollinated families of Eucalyptus with and without the use of competition covariables. Genetic values were determined for each family and tree and for the traits height, diameter at breast height and timber volume in a randomized block design, resulting in the variance components, genetic parameters, selection gains, effective size and selection coincidence, with and without the use of covariables. Intergenotypic competition is an important factor of environmental variation. The use of competition covariables generally reduces the estimates of variance components and influences genetic gains in the studied traits. Intergenotypic competition biases the selection of open-pollinated eucalypt progenies, and can result in an erroneous choice of superior genotypes; the inclusion of covariables in the model reduces this influence.

Host resistance mediated inter-genotype competition and temporal variation in Fusarium oxysporum f. sp. vasinfectum

Temporal variation in Fusarium oxysporum f. sp. vasinfectum (Fov) populations was determined by comparing the genetic diversity of pathogen isolates recovered from three consecutive cotton crops (2002, 2004 and 2006) in the Boggabilla area of New South Wales, Australia. A total of 288 isolates were collected, among which 25 distinct AFLP genotypes were identified. These genotypes were classified into two main groups corresponding to known vegetative compatibility groups (VCG)—01111 and 01112. The Fov populations were dominated by four genotypes (I-A, I-B, II-A, II-B) that accounted for 87.5% of the isolates. Significant temporal variation was observed in both sampled fields with 6.8% and 10.7% of total genetic variation being attributed to differences among collections in different years. Genetic diversity based on Nei’s gene diversity and the Shannon-Wiener index increased over time. Significant changes in the frequency of the dominant Fov genotypes were observed in one field, where genotype I-A declined from 84.8% to 40.0% over the study period (2002–2006), while genotype I-B increased from 7.6% to 35.4%. Strong inter-genotype competition was detected in glasshouse bioassays with 93.4% of symptomatic plants sampled from dual inoculation trials being infected by single genotypes. Competition was differentially mediated by cotton cultivars as the competitive ability of pathogen genotype I-B was enhanced on the resistant cultivar Sicot 189 relative to the susceptible cultivar Siokra 1–4. This suggests that host-mediated inter-genotype competition may play an important role in temporal variation in Fov populations in the field.

Nutrient enrichment enhances hidden differences in phenotype to drive a cryptic plant invasion

Many mechanisms of invasive species success have been elucidated, but those driving cryptic invasions of non-native genotypes remain least understood. In one of the most successful cryptic plant invasions in North America, we investigate the mechanisms underlying the displacement of native Phragmites australis by its Eurasian counterpart. Since invasive Phragmites’ populations have been especially prolific along eutrophic shorelines, we conducted a two-year field experiment involving native and invasive genotypes that manipulated nutrient level and competitor identity (inter- and intra-genotypic competition) to assess their relative importance in driving the loss of native Phragmites. Inter-genotypic competition suppressed aboveground biomass of both native and invasive plants regardless of nutrient treatment (∼ 27%), while nutrient addition disproportionately enhanced the aboveground biomass (by 67%) and lateral expansion (by > 3 × farther) of invasive Phragmites. Excavation of experimental plots indicated that nutrient addition generates these differences in aboveground growth by differentially affecting rhizome production in invasive vs native plants; invasive rhizome biomass and rhizome length increased by 595% and 32% with nutrient addition, respectively, while natives increased by only 278% and 15%. Regardless of nutrient level, native rhizomes produced twice as many roots compared to invasives, which field surveys revealed are heavily infected with mycorrhizal symbionts. These results suggest that native Phragmites competes well under nutrient-limited conditions because its rhizomes are laden with nutrient-harvesting roots and mycorrhizae. Invasive Phragmites’ vigorous aboveground response to nutrients and scarcity of lateral roots, in contrast, may reflect its historic distribution in eutrophic Eurasian wetlands and correspond to its prevalence in New England marshes characterized by elevated nutrient availability and relaxed nutrient competition. These findings reveal that discrete differences in phenotype can interact with anthropogenic modification of environmental conditions to help explain the success of cryptic invaders.

Genetic variation in tolerance of competition and neighbour suppression in Arabidopsis thaliana

Intraspecific competitive interactions can profoundly influence phenotypic evolution. However, prior studies have rarely evaluated the evolutionary potential of the two components of competitive ability, tolerance of competition and suppression of neighbours. Here, we grow a set of 20 Arabidopsis thaliana recombinant inbred lines in three competitive treatments (noncompetitive, intra-genotypic competition and inter-genotypic competition) to examine if there is genetic variation for the components of competitive ability and whether neighbour relatedness has an effect on fitness. We find evidence for genetic variation in tolerance of competition and neighbour suppression and that these two competitive strategies are correlated, such that genotypes that tolerate competition will also strongly suppress neighbours. We further observe that the effect of neighbour relatedness on fitness of target individuals depends on neighbour identity, i.e. whether target individuals perform better when competing against self vs. nonself individuals depends on the genotypic identity of the nonself neighbour. The results are particularly relevant to evolutionary responses under multi-level selection.

Indirect genetic effects and the lek paradox: inter-genotypic competition may strengthen genotype × environment interactions and conserve genetic variance

Understanding the evolutionary mechanisms that maintain genetic variation in natural populations is one of the fundamental goals of evolutionary biology. There is growing evidence that genotype-by-environment interaction (G x E) can maintain additive genetic variance (V (A)), but we lack information on the relative performance of genotypes under the competitive situations encountered in the field. Competing genotypes may influence each other, and this interaction is also subject to selection through indirect genetic effects (IGE). Here, we explore how genotypes perform when interacting and evaluate IGE in order to understand its influence on V (A) for sexually-selected traits in the lesser waxmoth, Achroia grisella. We found that inter-genotype differences and crossover interactions under joint rearing are equal to or greater than values when reared separately. A focal genotype exhibited different performances when jointly reared with various genotypes-suggesting that IGE may be responsible for the increased levels of crossover and differences in performance observed. We suggest that some genotypes are superior competitors for food acquisition in the larval stage, and that these differences influence the development and evolution of other genotypes through IGE. We reaffirm the role of G x E in maintaining V (A) and note the general importance of IGE in studies of evolutionary mechanisms.