Selection Intensity Research Articles

The mechanisms of labor division from the perspective of task urgency and game theory

Labor division is a prevalent phenomenon in nature, drawing the attention of researchers across various fields owing to its inherent cooperative dilemmas. The study of how groups of self-interested individuals maintain a harmonious division of labor is both fascinating and significant. However, the majority of existing game models, which are rooted in two-player interactions, often fail to accurately represent real-world scenarios where interactions between individuals are not widespread. To bridge this gap, we present the Division of Labor Game within Community (DOLC) model. This paper begins with an overview of the problem's background, progressing to the development of the DOLC mathematical model. Subsequent sections delve into theoretical analyses and simulations of the two-task variant of the DOLC, before exploring its extension to multi-task scenarios and investigating the impact of network structures on cooperative dynamics. Our research reveals critical insights: in the absence of the urgency coefficient, members of the community invariably choose the same task, hindering cooperative efforts. Conversely, the urgency coefficient positively influences the evolution of intra-group labor division, while the selection intensity tends to undermine it. These dynamics persist even in multi-task configurations of the DOLC model, and network circulation often hampers group collaboration. These findings have promising applications in enhancing the efficiency of unmanned systems and optimizing strategies for task allocation and scheduling.

Does selection index application for highly heritable traits need revisiting – A comprehensive study with bodyweight and shank length in Vanaraja male line chicken

Selection index (SI) is one of the best methods for estimating the breeding value of an animal combining all sources of information on the animal and its relatives. In the present study, the SI was constructed utilizing the five generations data of Vanaraja male line (PD-1) for body weight (BW-6) and shank length (SL-6) at 6 weeks of age with variance, covariance estimates and heritability of both the traits. The SI was employed on three generations data on simulation basis and the selection parameters were estimated and compared with the mass selection (MS) actually practiced in the population. The least squares mean of SL-6, the primary trait of selection increased from 76.63±0.002 (G-I) to 82.85 ±0.002 mm (G-II), and subsequently reduced to 80.17±001 mm (G-III). The BW-6 also followed similar trend. Generation had significant effect on both SL-6 and BW-6. The heritability estimates for SL-6 and BW-6 were moderate with 0.21 to 0.28 for SL-6 and 0.22 to 0.27 for BW-6. The two traits exhibited high degree of positive association with 0.87 to 0.92 correlation coefficient. The economic value estimated for weight and shank length was 1:8.95. Thus, the selection index constructed was I= 0.2260*BW6, g + 0.7717*SL6, mm. Selection differential was higher in SI method on pooled basis compared to MS in all three generations for the primary trait, SL-6. The response to selection and selection intensity was also higher in SI method compared to MS. A similar trend was observed for BW-6 with respect to selection differential and response to selection. The study concluded that SI was superior to mass selection based on the results in Vanaraja male line chicken.

Resistance to fenazaquin in broad mite, Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae): Realized heritability, risk assessment and cross‐resistance

AbstractThe broad mite, Polyphagotarsonemus latus (Banks), is an important phytophagous mite that causes extensive damage to a wide range of crop species across the world. Fenazaquin, a mitochondrial electron transport inhibitor (METI), is one of the commonly used acaricides for the management of P. latus. The response to fenazaquin selection over generations and the risk of development of resistance was estimated herein using a laboratory‐selected population of P. latus (FEN‐SEL). Repeated exposure to fenazaquin over generations resulted in decreased susceptibility (99.32 folds) as compared to the unselected counterpart. FEN‐SEL took 26 generations for a 10‐fold increase in resistance with a realized heritability (h2) of 0.12 which indicated a low genetic variation and high phenotypic variation. Over a selection intensity of 20%–80% mortality, the generations required for a 10‐fold increase in LC50 for fenazaquin were 14.21–55.75, 7.75–30.41 and 5.33–20.91 at h2 values of 0.12, 0.22 and 0.32, respectively, with a constant slope of 2.39. The FEN‐SEL population also exhibited moderate levels of cross‐resistance to diafenthiuron, dicofol and spiromesifen and low cross‐resistance to propargite. The findings suggest a rational and rotational application of fenazaquin in the field to delay the development of resistance and to prolong its efficacy against P. latus.

Genetic associations between stayability to consecutive calvings and traits of economic interest in taurine and zebu breeds.

Stayability (STAY) is a way to evaluate the productive longevity of females. Measuring the STAY at each cow calving allows earlier indicators of longevity to be obtained. Our objective with this study was to verify the association between STAY and consecutive calvings and traits potentially used as selection criteria in beef cattle, such as age at first calving (AFC), days to calving (DC), weaning weight (WW), and yearling weight (YW). Data from the Nelore, Angus/Brangus, and Hereford/Braford breeds were used. The estimation of variance components and subsequent prediction of breeding values were performed for all traits. The estimated breeding values (EBV) were used to analyse the association between STAY and the other traits. The Pearson's correlation estimated between the EBV for the intercept coefficient for STAY to consecutive calvings and those of AFC, DC, WW (direct and maternal effects), and YW was favourable and of low magnitude (<0.25) depending on the breed studied. The influence of the genetic merit of AFC on the chance of selection for STAY was favourable and relevant regardless of the intensity of selection and breed. DC and WW (maternal effect) traits were favourably influenced by the chance of selection for STAY, irrespective of breed. The WW (direct effect) did not affect the chance of selection for STAY for the Nelore and Hereford/Braford breeds and negatively influenced, but to a small extent, the Angus/Brangus breed. For YW, an increase in genetic merit affected the chances of selection for STAY, depending on the breed and selection intensity evaluated. The influence of the genetic merit for AFC, DC, and WW (maternal effect) on the chance of selection for STAY to consecutive calvings was favourable and relevant regardless of the selection intensity scenario evaluated. The WW (direct effect) did not influence the chance of selection for STAY. For the scenario with high selection intensity, the selection for YW favourably influenced the chance of selection for STAY in Angus/Brangus and Hereford/Braford breeds but not in Nelore.

Genetic gain in oil productivity from breeding program of Cajuput (Melaleuca cajuputi subsp. cajuputi) in Indonesia

A long-term breeding program of cajuput (Melaleuca cajuputi subsp. cajuputi) in Indonesia has aimed to increase oil productivity and quality through imposing selection for oil yield and 1,8-cineole content. This study examined the realized genetic gain for the two key variables of oil yield, oil concentration and leaf biomass. Data were collected from a trial based on seeds collected from two unimproved, and two improved sources with selection intensities (IS) of 1.1 (10% of trees selected) and > 2.5 (<1% of trees selected). The trial was laid-out in a randomized complete block design with five replications. It was measured at 10 years of age. The leaf oil concentration of the IS >2.5 seed source was significantly higher than for the other sources; a realized genetic gain ranging from 14% to 31%. However, although not significant, this seed source had the lowest leaf biomass. The correlation between gains in oil concentration and leaf biomass was weak and not significant (r = 0.15); while the correlation between oil yield and leaf biomass was very strong and highly significant (r = 0.96). These results highlight the importance of carefully incorporating leaf biomass as a selection criterion in cajuput breeding programs aimed at increasing oil yield.

Beyond classical theories: An integrative mathematical model of mating dynamics and parental care.

Classical theories, such as Bateman's principle and Trivers' parental investment theory, attempted to explain the coevolution of sexual selection and parental care through simple verbal arguments. Since then, quantitative models have demonstrated that it is rarely that simple because many non-intuitive structures and non-linear relationships are actually at play. In this study, we propose a new standard for models of mating dynamics and parental care, emphasizing the clarity and use of mathematical and probabilistic arguments, the meaning of consistency conditions, and the key role of spatial densities and the law of mass action. We used adaptive dynamics to calculate the evolutionary trajectory of the total care duration. Our results clearly show how the outcomes of parental care evolution can be diverse, depending on the quantitative balance between a set of dynamical forces arising from relevant differences and conditions in the male and female populations. The intensity of sexual selection, synergy of care, care quality, and relative mortality rates during mating interactions and caring activities act as forces driving evolutionary transitions between uniparental and biparental care. Sexual selection reduces the care duration of the selected sex, uniparental care evolves in the sex that offers the higher care quality, higher mortality during mating interactions of one sex leads to more care by that sex, and higher mortality during caring activities of one sex favours the evolution of uniparental care in the other sex. Both synergy and higher overall mortality during mating interactions can stabilize biparental care when sexual selection reduces the care duration of the selected sex. We discuss how the interaction between these forces influences the evolution of care patterns, and how sex ratios can vary and be interpreted in these contexts. We also propose new directions for future developments of our integrative model, creating new comparable analyses that share the same underlying assumptions and dynamical frameworks.

Distinguishing Hybrids of Golden Thailand and Malaysian Strains of Climbing Perch, Anabas testudineus (Bloch, 1792), Using Multivariate Analyses of Morpho-Meristic Traits

The climbing perch, Anabas testudineus (Bloch, 1792), is a commercially important freshwater fish in Southeast Asia. To meet demand, establishing stock development breeding programmes is essential. However, there is a lack of scientific literature on parent-hybrids differences. This study aims to use morphometric characteristics to identify important predictors and determine their heritability to address the knowledge gap. Two strains of A. testudineus and their corresponding hybrid groups, represented by T1–T4 (T1: golden Thai (♀) × golden Thai (♂), T2: golden Thai (♀) × Malaysian (♂), T3: Malaysian (♀) × Malaysian (♂) and T4: Malaysian (♀) × golden Thai (♂)) were used for the experiment. Thirty individuals of each strain were randomly selected from their respective tanks for morphometric characteristics assessment. Twenty-five morphometric measurements were taken, and adjustments were made for body size effects. These measurements were then subjected to multivariate analysis with a 5 % selection intensity for genetic advancement, focusing on body depth and base of anal fin length. The morphometric characters, including postorbital length, lowest body depth,the base of analfin length,total length, standard length, pre-pectoral fin length,the base of pectoralfin length, and base of pelvic fin length based on the canonical coefficient, were identified as distinguishing factors between hybrids and the parental population. The study showed that body length heritability was greater than 60 %, indicating a significant additive genetic effect that surpasses the impact of the environmental effect and thus could be used as a potential characteristic for selective breeding to improve the desired trait.

Ultrafast Yb:YAG laser oscillator with gigahertz repetition rate.

We present a SESAM modelocked Yb:YAG solid-state laser providing low-noise narrowband pulses with a pulse duration of 606 fs at a 1.09-GHz repetition rate, delivering up to 2.5 W of average output power. This laser provides access to a new parameter space that could previously not be reached by solid-state lasers and, to the best of our knowledge, is the first modelocked solid-state Yb:YAG laser in the gigahertz regime. This is achieved by introducing a single additional intracavity element, specifically a nonlinear birefringent YVO4 crystal, for soliton formation, polarization selection, and cavity intensity clamping. The isotropic pump absorption in Yb:YAG allows for stable and low-noise operation with multimode fiber pumping. This laser is ideally suited as a seed source for many commercial high-power Yb-doped amplification systems operating at a center wavelength around 1.03 µm. The laser exhibits a high power per comb line of 5.0 mW which also makes it interesting for applications in frequency comb spectroscopy, especially if it is used to pump an optical parametric oscillator. We measure a relative intensity noise (RIN) of 0.03%, integrated from 1 Hz to 10 MHz. Furthermore, we show that the laser timing jitter for noise frequencies >2 kHz is fully explained by a power-dependent shift in the center wavelength of 0.38 nm/W due to the quasi-three-level laser gain material. The narrow gain bandwidth of Yb:YAG reduces this contribution to noise in comparison to other SESAM modelocked Yb-doped lasers.

Genomic selection for salinity tolerance in japonica rice.

Improving plant performance in salinity-prone conditions is a significant challenge in breeding programs. Genomic selection is currently integrated into many plant breeding programs as a tool for increasing selection intensity and precision for complex traits and for reducing breeding cycle length. A rice reference panel (RP) of 241 Oryza sativa L. japonica accessions genotyped with 20,255 SNPs grown in control and mild salinity stress conditions was evaluated at the vegetative stage for eight morphological traits and ion mass fractions (Na and K). Weak to strong genotype-by-condition interactions were found for the traits considered. Cross-validation showed that the predictive ability of genomic prediction methods ranged from 0.25 to 0.64 for multi-environment models with morphological traits and from 0.05 to 0.40 for indices of stress response and ion mass fractions. The performances of a breeding population (BP) comprising 393 japonica accessions were predicted with models trained on the RP. For validation of the predictive performances of the models, a subset of 41 accessions was selected from the BP and phenotyped under the same experimental conditions as the RP. The predictive abilities estimated on this subset ranged from 0.00 to 0.66 for the multi-environment models, depending on the traits, and were strongly correlated with the predictive abilities on cross-validation in the RP in salt condition (r = 0.69). We show here that genomic selection is efficient for predicting the salt stress tolerance of breeding lines. Genomic selection could improve the efficiency of rice breeding strategies for salinity-prone environments.

Optimization of Multi-Generation Multi-location Genomic Prediction Models for Recurrent Genomic Selection in an Upland Rice Population

Genomic selection is a worthy breeding method to improve genetic gain in recurrent selection breeding schemes. The integration of multi-generation and multi-location information could significantly improve genomic prediction models in the context of shuttle breeding. The Cirad-CIAT upland rice breeding program applies recurrent genomic selection and seeks to optimize the scheme to increase genetic gain while reducing phenotyping efforts. We used a synthetic population (PCT27) of which S0 plants were all genotyped and advanced by selfing and bulk seed harvest to the S0:2, S0:3, and S0:4 generations. The PCT27 was then divided into two sets. The S0:2 and S0:3 progenies for PCT27A and the S0:4 progenies for PCT27B were phenotyped in two locations: Santa Rosa the target selection location, within the upland rice growing area, and Palmira, the surrogate location, far from the upland rice growing area but easier for experimentation. While the calibration used either one of the two sets phenotyped in one or two locations, the validation population was only the PCT27B phenotyped in Santa Rosa. Five scenarios of genomic prediction and 24 models were performed and compared. Training the prediction model with the PCT27B phenotyped in Santa Rosa resulted in predictive abilities ranging from 0.19 for grain zinc concentration to 0.30 for grain yield. Expanding the training set with the inclusion of the PCT27A resulted in greater predictive abilities for all traits but grain yield, with increases from 5% for plant height to 61% for grain zinc concentration. Models with the PCT27B phenotyped in two locations resulted in higher prediction accuracy when the models assumed no genotype-by-environment (G × E) interaction for flowering (0.38) and grain zinc concentration (0.27). For plant height, the model assuming a single G × E variance provided higher accuracy (0.28). The gain in predictive ability for grain yield was the greatest (0.25) when environment-specific variance deviation effect for G × E was considered. While the best scenario was specific to each trait, the results indicated that the gain in predictive ability provided by the multi-location and multi-generation calibration was low. Yet, this approach could lead to increased selection intensity, acceleration of the breeding cycle, and a sizable economic advantage for the program.

Monitoring selective logging intensities in central Africa with sentinel-1: A canopy disturbance experiment

Forest degradation is a major threat to tropical forests, and effective monitoring using remotely sensed data is subject to significant challenges. In particular, consistent methods for detecting subtle changes in the forest canopy structure caused by selective logging are lacking. Here, using a unique dataset collected in southeastern Cameroon, covering over 22,000 ha of monthly harvesting areas, >6000 locations of harvested trees, and an independent canopy gap dataset developed from an uninhabited aerial vehicle flight (UAV; RGB camera) of approximately 1500 ha, a new method was designed to monitor canopy disturbance and logging intensity in Central Africa. Using Sentinel-1 synthetic aperture radar (SAR) data, the method was conceptualised using a two-step, two-scale approach, which better matched logging practices. First, (non-)harvesting activity areas were identified using textural indices at a spatial resolution of 300 m (step 1), and within these harvesting activity areas, canopy gaps were detected at a resolution of 10 m (step 2). Both steps were based on monthly differences in the Sentinel-1 SAR time series computed using the average of the 12 months preceding and the average of the three months following the month of interest. This method identified harvesting activity areas (step 1 at 300 m resolution) of over 12,004 km2 with high accuracy (omission and commission errors for both classes ≤0.05) and, within them, detected canopy gaps (step 2 at 10 m resolution) with a global accuracy of 0.89. Although some canopy gaps were subject to omission and commission errors (0.39 and 0.05, respectively), this method yielded better results than other available approaches. Compared to the UAV canopy gaps, this method detected most of the small gaps (≤ 500 m2), which represent 80% of all disturbed areas, whereas other available approaches missed at least 70% of these and consequently missed most of the disturbance events occurring in a selectively logged forest. Furthermore, the predictions were correlated with logging intensity, i.e., the number of trees and volume cut per hectare, which are two important criteria for assessing the sustainability of logging activities. This two-step two-scale method for short-term, monthly monitoring of logging disturbances and intensity has strong practical implications for forest administration and certification bodies in Central Africa.

Phenotypically plastic responses to freshwater salinization in larval amphibians: Induced tolerance and induced sensitivity

Contamination of aquatic ecosystems is pervasive around the world and there has been a growing interest in understanding the ecological and evolutionary impacts. For contaminants such as pesticides, researchers are discovering widespread evolution of increased tolerance in target and non-target species and the role of phenotypic plasticity in facilitating this evolution. In contrast, we know much less about the evolution of tolerance in response to the increasing problem of freshwater salinization. In amphibians, recent studies have discovered that some populations from ponds with high salt pollution (from deicing road salts) have evolved higher tolerance. In this study, we examined whether populations of wood frog tadpoles (Rana sylvatica) possess rapid, inducible tolerance to salinity in a manner similar to their inducible tolerance to pesticides. Using newly hatched tadpoles from nine populations, we discovered that eight of the populations were able to alter their tolerance to salt. However, seven of the eight inducible populations experienced a higher sensitivity to salt while the eighth population experienced a higher tolerance to salt. Such inducible responses likely reflect the interplay of salt dynamics in the ponds, combined with the available genetic variation and selection intensity of each pond. This appears to be the first example of inducible salt tolerance in any animal and future studies should examine the generality of the response and how it may affect the evolution of tolerance to the global issue of freshwater salinization.

Growth rate, evolutionary entropy and ageing across the tree of life

The growth rate of a population serves as a measure of its Darwinian fitness, while its sensitivity indicates the intensity of selection. Generally, the sensitivity of r decreases with age, resulting in an expected increase in population mortality over time. However, this does not hold true for many populations, especially those exhibiting negative senescence. Both evolutionary entropy and its sensitivity serve as complementary measures for assessing fitness and the intensity of selection. The sensitivity of entropy is typically a convex function of age, implying stronger selection pressures in younger and older age groups. We show that the sensitivity functions of entropy exhibit a greater range of behaviours compared to those of the growth rate alone. This strongly suggests that evolutionary entropy offers an extremely valuable measure for capturing the diversity in aging patterns within populations, complementing what can be captured by the growth rate alone.

PHENOTYPIC VARIABILITY EVALUATION OF WHEAT VARIETIES FROM THE SUCEAVA GENE BANK COLLECTION

The intensity of selection, inadvertent pathways of domestication, and the influence of climate change collectively amplify the frequency of detrimental alleles. This phenomenon, in turn, triggers genetic drift, leading to an in-advertent decline in the diversity of plant genetic resources. Genetic variability is of utmost importance for a species’ adaptability and overall fitness. Our investigation centres on Triticum germplasm within the agroclimatic conditions of the Suceava Gene Bank, encompassing 2021–2022 field trials. Comprehensive morphophysiological characterisation was conducted across 200 cultivated varieties, spanning three Triticum species (T. aestivum, T. turgidum and T. monococcum). Initially, the data underwent meticulous processing involving the computation of amplitude of variation, variance (s2), standard deviation (√s), and coefficients of variation (s%) for three pivotal agronomical traits: plant height, spikelets per spike, and total seeds per spike. Furthermore, an extensive cluster analysis was performed, encompassing multiple vital plant descriptors. The findings unveiled a remarkable dispersion of data, with standard deviation, amplitude of variation, and coefficient of variation collectively indicating substantial variability among the cultivated varieties. Within the same population, an intriguing observation emerged; of the 200 genotypes analysed, 83 exhibited immunity to Septoria tritici. Delving deeper into the statistical analysis, we identified two primary clusters within the population. Overall, a significant proportion of this germplasm showcased elevated phenotype scores, rendering them well-suited for further exploration as foundational material in pre-breeding initiatives.

New protocol for rapid cassava multiplication in field conditions: a perspective on speed breeding.

Despite the economic and social importance, high-yielding cassava cultivars are only released after extensive research, mainly due to the low multiplication rate. This study aimed to assess the impact of using smaller-sized seed cuttings treated with agrochemicals (8MP) compared to the conventional planting size (16 cm) on genetic parameters, agronomic performance, and the ranking of cassava clones based on yield and growth attributes. The evaluation was carried out in clonal evaluation trial (CET), preliminary yield trial (PYT), and uniform yield trials (UYT). Additionally, a new selection scheme for cassava breeding programs was proposed. A total of 169 clones were evaluated, including 154 improved clones at different stages of selection and 15 local varieties used as checks. Field trials were conducted using both sizes of propagative material (8MP and 16 cm) in each phase of the breeding program. The data were analyzed using mixed models, considering the random effects of genotype and genotype-environment interaction (G×E) to determine variances and heritabilities. Bland-Altman concordance and correlation analysis of selection indices were employed to examine the consistency in the ranking of cassava clones using different seed cutting sizes. The distribution of variance components, heritabilities, means, and range of the 8MP and 16 cm trials in different phases of the cassava breeding program exhibited remarkable similarity, thereby enabling a comparative assessment of similar genetic effects. With a selection intensity of 30%, the concordance in clone ranking was 0.41, 0.57, and 0.85 in CET, PYT, and UYT trials, respectively, when comparing the selection based on 8MP and 16 cm trials. It is worth noting that the ranking of the top 15% remained largely unchanged. Based on the findings, proposed changes in the cassava selection scheme involve increasing the number of trials starting from the CET phase, early incorporation of G×E interaction, elimination of the PYT trial, reduction of the breeding cycle from 5 to 3 years, and a decrease in the time required for variety development from 11 to 9 years. These modifications are expected to lead to cost reduction and enhance the effectiveness of cassava breeding programs.

Recent advances in population improvement through RGA under Irrigated Boro rice breeding program in Bangladesh

Development of new high yielding varieties needs highly accelerated breeding approaches to meet the demand of increased rice production now a days. To address this issue, Rapid Generation Advance (RGA) of segregating rice population and Line Stage Testing (LST) of fixed breeding lines has been adopted as a routine work in Bangladesh Rice Research Institute. In the present study, we described the evidence of advancing a large number of segregating population and high selection pressure at LST to isolate fixed lines in the Irrigated Boro rice breeding program. This program was implemented under development of Favourable Boro Rice and Cold Tolerant Rice. In both programs, wide variation was observed among the number of population and segregating generation at RGA nursery. A total of 62,269 individual progenies from 64 crosses were advanced through RGA in 2019 whereas 12,122 individual progenies from 45 crosses were advanced in 2020 under the FBR program. In contrast, 68,531 segregating progenies from 82 crosses and 15,004 progenies from 52 crosses were advanced through RGA under CTR program during 2019 and 2020, respectively. During LST, selection pressure was imposed for the first time to isolate homozygous lines from a pool of large number of breeding lines. The selection intensity ranged between 0.21-20.1% and 0.6-14.9% for FBR and CTR, respectively. A total of 794 fixed breeding lines having different combinations of favourable alleles of BLB, Blast and different grain quality traits were isolated from 17,633 RGA derived lines. The results obtained from this study suggested that the RGA system has become an effective tool for population improvement in a breeding program. Bangladesh Rice J.26 (1): 33-46, 2022

Genetic-Demographic Analysis of Natural Reproduction Parameters and Crow’s Indices in Ethnic Groups of Moscow and St. Petersburg (Based on the 2010 Russia’s Population Census)

Based on the analysis of the materials of the 2010 All-Russia’s Population Census and the demographic statistics of Rosstat Agency, the genetic-demographic parameters of temporal and interethnic variability of natural reproduction parameters and selection parameters (Crow indices) were calculated for the most numerous ethnic groups of Moscow and St. Petersburg. A decrease in the selection component due to differential prereproductive mortality was shown to decrease to the minimum possible values (index Im 0.01). In both megacities, interethnic differences were revealed in the parameters of natural reproduction and the selection component due to differential fertility, while the birth rate in both capitals for all ethnic groups, except for Uzbeks in St. Petersburg, is lower than required even for simple reproduction of the population, and hence stable reproduction of the gene pool. This indicates the unfavorable nature of the genetic and demographic processes in all the represented nationalities of the megacities. The If index ranges from 0.2 to 0.5. The temporal dynamics of the average number of offspring and its variance, as well as the If index, traced according to the data on the age cohorts of women born in the 1940s–1960s, is weakly expressed – the tendency to selection relaxation is not observed for all the studied ethnic groups. It is shown that the intensity of intergroup selection, due to interethnic differences in fertility, in the population of St. Petersburg increases from older age cohorts to younger ones, while in the population of Moscow it does not change significantly, while the temporal dynamics of this indicator, calculated on the base of the materials of the 2002 All-Russia’s Population Census for cohorts born in 1930s–1950s has the opposite direction. The genetic-demographic consequences of the revealed tendencies are discussed.

Cinco ciclos de seleção recorrente intrapopulacional em progênies de meioirmãos de milho fresco

ABSTRACT Fresh corn is a highly appreciated vegetable in Brazil; this crop has high added value and profitability when compared to dry corn. Despite the consumer market demand for quality, cultivars are not launched every crop season and there is a small number of cultivars available to growers. This denotes a need for breeding programs focused on generating information and genotypes that can occupy this market niche. The objective of this work was to evaluate the progress of five cycles of intrapopulation recurrent selection in half-sib progenies of fresh corn, in the southwest region of Goiás. A randomized block experimental design was used, with evaluation of 64 progenies of corn half-sib progenies and selection intensity of 30% per cycle, with three replications, in the 2011-2012, 2013-2014, 2015-2016, 2017-2018, and 2020-2021 summer crop seasons. The half-sib progenies of fresh corn exhibited genetic variability through intrapopulation recurrent selection in the different selection cycles, which is still promising for further selections after five cycles, with evaluation of 64 progenies per cycle. The base population from crossings between hybrids for tropical and temperate climates showed to be promising for increasing the genetic base of fresh corn populations, with satisfactory gains over the five cycles, presenting mean heritability between the cycles of approximately 78.9% for relative chlorophyll index, 62.2% for plant height, 75.1% for ear insertion height, 70% for ear diameter, 56.6% for ear length, 71.4% for unhusked ear yield, and 71% for marketable ear yield.

Sexual Dimorphism in the Limb Bones of Asiatic Toad (Bufo gargarizans) in Relation to Sexual Selection.

Sexual dimorphism is often considered to be the result of differences in the intensity of sexual selection between sexes. From this point of view, the sexual dimorphism of the limb bones of the Bufo gargarizans in southwest China was studied. Results showed that the fore- and hindlimb skeletons of this species were sexually dimorphic in anatomy. The humerus, radioulna, and total lengths of the forelimb skeleton of males were substantially longer than those of females, but the hand length of males was smaller than that of females. Several other features of males, such as deltoid and medial crest areas and humerus and radioulnar weights, were also significantly larger than those of females. The femoris, tibiofibula, talus-calcaneus, and foot lengths; total hindlimb skeleton length; and femoral upper crest areas of males were significantly greater than those of females. However, no significant intersexual difference in femoris and tibiofibular weights was observed. These findings suggested that robust forelimb bones and long hindlimb bones could contribute to the mating success of males; if so, sexual selection promotes the evolution of sexual size and shape dimorphism in the limb bones of the B. gargarizans.

The general significance of variability in cave regressive traits for evolution

Abstract Rudimentary structures are variable, which is most impressively demonstrated by the eyes and dark body pigmentation of species evolving in caves. As these can often still be crossed with their ancestral surface sister forms, variability is usually attributed to hybridization. For two invertebrate and two vertebrate cave species, I show here that in spite of genetic separation between surface and cave forms, variability of the rudimentary structures is nonetheless present. This probably results from the loss of stabilizing selection, because neutral deleterious mutations are no longer eliminated. In contrast, compensatory traits in caves do not differ from their surface forms with respect to variability, because both are subject to selection. In the phylogenetically young Astyanax cave populations, traits compensatory to cave life have achieved different stages of adaptation compared to the phylogenetically old populations. They may show the same degree of differentiation, be intermediate or do not differ from the surface ancestor. This is attributed to different intensities of selection.