Integrating natural and sexual selection across the biphasic life cycle

An alternation between diploid and haploid phases is universal among sexual eukaryotes. Across this biphasic cycle, natural selection and sexual selection occur in both phases. Together, these four stages of selection act on the phenotypes of individuals and influence the evolutionary trajectories of populations, but are rarely studied holistically. Here, we provide a conceptual framework that transcends taxonomic groups, and unifies the entire selection landscape within and across the diploid and haploid phases. Our synthesis produces six direct links among four selection stages, and from this we define four types of parental effect. We argue that knowledge of the complex and intertwined opportunities for selection within biphasic life cycles will offer clearer insights into key ecological and evolutionary processes, with benefits to applied science.

Phenotypic Plasticity and Parental Effect on Rearing of Two Diverse Habitat Environment for Laboratory Reared Sympetrum Meridionale

Laboratory observations on rearing experiment of Odonata serve to answer many evolutionary and ecological questions. In order to evidences the role of species parental habitat provenience in the development behaviour of their offspring, we surveyed several life history traits of two rearing populations of Sympetrum meridionale (Anisoptera: Sympetrinae), coming from two different habitats across north-eastern Algeria. The first one is a RAMSAR wetland called ‘Mekhada’ (a perennial water body), and the second one is a temporary pond located at “Maouna” Mountain (1400 m altitude). Overall, the development patterns of the two populations of dragonflies vary with the type of habitat the parental generation of the species occupy (Factorial ANCOVA: all p < 0.05). Firstly, egg mortality was very low in dragonfly population inhabiting the RAMSAR wetland compared of those belonging to Maouna Mountain. Secondly new-borne larvae stemming from females inhabiting the Mekhada wetland develop more slowly than did those coming from the “Maouna” Mountain pond. Finally, larvae of Sympetrum meridionale stemming from females inhabiting the temporary wetland were heavier than those inhabiting the perennial wetland. Such studies will ads considerably to our understanding of the mechanisms that are responsible for possible effects of environmental changes on life history traits of dragonflies across the southern part of their distribution range.

Sex-specific nicotine sensitization and imprinting of self-administration in rats inform GWAS findings on human addiction phenotypes

Repeated nicotine exposure leads to sensitization (SST) and enhances self-administration (SA) in rodents. However, the molecular basis of nicotine SST and SA and their biological relevance to the mounting genome-wide association study (GWAS) loci of human addictive behaviors are poorly understood. Considering a gateway drug role of nicotine, we modeled nicotine SST and SA in F1 progeny of inbred rats (F344/BN) and conducted integrative genomics analyses. We unexpectedly observed male-specific nicotine SST and a parental effect of SA only present in paternal F344 crosses. Transcriptional profiling in the ventral tegmental area (VTA) and nucleus accumbens (NAc) core and shell further revealed sex- and brain region-specific transcriptomic signatures of SST and SA. We found that genes associated with SST and SA were enriched for those related to synaptic processes, myelin sheath, and tobacco use disorder or chemdependency. Interestingly, SST-associated genes were often downregulated in male VTA but upregulated in female VTA, and strongly enriched for smoking GWAS risk variants, possibly explaining the male-specific SST. For SA, we found widespread region-specific allelic imbalance of expression (AIE), of which genes showing AIE bias toward paternal F344 alleles in NAc core were strongly enriched for SA-associated genes and for GWAS risk variants of smoking initiation, likely contributing to the parental effect of SA. Our study suggests a mechanistic link between transcriptional changes underlying the NIC SST and SA and human nicotine addiction, providing a resource for understanding the neurobiology basis of the GWAS findings on human smoking and other addictive phenotypes.

Beneficial cumulative effects of old parental age on offspring fitness

Old parental age is commonly associated with negative effects on offspring life-history traits. Such parental effect senescence is predicted to have a cumulative detrimental effect over successive generations. However, old parents may benefit from producing high-quality offspring when these compete for seasonal resources. Thus, old parents may choose to increase investment in their offspring, thereby producing fewer but larger and more competitive progeny. We show that Caenorhabditis elegans hermaphrodites increase parental investment with advancing age, resulting in fitter offspring who reach their reproductive peak earlier. Remarkably, these effects increased over six successive generations of breeding from old parents and were subsequently reversed following a single generation of breeding from a young parent. These results contradict the theory that old parents transfer a cumulative detrimental “ageing factor” to their offspring. Instead, our findings support the hypothesis that offspring of old parents receive more resources and convert them into increasingly faster life-histories.

Biparental contributions of the H2A.B histone variant control embryonic development in mice

Histone variants expand chromatin functions in eukaryote genomes. H2A.B genes are testis-expressed short histone H2A variants that arose in placental mammals. Their biological functions remain largely unknown. To investigate their function, we generated a knockout (KO) model that disrupts all 3 H2A.B genes in mice. We show that H2A.B KO males have globally altered chromatin structure in postmeiotic germ cells. Yet, they do not show impaired spermatogenesis or testis function. Instead, we find that H2A.B plays a crucial role postfertilization. Crosses between H2A.B KO males and females yield embryos with lower viability and reduced size. Using a series of genetic crosses that separate parental and zygotic contributions, we show that the H2A.B status of both the father and mother, but not of the zygote, affects embryonic viability and growth during gestation. We conclude that H2A.B is a novel parental-effect gene, establishing a role for short H2A histone variants in mammalian development. We posit that parental antagonism over embryonic growth drove the origin and ongoing diversification of short histone H2A variants in placental mammals.

Transcriptomic signatures of sex-specific nicotine sensitization and imprinting of self-administration in rats inform GWAS findings on human addiction phenotypes

Rodents are frequently used to model drug addiction, yet their genetic relevance to human addictive behaviors especially the mounting genome-wide association study (GWAS) findings is poorly understood. Considering a possible gateway drug role of nicotine (NIC), we modeled NIC addiction, specifically NIC sensitization (SST) and self-administration (SA), in F1 progeny of inbred Envigo rats (F344/BN) and conducted integrative genomics analyses. We unexpectedly observed male-specific NIC SST and a parental effect of SA only present in paternal F344 crosses. Transcriptional profiling in the ventral tegmental area (VTA) and nucleus accumbens (NAc) core and shell further revealed sex and brain region-specific transcriptomic signatures of SST and SA. We found that genes associated with SST and SA were enriched for those related to synaptic processes, myelin sheath, and tobacco use disorder or chemdependency. Interestingly, SST-associated genes were often downregulated in male VTA but upregulated in female VTA, and strongly enriched for smoking GWAS risk variants, possibly explaining the male-specific SST. For SA, we found widespread region-specific allelic imbalance of expression (AIE), of which genes showing AIE bias towards paternal F344 alleles in NAc core were strongly enriched for SA-associated genes and for GWAS risk variants of smoking initiation, likely contributing to the parental effect of SA. The transcriptional signatures of sex-specific nicotine SST and SA suggest a mechanistic link between genes underlying these processes and human nicotine addiction, providing a resource for understanding the biology underlying the GWAS findings on human smoking and other addictive phenotypes.

Like Parents, Like Offspring? Susceptibility to Bt Toxins, Development on Dual-Gene Bt Cotton, and Parental Effect of Cry1Ac on a Nontarget Lepidopteran Pest

An important step to devise appropriate pest management strategies for armyworms (Lepidoptera: Noctuidae) in Bacillus thuringiensis Berliner (Bt) crops is to determine the lethal, sublethal, and parental effects of Bt toxins on target and nontarget pest species. Here we documented the susceptibility of black armyworm, Spodoptera cosmioides (Walker), to three Cry toxins and its life-history traits feeding on dual-toxin Bt cotton and an artificial diet containing sublethal concentrations of Cry1Ac. In concentration–response bioassays, black armyworm larvae showed low susceptibility to Cry toxins, with 853 ng/cm2 as the lowest value estimated for the median lethal concentration (LC50). The decreasing rank of toxicity was Cry1F, Cry2Aa, and Cry1Ac. Foliage of dual-toxin Bt cotton varieties (Cry1Ac + Cry1F and Cry1Ab + Cry2Ae) caused higher larval mortality than Cry1Ac-expressing cotton. Black armyworms showed reduced larval weight when growing on the Cry1Ac-treated diet, yet they reached adulthood and produced offspring. Interestingly, these larvae were grown on the control diet and showed reduced weight gain associated with the toxin exposure of the previous generation, indicating a parental effect of the exposure to Cy1Ac. The reduced larval weight was recovered in later instars, and there was no significant change in the population fitness of the parental armyworms or their offspring. To our knowledge, this is the first study documenting the parental effects of Bt toxins in insects. These results advance our understanding of potential responses of nontarget species when exposed to Bt toxins and contribute to design pest management programs for armyworms and other nontarget lepidopteran species exposed to Bt crops.

A Paradigm Model of Traditional Iranian Neighborhood (Mahalleh): A Grounded Theory Approach

Contemporary interventions in historical Mahalleh and the design of new settlements in Iran rely on Western micro-urbanism patterns such as urban villages and new urbanism. Although the urban lifestyle in Iran affects the Mahalleh identity, this context-oriented pattern is more appropriate than the Western ones with all weaknesses and critiques; namely, social engineering and physical determinism. This paper aims to present a paradigm model for the Iranian micro-urbanism (Mahalleh), applying grounded theory methodology. The literature of micro-urbanism is discussed first, followed by exploring the categories of Mahalleh and integrating them around the core category in a paradigm model. Influenced by specific conditions: “collectivism” and “ecological balance” as causal conditions; “social identity” as an intervening condition; “physical and functional organization” as contextual conditions, “familiarity” emerges as a core category in the proposed model. Furthermore, residents of the Mahalleh have special interactions contributing to the “social capital,” “changeability,” and “parental effect.” Finally, “Mahalleh as the home of the families” is a consequence of the actions and interactions done under such conditions.

Intergenerational effects of early adversity on survival in wild baboons

Early life adversity can affect an individual’s health, survival, and fertility for many years after the adverse experience. Whether early life adversity also imposes intergenerational effects on the exposed individual’s offspring is not well understood. We fill this gap by leveraging prospective, longitudinal data on a wild, long-lived primate. We find that juveniles whose mothers experienced early life adversity exhibit high mortality before age 4, independent of the juvenile’s own experience of early adversity. These juveniles often preceded their mothers in death by 1 to 2 years, indicating that high adversity females decline in their ability to raise offspring near the end of life. While we cannot exclude direct effects of a parent’s environment on offspring quality (e.g., inherited epigenetic changes), our results are completely consistent with a classic parental effect, in which the environment experienced by a parent affects its future phenotype and therefore its offspring’s phenotype.

Environmental variation mediates the evolution of anticipatory parental effects

Theory maintains that when future environment is predictable, parents should adjust the phenotype of their offspring to match the anticipated environment. The plausibility of positive anticipatory parental effects is hotly debated and the experimental evidence for the evolution of such effects is currently lacking. We experimentally investigated the evolution of anticipatory maternal effects in a range of environments that differ drastically in how predictable they are. Populations of the nematode Caenorhabditis remanei, adapted to 20°C, were exposed to a novel temperature (25°C) for 30 generations with either positive or zero correlation between parent and offspring environment. We found that populations evolving in novel environments that were predictable across generations evolved a positive anticipatory maternal effect, since they required maternal exposure to 25°C to achieve maximum reproduction in that temperature. In contrast, populations evolving under zero environmental correlation had lost this anticipatory maternal effect. Similar but weaker patterns were found if instead rate-sensitive population growth was used as a fitness measure. These findings demonstrate that anticipatory parental effects evolve in response to environmental change so that ill-fitting parental effects can be rapidly lost. Evolution of positive anticipatory parental effects can aid population viability in rapidly changing but predictable environments.Impact summaryParents can help their offspring by adjusting offspring’s phenotype to match their environment. Such anticipatory parental effects would be beneficial, but only if parents can accurately predict the environment in which their offspring will develop and live. The plausibility of such anticipatory parental effects is hotly debated. The theory is clear that the predictability of the environment should play a defining role. We used an “experimental evolution” approach in a fast reproducing nematode worm Caenorhabditis remanei to tackle this question and follow the evolution of parental effects in different environments in real-time. We found that populations evolving in a novel but predictable environment indeed had anticipatory parental effects that increased fitness of their offspring in that environment. In contrast, when evolving in an unpredictable environment where such parental effects would be disadvantageous, the parental effect was rapidly lost in evolution. Our novel experimental environments were constructed by exposing worms to increased temperature. Anticipatory parental effects play an important role in adaptation to novel environments and will affect the viability of populations under climate heating.