Search Results (5)

The wide distribution of Frankliniella occidentalis is largely due to its extreme temperature adaptability. In current studies, most scholars consider environmental changes to be the main factor affecting insect temperature adaptation. However, our previous studies have shown that the adaptability of F. occidentalis to extreme temperature conditions can be strengthened through domestication. In this study, the population of F. occidentalis raised in the laboratory for a long time (2008–2022) under relatively constant temperature and humidity conditions was used as the experimental material. Over 14 years, changes in temperature tolerance after the same high- and low-temperature stress were evaluated by comparing the survival data of the 2010 population, 2016 population (more than 100 generations), and 2022 population (more than 200 generations). The survival data and LT₅₀ values demonstrated significant stage- and sex-specific differences in thermal tolerance: The cold tolerance of F. occidentalis improved significantly, with LT₅₀ decreasing from −12.5 °C (P2010) to −13.4 °C (P2022) for females and −11.5 °C to −13.0 °C for males. Notably, male adults showed higher survival rates than females at −14 °C and −15 °C. Meanwhile, heat tolerance increased most markedly in 2nd instar larvae (ΔLT50 = +4.1 °C). These findings indicate an environment-independent evolutionary pathway within the population, providing a new research direction for insect population evolution. Full article

Recently, it was pointed out that classic models for the evolution of anisogamy do not take into account the possibility of parthenogenetic reproduction, even though sex is facultative in many relevant taxa (e.g., algae) that harbour both anisogamous and isogamous species. Here, we complement this recent analysis with an approach where we assume that the relationship between progeny size and its survival may differ between parthenogenetically and sexually produced progeny, favouring either the former or the latter. We show that previous findings that parthenogenesis can stabilise isogamy relative to the obligate sex case, extend to our scenarios. We additionally investigate two different ways for one mating type to take over the entire population. First, parthenogenesis can lead to biased sex ratios that are sufficiently extreme that one type can displace the other, leading to de facto asexuality for the remaining type that now lacks partners to fuse with. This process involves positive feedback: microgametes, being numerous, lack opportunities for syngamy, and should they proliferate parthenogenetically, the next generation makes this asexual route even more prominent for microgametes. Second, we consider mutations to strict asexuality in producers of micro- or macrogametes, and show that the prospects of asexual invasion depend strongly on the mating type in which the mutation arises. Perhaps most interestingly, we also find scenarios in which parthenogens have an intrinsic survival advantage yet facultatively sexual isogamous populations are robust to the invasion of asexuals, despite us assuming no genetic benefits of recombination. Here, equal contribution from both mating types to zygotes that are sufficiently well provisioned can outweigh the additional costs associated with syngamy. Full article

Investigation of mating-induced trade-offs between reproduction and survival is conducive to provide evolutionary insights into reproductive strategies and aging. Here, we used RNAseq and bioinformatics to reveal mating-induced changes of genes and pathways related to reproduction and survival in female Cephalcia chuxiongica, a pine defoliator with facultative parthenogenesis and long larval dormancy. Results showed that mating induced substantial downregulation on genes and pathways associated to immunity, stress response, and longevity. However, mating induced divergent reproductive response, with downregulation on genes and pathways related to egg production while upregulation on genes and pathways related to egg fertilization. Considering the nature of limited resources in adults, low fecundity, and egg protection behavior in C. chuxiongica, we suggest that mating triggers trade-offs between reproduction and survival in this insect and females of this species may have evolved specific strategies to adapt to the environmental and hosts’ conditions, e.g., restrict whole fecundity to ensure higher fertilization and offspring’s survival. Moreover, mating induced significant responses on genes and pathways that play important roles in vertebrate reproduction while their function in insects are unclear, such as the progesterone-mediated oocyte maturation pathway; the significant regulation after mating suggests that their function may be evolutionarily conserved in animal kingdom. Full article

Parker, Baker, and Smith provided the first robust theory explaining why anisogamy evolves in parallel in multicellular organisms. Anisogamy sets the stage for the emergence of separate sexes, and for another phenomenon with which Parker is associated: sperm competition. In outcrossing taxa with separate sexes, Fisher proposed that the sex ratio will tend towards unity in large, randomly mating populations due to a fitness advantage that accrues in individuals of the rarer sex. This creates a vast excess of sperm over that required to fertilize all available eggs, and intense competition as a result. However, small, inbred populations can experience selection for skewed sex ratios. This is widely appreciated in haplodiploid organisms, in which females can control the sex ratio behaviorally. In this review, we discuss recent research in nematodes that has characterized the mechanisms underlying highly skewed sex ratios in fully diploid systems. These include self-fertile hermaphroditism and the adaptive elimination of sperm competition factors, facultative parthenogenesis, non-Mendelian meiotic oddities involving the sex chromosomes, and environmental sex determination. By connecting sex ratio evolution and sperm biology in surprising ways, these phenomena link two “seminal” contributions of G. A. Parker. Full article

Polyploidization and the shift to apomictic reproduction are connected to changes in DNA cytosine-methylation. Cytosine-methylation is further sensitive to environmental conditions. We, therefore, hypothesize that DNA methylation patterns would differentiate within species with geographical parthenogenesis, i.e., when diploid sexual and polyploid apomictic populations exhibit different spatial distributions. On natural populations of the alpine plant Ranunculus kuepferi, we tested differences in methylation patterns across two cytotypes (diploid, tetraploid) and three reproduction modes (sexual, mixed, apomictic), and their correlation to environmental data and geographical distributions. We used methylation-sensitive amplified fragment-length polymorphism (methylation-sensitive AFLPs) and scored three types of epiloci. Methylation patterns differed independently between cytotypes versus modes of reproduction and separated three distinct combined groups (2x sexual + mixed, 4x mixed, and 4x apomictic), with differentiation of 4x apomicts in all epiloci. We found no global spatial autocorrelation, but instead correlations to elevation and temperature gradients in 22 and 36 epiloci, respectively. Results suggest that methylation patterns in R. kuepferi were altered by cold conditions during postglacial recolonization of the Alps, and by the concomitant shift to facultative apomixis, and by polyploidization. Obligate apomictic tetraploids at the highest elevations established a distinct methylation profile. Methylation patterns reflect an ecological gradient rather than the geographical differentiation. Full article