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opencc-zeroAug 2020View details →

Data from: Carryover effects and the evolution of polyphenism

An individual's early-life environment and phenotype often influence its traits and performance as an adult. We investigated whether such 'carryover effects' are associated with alternative, environmentally induced phenotypes ('polyphenism'), and, if so, whether they influence polyphenism's evolution. To do so, we studied spadefoot toads, Spea multiplicata, which have evolved a polyphenism consisting of two, dramatically different forms: a carnivore morph and an omnivore morph. We sampled both morphs from a fast-drying and a slow-drying pond and reared them to sexual maturity. Larval environment (pond) strongly influenced survival as well as age and size at metamorphosis and sexual maturity; i.e., environment-dependent carryover effects were present. By contrast, larval phenotype (morph) did not affect life-history traits at sexual maturity; i.e., phenotype-dependent carryover effects were absent. These results are consistent with theory, which suggests that by amplifying selective trade-offs in heterogenous environments, environment-dependent carryover effects might foster polyphenism's evolution. At the same time, by freeing selection to refine a novel phenotype without altering the existing form, the absence of phenotype-dependent carryover effects might enable polyphenism to evolve in the first place. Generally, carryover effects might play an underappreciated role in polyphenism's evolution.

opencc-zeroDec 2015View details →

Data from: Specialization of a polyphenism switch gene following serial duplications in Pristionchus nematodes

Polyphenism is an extreme manifestation of developmental plasticity, requiring distinct developmental programs and the addition of a switch mechanism. Because the genetic basis of polyphenism switches has only begun to be understood, how their mechanisms arise is unclear. In the nematode Pristionchus pacificus, which has a mouthpart polyphenism specialized for alternative diets, a gene (eud-1) executing the polyphenism switch was recently identified as the product of lineage-specific duplications. Here, we infer the role of gene duplications in producing a switch gene. Using reverse genetics and population genetic analyses, we examine evidence for competing scenarios of degeneration and complementation, neutral evolution, and functional specialization. Of the daughter genes, eud-1 alone has assumed switch-like regulation of the mouth polyphenism. Measurements of life-history traits in single, double, and triple sulfatase mutants did not, given a benign environment, identify alternative or complementary roles for eud-1 paralogs. Although possible roles are still unknown, selection analyses of the sister species and 104 natural isolates of P. pacificus detected purifying selection on the genes, suggesting their functionality by their fixation and evolutionary maintenance. Our approach shows the tractability of reverse genetics in a nontraditional model system to study evolution by gene duplication.

opencc-zeroDec 2017View details →

Data from: Disruptive sexual selection on body size in the polyphenic black scavenger fly Sepsis thoracica

Sexual selection has two main components, female preference and male-male competition, which can lead males to adopt alternative reproductive tactics to optimize their reproductive success. Two traits that significantly influence reproductive success are body size and coloration, as they can facilitate access to females through male contests or as female attractors. We investigated whether, and if so which mechanism of sexual selection contributes to the maintenance, and possibly even the establishment, of two almost discrete male morphs in the polyphenic black scavenger fly Sepsis thoracica (Diptera: Sepsidae): small and black, or large and amber. We performed two complementary laboratory experiments to evaluate the mating success of the different male morphs and the behaviors (of both males and females) presumably mediating their mating success. We found evidence for intraspecific disruptive sexual selection on male body size that is mediated by male-male interactions, and significant positive directional selection on body size that interacted with (directional) selection on coloration, likely contributing to the origin and/or maintenance of the threshold relationship between the two traits in this species. The simultaneous occurrence of disruptive selection and polyphenism in S. thoracica supports the role of sexual selection in the intraspecific diversification of coupled traits (here body size and coloration), which could be a speciation starting point.

opencc-zeroDec 2015View details →

Data from: Specialization of a polyphenism switch gene following serial duplications in Pristionchus nematodes

opencc-zeroDec 2015View details →

Data from: A case for a joint strategy of diversified bet hedging and plasticity in the pea aphid wing polyphenism

Phenotypic plasticity and diversified bet hedging are strategies for coping with variable environments. Plasticity is favoured when an organism can predict future conditions using environmental cues, while bet hedging is favoured when predictive cues are not available. Theoretical analyses suggest that many organisms should use a mixture of both strategies, because environments often present both scenarios. Here, we examine if the pea aphid wing polyphenism, a well-known case of plasticity, is potentially a mixture of plasticity and bet hedging. In this polyphenism, asexual females produce more winged offspring in crowded conditions, and wingless offspring in uncrowded conditions. We find that pea aphids use plasticity to respond to crowding and we find considerable genetic variation for this response. We further show that individual aphids produce both winged and wingless offspring, consistent with the variability expected in a bet hedging trait. We conclude that the pea aphid wing polyphenism system is probably a mixture of plasticity and bet hedging. Our study adds to a limited list of empirical studies examining mixed strategy usage, and suggests that mixed strategies may be common in dispersal traits.

opencc-zeroDec 2018View details →

Data from: Lifetime fitness, sex-specific life history, and the maintenance of a polyphenism

Polyphenisms, alternative morphs produced through plasticity, can reveal the evolutionary and ecological processes that initiate and maintain diversity within populations. We examined lifetime fitness consequences of two morphs in a polyphenic population of Arizona Tiger Salamanders using a 27-year data set with 1,317 adults and 6,862 captures across eight generations. Larval salamanders develop into either an aquatic paedomorph that retains larval traits and stays in its natal pond or a terrestrial metamorph that undergoes metamorphosis. To evaluate the adaptive significance of this polyphenism, we compared lifetime reproductive success of each morph and assessed how life history strategies and spatiotemporal variation explained fitness. We found sex-specific differences in lifetime fitness between morphs. For males, paedomorphs had more reproductive opportunities than metamorphs when we accounted for the potential mating advantage of larger males. For females, in contrast, metamorphs had higher estimated egg production than paedomorphs. Life history strategies differed between morphs largely because the morphs maximize different ends of the trade-off between age at first reproduction and longevity. Spatiotemporal variation affected larval more than adult life history traits with little to no effect on lifetime fitness. Thus, environmental variation likely explains differences in morph production across time and space but contributes little to lifetime fitness differences between morphs and sexes. Our long-term study and measures of lifetime fitness provide unique insight into the complex selective regimes potentially acting on each morph and sex. Our findings motivate future work to examine how sex-specific selection may contribute to the maintenance of polyphenism.

opencc-zeroDec 2016View details →

Data from: Climatic factors shape plastic trade-offs in the polyphenic black scavenger fly Sepsis thoracica (Diptera: Sepsidae)

Aim: Trade-offs allow individuals to optimize their fitness by tailoring the investment into different traits to variable environmental conditions, such as along geographic gradients. Trade-offs thus can help in adjusting to changing thermal and insolation profiles, especially in small ectotherms, whose body temperature typically follows environmental temperatures closely. Two traits usually involved in latitudinal adaptation are body size and melanism. Since both traits are costly, individuals need to optimize investment into each trait. Here we studied how environmental factors influence this trade-off in the short and long term. Location: Europe Methods: We raised flies from 15 latitudinal populations at three constant temperatures in a laboratory common garden to differentiate plastic and evolutionary responses to temperature. We further analysed how the different insolation components of the populations' habitats influenced the evolution of the trade-off. Results: Male Sepsis thoracica (Diptera: Sepsidae) feature a sigmoid relationship between melanism and body size, defining two strikingly different male morphs: obsidian (small and black) and amber (large and orange). This relationship was altered by the developmental temperature, documenting its plasticity. The relationship further evolved across populations in response to the environmental characteristics of their habitat, notably temperature, insolation and UV radiation, suggesting that plasticity also has an underlying genetic basis. Nevertheless, melanism, but not body size, merely slightly increased with latitude. Main Conclusions: As the plastic and evolutionary responses of the relationship to temperature differed, plasticity does not necessarily follow the direction of evolution of this trade-off, but rather adds to it. Our study evinces the role of several environmental factors in shaping the evolution of a plastic melanism – body size relationship defining a rare male polymorphism in temperate sepsid flies.

opencc-zeroJan 2024View details →

Supplementary material 1 from: Tanaka S (2024) Geographic variation in body size of the migratory locust Locusta migratoria (Orthoptera, Acrididae): Masaki's cline and phase polyphenism. Journal of Orthoptera Research 33(1): 27-40. https://doi.org/10.3897/jor.33.107242

Supplementary material 1 from: Tanaka S (2024) Geographic variation in body size of the migratory locust Locusta migratoria (Orthoptera, Acrididae): Masaki's cline and phase polyphenism. Journal of Orthoptera Research 33(1): 27-40. https://doi.org/10.3897/jor.33.107242

opencc-zeroFeb 2022View details →

Comparative reconstruction of the predatory feeding structures of the polyphenic nematode Pristionchus pacificus

Pristionchus pacificus is a nematode model for the developmental genetics of morphological polyphenism, especially at the level of individual cells. Morphological polyphenism in this species includes an evolutionary novelty, moveable teeth, which have enabled predatory feeding in this species and others in its family (Diplogastridae). From transmission electron micrographs of serial thin sections through an adult hermaphrodite of P. pacificus, we three-dimensionally reconstructed all epithelial and myoepithelial cells and syncytia, corresponding to 74 nuclei, of its face, mouth, and pharynx. We found that the epithelia that produce the predatory morphology of P. pacificus are identical to Caenorhabditis elegans in the number of cell classes and nuclei. However, differences in cell form, spatial relationships, and nucleus position correlate with gross morphological differences from C. elegans and outgroups. Moreover, we identified fine-structural features, especially in the anteriormost pharyngeal muscles, that underlie the conspicuous, left-right asymmetry that characterizes the P. pacificus feeding apparatus. Our reconstruction provides an anatomical map for studying the genetics of polyphenism, feeding behavior, and the development of novel form in a satellite model to C. elegans.

Fig. 5 in Integrative taxonomy of the seasonally polyphenic scorpionfly Panorpa liui Hua, 1997 (Mecoptera: Panorpidae)

Fig. 5 Phylogenetic tree and haplotype network of Panorpa liui. a Phylogenetic tree of Bayesian inference based on combined data of COI, COII, and 28S rRNA; Bayesian posterior probabilities and ML

Fig. 4 in Integrative taxonomy of the seasonally polyphenic scorpionfly Panorpa liui Hua, 1997 (Mecoptera: Panorpidae)

Fig. 4 Variation of wing size and shape of Panorpa liui. a Boxplot of centroid size for different color morphs/populations. b Scatter plots of canonical variates CV1 vs CV2 for different color morphs/populations. c Shape variations along CV1 and CV2 illustrated by deformation grid graphs

Fig. 2 in Integrative taxonomy of the seasonally polyphenic scorpionfly Panorpa liui Hua, 1997 (Mecoptera: Panorpidae)

Fig. 2 Adults of Panorpa liui in habitat. a, d Yellow morph. b Intermediate morph. c, f Black morph. e Deep black morph

Fig. 1 in Integrative taxonomy of the seasonally polyphenic scorpionfly Panorpa liui Hua, 1997 (Mecoptera: Panorpidae)

Fig. 1 Geographic distribution of the four color morphs for Panorpa liui. Population ID provided in Table S1

Fig. 3 in Integrative taxonomy of the seasonally polyphenic scorpionfly Panorpa liui Hua, 1997 (Mecoptera: Panorpidae)

Fig. 3 Variation of the male genitalia of Panorpa liui, ventral views. a–c Yellow morph. d, h Deep black morph. e–g Black morph. bst, basal stalk; gcx, gonocoxite; gs, gonostylus; hv, hypovalve; vv, ventral valve; scale bars = 0.5 mm

opencc-zeroDec 2017View details →

Data from: Viability selection by invertebrate predators in the polyphenic scavenger fly Sepsis thoracica

Predation is a major factor influencing the fitness and life history of animals. Two key traits affecting prey survival are body size and coloration. Sepsis thoracica males display a sigmoid relationship between these two traits, defining a size threshold above which investment in melanin drastically drops, producing small melanic (black) or large amber morphs. In trying to understand the evolution of this rare dimorphism, we performed laboratory predation experiments to estimate the intensity of adult viability selection exerted by various arthropod predators (bugs, flies, spiders) on male body size and coloration. Selection was performed against two different backgrounds mimicking the natural habitat (dung and grass) in which the camouflage and/or warning effect of the morphs should vary. Body size was mainly under positive selection (larger survived better), which overpowered selection on coloration and varied somewhat among predator species but not backgrounds. No disruptive selection was found, nor did selection change the sigmoid relationship between the two traits. We conclude that, for this fly, predator evasion and escaping skills determined by body size are more effective against invertebrate predators than its conspicuousness determined by coloration, contrasting what has been found for vertebrate predators, where prey coloration is important and negative selection on size dominates. Because arthropod predators have strong effects on insect populations, the positive directional selection imposed by invertebrate predators is likely an important force driving the evolution of body size in S. thoracica and insects in general.

opennotspecifiedSep 2018View details →

Figure 5 in Consistent seasonal polyphenism in male genitalia of three Leptidea butterfly species (Lepidoptera: Pieridae)

Figure 5. Between-species pairwise comparisons of phallus and saccus performed in form space using outlines (each representing the mean shape for the species).