Numerous studies have examined the adaptive significance of seed color using natural variation within species or cultivars, yet our overall understanding remains limited. In this study, we used evolutionary contrasts between cultivated lines and their de-domesticated counterparts as a useful framework for investigating the adaptive significance of seed color. We hypothesized that the naturally expressed red-pericarp phenotype of de-domesticated rice may be associated with seed-based resistance to insect feeding. We compared Japanese weedy rice (Oryza sativa), a de-domesticated lineage characterized by a red proanthocyanidin pericarp, with a cultivated line (Oryza sativa) with a white pericarp. We compared the larval development of red flour beetles (Tribolium castaneum (Herbst)) fed cultivated rice with that fed weedy rice under flour-based bioassay conditions. We predicted that if weedy rice conferred resistance to T. castaneum, the larval mortality rate and developmental time would increase, and adult body biomass at eclosion would decrease, respectively. Contrary to our hypothesis, whole grains (containing the endosperm and pericarp) of all four Japanese weedy rice strains exhibited lower apparent resistance to T. castaneum than the cultivated rice. Larvae fed weedy rice reached eclosion significantly earlier, and adult body biomass was higher than that of larvae fed cultivated rice, with no difference in mortality rates. To partially separate the contribution of the pericarp fraction from that of the endosperm, we reciprocally exchanged the pericarp between the weedy and cultivated rice. This experiment showed that mortality rate of beetles fed weedy rice with red pericarps was lowest (15
Environmental stressors strongly influence reproductive success, with diet quality and heat stress directly affecting physiological condition and reproductive performance. The ladybird beetle, Cheilomenes sexmaculata exhibits color polymorphism, with typical and melanic morphs differing in ecological and physiological traits that may affect their responses to environmental challenges. Understanding how these morphs cope with stress is important for assessing the adaptive significance of polymorphism and its role in population persistence under changing environmental conditions. Sperm allocation is a key component of male reproductive investment, as alterations in sperm transfer under stressful conditions can directly affect fertilization success and population fitness. This study aimed to evaluate the independent effects of diet quality and heat-shock on reproductive behavior and sperm allocation patterns in two morphs (typical and melanic) of C. sexmaculata. In this study, the diet quality has been manipulated by rearing the beetles on two different diets, the most preferred prey, Aphis craccivora, and the least preferred prey, Aphis nerii. Heat-shock was given by exposing the adult males to sublethal temperature (45℃ for 5 min). The results revealed a non-significant effect of both the diet quality and heat-shock on mating behavior and sperm allocation patterns of C. sexmaculata. It indicates that males maintain stable mating performance and sperm investment in a single mating event despite variation in diet quality and short-term heat stress. Such resilience is advantageous in natural habitats where prey availability and temperature vary frequently, potentially contributing to reproductive stability under the specific conditions tested.
Damselflies (Odonata: Zygoptera) have evolved highly developed visual systems for mate recognition, flight and prey detection. Wing Interference Patterns (WIPs), which are colors generated by thin-film interference in the wing membrane, could function as visual signals and play a role in sexual selection. Because the color of these signals depends on membrane thickness, a potential conflict exists between changes in wing area and the need to maintain a consistent signal. We examined how wing membrane thickness scales with wing area in two damselfly species, Ischnura elegans and Enallagma cyathigerum. Using hyperspectral imaging, we found that while wing area was highly variable, membrane thickness showed low intraspecific variability. We found no evidence for any significant correlation between wing thickness and wing area or any support for sexual selection operating on these traits. Low intraspecific variation of the membrane thickness results in a consistent Wing Interference Signal (WIS), which is useful for species identification with remote sensing approaches.
Exaggerated male traits used in intrasexual contests are often condition dependent and, in many taxa, intrasexual dimorphism in these traits arise in association with alternative reproductive tactics. Although it is frequently assumed that trait exaggeration and intrasexual dimorphism evolve in concert, this hypothesis has not yet been tested within a comparative framework. Here, we investigate whether the degree of exaggeration of contest-related traits is evolutionarily correlated with intrasexual dimorphism across species of Neotropical harvestmen. We focus on two subfamilies of Gonyleptidae—Goniosomatinae and Mitobatinae—in which males use extremely elongated legs as threat devices during ritualized contests. Using morphological data from individuals representing 46 species, we quantified leg exaggeration as relative leg length and estimated the degree of intrasexual dimorphism using bootstrap-supported mixture models. We then applied phylogenetic comparative analyses in a Bayesian framework to test for correlated evolution between these traits. In Goniosomatinae, we detected moderate positive phylogenetic correlation between leg exaggeration and intrasexual dimorphism. In contrast, no evidence of correlated evolution was found in Mitobatinae, where many species exhibit pronounced leg exaggeration without intrasexual dimorphism. Together, these patterns suggest that although trait exaggeration may be a necessary condition for the evolution of intrasexual dimorphism, it is not sufficient on its own. Instead, the macroevolutionary association between trait exaggeration and intrasexual dimorphism appears to depend on functional constraints, behavioral flexibility, and the genetic architecture underlying condition-dependent trait expression.
Quantity discrimination affects a range of behaviours essential for fitness, including social interactions, navigation, and foraging and is widespread across animal taxa. However, in reptiles, evidence for this ability — particularly for small number contrasts — remains limited and mixed. Early-life conditions, such as hormonal exposure and temperature, can also shape brain development and cognitive performance, potentially affecting numerical abilities. Here, we tested the ability of the common garden skink (Lampropholis guichenoti) to discriminate between quantities and the effects of elevated prenatal glucocorticoids and incubation temperature on quantity discrimination and decision-making. We assessed quantity discrimination using a spontaneous choice test with food as a stimulus. We subjected lizards to five two-choice tests differing in the number of items (1 VS 4, 1 VS 3, 2 VS 4, 2 VS 3, 3 VS 4) while controlling for total length and area. Contrary to our predictions, lizards did not show clear preferences toward the larger items, providing no evidence of spontaneous quantity discrimination in L. guichenoti. Furthermore, prenatal conditions did not influence latency to make a choice, also a proxy for decision-making. Despite these results, further investigation of quantity discrimination in live-prey-feeding reptiles and the impact of early conditions on other taxa remains an important area of research.
The niche concept is a central paradigm in ecology, inspiring several ecological theories such as the acoustic niche hypothesis (ANH), which postulates that acoustic space is partitioned through temporal and spectral adjustments shaped by selection to reduce competition via masking interference among sympatric species. By measuring the acoustic overlap and sound signal discrimination between two closely related and syntopic treefrog species — Dendropsophus oliveirai and D. tapacurensis — we tested key predictions of the ANH, including partitioning and overlap in acoustic space. We combined traditional analyses of call stereotypy — descriptive statistics, coefficients of variation, analyses of variance — with acoustic space overlap metrics — kernel density estimation and fine-scale overlap — and Random Forest classification models. Despite an acoustic overlap that tended to increase with geographic distance from syntopic sites, significant differences between species occurred in most advertisement call parameters, particularly regarding spectral range and fine-scale pulse structure. Both species also displayed high within-species stereotypy in their signals. These findings indicates that reproductive isolation between the species is complete or in an advanced stage of differentiation driven by fine-scale acoustic adjustments. The patterns we uncovered illustrate general principles of the ANH, which are broadly relevant to understanding mechanisms of species coexistence in animal communities.
Climate change and socioeconomic factors are increasing fire recurrence. Landscapes affected by fire recurrence are mostly open with patches of grass understory, bare soil, and visible rocky structures. Animals inhabiting these landscapes are exposed to altered environmental conditions and potentially higher predation pressure. They are hence expected to respond with phenotypic changes (plastically or through adaptation) compared to those inhabiting long-unburned areas to maintain their fitness. We performed lab and field experiments to test for variation in behavior, locomotor performance, and morphological phenotypic responses of the wall lizard Podarcis lusitanicus from six populations across northern Portugal. These sites follow a gradient in fire recurrence (0 to 8 fires in the last 40 years), time since the last fire (from long unburned to 5–6 years since the last fire), and landscape openness. The normalized difference vegetation index and two microenvironmental variables (temperature and humidity recorded with data loggers) supported differences in landscape openness from long-unburned to recurrent-fire sites. Our results showed that wall lizards modified their antipredator behavior according to the fire history of each population; in contrast, lizards’ morphology and locomotor performance did not vary among populations. Our results suggest that adjustments in escape behavior may contribute to coping with environmental conditions derived from fire recurrence regimes, while the other phenotypic traits analysed remained conservative. Genomic analyses and common garden experiments are needed to identify the nature of phenotypic variation in wall lizards exposed to recurrent burned landscapes.
