Non-random mortality of seeds in storage can result in a change in mean adult traits known as the “invisible fraction problem”. This issue can bias the results of resurrection studies and pose challenges for restoration. While this phenomenon has been documented, it remains unclear how relevant the invisible fraction problem is across wild species. To address this knowledge gap, we simulated long-term storage by exposing seeds of 6 grassland species to artificial ageing (60
The Carolina grasshopper (Dissosteira carolina) is cryptic at rest but flies in a manner reminiscent of a butterfly, while displaying conspicuous black hindwings with yellow margins. One hypothesis for these “flash” displays is that they have evolved to mislead would-be predators into adopting an inappropriate search strategy for the prey once they have settled (search disruption). Another possibility is that the grasshopper has evolved to resemble a butterfly that is much harder to catch (pursuit deterrence). Motivated by anecdotal accounts of between-order mimicry, we quantified the degree of behavioural similarity of flight characteristics and colour resemblance between the Carolina grasshopper and the mourning cloak butterfly (Nymphalis antiopa), a sympatric species with which it is commonly confused by human observers. Among the five Orthoptera sampled, D. carolina had the multivariate flight phenotype most similar to that of N. antiopa. The corresponding dark and light wing patches of the focal pair showed modest chromatic and achromatic separation under an avian visual model. Together with their qualitative resemblance in wing pattern, these results are consistent with a possible mimetic relationship, although experiments with natural predators would be required to test this hypothesis definitively. If it is mimicry, then search disruption and pursuit deterrence would remain complementary explanations for mimetic resemblance since both mechanisms benefit from mimicry but act at different stages of the predation sequence.
Calopterigids and other damselflies have been widely studied as model organisms for sperm removal behavior, an offensive adaptation to sperm competition. Male Calopteryx cornelia possess a recurved shaft (ligula) that removes rival sperm from the bursa copulatrix, a spherical sperm storage organ in females. The ligula bears paired but laterally asymmetrical spiny processes, of which only the left process is considered capable of removing sperm from the left branch of another storage organ (the paired spermathecal tubes). Consequently, the right spermathecal tube could serve as a “safe harbor” from left-handed males, potentially favoring rare right-handed mutants if they were to arise. We examined a simple theoretical model to test this prediction and conducted individual-based evolutionary simulations to explore more realistic scenarios. Using parameter values close to empirical estimates (i.e., 30
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.
