Sexual differences in morphology can evolve by sexual selection and/or natural selection.In some species,only males have morphological structures that are used as weapons.Since some weapons may also be used for defens...Sexual differences in morphology can evolve by sexual selection and/or natural selection.In some species,only males have morphological structures that are used as weapons.Since some weapons may also be used for defensive purposes,males and females may behave differently towards predators.In some species of harvestmen(Arachnida and Opiliones),males have sharp apophyses("spines")on their 4th pair of legs whereas females lack them.Those apophyses are used in malemale fights and in antipredatory behaviors.The harvestmen antipredatory repertory also encompasses passive defenses such as thanatosis(death feigning),retaliation(attack on predators),and chemical defense.Due to the sexual differences on weaponry,we hypothesized that males and females of Mischonyx cuspidatus(Gonyleptidae)rely on different defensive strategies.We experimentally induced males and females to perform 3 defensive behaviors:thanatosis,pinching with legs,and chemical release.We predicted that females would engage more in passive and chemical defenses than males,whereas males would rely more on retaliation than females.As expected,females performed thanatosis more often than males.Likewise,males performed retaliation more often than females.We did not find differences in the rate of chemical defense use between the sexes.This study provides evidence that due to sexual dimorphism,alternative antipredatory behaviors may have been selected in the different sexes in M.cuspidatus.展开更多
Our research addresses questions about how micro-climate affects activity abundance of a common and widespread harvestman in an alpine ecosystem. Activity patterns of the Harvestman Mitopus morio(Fabricius, 1779) were...Our research addresses questions about how micro-climate affects activity abundance of a common and widespread harvestman in an alpine ecosystem. Activity patterns of the Harvestman Mitopus morio(Fabricius, 1779) were studied along different alpine gradients in the central Norwegian Scandes. Within a nested design, we surveyed 18 alpine habitats with pitfall traps and microclimatological equipment along oceanic-continental, two elevational, and(fine-scaled) microtopographic gradients. Sites in the oceanic region of the Scandes showed generally higher abundance of M. morio than sites in the continental region. Furthermore, along the elevational gradient, middle-alpine sites showed higher abundances than low-alpine sites. These general patterns are best explained by higher humidity in the oceanic region and in the middlealpine belt. Focusing at a finer scale, i.e. one elevational level within each region, revealed partly opposing activity patterns within relatively short distances. While in the western middle-alpine belt these patterns were best explained by humidityrelated measures but now with higher activity abundance during drier conditions, in the drier eastern middle-alpine belt heat sums rather than humidity were found to be the best explanatoryvariables for the observed patterns. Hence, our results imply a pronounced different reaction of the two populations towards climatic variables that partly even contradict the previously described general pattern. Regardless whether these differences in activity abundance in M. morio are a form of phenotypic plasticity or adaptation, our findings stress the importance of detailed autecological knowledge combined with fine-scaled climatic measurements when aiming at predictions about possible future ecosystem structures and spatiotemporal phenomena. M. morio proves to be an ideal biogeographic model organism for understanding spatio-temporal responses of alpine ecosystems under modified climatic conditions.展开更多
文摘Sexual differences in morphology can evolve by sexual selection and/or natural selection.In some species,only males have morphological structures that are used as weapons.Since some weapons may also be used for defensive purposes,males and females may behave differently towards predators.In some species of harvestmen(Arachnida and Opiliones),males have sharp apophyses("spines")on their 4th pair of legs whereas females lack them.Those apophyses are used in malemale fights and in antipredatory behaviors.The harvestmen antipredatory repertory also encompasses passive defenses such as thanatosis(death feigning),retaliation(attack on predators),and chemical defense.Due to the sexual differences on weaponry,we hypothesized that males and females of Mischonyx cuspidatus(Gonyleptidae)rely on different defensive strategies.We experimentally induced males and females to perform 3 defensive behaviors:thanatosis,pinching with legs,and chemical release.We predicted that females would engage more in passive and chemical defenses than males,whereas males would rely more on retaliation than females.As expected,females performed thanatosis more often than males.Likewise,males performed retaliation more often than females.We did not find differences in the rate of chemical defense use between the sexes.This study provides evidence that due to sexual dimorphism,alternative antipredatory behaviors may have been selected in the different sexes in M.cuspidatus.
基金partly sponsored by Color Line Aksjeselskap, Oslo
文摘Our research addresses questions about how micro-climate affects activity abundance of a common and widespread harvestman in an alpine ecosystem. Activity patterns of the Harvestman Mitopus morio(Fabricius, 1779) were studied along different alpine gradients in the central Norwegian Scandes. Within a nested design, we surveyed 18 alpine habitats with pitfall traps and microclimatological equipment along oceanic-continental, two elevational, and(fine-scaled) microtopographic gradients. Sites in the oceanic region of the Scandes showed generally higher abundance of M. morio than sites in the continental region. Furthermore, along the elevational gradient, middle-alpine sites showed higher abundances than low-alpine sites. These general patterns are best explained by higher humidity in the oceanic region and in the middlealpine belt. Focusing at a finer scale, i.e. one elevational level within each region, revealed partly opposing activity patterns within relatively short distances. While in the western middle-alpine belt these patterns were best explained by humidityrelated measures but now with higher activity abundance during drier conditions, in the drier eastern middle-alpine belt heat sums rather than humidity were found to be the best explanatoryvariables for the observed patterns. Hence, our results imply a pronounced different reaction of the two populations towards climatic variables that partly even contradict the previously described general pattern. Regardless whether these differences in activity abundance in M. morio are a form of phenotypic plasticity or adaptation, our findings stress the importance of detailed autecological knowledge combined with fine-scaled climatic measurements when aiming at predictions about possible future ecosystem structures and spatiotemporal phenomena. M. morio proves to be an ideal biogeographic model organism for understanding spatio-temporal responses of alpine ecosystems under modified climatic conditions.
