Adaptations and responses of the common dandelion to low atmospheric pressure in high‐altitude environments

Atmospheric pressure is an important, yet understudied factor that may shape plant ecology and evolution. By growing plants under controlled conditions at different experimental stations in the Swiss alps, we evaluated the impact of ecologically realistic atmospheric pressures between 660 and 950 hPa on the growth and defence of different dandelion populations. Low atmospheric pressure was associated with reduced root growth and defensive sesquiterpene lactone production. Defence suppression only occurred in populations originating from lower altitudes. Populations from higher altitudes constitutively produced less sesquiterpene lactones and did not suffer from suppression under low atmospheric pressure. Synthesis. We conclude that atmospheric pressure modulates root growth and defence traits, and that evolutionary history shapes plant phenotypic responses to atmospheric pressure. Our findings have important implications for our understanding of altitudinal gradients and the future use of plants as a source of food and bioactive metabolites in extraterrestrial habitats

Nonaggressive behavior : A strategy employed by an obligate nest invader to avoid conflict with its host species

In addition to its builders, termite nests are known to house a variety of secondary, opportunistic termite species, but little is known about the mechanisms governing the maintenance of such associations. In a single nest, host and intruder are likely to engage in intense conflict, due to their nestmate discrimination system. An intriguing question is how individuals cope with such a burden in the long term. Evasive behaviour has been previously suggested as a mechanism that reduces the frequency of encounters between non-nestmates. However, due to confinement imposed by the nests’ physical boundaries, it is likely that hosts and inquilines would eventually come across each other. Under these circumstances, it is plausible that inquilines would be required to behave accordingly to secure their housing. Here, we tested this hypothesis predicting that, once inevitably exposed to hosts, inquiline individuals would modulate their behaviour to circumvent conflict. While exploring the behavioural dynamics of the encounter between both cohabitants, we find evidence for an unusual lack of aggressiveness by inquilines towards hosts. Such a non-aggressive behaviour is characterised by evasive manoeuvres that include reversing direction, bypassing and a defensive mechanism using defecation to repel hosts. The behavioural adaptations we describe may play an intrinsic role in the stability of cohabitations between termite species: by reducing the costs of conflicts to both cohabitants, it may improve the chances for stable nest-sharing considerably.publishe

Heterospecific detection of host alarm cues by an inquiline termite species (Blattodea: Isoptera: Termitidae)

Artigo da EntomologiaTermite inquilines specialize on living in and feeding on a host termite nest. However, the mechanisms allowing survival of two mutually hostile populations confined to a single nest are not understood. Here we report on inquiline termites that respond to their host's alarm cues. Upon detecting these cues, the inquilines do not join in with the host's nest defence, but use this information for their own benefit, to escape danger. Using behavioural bioassays under laboratory conditions, we show that the obligatory inquiline Inquilinitermes microcerus (Termitidae: Termitinae) responds both to its own alarm signal and to alarm cues from its host, Constrictotermes cyphergaster (Termitidae: Nasutitermitinae). Conversely, this host responded only to its own alarm signal. Despite perceiving their host's alarm cues, inquilines were never observed sharing nest defence with their host in experimentally damaged nests in the field. We argue that this allows inquilines not only to minimize encounters and hence conflict with their hosts, but also to use their host alarm information to escape the host's enemies, which are also likely to be enemies of the inquilines. Our results show a new benefit that inquilines gain from the host, and we discuss the inquiline way-of-life from an evolutionary perspective, as the outcome of constraints and benefits imposed by living in host nests

The nature of alarm communication in Constrictotermes cyphergaster (Blattodea: Termitoidea: Termitidae): the integration of chemical and vibroacoustic signals

Alarm signalling is of paramount importance to communication in all social insects. In termites, vibroacoustic and chemical alarm signalling are bound to operate synergistically but have never been studied simultaneously in a single species. Here, we inspected the functional significance of both communication channels in Constrictotermes cyphergaster (Termitidae: Nasutitermitinae), confirming the hypothesis that these are not exclusive, but rather complementary processes. In natural situations, the alarm predominantly attracts soldiers, which actively search for the source of a disturbance. Laboratory testing revealed that the frontal gland of soldiers produces a rich mixture of terpenoid compounds including an alarm pheromone. Extensive testing led to identification of the alarm pheromone being composed of abundant monoterpene hydrocarbons (1S)-α-pinene and myrcene, along with a minor component, (E)-β-ocimene. The vibratory alarm signalling consists of vibratory movements evidenced as bursts; a series of beats produced predominantly by soldiers. Exposing termite groups to various mixtures containing the alarm pheromone (crushed soldier heads, frontal gland extracts, mixture of all monoterpenes, and the alarm pheromone mixture made of standards) resulted in significantly higher activity in the tested groups and also increased intensity of the vibratory alarm communication, with the responses clearly dose-dependent. Lower doses of the pheromone provoked higher numbers of vibratory signals compared to higher doses. Higher doses induced long-term running of all termites without stops necessary to perform vibratory behaviour. Surprisingly, even crushed worker heads led to low (but significant) increases in the alarm responses, suggesting that other unknown compound in the worker's head is perceived and answered by termites. Our results demonstrate the existence of different alarm levels in termites, with lower levels being communicated through vibratory signals, and higher levels causing general alarm or retreat being communicated through the alarm pheromone

The nature of alarm communication in Constrictotermes cyphergaster (Blattodea: Termitoidea: Termitidae): the integration of chemical and vibroacoustic signals

Alarm signalling is of paramount importance to communication in all social insects. In termites, vibroacoustic and chemical alarm signalling are bound to operate synergistically but have never been studied simultaneously in a single species. Here, we inspected the functional significance of both communication channels in Constrictotermes cyphergaster (Termitidae: Nasutitermitinae), confirming the hypothesis that these are not exclusive, but rather complementary processes. In natural situations, the alarm predominantly attracts soldiers, which actively search for the source of a disturbance. Laboratory testing revealed that the frontal gland of soldiers produces a rich mixture of terpenoid compounds including an alarm pheromone. Extensive testing led to identification of the alarm pheromone being composed of abundant monoterpene hydrocarbons (1S)-α-pinene and myrcene, along with a minor component, (E)-β-ocimene. The vibratory alarm signalling consists of vibratory movements evidenced as bursts; a series of beats produced predominantly by soldiers. Exposing termite groups to various mixtures containing the alarm pheromone (crushed soldier heads, frontal gland extracts, mixture of all monoterpenes, and the alarm pheromone mixture made of standards) resulted in significantly higher activity in the tested groups and also increased intensity of the vibratory alarm communication, with the responses clearly dose-dependent. Lower doses of the pheromone provoked higher numbers of vibratory signals compared to higher doses. Higher doses induced long-term running of all termites without stops necessary to perform vibratory behaviour. Surprisingly, even crushed worker heads led to low (but significant) increases in the alarm responses, suggesting that other unknown compound in the worker's head is perceived and answered by termites. Our results demonstrate the existence of different alarm levels in termites, with lower levels being communicated through vibratory signals, and higher levels causing general alarm or retreat being communicated through the alarm pheromone

Nematode Root Herbivory in Tomato Increases Leaf Defenses and Reduces Leaf Miner Oviposition and Performance

The outcome of plant-mediated interactions among herbivores from several feeding guilds has been studied intensively. However, our understanding on the effects of nematode root herbivory on leaf miner oviposition behavior and performance remain limited. In this study, we evaluated whether Meloidogyne incognita root herbivory affects Tuta absoluta oviposition preference on Solanum lycopersicum plants and the development of the resulting offspring. To investigate the M. incognita-herbivory induced plant systemic responses that might explain the observed biological effects, we measured photosynthetic rates, leaf trypsin protease inhibitor activities, and analyzed the profile of volatiles emitted by the leaves of root-infested and non-infested plants. We found that T. absoluta females avoided laying eggs on the leaves of root-infested plants, and that root infestation negatively affected the pupation process of T. absoluta. These effects were accompanied by a strong suppression of leaf volatile emissions, a decrease in photosynthetic rates, and an increase in the activity of leaf trypsin protease inhibitors. Our study reveals that root attack by nematodes can shape leaf physiology, and thereby increases plant resistance

Alternative control of Aedes aegypti resistant to pyrethroids: lethal and sublethal effects of monoterpenes bioinsecticides

The mosquito Aedes aegypti is intensely controlled because it is vector of viruses that cause innumerous diseases, especially in tropical regions. Due to the indiscriminate use of insecticides, populations from different regions have been resistant to pyrethroids. Here, we analyzed the lethal and sublethal effects of essential oil of Aristolochia trilobata and its major compounds on A. aegypti from susceptible and pyrethroid resistant populations. Our results showed that the toxicity and behavioral changes to different compounds are dependent of the stage of the insect life cycle. The monoterpene ρ-cymene caused high mortality in both larvae and adult females of A. aegypti, including those from the pyrethroid resistant population. The monoterpenes limonene and linalool caused a sublethal effect in the larvae triggering changes in the swimming pattern. This study highlights the potential of the essential oil of A. trilobata, ρ-cymene and limonene to the control of A. aegypti and reveals the importance of analyzing the sublethal effects for the population dynamics of the A. aegypti mosquito

Essential oil of Lippia sidoides and its major compound thymol: toxicity and walking response of populations of Sitophilus zeamais (Coleoptera: Curculionidae)

The maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae), is the main pest of stored grains across tropical regions. An alternative strategy to the use of synthetic insecticides for the management of S. zeamais is the development of botanical insecticides based in the essential oils (EOs) from aromatic plants. In the present study, we evaluated the lethal and sublethal effects of the EO of Lippia sidoides (Cham.) and its major compounds (thymol and ρ-cymene) on different populations of S. zeamais. For this, we determined toxicity by fumigation of treatments of five populations from different Brazilian regions and assessed the lethal time and walking behavior for the most tolerant and susceptible populations. The lethal concentration required to kill 50% of S. zeamais populations ranged from 35.48 to 118.29 μL L^−1 air for EO of L. sidoides, 65.00–91.23 μL L^−1 air for thymol and 801.24 to 2188,83 μL L^−1 air for ρ-cymene. Population from Jacarezinho was the most tolerant to treatments, while population of Rio Branco was the most susceptible one. The survival of S. zeamais populations was significantly affected by treatments and ρ-cymene showed the faster action on both Jacarezinho and Rio Branco populations (LT50 = 0.3 h). The walking behavior of maize weevil showed that the EO of L. sidoides and thymol present repellent effect, however, ρ-cymene present attractive effect. Therefore, the EO of L. sidoides and its major compound thymol are promising source to develop bioinsecticides for the management of S. zeamais populations with different levels of resistance