Oviposition Cues for a Specialist Butterfly–Plant Chemistry and Size

The oviposition choice of an insect herbivore is based on a complex set of stimuli and responses. In this study, we examined the effect of plant secondary chemistry (the iridoid glycosides aucubin and catalpol) and aspects of size of the plant Plantago lanceolata, on the oviposition behavior of the specialist butterfly Melitaea cinxia. Iridoid glycosides are known to deter feeding or decrease the growth rate of generalist insect herbivores, but can act as oviposition cues and feeding stimulants for specialized herbivores. In a previous observational study of M. cinxia in the field, oviposition was associated with high levels of aucubin. However, this association could have been the cause (butterfly choice) or consequence (plant induction) of oviposition. We conducted a set of dual- and multiple-choice experiments in cages and in the field. In the cages, we found a positive association between the pre-oviposition level of aucubin and the number of ovipositions. The association reflects the butterfly oviposition selection rather than plant induction that follows oviposition. Our results also suggest a threshold concentration below which females do not distinguish between levels of iridoid glycosides. In the field, the size of the plant appeared to be a more important stimulus than iridoid glycoside content, with bigger plants receiving more oviposition than smaller plants, regardless of their secondary chemistry. Our results illustrate that the rank of a cue used for oviposition may be dependent on environmental context

From Plants to Birds: Higher Avian Predation Rates in Trees Responding to Insect Herbivory

BACKGROUND: An understanding of the evolution of potential signals from plants to the predators of their herbivores may provide exciting examples of co-evolution among multiple trophic levels. Understanding the mechanism behind the attraction of predators to plants is crucial to conclusions about co-evolution. For example, insectivorous birds are attracted to herbivore-damaged trees without seeing the herbivores or the defoliated parts, but it is not known whether birds use cues from herbivore-damaged plants with a specific adaptation of plants for this purpose. METHODOLOGY: We examined whether signals from damaged trees attract avian predators in the wild and whether birds could use volatile organic compound (VOC) emissions or net photosynthesis of leaves as cues to detect herbivore-rich trees. We conducted a field experiment with mountain birches (Betula pubescens ssp. czerepanovii), their main herbivore (Epirrita autumnata) and insectivorous birds. Half of the trees had herbivore larvae defoliating trees hidden inside branch bags and half had empty bags as controls. We measured predation rate of birds towards artificial larvae on tree branches, and VOC emissions and net photosynthesis of leaves. PRINCIPAL FINDINGS AND SIGNIFICANCE: The predation rate was higher in the herbivore trees than in the control trees. This confirms that birds use cues from trees to locate insect-rich trees in the wild. The herbivore trees had decreased photosynthesis and elevated emissions of many VOCs, which suggests that birds could use either one, or both, as cues. There was, however, large variation in how the VOC emission correlated with predation rate. Emissions of (E)-DMNT [(E)-4,8-dimethyl-1,3,7-nonatriene], beta-ocimene and linalool were positively correlated with predation rate, while those of highly inducible green leaf volatiles were not. These three VOCs are also involved in the attraction of insect parasitoids and predatory mites to herbivore-damaged plants, which suggests that plants may not have specific adaptations to signal only to birds

A Novel NoC-Architecture for Fault Tolerance and Power Saving

Networks on chips (NoCs) have become a promising candidate for communication in future many-core architectures. However, manufacturing defects and aging effects are expected to cause permanent errors in future technology nodes, which are targeted by NoC-based architectures. Consequently, fault tolerance concepts are necessary in order to deal with these permanent errors. In this work, we propose a novel approach for fault tolerance in NoC-based architectures. We introduce an additional network layer to take over the duties of defective routers. In contrast to existing approaches, the proposed concept is independent of the routing algorithm and can substitute the bandwidth of defective routers. In addition, we show the potential of the concept for power saving. An ASIC implementation of the proposed design is used for performance and power saving evaluation as well as for overhead analysis

Fault-tolerant Communication in Invasive Networks on Chip

Dependability and fault tolerance will play an ever increasing role when using future technology nodes. The paper presents a fault-tolerance strategy for invasive networks on chip (i-NoC). The strategy focuses on permanent faults, resulting from either process fluctuations or aging effects and briefly outlines counter measurements against transient faults. We propose a scalable scheme for detection and localization of defects in NoCs. The localization scheme is used as a basis for disabling faulty routers. We propose a transparent bypass scheme to circumvent faulty routers and regions. It uses an architecture extension in the form of an additional lightweight network layer. The fault tolerance layer can be configured at run time according to the current fault map of the architecture. The presented evaluations analyze the fault coverage of the proposed detection and localization strategy. We also investigate the implementation cost and performance impact of the fault tolerance network layer