Modality matters for the expression of inducible defenses: introducing a concept of predator modality

Background: Inducible defenses are a common and widespread form of phenotypic plasticity. A fundamental factor driving their evolution is an unpredictable and heterogeneous predation pressure. This heterogeneity is often used synonymously to quantitative changes in predation risk, depending on the abundance and impact of predators. However, differences in `modality', that is, the qualitative aspect of natural selection caused by predators, can also cause heterogeneity. For instance, predators of the small planktonic crustacean Daphnia have been divided into two functional groups of predators: vertebrates and invertebrates. Predators of both groups are known to cause different defenses, yet predators of the same group are considered to cause similar responses. In our study we question that thought and address the issue of how multiple predators affect the expression and evolution of inducible defenses. Results: We exposed D. barbata to chemical cues released by Triops cancriformis and Notonecta glauca, respectively. We found for the first time that two invertebrate predators induce different shapes of the same morphological defensive traits in Daphnia, rather than showing gradual or opposing reaction norms. Additionally, we investigated the adaptive value of those defenses in direct predation trials, pairing each morphotype (non-induced, Triops-induced, Notonecta-induced) against the other two and exposed them to one of the two predators. Interestingly, against Triops, both induced morphotypes offered equal protection. To explain this paradox we introduce a `concept of modality' in multipredator regimes. Our concept categorizes two-predator-prey systems into three major groups (functionally equivalent, functionally inverse and functionally diverse). Furthermore, the concept includes optimal responses and costs of maladaptions of prey phenotypes in environments where both predators co-occur or where they alternate. Conclusion: With D. barbata, we introduce a new multipredator-prey system with a wide array of morphological inducible defenses. Based on a `concept of modality', we give possible explanations how evolution can favor specialized defenses over a general defense. Additionally, our concept not only helps to classify different multipredator-systems, but also stresses the significance of costs of phenotype-environment mismatching in addition to classic `costs of plasticity'. With that, we suggest that `modality' matters as an important factor in understanding and explaining the evolution of inducible defenses

Deciphering the Chemical Basis of Nestmate Recognition

Social insects maintain colony cohesion by recognizing and, if necessary, discriminating against conspecifics that are not part of the colony. This recognition ability is encoded by a complex mixture of cuticular hydrocarbons (CHCs), although it is largely unclear how social insects interpret such a multifaceted signal. CHC profiles often contain several series of homologous hydrocarbons, possessing the same methyl branch position but differing in chain length (e.g., 15-methyl-pentatriacontane, 15-methyl-heptatriacontane, 15-methyl-nonatriacontane). Recent studies have revealed that within species these homologs can occur in correlated concentrations. In such cases, single compounds may convey the same information as the homologs. In this study, we used behavioral bioassays to explore how social insects perceive and interpret different hydrocarbons. We tested the aggressive response of Argentine ants, Linepithema humile, toward nest-mate CHC profiles that were augmented with one of eight synthetic hydrocarbons that differed in branch position, chain length, or both. We found that Argentine ants showed similar levels of aggression toward nest-mate CHC profiles augmented with compounds that had the same branch position but differed in chain length. Conversely, Argentine ants displayed different levels of aggression toward nest-mate CHC profiles augmented with compounds that had different branch positions but the same chain length. While this was true in almost all cases, one CHC we tested elicited a greater aggressive response than its homologs. Interestingly, this was the only compound that did not occur naturally in correlated concentrations with its homologs in CHC profiles. Combined, these data suggest that CHCs of a homologous series elicit the same aggressive response because they convey the same information, rather than Argentine ants being unable to discriminate between different homologs. This study contributes to our understanding of the chemical basis of nestmate recognition by showing that, similar to spoken language, the chemical language of social insects contains “synonyms,” chemicals that differ in structure, but not meaning

Queen mandibular pheromone: questions that remain to be resolved

The discovery of ‘queen substance’, and the subsequent identification and synthesis of keycomponents of queen mandibular pheromone, has been of significant importance to beekeepers and to thebeekeeping industry. Fifty years on, there is greater appreciation of the importance and complexity of queenpheromones, but many mysteries remain about the mechanisms through which pheromones operate. Thediscovery of sex pheromone communication in moths occurred within the same time period, but in this case,intense pressure to find better means of pest management resulted in a remarkable focusing of research activityon understanding pheromone detection mechanisms and the central processing of pheromone signals in themoth. We can benefit from this work and here, studies on moths are used to highlight some of the gaps in ourknowledge of pheromone communication in bees. A better understanding of pheromone communication inhoney bees promises improved strategies for the successful management of these extraordinary animals

The Tyrant's Fear. Part 2.

Literary and dramatic representations of tyranny abound since antiquity alongside critical distinctions between different forms of totalitarian and oppressive regimes. Yet, book-length studies on the topic of the tyrant\u2019s fear are relatively few. The second part of this special issue (part 1: 51.4. 2017) includes seven articles which explore the tyrant\u2019s fear as dramatized in the Oresteia and Macbeth through discussions of classical and early modern psychological, cultural and performative interdictions to say and show on stage the murder of the king (1 and 2); of affect and stage/audience liminality (3 and 4); and of the tyrant\u2019s fear from the perspective of the dangers and fears of staging these two plays in contemporary tyrannical regimes, from Czechoslovakia to Francoist Spain to authoritarian Greece (5, 6, 7). How do these plays lend themselves to unflattering renderings of contemporary tyrannical regimes? Have they been \u2018unmountable\u2019 at particular moments in time or in certain cultural contexts where censorship was, and still is, strong? Along these lines, can different (possibly depoliticized) stagings communicate the themes and ideas of the plays in order not to offend the regime within which the performance is produced

Sken\ue8. Journal of Theatre and Drama Studies, I, 2, 2015: Short Forms

Il numero monografico di Sken\ue8 \ue8 dedicato alle forme brevi nel teatro da inizio Novecento a oggi. Dealla forma breve, esaminata sia a livello testuale che spettacolare si prendono in esame, attraverso diversi case studies relativi al teatro europeo, le peculiarit\ue0 estetiche e comunicative rispetto all'analogo formato in ambito letterario e cinematografic