Differential Performance of a Specialist and Two Generalist Herbivores and Their Parasitoids on Plantago lanceolata

The ability to cope with plant defense chemicals differs between specialist and generalist species. In this study, we examined the effects of the concentration of the two main iridoid glycosides (IGs) in Plantago lanceolata, aucubin and catalpol, on the performance of a specialist and two generalist herbivores and their respective endoparasitoids. Development of the specialist herbivore Melitaea cinxia was unaffected by the total leaf IG concentration in its host plant. By contrast, the generalist herbivores Spodoptera exigua and Chrysodeixis chalcites showed delayed larval and pupal development on plant genotypes with high leaf IG concentrations, respectively. This result is in line with the idea that specialist herbivores are better adapted to allelochemicals in host plants on which they are specialized. Melitaea cinxia experienced less post-diapause larval and pupal mortality on its local Finnish P. lanceolata than on Dutch genotypes. This could not be explained by differences in IG profiles, suggesting that M. cinxia has adapted in response to attributes of its local host plants other than to IG chemistry. Development of the specialist parasitoid Cotesia melitaearum was unaffected by IG variation in the diet of its host M. cinxia, a response that was concordant with that of its host. By contrast, the development time responses of the generalist parasitoids Hyposoter didymator and Cotesia marginiventris differed from those of their generalist hosts, S. exigua and C. chalcites. While their hosts developed slowly on high-IG genotypes, development time of H. didymator was unaffected. Cotesia marginiventris actually developed faster on hosts fed high-IG genotypes, although they then had short adult longevity. The faster development of C. marginiventris on hosts that ate high-IG genotypes is in line with the “immunocompromized host” hypothesis, emphasizing the potential negative effects of toxic allelochemicals on the host’s immune response

Evolution of host plant use and diversification in a species complex of parasitic weevils (Coleoptera: Curculionidae)

Weevils (Coleoptera: Curculionoidea) represent one of the most diverse groups of organisms on Earth; interactions with their host plants have been recognized to play a central role in their remarkable diversity, yet the exact mechanisms and factors still remain poorly understood. Using phylogenetic comparative analyses, here we investigate the evolution of host use and its possible role in diversification processes of Rhinusa and Gymnetron, two closely related groups of weevils that feed and develop inside plant tissues of hosts within the families Scrophulariaceae and Plantaginaceae. We found strong evidence for phylogenetic conservatism of host use at the plant family level, most likely due to substantial differences in the chemical composition of hosts, reducing the probability of shifts between host families. In contrast, the use of different plant organs represents a more labile ecological trait and ecological niche expansion that allows a finer partitioning of resources. Rhinusa and Gymnetron weevils initially specialized on plants within Scrophulariaceae and then shifted to the closely related Plantaginaceae; likewise, a gall inducing behavior evolved from non-galler weevils, possibly in response to resource competition, as galls facilitate larval development by providing enhanced nutrition and a favorable microhabitat. Results from trait-dependent diversification analyses suggest that both use of hosts within Plantaginaceae and parasitism on fruits and seed capsules are associated with enhanced diversification of Rhinusa and Gymnetron via low extinction rates. Our study provides quantitative evidence and insights on the ecological factors that can promote diversification in phytophagous insects that feed and develop inside plant tissues

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

Tirocinia critica in Dionysii Halicarnassensis Antiquitates Romanas [microform] /

Filmed with: Rück, K. / De M. Tulli Ciceronis oratione De domo sua ad pontifices -- Rosenthal, W. / De Antiphontis in particularum usu proprietate -- Poschmann, B. / Hat Augustinus die Privatbusse eingeführt? -- Ritter, K. / De Pindari studio nomina variandi -- Schering, O. / Symbola ad Socratis et Socraticorum epistulas explicandas -- Schinck, A. / De interjectionum epiphonematumque vi et usu apud Aristophanem -- Schiller, H. / Beiträge zur Entstehungsgeschichte der Odyssee -- Scherrer, J. / Gallier und ihre Verfassung -- Remark, P. / De amphorarum inscriptionibus Latinis quaestiones selectae -- Schmid, E. / Megariker -- Schmidt, B. / De Cornuti theologiae Graecae compendio capita duo -- Retzlaff, O. / Vorschule zu Homer -- Proskauer, C. / auslautende -s auf den lateinischen Inschriften -- Rasch, F. / De productione brevium syllabarum in Homeri Iliade -- Raschke, R. / De Alberico mythologo -- Steinacher, J. / Syntax des Hesiodischen Infinitivs -- Steinmeyer, E. von / De glossis quibusdam Vergilianis -- Strobl, K. / Euripides und die Bedeutung seiner Aussprüche über göttliches und allgemein menschliches Wesen -- Struck, E. / De Terentio et Donato -- Ring, M. / Zur Tropik Pindar's -- Rohde, E. / Ueber Lucian's Schrift Loukios e onos -- Riehemann, J. / De litis instrumentis -- Richardson, G. M. / De dum particulae apud priscos scriptores Latinos -- Ruckdeschel, F. / Archaismen und Vulgarismen in der Sprache des Horaz.Diss.Includes bibliographical references.Microfilm.Mode of access: Internet