Sequestration of Defenses against Predators Drives Specialized Host Plant Associations in Preadapted Milkweed Bugs (Heteroptera: Lygaeinae)

AbstractHost plant specialization across herbivorous insects varies dramatically, but while the molecular mechanisms of host plant adaptations are increasingly known, we often lack a comprehensive understanding of the selective forces that favor specialization. The milkweed bugs (Heteroptera: Lygaeinae) are ancestrally associated with plants of the Apocynaceae from which they commonly sequester cardiac glycosides for defense, facilitated by resistant NaNa+/K+-ATPases and adaptations for transport, storage, and discharge of toxins. Here, we show that three Lygaeinae species independently colonized four novel nonapocynaceous hosts that convergently produce cardiac glycosides. A fourth species shifted to a new source of toxins by tolerating and sequestering alkaloids from meadow saffron (Colchicum autumnale, Colchicaceae). Across three milkweed bug species tested, feeding on seeds containing toxins did not improve growth or speed of development and even impaired growth and development in two species, but sequestration mediated protection of milkweed bugs against two natural predators: lacewing larvae and passerine birds. We conclude that physiological preadaptations and convergent phytochemistry facilitated novel specialized host associations. Since toxic seeds did not improve growth but either impaired growth or, at most, had neutral effects, selection by predators on sequestration of defenses, rather than the exploitation of additional profitable dietary resources, can lead to obligatory specialized host associations in otherwise generalist insects

Jiří Žáček's drama for children

Bakalářská práce se zabývá dramatickou tvorbou Jiřího Žáčka pro děti. Zaměřuje se na jeho čtyři divadelní pohádky určené pro loutky i živé herce. Vychází z charakteristických rysů jeho poezie pro děti, na jejímž pozadí se snaží ukázat a popsat prostředky a postupy, které autor ve svých dramatických textech volí. Soustřeďuje se na autorovu práci s jazykem a inspiračními zdroji a zamýšlí se nad úrovní Žáčkových divadelních pohádek v kontrastu s neporozuměními, která se v dramatických textech pro děti hojně vyskytují. Powered by TCPDF (www.tcpdf.org)My bachelor thesis deals with Jiří Žáček's dramatic work for children. It focuses on his four theatrical tales for puppets and live actors. It is based on distinctive features of author's poetry for children and tries to show and discribes on it's background means and procedures which author chooses in his dramatic texts. It concentrates on author's work with language and sources of inspiration and contemplates on level of Žáček's theatrical tales in contrast with a misunderstanding which occure in dramatical text for children profusely. Powered by TCPDF (www.tcpdf.org)Departement of Theatre StudiesKatedra divadelní vědyFilozofická fakultaFaculty of Art

Jiří Žáček's drama for children

My bachelor thesis deals with Jiří Žáček's dramatic work for children. It focuses on his four theatrical tales for puppets and live actors. It is based on distinctive features of author's poetry for children and tries to show and discribes on it's background means and procedures which author chooses in his dramatic texts. It concentrates on author's work with language and sources of inspiration and contemplates on level of Žáček's theatrical tales in contrast with a misunderstanding which occure in dramatical text for children profusely. Powered by TCPDF (www.tcpdf.org

Scared by shiny? The value of iridescence in aposematic signalling of the hibiscus harlequin bug

Studies on aposematism have generally focused on the benefits of red or yellow coloration, occasionally in contrast with green or brown, but rarely blue or orange. Furthermore, almost no studies have explicitly studied the utility of iridescent coloration in aposematism. To evaluate the survival benefit of iridescent coloration, we tested the ability of the natural colour extremes of Tectocoris diophthalmus jewelbugs to induce initial avoidance, learned avoidance, discrimination from palatable alternatives and broad generalization against avian predators: naïve hand-reared and experienced wild-caught great tits, Parus major. Artificial baits were created by hollowing out bugs and inserting pieces of mealworm. Preference tests presented iridescent and orange baits simultaneously, then birds were divided into training groups and sequentially exposed to palatable black baits alternated with iridescent or orange baits made unpalatable by soaking mealworms in quinine solution. This was followed by simultaneous black/coloured discrimination tests, then a generalization test with both previously experienced and novel baits (all palatable). All groups showed a preference for orange baits over ones with iridescent patches. For wild-caught birds, attack latencies of iridescent and orange training groups were statistically indistinguishable, although only orange caused increased attack latency over the sequence. Hand-reared birds showed no change in attack rate/latency towards iridescent bugs over the sequence. In postlearning discrimination tests, all groups showed equally strong preference for palatable black baits and their unpalatable training baits. In generalization tests, hand-reared birds were most averse towards trained baits, but increased avoidance of iridescent-and-black baits suggests iridescence alone can contribute to aposematism. Wild-caught birds showed strong aversion to iridescent and novel orange-and-black baits regardless of training, suggesting birds may be broadly generalizing experience from local red-and-black aposematic bugs. Results suggest iridescent coloration and patterning can be an effective aposematic signal, especially in the presence of alternative palatable prey and/or other aposematic species.11 page(s

Evolution of multiple prey defences: From predator cognition to community ecology

Exnerová A, Kang C, Rowland HM, Kikuchi DW. Evolution of multiple prey defences: From predator cognition to community ecology. Journal of Evolutionary Biology. 2023;36(7):961-966

No evidence for self-recognition in a small passerine, the great tit (Parus major) judged from the mark/mirror test

Self-recognition is a trait presumed to be associated with high levels of cognition and something previously considered to be exclusive to humans and possibly apes. The most common test of self-recognition is the mark/mirror test of whether an animal can understand that it sees its own reflection in a mirror. The usual design is that an animal is marked with a colour spot somewhere on the body where the spot can only be seen by the animal by using a mirror. Very few species have passed this test, and among birds, only magpies have been affirmatively demonstrated to pass it. In this study, we tested great tits (Parus major), small passerines, that are known for their innovative foraging skills and good problem-solving abilities, in the mirror self-recognition test. We found no indication that they have any ability of this kind and believe that they are unlikely to be capable of this type of self-recognition

Personality matters: individual variation in reactions of naive bird predators to aposematic prey

Variation in reactions to aposematic prey is common among conspecific individuals of bird predators. It may result from different individual experience but it also exists among naive birds. This variation may possibly be explained by the effect of personality—a complex of correlated, heritable behavioural traits consistent across contexts. In the great tit (Parus major), two extreme personality types have been defined. ‘Fast’ explorers are bold, aggressive and routine-forming; ‘slow’ explorers are shy, non-aggressive and innovative. Influence of personality type on unlearned reaction to aposematic prey, rate of avoidance learning and memory were tested in naive, hand-reared great tits from two opposite lines selected for exploration (slow against fast). The birds were subjected to a sequence of trials in which they were offered aposematic adult firebugs (Pyrrhocoris apterus). Slow birds showed a greater degree of unlearned wariness and learned to avoid the firebugs faster than fast birds. Although birds of both personality types remembered their experience, slow birds were more cautious in the memory test. We conclude that not only different species but also populations of predators that differ in proportions of personality types may have different impacts on survival of aposematic insects under natural conditions