Schöne Utopie

Trotz Amokläufe, Blutrache, und anderen Formen von übertrieben ausgelebtem Zorn ist es wohl eine schöne Utopie zu glauben, dass Zorn und Rache grundsätzlich nichts mit sozialer Gerechtigkeit zu tun habe und deshalb „Gift für eine Gesellschaft“ sei. Das Gegenteil ist wohl eher die Regel, zumindest gemäss neuster Erkenntnisse aus der Evolutionsbiologie und Spieltheorie. Wenn Zorn dazu führt, dass anderen Schaden zugefügt wird, dann scheint das erst einmal nur destruktiv und unnütz. Auf lange Sicht kann aber der Zorn, den man bei anderen auslösen könnte, das eigene Verhalten stark beeinflussen. Diese Angst vor dem Zorn führt dann typischerweise dazu, dass wir uns insgesamt kooperativer und grosszügiger verhalten. Nimmt man zum Beispiel in einem anonymisierten Experiment, bei dem um Geld und Grosszügigkeit geht, die Möglichkeit zur Rache, dann wird insgesamt weniger grosszügig entschieden und damit auch weniger Wert für die soziale Gruppe kreiert (da ein gewisses Mass an Grosszügigkeit sehr oft Mehrwert kreiert). Dieser Verlust an Mehrwert kann in der experimentellen Situation deutlich höher sein als der gesamte Schaden, der durch Bestrafungen normalerweise entsteht. Zorn und Rache kann also Grosszügigkeit innerhalb sozialer Gruppen fördern und hat damit eine wichtige evolutionäre Funktion. Institutionalisierte Bestrafung (durch Polizei und Gerichte) kann diese Funktion nur zum Teil ersetzen. Ich denke deshalb, es ist möglicherweise irreführend, Zorn und Rache an sich zu verurteilen. Stattdessen sollte man sich wohl darauf konzentrieren, die Ursachen von übertrieben ausgelebtem oder fehlgeleitetem Zorn besser zu verstehen um sie effektiver zu bekämpfen

Size-dependent discrimination of mating partners in the simultaneous hermaphroditic cestode Schistocephalus solidus

The cestode Schistocephalus solidus is a simultaneous hermaphrodite that reproduces in the gut of birds, or for this study in an in vitro system that simulates the gut of the bird. Like many other helminth parasites, S. solidus can reproduce by self- and cross-fertilization. Hermaphrodites are expected to mate not primarily to get their own eggs fertilized, but rather to get the opportunity to fertilize a partner's eggs. Because S. solidus has a size-dependent sex allocation (i.e., larger worms are more biased toward female allocation and produce more egg mass), we expect larger individuals to be attractive mating partners for smaller ones. However, this may be a one-directional preference, as smaller individuals may not be attractive to larger ones. We tested this experimentally by studying the reaction of focal worms of different sizes to a compartment containing a potential mating partner that was either smaller or larger than the focal worm. The focal worms were, on average, closer to the compartment containing the stimulus than to an empty control compartment. Moreover, they indeed showed a preference for larger stimulus worms than for smaller ones. They even tended to avoid being close to stimulus worms of very small size compared to themselves. This may reveal a general preference for cross-fertilization over selfing, but it also indicates that all the genetic benefits from outcrossing do not necessarily outweigh the costs of mating with a relatively small individual and that the worms may take this into account in their reproductive decision

Examining punishment at different explanatory levels

Experimental studies on punishment have sometimes been over-interpreted not only for the reasons Guala lists, but also because of a frequent conflation of proximate and ultimate explanatory levels that Guala's review perpetuates. Moreover, for future analyses we may need a clearer classification of different kinds of punishmen

Copepod reaction to odor stimuli influenced by cestode infection

The cestode Schistocephalus solidus uses copepods as first and sticklebacks as second intermediate hosts. For transmission, an infected copepod has to be preyed upon by a stickleback. We used copepods of the species Macrocy albidus to test whether infected and uninfected copepods differ in their reaction to two kind of simultaneously presented odors: odors of sticklebacks and odors of sticklebacks and conspecificz. By giving this choice, we attempted to force the copepods to make a trade-off between the benefit of risk dilution and possible predator confusion and the costs of food competition and other disadvantages induced by conspecifics. Within 1-8 h after last feeding, uninfected copepods clearly preferred the odors of conspeciflcs under the chemically simulated threat of predation. This was in contrast to the infected copepods, who tended to avoid the odor of conspecifics. When the time between experiment and last feeding varied, infected copepods showed an increas preference for fish water only (or avoided conspecthcs) with increasing hunger level This suggests that S. solidus benefits from hunger-induced behavioral changes of its copepod host by influencing its microhabitat selection. The same effect could be found in both sexes; however, it was significantly more pronounced in male than in female copepods. We propose several hypotheses that could explain the difference between the sexes in their infection-dependent microhabitat selectio

Change in individual growth rate and its link to gill-net fishing in two sympatric whitefish species

Size-selective fishing is expected to affect traits such as individual growth rate, but the relationship between the fishery-linked selection differentials and the corresponding phenotypic changes is not well understood. We analysed a 25-year monitoring survey of sympatric populations of the two Alpine whitefish Coregonus albellus and C. fatioi. We determined the fishing-induced selection differentials on growth rates, the actual change of growth rates over time, and potential indicators of reproductive strategies that may change over time. We found marked declines in adult growth rate and significant selection differentials that may partly explain the observed declines. However, when comparing the two sympatric species, the selection differentials on adult growth were stronger in C. albellus while the decline in adult growth rate seemed more pronounced in C. fatioi. Moreover, the selection differential on juvenile growth was significant in C. albellus but not in C. fatioi, while a significant reduction in juvenile growth over the last 25years was only found in C. fatioi. Our results suggest that size-selective fishing affects the genetics for individual growth in these whitefish, and that the link between selection differentials and phenotypic changes is influenced by species-specific factor

Pathogen-induced hatching and population-specific life-history response to waterborne cues in brown trout ( Salmo trutta )

Hatching is an important niche shift, and embryos in a wide range of taxa can either accelerate or delay this life-history switch in order to avoid stage-specific risks. Such behavior can occur in response to stress itself and to chemical cues that allow anticipation of stress. We studied the genetic organization of this phenotypic plasticity and tested whether there are differences among populations and across environments in order to learn more about the evolutionary potential of stress-induced hatching. As a study species, we chose the brown trout (Salmo trutta; Salmonidae). Gametes were collected from five natural populations (within one river network) and used for full-factorial in vitro fertilizations. The resulting embryos were either directly infected with Pseudomonas fluorescens or were exposed to waterborne cues from P. fluorescens-infected conspecifics. We found that direct inoculation with P. fluorescens increased embryonic mortality and induced hatching in all host populations. Exposure to waterborne cues revealed population-specific responses. We found significant additive genetic variation for hatching time, and genetic variation in trait plasticity. In conclusion, hatching is induced in response to infection and can be affected by waterborne cues of infection, but populations and families differ in their reaction to the latte

The separate and combined effects of MHC genotype, parasite clone, and host gender on the course of malaria in mice

BACKGROUND: The link between host MHC (major histocompatibility complex) genotype and malaria is largely based on correlative data with little or no experimental control of potential confounding factors. We used an experimental mouse model to test for main effects of MHC-haplotypes, MHC heterozygosity, and MHC × parasite clone interactions. We experimentally infected MHC-congenic mice (F2 segregants, homo- and heterozygotes, males and females) with one of two clones of Plasmodium chabaudi and recorded disease progression. RESULTS: We found that MHC haplotype and parasite clone each have a significant influence on the course of the disease, but there was no significant host genotype by parasite genotype interaction. We found no evidence for overdominance nor any other sort of heterozygote advantage or disadvantage. CONCLUSION: When tested under experimental conditions, variation in the MHC can significantly influence the course of malaria. However, MHC heterozygote advantage through overdominance or dominance of resistance cannot be assumed in the case of single-strain infections. Future studies might focus on the interaction between MHC heterozygosity and multiple-clone infections

Predicting the mating system from phenotypic correlations between life-history and sperm quality traits in the Alpine whitefish Coregonus zugensis

The mating behavior and reproductive strategies of Alpine whitefish like Coregonus zugensis (Nüsslin) are poorly understood, probably because they spawn in deep water where direct observations are difficult. In this study, we interpret life-history and sperm quality traits of fish that we caught from their spawning place. We found that males invest heavily into gonadal tissue (up to 5.6% of their body weight), which is, in comparison to other fish, consistent with external fertilization, distinct pairing and moderate to high communal spawning, or no pairing and low to moderate communal spawning. Sperm competition theory and recent experimental studies on other salmonids predict that males optimize ejaculate characteristics in relation to the costs of sperm and the level of competition they have to expect: dominant males are predicted to invest less into ejaculate quality and to have slower spermatozoa than subdominant males. We found that spermatozoa of older males are slower than those of younger males. Moreover, older males have larger breeding tubercles, a secondary sexual trait that has, in some previous studies, been found to be linked to good condition and to good genetic quality. Our results suggest that C. zugensis has age-linked reproductive strategies, that multimale spawning is common, i.e., that sperm competition plays a significant role, and that older males are on average dominant over younger males at the spawning plac

Size-dependent discrimination of mating partners in the simultaneous hermaphroditic cestode Schistocephalus solidus

The cestode Schistocephalus solidus is a simultaneous hermaphrodite that reproduces in the gut of birds, or for this study in an in vitro system that simulates the gut of the bird. Like many other helminth parasites, S. solidus can reproduce by self- and cross-fertilization. Hermaphrodites are expected to mate not primarily to get their own eggs fertilized, but rather to get the opportunity to fertilize a partner''s eggs. Because S. solidus has a size-dependent sex allocation (i.e., larger worms are more biased toward female allocation and produce more egg mass), we expect larger individuals to be attractive mating partners for smaller ones. However, this may be a one- directional preference, as smaller individuals may not be attractive to larger ones. We tested this experimentally by studying the reaction of focal worms of different sizes to a compartment containing a potential mating partner that was either smaller or larger than the focal worm. The focal worn-is were, on average, closer to the compartment containing the stimulus than to an empty control compartment. Moreover, they indeed showed a preference for larger stimulus worms than for smaller ones. They even tended to avoid being close to stimulus worms of very small size compared to themselves. This may reveal a general preference for cross-fertilization over selfing, but it also indicates that all the genetic benefits from outcrossing do not necessarily outweigh the costs of mating with a relatively small individual and that the worms may take this into account in their reproductive decisions

Different Carotenoids and Potential Information Content of Red Coloration of Male Three-Spined Stickleback

Female sticklebacks (Gasterosteus aculeatus) use the red coloration of males as a criterion for mate choice. Redder males are more attractive. However, males often differ not only in the intensity of their coloration (from dull to bright red) but also in color quality (from yellowish to purple-red). We investigated whether the red coloration of the stickleback is actually a multiple signal made by several pigments. We kept wild caught males singly in tanks until they had built a nest and were ready to accept females. Then, we took standard photographs and measured their colors by spectrometer analyses of the slides and by descriptions of human observers. These two measurements were highly correlated. When analyzing the carotenoid content of the sticklebacks' skin we found two groups of carotenoids (astaxanthin and tunaxanthin/lutein) that were quantified for each individual. The differences in color observed in the fish are correlated to this pigment quantification. Redder fish have more astaxanthin in their skin than yellowish fish, while the color of the yellowish fish appears to be made by tunaxanthin/lutein. Our results suggest that the red coloration of sticklebacks is a multiple trait that is made of at least two different carotenoids. This opens the possibility that male sticklebacks signal more detailed information to females than a one-dimensional trait would allo