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T C Bakker

Publications and source records attributed to T C Bakker.

6 recordsLinked to original sources
PubMed2001

Cooperation through indirect reciprocity: image scoring or standing strategy?

Theorists have only recently shown that cooperation through indirect reciprocity can evolve. The first modelling approach favoured a mechanism called image scoring. Helping someone increases one's image score, whereas refusing to help reduces it. The evolutionary outcome was a discriminator image scoring strategy that helps everybody who has, for example, a positive image score. Two experimental studies with humans found results that were compatible with discriminator image scoring. However, a new analysis of other theorists, based on another population structure, has cast doubts on the evolutionary stability of strategies using the recipient's score as a sole basis for decision. The new theoretical study confirmed that a strategy aiming at "good standing" has superior properties and easily beats image scoring. An individual loses good standing by failing to help a recipient in good standing, whereas failing to help recipients who lack good standing does not damage the standing of a potential donor (but would reduce his image score). The present empirical study with 23 groups of seven human subjects each was designed for distinguishing between the two proposed mechanisms experimentally. The results differed strongly from standing strategies, which might demand too much working memory capacity, but were compatible with image scoring or a similar strategy to a large extent. Furthermore, donors of constant "NO players" compensated for their refusing to help these players by being more generous to others.

Cooperative Behavior↗
PubMed2001

Genetic analysis of sneaking and egg-thievery in a natural population of the three-spined stickleback (Gasterosteus aculeatus L.).

Among the fish species that show exclusive male parental care, the three-spined stickleback represents one of the most intensively studied species with regard to reproductive behaviour. In this species, the most common 'parasitic' male tactics in relation to male reproductive behaviour are sneaking and egg thievery, which are often collectively referred to as nest-raiding. However, little is known about the genetic consequences of sneaking and egg thievery in natural populations. Here we assessed the frequency of sneaking and egg-stealing in a natural population, male traits that are associated with the victims of sneaking, and the impact of sneaking and egg-stealing on the reproductive success of nesting males as deduced from the number of offspring in their nests. Fourteen nest-guarding males and a random sample of about 100 eggs/fry of each nest from a natural freshwater population of three-spined sticklebacks were analysed at three microsatellite loci. The analysis revealed a high frequency of genetically successful nest raiding (sneaking or egg thievery), i.e. more than half (57%) of the 14 nests contained offspring (1-94%) which were unrelated to the guardian male. Three of the 14 nests (21%) contained progeny of sneaking males and four of the nests (28%) contained offspring which were unrelated to the guardian male and which probably originated from egg-stealing events. Victims of sneaking were significantly smaller than other guardian males. Moreover, reproductive success correlated positively with male body size.

Animals↗
PubMed2000

Pectoral fins and paternal quality in sticklebacks.

Sexual selection through female mate choice exerts a strong selection pressure on males' sexual traits, particularly when direct benefits are involved. In species with male parental care, one would expect sexual selection to favour paternal quality, for instance through selection on morphological structures which promote quality. We experimentally studied the influence of pectoral fins on paternal quality in male three-spined sticklebacks (Gasterosteus aculeatus L.). After reductions of fin area to different degrees, similar-sized males had to perform a complete reproductive cycle in enclosures in the field. The collected data on fanning behaviour and egg development showed that a reduction in pectoral fin size affected paternal quality probably through an increased beat frequency of the pectorals. Thus, pectoral fins can potentially signal paternal quality to choosy females.

Animals↗
PubMed1981

Artificial selection for short and long attack latencies in wild Mus musculus domesticus.

Artificial selection for short and long attack latency levels in wild male Mus musculus over 11 generations was successful for short latencies. The realized heritability of 0.30 is comparable to those found in other selection studies on aggression. In part selection may have been for faster onto-genetic development of short attack latencies. Four attempts to select for longer attack latencies failed because the lines died out immediately or within two generations for unknown reasons. But neither the physical condition of the animals nor their behavior appeared to have been the cause. Female aggressiveness as measured in female-female encounters was not affected by the selection exerted on the males. This suggests that no genetic correlation exists between aggressiveness of males and females, confirming results of P. D. Ebert and J. S. Hyde [(1976). Behav. Genet. 6:291-304] obtained in a selection experiment on aggression using females.

Aggression↗