1,720,959 research outputs found
Individual differences in the courtship displays of male Golden-collared Manakins: The bases for mate choice?
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The distribution of steroid receptors and aromatase in the brain and spinal cord of a suboscine bird with elaborate courtship display, the Golden-collared manakin
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Distinctive expression of androgen receptor in the brain of a sub-oscine bird with elaborate courtship displays
No full textMate choice influences differential introgression in a hybrid zone
No full textHybrid zones are widely recognized as important sources of genetic variation, and conduits for the exchange of genes from one species to another. How and which traits move, or introgress, is an important area of study in evolutionary biology. A hybrid zone between two manakin (Pipridae) species, Manacus candei and Manacus vitellinus, exists in Bocas del Toro Province, in western Panama. The hybrid zone is unique in that the plumage genes of Manacus vitellinus introgress up to 50 km beyond the genetic center of the hybrid zone, into populations that are morphologically and genetically similar to M. candei. M.vitellinus males are more aggressive than Manacus candei males in mixed leks where both species occur. If M. candei females preferred males with M. vitellinus plumage traits, introgression of M. vitellinus plumage genes would be explained by both intra- and inter-sexual selection. Manacus spp. have a lek mating system; males perform elaborate, acrobatic courtship displays on small arenas on the forest floor, producing loud ‘wingsnaps’ and maximizing the visibility of their colored throat feathers. We have recently shown that display performance is associated with female preference in M. vitellinus, with females perferring males that perform certain moves faster. Thus, we hypothesized that female choice based on courtship display drives asymmetrical trait introgression. We studied whether display performance differs between the two species. Using high speed videography to film courtship displays of males of the two species, we compared them for those traits which in M. vitellinus are correlated to female preference. Contrary to our expectations, we found that M. candei males outperform M. vitellinus males. We propose that vitellinus-like plumage is preferred by females, but only when it recombines with the candei morphometric background, and hence, the superior display ability of M. candei
Expression of androgen receptor, estrogen receptor, and aromatase in the brain of a tropical bird, the spotted antbird: Mapping and seasonal comparison
No full textLow sex steroids, high steroid receptors: Increasing the sensitivity of the nonreproductive brain
No full textMale aggressive behavior is generally regulated by testosterone (T). In most temperate breeding males, aggressive behavior is only expressed during the reproductive period. At this time circulating T concentrations, brain steroid receptors, and steroid metabolic enzymes are elevated in many species relative to the nonreproductive period. Many tropical birds, however, display aggressive behavior both during the breeding and the nonbreeding season, but plasma! levels of T can remain low throughout the year and show little seasonal fluctuation. Studies on the year-round territorial spotted antbird (Hylophylax n. naevioides) suggest that T nevertheless regulates aggressive behavior in both the breeding and nonbreeding season. We hypothesize that to regulate aggressive behaviors during the nonbreeding season, when T is at its minimum, male spotted antbirds increase brain sensitivity to steroids. This can be achieved by locally up-regulating androgen receptors (ARs), estrogen receptors (ERs), or the enzyme aromatase (AROM) that converts T into estradiol. We therefore compared mRNA expression of AR, ERm, and AROM in free-living male spotted antbirds across reproductive and nonreproductive seasons in two brain regions known to regulate both reproductive and aggressive behaviors. mRNA expression of ERa in the preoptic area and AR in the nucleus taeniae were elevated in male spotted antbirds during the nonbreeding season when circulating T concentrations were low. This unusual seasonal receptor regulation may represent a means for the year-round regulation of vertebrate aggressive behavior via steroids by increasing the brain's sensitivity to sex steroids during the nonbreeding season. (c) 2006 Wiley Periodicals, Inc
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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