1,720,957 research outputs found
Does more choice equal a better choice? Courtship behavior, mating propensity and female fitness in relation to the number and density of potential partners
No full textThe good genes hypothesis predicts that females discriminate among potential mates on the basis of their genetic quality. We measured the indirect benefits received by females with different levels of choice---from no choice to choosing among 5 males---in the housefly, Musca domestica , at high and low density. Secondly, we tested how the degree of choice affected the courtship behavior of both sexes and whether this behavior was correlated to female reproductive success. Opportunity for choice did not affect mating propensity or offspring survivorship, but did affect male courtship rate and the number of eggs females laid in their first clutch. Females at low density were more likely to mate, laid more eggs in their first clutches, and had greater egg-to-adult viability than females mated at high density. Overall, the degree of choice affected some aspects of mating behavior and fitness, but the effects were primarily density dependent
The effects of population density on courtship behavior in the housefly, Musca domestica
No full textThe housefly, Musca domestica, was used to test the short-term and long-term environmental effects of high population density. The first phase addresses the issue that there are two main selection forces that drive mating behavior, inter- and intrasexual selection. In intersexual selection the females are actively discriminating when choosing a mate and, thus, these male-female interactions are what predominantly define that population. However, in intrasexual selection, males potentially compete against each other over the pool of receptive females. I tested the hypothesis that a less complex courtship would be optimal in a high-density environment, short-term (i.e., one generation). Specifically, I videotaped the mating behavior of individuals subjected to one of two treatments: high-density or low-density (i.e., 200 virgin male-female pairs in a 2 L or 114 L cage, respectively). In both treatments, the flies were allowed to mate for 30 minutes while being videotaped. The proportion of time spent in three male courtship behaviors (HOLD, FORWARD, BUZZ) and one female courtship behavior (WINGOUT) were determined. I found that the mating propensity (percent of mated pairs) was significantly greater in the high-density environment. The courtships in the high-density environment were also significantly less complex (i.e., less FORWARD, less HOLD). My findings suggest that high-density environments stimulated competition among males causing the intrasexual selection processes to outweigh the intersexual processes. The second phase tests the prediction that long-term (i.e., eight generations), high population density will drive the evolution of courtship repertoire towards decreased complexity. I applied the previously outlined methods. Additionally, only those pairs that mated within the allotted time were allowed to contribute to the following generation. The courtship behavior assays suggest that the synergistic effects of high density on the males and inbreeding depression drove the evolution of increased courtship complexity and exaggerated inbreeding depression, therefore, not supporting the prediction or the results of first phase. In the low-density treatment, courtship became less complex and mating propensity increased. These results are applicable to populations with unnaturally high densities and potential for inbreeding such as those in laboratory agricultural pest control, and conservation projects
Experience-dependent courtship modification in the housefly, Musca domestica
No full textThe genetics of mating behavior may be complicated by factors such as an association with fitness, social interactions, and genotype-by-environment interactions. In order to evaluate the potential consequences of these factors, I analyzed courtship behavior in the housefly, Musca domestica L. by specifically examining (1) mating success, (2) experience-dependent courtship modification (learning), and (3) heritability. Males (N = 120) were paired with six virgin females over the course of three days and videotaped for a maximum of 30 minutes, or until copulation occurred. Courtships were analyzed for six behaviors within and among females. Successful courtships, in comparison to unsuccessful attempts, were characterized by a shorter Duration of Courtship, less intense Lunge and Wingout, and more intense Buzz, Hold, and Lift. Among courtship attempts within females, males decreased Buzz and increased Lunge. The females also adjusted their behavior by modifying Wingout, which demonstrates a male-female interaction component of mating success. Among courtship attempts across serially mated females, males decreased the Duration of Courtship and Lunge. Analyses were also completed using both within and across female data, and there was a general trend for a decrease in the behavior traits, except for Buzz, which did not change. Also, males decreased the number of courtship attempts with successively mated females, indicating the ability to learn through improved courtship technique. Weibull functions showed that the males had significant learning curve functions for individual behavior traits, although the tests for the repeatability and heritability of such functions were not significant. Finally, repeatabilities and heritabilities (estimated by a broad-sense family effect) were calculated for the courtship traits. Pooled analyses on successful and unsuccessful courtship attempts revealed significant repeatabilities (0.05-0.67) and heritabilities (0.07-0.50) for almost all of the courtship traits, although analyses on just the successful courtships failed to replicate the significant effects, except for the male display, Hold (0.29). These results demonstrate that male courtship behavior is multifaceted in that it consists of not only a learning component, but a genetic component, too. Although previous housefly experiments have shown indirect support, this is the first direct evidence for male learning within courtship behavior
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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