1,721,122 research outputs found
Experimental test of the mechanism underlying sexual segregation at communal roosts of harvestmen (<i>Prionostemma</i>spp.)
Get PDFClosely related, ecologically similar species often roost in distinctly different habitats, and roosting patterns also vary within species in relation to sex, age and season. The causes of such variation are not well understood at either a proximate or ultimate level. We studied communal roosting in two congeneric species of Prionostemma harvestmen at a rainforest site in Nicaragua. Previous research showed that Prionostemma sp. 1 forms male-biased communal roosts in tree-root cavities, while Prionostemma sp. 2 forms communal roosts of variable but temporally stable sex ratios on spiny palms. Here, we investigate potential mechanisms underlying variation in roosting site choice between and within these syntopic species. First, we present the results of a field experiment designed to probe the mechanism underlying skewed roost sex ratios in Prionostemma sp. 2. Previous studies have suggested that these harvestmen use conspecific scent to locate communal roosts and that new roosts can be established via group translocation. Therefore, to test the hypothesis that skewed roost sex ratios in this species arise from sex differences in scent marks, we translocated single-sex groups of ca. 30 individuals to each of 20 previously unoccupied spiny palms. Female release sites attracted new recruits of both sexes, while male release sites attracted almost exclusively males. We infer that Prionostemma sp. 2 females preferentially roost in sites scent-marked by females and that this mechanism is sufficient to explain the skewed roost ratios. Further adding to knowledge of Prionostemma roosting behavior, we show that Prionostemma sp. 1 forms female-biased communal roosts on spiny palms, that some roosts contain both species, and that the species composition is stable on a time scale of at least 2 weeks. To the best of our knowledge, this study is the first experimental test of mechanisms underlying sexual segregation at communal roosts in any taxon
Attention-altering Signal Interactions in the Multimodal Courtship Display of the Wolf Spider \u3cem\u3eSchizocosa uetzi\u3c/em\u3e
Get PDFComplex signals are common throughout the animal kingdom, consisting of one or more signals in one or more sensory modalities presented within a single display. I tested an efficacy-based backup hypothesis of complex signal function using the bimodal courtship signaling wolf spider Schizocosa uetzi. This hypothesis predicts that the visual and vibratory courtship displays function as backups to each other in the presence of environmental variability. I compared mating frequencies across four environmental treatments in which the visual and vibratory environments were manipulated independently in a 2 × 2 design with visual treatments of light/dark (i.e., visual signal present/absent) and vibratory treatments of filter paper substratum/granite substratum (i.e., vibratory signal present/absent). Results did not match the predictions of an efficacy-based backup hypothesis. The vibratory environment affected mating frequency, with more mating occurring in the vibration-present treatments compared to the vibration-absent treatments, but the visual environment had no effect on mating frequency. A second experiment was then conducted to test for an inter-signal interaction. Using the video-playback technique, I presented females with manipulated video sequences simultaneous with a controlled vibratory signal to test the hypothesis that the presence of a vibratory signal alters a female’s response to the visual signal. In the presence of a vibratory courtship signal, females were more receptive to more visually ornamented males. This increased receptivity to increased visual ornamentation was not seen in a previous study conducted on S. uetzi in the absence of a vibratory signal, suggesting a potential inter-signal interaction. In a third experiment, I tested whether a female’s visual attention was altered by the vibratory signal by examining female response to a visual “predator” while exposed to all possible combinations of male courtship signals. Females were more likely to get caught, and thus less likely to notice a predatory visual stimulus when exposed to a courtship vibration, supporting the hypothesis that the vibratory signal alters a female’s visual attention
Subadult experience influences adult mate choice in an arthropod: Exposed female wolf spiders prefer males of a familiar phenotype
Get PDFCurrent sexual selection theory proposes several potential mechanisms driving the evolution of female mating preferences, few of which involve social interactions. Although vertebrate examples of socially influenced mating preferences do exist, the invertebrate examples are virtually nonexistent. Here I demonstrate that the mating preferences of female wolf spiders can be acquired through exposure as subadults to unrelated, sexually active adult males. I first conducted exposure trials during which subadult females of the wolf spider Schizocosa uetzi were allowed to interact with mature males of an experimentally manipulated phenotype (either black or brown forelegs). After maturation, these previously exposed females were paired with a male of either a familiar or unfamiliar manipulated phenotype for mate-choice trials. Subadult females that were exposed to directed courtship by mature males of a particular morphological phenotype were subsequently more likely to mate with a male of a familiar phenotype as adults. Furthermore, females that were exposed as subadults were more likely, as adults, to cannibalize a courting male with an unfamiliar phenotype. Unexposed females did not distinguish between phenotypes in either mate choice or cannibalism frequency. These results suggest a previously uncharacterized mechanism influencing the origin of female mating preferences and ultimately the evolution of male traits: subadult experience. This study also stresses the potential importance of learning and memory on adult mate choice in an arthropod
Seismic signal dominance in the multimodal courtship display of the wolf spider \u3ci\u3eSchizocosa stridulans\u3c/i\u3e Stratton 1991
Get PDFUnraveling the function and evolutionary history of multimodal signaling is a difficult, yet common task of much research in animal communication. Here, I investigated multimodal signal function in the visual and seismic courtship display of the wolf spider Schizocosa stridulans and found that only the seismic courtship signal was important for mating success. First, copulation frequency was assessed in the presence/ absence of both visual and seismic courtship signals. The seismic signal was sufficient for successful copulation, whereas the visual signal was neither necessary nor sufficient, suggesting that the signals are not redundant and do not function as backups. Next, female receptivity to video courtship sequences with altered male ornamentation was assessed in the presence of a live male’s seismic signal. Female receptivity did not depend on male foreleg ornamentation. Instead, females performed receptivity displays equally to all video stimuli, demonstrating that in the presence of seismic signaling, receptivity is independent of visual signaling—indicating seismic signal dominance. Finally, female responses to isolated seismic cues from crickets and courting males suggest that seismic courtship signals carry both location and identification information. Schizocosa stridulans represents one of the few examples in which a single component likely dominates a multimodal signal.
Includes Supplemental Video of male courtship display, attached as Related File (below)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Current Status and Future Directions of Research in Complex Signaling
Get PDFThe term ‘complex signaling’ reflects a recent scientific focus on the multiple elements frequently incorporated into animal signals (reviewed in Candolin, 2003; Hebets and Papaj, 2005; Partan and Marler, 2005; Bro-Jorgensen, 2010). It embodies a new appreciation that signals used in communication are regularly composed of numerous components and that each component may individually vary in a number of ways. For example, signal components may vary in their time or mechanism of production, in the efficacy of their transmission, and/or in their mechanism of reception, among others. Employing the term ‘complex signaling’ reminds us of the need to maintain a broad, inclusive view of the dynamic, interactive nature of communication when trying to understand its evolutionary history and current function
Relating the unique sensory system of amblypygids to the ecology and behavior of \u3ci\u3ePhrynus parvulus\u3c/i\u3e from Costa Rica (Arachnida, Amblypygi)
Get PDFAbstract: While the unique sensory system and neuroanatomy of amblypygids suggest that olfaction is important in their lives, to date no behavioral data exist to support this suggestion. To gain insight into amblypygid ecology and behavior, an individual mark–recapture study was conducted on the Costa Rican amblypygid Phrynus parvulus. Within two 50 by 25 m plots, the distribution and movement patterns of individual amblypygids were recorded for over 2 months. A total of 88 adult individuals (60 males and 28 females) were marked, with an average 51% resighted. Females were resighted more frequently than males (75% females, 40% males). The sexes did not differ in their frequency or movement distance, but females were more likely to be seen on the same tree over time. While both sexes potentially wander in search of mates, females may also be searching for a good crevice, or diurnal hideout. Once a female has mated and laid eggs, she likely remains stationary. Movement patterns and tree choice seem to be dictated by both the presence of conspecifics and environmental factors such as tree surface area, moss cover, and the presence of buttressing. Cumulative observational data collected over 3 years suggest that the main breeding season for this species is October–January. Both mate attraction and navigation may be facilitated by the olfactory capabilities of amblypygids, while their giant interneurons may be involved in their foraging behavior. Résumé : Bien que le système sensoriel et la neuroanatomie très particuliers des amblypyges laissent croire que l’olfaction joue un rôle important dans leur vie, il n’existe pas à ce jour de données comportementales qui appuient cette hypothèse. Une étude de marquage et de recapture de l’amblypyge, Phrynus parvulus, du Costa Rica nous à permis d’en connaître plus sur l’écologie et le comportement des amblypyges. La répartition et les mouvements d’individus ont pu être notés pendant plus de 2 mois dans deux enceintes de 50 par 25 m. En tout, 88 adultes ont été marqués (60 mâles et 28 femelles) et en moyenne 51 % d’entre eux ont été revus, les femelles (75 %) plus fréquemment que les mâles (40 %). Il n’y a pas de différence sexuelle dans la fréquence ou la distance des déplacements, mais, dans le temps, les femelles tendent à être plus susceptibles d’être revues sur le même arbre. Alors que les individus des deux sexes sont probablement à la recherche de partenaires, les femelles cherchent peut-être aussi une bonne crevasse ou un refuge pour la journée. Une fois qu’une femelle s’est accouplée et qu’elle a pondu, elle reste probablement stationnaire. Les patterns de déplacement et le choix d’arbres semblent être dictés par la présence d’autres individus de la même espèce, mais aussi par des facteurs de l’environnement, tels que l’importance de la surface de l’arbre, la couverture de mousses et la présence de contreorts. Nos données, accumulées pendant 3 années, indiquent que la période principale de reproduction pour cette espèce se situe d’octobre à janvier. Tant l’attraction des partenaires que la navigation peuvent être facilitées par les capacités olfactives des amblypyges, alors que leurs interneurones géants jouent sans doute un rôle dans les comportements de quête de nourriture
Subadult Female Experience Does Not Influence Species Recognition in the Wolf Spider \u3cem\u3eSchizocosa uetzi \u3c/em\u3eStratton 1997
Get PDFIn many vertebrate systems, early experience has been linked to the learning of species specific traits that are subsequently assessed during mate choice, thus ensuring conspecific matings. In invertebrate systems, however, early experience was not thought to play a role in mate choice until a recent study using Schizocosa uetzi Stratton 1997 wolf spiders demonstrated that females mate more readily with males of a familiar versus unfamiliar phenotype. The function of early mate choice learning in this system is not yet known, but a role in learning species-specific traits seems unlikely. In northwestern Mississippi, S. uetzi is found sympatrically with S. stridulans Stratton 1991, which matures slightly earlier in the season. If S. uetzi early mate choice learning functions in learning species-specific traits used in mate choice, as is often the case in vertebrate systems, then subadult female exposure to heterospecifics (S. stridulans) could result in heterospecific matings. Here, I exposed subadult S. uetzi females to courtship advances from mature males of either S. uetzi (conspecifics) or S. stridulans (heterospecifics) in order to test a species-specific mate choice learning function. Previously exposed females were paired with a mature male of the same, or the opposite, species as their exposure male. As expected, the results do not support a species-specific mate choice learning function. Previously exposed females mated significantly more with conspecific males regardless of their exposure treatment, as did unexposed females. The highest premating sexual cannibalism rates occurred in heterospecific mate choice trials regardless of the exposure treatment, and exposed females were more likely to cannibalize males than unexposed females. While previous results demonstrate that subadult experience influences conspecific mate choice, a species recognition template seems to exist that is independent of the influence of early experience. The potential influence of multimodal signal interactions on conspecific mate choice learning is discussed
Variations on the Author
Get PDF“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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