1,720,991 research outputs found
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
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
Right under your nose: How olfactory cues influence Cyphomyrmex costatus' recognition and preference of fungal symbionts
Get PDFAnimal and Insect Sciences (The Ohio State University Denman Undergraduate Research Forum)For at least 55 million years, fungus-growing ants (tribe: Attini) have maintained an intimate mutualism with their co-evolved fungal cultivar (Branstetter et al., 2017). The farmer ants provide their fungus gardens with resources for cultivation, and in turn, the fungus serves as an obligate food source and a place to raise young. Fungus-growing ant species are exclusive to their cultivar strain despite others being readily available. We examine the precision of Cyphomyrmex costatus' ability to differentiate between closely related fungi, including strains that are associated with another Cyphomyrmex species, C. muelleri. We hypothesize that if given the choice, Cyphomyrmex ants will show preference for fungal strains that are most genetically similar to their original garden. This ability to differentiate gardens is most likely driven by the ant's ability to detect chemical differences between strains; however, the chemistry of these gardens remains unknown. We have been actively isolating cultivar from our laboratory colonies (39 C. costatus and 8 C. muelleri) onto PDA-Cl agar plates. We performed DNA extractions on isolated cultivar and constructed a preliminary phylogeny (species-relatedness tree) utilizing previously published DNA sequences in addition to our novel extractions. Furthermore, we use behavioral assays to test our hypothesis that Cyphomyrmex ants "prefer" gardens that are most closely related to their native cultivar when given a choice between two fungal isolates. These behavioral and genetic studies will inform future questions about the importance of certain chemical cues in ant decision-making, and if there is a genetic basis for chemical volatiles associated with the mutualistic fungi.No embargoAcademic Major: BiologyAcademic Major: Germa
Fight or Flight: Reactions of a Rainforest Ant to the Venom of a Natural Enemy
No full textThe well-studied Megalomyrmex ant parasites are known for their use of venom alkaloids to reduce aggression and confuse their fungus-growing ant hosts. However, most Megalomyrmex species are not restricted to a parasitic lifestyle. In fact, many are free-living ants that compete with other ant species by foraging from insect carcasses and other food sources on the rainforest floor, one such example being Megalomyrmex peetersi. Another ant, Aphaenogaster araneoides, is a sympatric species that is often the first to arrive at a food source. Our field observations suggest that, despite arriving later, M. peetersi dominate baits and cause A. araneoides to flee. Megalomyrmex peetersi appears to use venom to behaviorally manipulate and outcompete other ant species to gain control of food resources. To test this hypothesis, we exposed foraging Aphaenogaster workers to M. peetersi venom extracts at two field locations (one with M. peetersi presence [n=26], and one without [n=26]) . We controlled for the venom extract’s solvent and the act of applying the stimuli. Behaviors were video recorded and scored using BORIS software. We predicted that M. peetersi venom exposure will cause A. araneoides foragers to react submissively (i.e., repulsion, recoil, or flight) compared to the controls. We did not find support for our hypothesis, but a trend that suggests A. araneoides react more submissively when exposed to M. peetersi venom. We also found that the presence of food significantly increased the latency of submissive A. araneoides reactions. This work suggests that venom may not be the only mechanism used by M. peetersi to dominate a food source when competing with A. araneoides, and that the lack of support for our hypothesis may be influenced by A. araneoides' sensitivity to overhead motion. This suggests that studies that account for visual stimuli are needed, as multiple stimuli likely influence A. araneoides' behavior. These additional field studies will enhance our understanding of the complex dynamics that surround resource competition and venom use between these ant species.National Science FoundationAcademic Major: Evolution and EcologyAcademic Major: Entomolog
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Population structure of Sericomyrmex amabilis, fungus-growing host of a rare parasite
Get PDFSymbiotic interactions are ubiquitous, found in all habitat types from oceans to tropical rainforests. These coevolving organisms or symbiotic species networks are not only central components of biodiversity but enable community resilience to environmental change. Different communities vary in species makeup and environmental factors. Thus, coevolution among symbiotic species inherently is tied to biotic and abiotic factors resulting in a geographic mosaic of differing selective environments. The mercenary ant symbiotic species network includes the fungus-growing ant, Sericomyrmex amabilis host, and two antagonistic parasitic species. The first is an obligate long-term guest ant social parasite, Megalomyrmex symmetochus, and the second is the raider ant, Gnamptogenys hartmani. The guest ant is a protective symbiont that shields the farmer ants from destructive Gnamptogenys raids, acting like the farmer ant’s mercenary soldiers. These species are found in Central and South America, but exact ranges and populations are unclear. Determining the population structure of the host species is the first step toward understanding the coevolutionary dynamics among these species. To investigate the population genetics of the farmer ant hosts found in Panama and Costa Rica, we used eight microsatellite markers (genetic loci) to answer the following questions: 1) Is there significant genetic differences among S. amabilis sub-populations in Panama? and 2) Is there detectable isolation-by-distance when comparing samples from sites along the Panama Canal (PLR, BCI, Plantation Road, Fort Sherman), El Llano, Panama, and La Selva, Costa Rica? We analyzed 79 samples and found that the Costa Rica S. amabilis subgroup is a genetically distinct population compared to Panamanian populations. Further, gene flow between Barro Colorado Island and the mainland appears to be slightly restricted, which eventually could form an even more distinct inbred island population in Panama.Undergraduate Research Apprenticeship ProgramNSFNo embargoAcademic Major: Zoolog
Worker-queen dimorphism and queen winglessness in Megalomyrmex Forel, 1885
Get PDFThe evolutionary success of eusocial insects, such as ants, is attributed to their division of labor between reproductive and non-reproductive castes. For most ant species, reproduction is carried out by winged queens. However, for some species, ergatoid queens (wingless queens) – with intermediate morphologies between winged queens and workers – have replaced winged queens. In the ant genus Megalomyrmex Forel, 1885, 16 of the 45 species described have ergatoid queens. As a consequence of flight loss, wingless queens are dependent on their parent colony when founding. They disperse on foot with a subset of their sisters from their natal nest (i.e., budding). In Megalomyrmex, queen winglessness has been gained and lost multiple times throughout its evolutionary history and in the instance of four species, it may occur simultaneously with the winged queen strategy in the same species. Using extensive morphological measurements, we examine worker-queen dimorphism of wingless queens in Megalomyrmex. These include measurements of the head, eyes, mesosoma, and metasoma. Focusing primarily on the head and eye morphology, we explore the relationship of these traits between castes within the genus. Our findings support the established trend that winged queens are typically larger while ergatoid queens are more worker-like. Additionally, we find that the eyes of winged queens are larger than that of ergatoid queens relative to their body size, which may suggest a similar relationship between winged and ergatoid queens with regards to eye morphology. Our study contributes to the growing body of knowledge on ergatoid queen evolution, as well as the evolutionary relationship between morphology, natural history, and colony reproduction.Undergraduate Research Apprenticeship Program (URAP) GrantA three-year embargo was granted for this item.Academic Major: Biolog
Shared Alkaloids and Subtle Surprises in Ohio Aphaenogaster Ants
No full textAphaenogaster is an ecologically dominant ant genus found throughout the woodlands of the eastern United States. The genus is characterized by rapid nestmate recruitment and a submissive demeanor. Additionally, the mandibular and venom glands of some species contain unusual alkaloids. Alkaloids are a diverse class of heterocyclic nitrogenous compounds that are often used as a chemical defense by plants. However, they are also present in some arthropod and fungal groups. In ants, alkaloids can be found in the mandibular, pygial, and venom glands, where they are used for a variety of purposes. Aphaenogaster ants are known to contain alkaloids, but the full scope of alkaloid diversity and species-specificity within the genus remains unknown. In this paper, we investigate alkaloid presence and diversity by examining gaster and head extracts collected from five Aphaenogaster species at nine sites. Samples were analyzed using gas-chromatography mass spectrometry (GC-MS) and their Cytochrome C Oxidase Subunit 1 (COI) gene sequenced to confirm species. We compared percent abundances of frequently occurring alkaloids from the heads and gasters using a one-way permutational multivariate analysis of variance (PERMANOVA). Upon completing our analysis, we found that alkaloid presence is conserved across Ohio Aphaenogaster, but relative abundance of those alkaloids varies between species, especially those with differing natural histories. Additionally, we discovered eight frequently occurring alkaloids that have not previously been associated with Aphaenogaster ants. Lastly, we provide genetic evidence of sympatric distributions for undescribed Aphaenogaster species within the A. rudis and A. picea species complexes. This work bridges a knowledge gap in the alkaloid diversity of Aphaenogaster and provides a basis for future work to contextualize the importance of natural history, niche acquisition, and speciation on chemical evolution within Aphaenogaster.NSFURAPA three-year embargo was granted for this item.Academic Major: Evolution and EcologyAcademic Major: Entomolog
Drawn to the Dead or Just Decoration? Cyphomyrmex costatus Collect Arthropod Body Parts
No full textCyphomyrmex costatus Mann 1922 is a small fungus-growing ant, distributed in warm temperate regions in southern Mexico to northern South America. Like all fungus-growing ants, C. costatus colonies have a mutualistic relationship with their garden in which they collect material to nourish it while simultaneously feeding on it. Along with insect droppings and scraps of vegetation fed to the garden, worker ants collect the remains of various arthropods. Weber (1957) reported the use of empty arthropod carcasses in C. costatus gardens as garden substrate, yet no one has analyzed the species richness and evenness (e.g., faunal profile) of these arthropods, nor tested predictions regarding their potential function. Cyphomyrmex costatus line their nest chambers with dozens of exoskeletons that range from arachnids to other ant species. This study explores possible explanations for this unusual foraging behavior of C. costatus, collected in Soberanía National Park, Panama. One hypothesis is that these "arthropod remains" act as another kind of substrate for the fungus to consume (Weber, 1957), but observations in our laboratory and the field have cast doubt. Instead, we predict that the remains serve as either chemical or visual signals to dissuade other arthropods from entering the nest. This study aims to determine if C. costatus workers, (1) preferentially select ant heads with intact chemical profiles versus controls (solvent-washed heads), (2) preferentially select ant heads that originated from another ant nest, and (3) preferentially gather insect remains of particular species in nature. Our behavioral choice assay results indicated that chemical profile presence as well as ant head origin did not dissuade the C. costatus ants from collecting ant head presented to them. When analyzing the taxonomic diversity of the collected body parts for 13 colonies, we could identify 82.6% of the 884 body parts to the order, family, subfamily or genus taxonomic level. Among the identified material, 77% were species of ants. We also discuss the availability and abundance of the collected ant species in the environment. Our investigation provides new insights regarding C. costatus ecology and interspecific interactionsUndergraduate Research Apprenticeship Program of The Ohio State UniversityIOS grant NSF# 2127521A three-year embargo was granted for this item.Academic Major: Biolog
- …
