1,721,083 research outputs found
How decision problems arise and are solved by phytophagous insects
Full text linkBei der Eiablage müssen sich Pflanzen fressende Insekten wiederholt entscheiden, Eier auf Wirtspflanzen niedriger Qualität zu legen oder auf bessere Pflanzen zu warten. Diese Entscheidungen sind Fitness relevant, weil Larven sich je nach Wirt unterschiedlich entwickeln und weil Weibchen in diesem inter-temporären Optimierungsproblem sowohl zu wählerisch als auch nicht wählerisch genug sein und so nicht alle Eier bzw. Eier in zu geringer Qualität legen können. Meine Arbeit nutzt vier Ansätze um zu untersuchen, wie diese Entscheidungsprobleme entstehen und wie Weibchen diese strategisch lösen. Erstens benutze ich analytische Optimierungsmodelle um zu zeigen, dass ein evolutionärer Trade-Off zwischen Vermehrung und Überleben variierender evolutionär stabiler Ei- und Zeit-Limitierung führen kann, dass aber keiner dieser zwei Faktoren ignoriert werden darf. Zweitens stelle ich klar, dass in der Vergangenheit vorgeschlagene schematische Zeit- und Ei-Kosten der Eiablage sich nicht mit den wirklichen Selektionskräften auf die Ei-Anzahl decken und daher kein gutes Werkzeug zur Analyse von Eiablage-Strategien darstellen. Drittens zeige ich mit Optimierungs- und populationsgenetischen Modellen, dass räumliche Heterogenität in der Wirtsverfügbarkeit keine notwendige Bedingung für die Evolution von Generalismus ist, weil emergente Quellen-Senken Dynamiken die Anpassung der Insekten an marginale Habitate verhindern, wenn Migrationsraten nicht hoch sind. Viertens zeige ich an Agenten basierte Simulationen zum Beispiel des Aurorafalters, Anthocharis cardamines, dass der phänologische Spezialismus der Larven dieser Art den Eiablage-Generalismus der Weibchen zur Folge hat. Insgesamt zeigen diese vier Ergebnisse, wie nützlich theoretische Ansätze zur Untersuchung spezifischer Szenarios der strategischen Eiablage sein können und machen deutlich, dass die Evolution von Generalismus leichter aus zeitlicher denn aus räumlicher Heterogenität folgt.Ovipositing phytophagous insects repeatedly face the decision problem of laying eggs on lower-quality host plants or waiting out for higher-quality ones. These choices carry fitness costs and benefits because larvae develop differentially on different hosts and because, in this inter-temporal optimization task, females may be too choosy and die before laying all eggs (i.e. become time-limited) or not be choosy enough and run out of eggs before their death (i.e. become egg-limited). This thesis employs four approaches to examine how oviposition decision problems arise and how they are strategically solved by female insects. First, I use analytical optimization models to show that a life-history trade-off between survival and reproduction can lead to varying evolutionarily stable levels of egg and time limitation, but that neither egg nor time limitation can be ignored in evolutionary analyses of oviposition. Second, I highlight that such schematic time and egg costs of oviposition as advocated in the past do not match the actual forces of natural selection on egg number as partitioned between egg and time limitation and therefore represent a less useful practice to analyze oviposition strategies. Third, I use optimality and population genetic models to show that spatial heterogeneity in host availability is not a sufficient condition for the evolution of generalism because emergent source-sink dynamics preclude adaptation of insects to marginal habitats unless migration rates are high. Fourth, I employ individual-based simulations built around the case study of the orange tip butterfly, Anthocharis cardamines, to show that this species’ larvae’s phenological specialism may drive the adult females’ oviposition generalism. All these findings show the usefulness of theoretical approaches to examine specific questions of strategic oviposition. Moreover, they demonstrate that evolution of generalism more likely results from resource unpredictability in time than in space
Learning leads to bounded rationality and the evolution of cognitive bias in public goods games
Full text linkIn social interactions, including cooperation and conflict, individuals can adjust their behaviour over the shorter term through learning within a generation, and natural selection can change behaviour over the longer term of many generations. Here we investigate the evolution of cognitive bias by individuals investing into a project that delivers joint benefits. For members of a group that learn how much to invest using the costs and benefits they experience in repeated interactions, we show that overestimation of the cost of investing can evolve. The bias causes individuals to invest less into the project. Our explanation is that learning responds to immediate rather than longer-term rewards. There are thus cognitive limitations in learning, which can be seen as bounded rationality. Over a time horizon of several rounds of interaction, individuals respond to each other’s investments, for instance by partially compensating for another’s shortfall. However, learning individuals fail to strategically take into account that social partners respond in this way. Learning instead converges to a one-shot Nash equilibrium of a game with perceived rewards as payoffs. Evolution of bias can then compensate for the cognitive limitations of learning.</p
Naaraiden seksuaalisten signaalien kustannukset ja seuraukset
No full textAbstractSexual ornaments have developed in a very wide variety of animal taxa to increase fitness by improving mating success. How increased mating rate improves fitness is obvious in the case of most males: each mating provides more offspring. Whether more matings benefit females, whose fecundity is limited by resources and not mates, is unclear. Mate choice is linked to ornamentation, when individuals of one sex choose who to mate with based on the ornamentation in members of the other sex. Ornaments may work as a basis for mate choice due to conveying information about the quality of the mate. Mate choice may then lead to intrasexual competition for mates in the chosen sex as animals try to outcompete their neighbours and attract more mates.My aim in this thesis is to study the purpose and costs of female ornamentation as well as female competition for males. The main questions revolve around understanding what information female ornaments provide about the bearer and how males choose between females. I also examine how females compete against each other and what the costs of being ornamented are for a female. To study these questions I use the common glow-worm (Lampyris noctiluca Linnaeus, Lampyridae), whose females glow at night to attract flying males.According to my results, a female’s glowing provides accurate information about fecundity and males base their choice of mate on the intensity of female glowing. I showed that the perceived strength of an ornament in comparison to others close by is more important than the actual strength of an ornament. In the glow-worm, the perceived strength of an ornament depends on distance to the observer, making the system open to exploitation. A mathematical model I developed suggested that dull females could outcompete brighter ones by choosing optimal locations, and experimentation showed this to be the case. Finally, my results show that glow-worm females lose eggs each day they remain unmated. This suggests that the evolution of female ornamentation may have been driven in part by the need to find a mate as soon as possible after eclosion. Which in turn means that female and male ornamentation may have fundamentally different purposes: for females mating soon may be important, where for males the total number of offspring fertilized is critical.TiivistelmäSeksuaalisia ornamentteja on kehittynyt hyvin laajaan kirjoon eläinlajeja parantamaan yksilöiden kelpoisuutta nostamalla niiden parittelutodennäköisyyttä. Koirailla parittelutodennäköisyyden ja kelpoisuuden välinen yhteys on yleensä selvä: jokainen parittelu nostaa jälkeläismäärää. Naarailla yhteys ei ole yhtä selvä, sillä niillä jälkeläismäärä yleensä riippuu resurssien saatavuudesta eikä kumppanien määrästä. Parinvalinta on kiinteästi yhteydessä ornamentaatioon: Yhden sukupuolen yksilöt päättävät kenen kanssa paritella toisen sukupuolen yksilöiden ornamenttien laadun perusteella. Ornamentit toimivat valinnan perusteena välittämällä tietoa parin laadusta. Parinvalinta voi johtaa yksilöiden väliseen kilpailuun kumppaneista valitun sukupuolen sisällä.Tässä väitöskirjassa tarkoituksenani on tutkia naaraiden ornamenttien tarkoitusta ja kustannuksia sekä tutkia miten naaraat voivat kilpailla toisiaan vastaan koiraista. Pääkysymykset liittyvät ornamenttien välittämään informaatioon ja siihen miten koiraat valitsevat kumppaninsa. Lisäksi tarkastelen miten naaraat voivat kilpailla keskenään ja mitä kustannuksia ornamenteista on naaraille. Kysymysten selvittämiseksi käytän tutkimuslajina kiiltomatoa (Lampyris noctiluca Linnaeus, Lampyridae), lajia jonka naaraat loistavat öisin houkutellakseen lentäviä koiraita.Tulosteni mukaan kiiltomatonaaraan loiste välittää tarkkaa informaatiota niiden munamäärästä ja koiraat osaavat valita parinsa tämän perusteella. Osoitin, että ornamentin havaittu vahvuus verrattuna ympärillä oleviin on tärkeämpää kuin ornamentin todellinen vahvuus. Kiiltomadolla havaittu kirkkaus riippuu etäisyydestä havaitsijaan, mikä tekee signallointijärjestelmästä avoimen väärinkäytölle. Laatimani matemaattisen mallin mukaan himmeät naaraat voisivat päihittää kilpailussa kirkkaampia valitsemalla parempia loistamispaikkoja. Käytännön kokeet osoittivat tämän pitävän paikkansa. Viimeinen tulokseni oli, että kiiltomadolla naaras menettää osan munistaan joka päivä jonka se joutuu odottamaan parittelua. Tästä voi päätellä, että naaraan ornamentin evoluutiota on voinut osaltaan ajaa tarve paritella mahdollisimman pian aikuistumisen jälkeen. Naaraiden ja koiraiden ornamenttien syyt voivat olla hyvin erilaiset: naarailla parittelu mahdollisimman pian voi olla tärkeintä, kun koiraalla parittelukumppanien määrä on tärkein.Academic dissertation to be presented with the assent of the Doctoral Training Committee of Technology and Natural Sciences of the University of Oulu for public defence in the Arina auditorium (TA105), Linnanmaa, on 9 November 2018, at 12 niinAbstract
Sexual ornaments have developed in a very wide variety of animal taxa to increase fitness by improving mating success. How increased mating rate improves fitness is obvious in the case of most males: each mating provides more offspring. Whether more matings benefit females, whose fecundity is limited by resources and not mates, is unclear. Mate choice is linked to ornamentation, when individuals of one sex choose who to mate with based on the ornamentation in members of the other sex. Ornaments may work as a basis for mate choice due to conveying information about the quality of the mate. Mate choice may then lead to intrasexual competition for mates in the chosen sex as animals try to outcompete their neighbours and attract more mates.
My aim in this thesis is to study the purpose and costs of female ornamentation as well as female competition for males. The main questions revolve around understanding what information female ornaments provide about the bearer and how males choose between females. I also examine how females compete against each other and what the costs of being ornamented are for a female. To study these questions I use the common glow-worm (Lampyris noctiluca Linnaeus, Lampyridae), whose females glow at night to attract flying males.
According to my results, a female’s glowing provides accurate information about fecundity and males base their choice of mate on the intensity of female glowing. I showed that the perceived strength of an ornament in comparison to others close by is more important than the actual strength of an ornament. In the glow-worm, the perceived strength of an ornament depends on distance to the observer, making the system open to exploitation. A mathematical model I developed suggested that dull females could outcompete brighter ones by choosing optimal locations, and experimentation showed this to be the case. Finally, my results show that glow-worm females lose eggs each day they remain unmated. This suggests that the evolution of female ornamentation may have been driven in part by the need to find a mate as soon as possible after eclosion. Which in turn means that female and male ornamentation may have fundamentally different purposes: for females mating soon may be important, where for males the total number of offspring fertilized is critical.Tiivistelmä
Seksuaalisia ornamentteja on kehittynyt hyvin laajaan kirjoon eläinlajeja parantamaan yksilöiden kelpoisuutta nostamalla niiden parittelutodennäköisyyttä. Koirailla parittelutodennäköisyyden ja kelpoisuuden välinen yhteys on yleensä selvä: jokainen parittelu nostaa jälkeläismäärää. Naarailla yhteys ei ole yhtä selvä, sillä niillä jälkeläismäärä yleensä riippuu resurssien saatavuudesta eikä kumppanien määrästä. Parinvalinta on kiinteästi yhteydessä ornamentaatioon: Yhden sukupuolen yksilöt päättävät kenen kanssa paritella toisen sukupuolen yksilöiden ornamenttien laadun perusteella. Ornamentit toimivat valinnan perusteena välittämällä tietoa parin laadusta. Parinvalinta voi johtaa yksilöiden väliseen kilpailuun kumppaneista valitun sukupuolen sisällä.
Tässä väitöskirjassa tarkoituksenani on tutkia naaraiden ornamenttien tarkoitusta ja kustannuksia sekä tutkia miten naaraat voivat kilpailla toisiaan vastaan koiraista. Pääkysymykset liittyvät ornamenttien välittämään informaatioon ja siihen miten koiraat valitsevat kumppaninsa. Lisäksi tarkastelen miten naaraat voivat kilpailla keskenään ja mitä kustannuksia ornamenteista on naaraille. Kysymysten selvittämiseksi käytän tutkimuslajina kiiltomatoa (Lampyris noctiluca Linnaeus, Lampyridae), lajia jonka naaraat loistavat öisin houkutellakseen lentäviä koiraita.
Tulosteni mukaan kiiltomatonaaraan loiste välittää tarkkaa informaatiota niiden munamäärästä ja koiraat osaavat valita parinsa tämän perusteella. Osoitin, että ornamentin havaittu vahvuus verrattuna ympärillä oleviin on tärkeämpää kuin ornamentin todellinen vahvuus. Kiiltomadolla havaittu kirkkaus riippuu etäisyydestä havaitsijaan, mikä tekee signallointijärjestelmästä avoimen väärinkäytölle. Laatimani matemaattisen mallin mukaan himmeät naaraat voisivat päihittää kilpailussa kirkkaampia valitsemalla parempia loistamispaikkoja. Käytännön kokeet osoittivat tämän pitävän paikkansa. Viimeinen tulokseni oli, että kiiltomadolla naaras menettää osan munistaan joka päivä jonka se joutuu odottamaan parittelua. Tästä voi päätellä, että naaraan ornamentin evoluutiota on voinut osaltaan ajaa tarve paritella mahdollisimman pian aikuistumisen jälkeen. Naaraiden ja koiraiden ornamenttien syyt voivat olla hyvin erilaiset: naarailla parittelu mahdollisimman pian voi olla tärkeintä, kun koiraalla parittelukumppanien määrä on tärkein
The Evolution of Social Dominance through Reinforcement Learning
No full textGroups of social animals are often organized into dominance hierarchies that are formed through pairwise interactions. There is much experimental data on hierarchies, examining such things as winner, loser, and bystander effects, as well as the linearity and replicability of hierarchies, but there is a lack evolutionary analyses of these basic observations. Here I present a game theory model of hierarchy formation in which individuals adjust their aggressive behavior toward other group members through reinforcement learning. Individual traits such as the tendency to generalize learning between interactions with different individuals, the rate of learning, and the initial tendency to be aggressive are genetically determined and can be tuned by evolution. I find that evolution favors individuals with high social competence, making use of individual recognition, bystander observational learning, and, to a limited extent, generalizing learned behavior between opponents when adjusting their behavior toward other group members. The results are in qualitative agreement with experimental data, for instance, in finding weaker winner effects compared to loser effects.</p
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
Environmental and genetic cues in the evolution of phenotypic polymorphism
No full textPhenotypic polymorphism is a consequence of developmental plasticity, in which the trajectories of developing organisms diverge under the influence of cues. Environmental and genetic phenotype determination are the two main categories of polymorphic development. Even though both may evolve as a response to varied environments, they are traditionally regarded as fundamentally distinct phenomena. They can however be joined into a single framework that emphasizes the parallel roles of environmental and genetic cues in phenotype determination. First, from the point of view of immediate causation, it is common that phenotypic variants can be induced either by environmental or by allelic variation, and this is referred to as gene-environment interchangeability. Second, from the point of view of adaptation, genetic cues in the form of allelic variation at polymorphic loci can play similar roles as environmental cues in providing information to the developmental system about coming selective conditions. Both types of cues can help a developing organism to fit its phenotype to selective circumstances. This perspective of information in environmental and genetic cues can produce testable hypotheses about phenotype determination, and can thus increase our understanding of the evolution of phenotypic polymorphism.</p
Multidimensional convergence stability
No full textQuestions: Are there general stability conditions for the evolution Of Multidimensional traits, regardless of genetic correlations between traits? Can genetic correlations influence whether evolution converges to a stable trait vector? Mathematical methods: Adaptive dynamics theory and the weak selection limit of quantitative genetics. Key assumptions: Evolutionary change is represented as either (i) any gradualistic adaptive path in trait space, consisting of a sequence of small-effect mutant invasions, allowing for pleiotropic mutants, or (ii) a solution to the 'canonical equation' of adaptive dynamics with a gradually varying mutational covariance matrix. Assumption (ii) is a special case of (i). Conclusions: It is possible to formulate robust stability conditions for multidimensional traits, but most evolutionary equilibria will not satisfy these conditions. Under the liberal assumption (i), there will in general be no 'absolutely convergence stable' equilibria in multidimensional trait spaces (except for simplified models). Under the more restrictive assumption (ii), a Much larger proportion of evolutionary equilibria is 'strongly convergence stable', i.e. are stable irrespective of genetic correlations.</p
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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