Le NVP (Problème du Vendeur de Journaux) a été étudiée de façon continue au cours des dernières décennies pour la prise de décision dans les industries manufacturières et de services. Bien que beaucoup de travail a été fait dans le domaine du NVP, l'intérêt sur ce sujet ne diminue pas. Alors que de nouvelles tendances émergent dans les affaires, par exemple flux internationaux de produits et de e-commerce, les détaillants sont confrontés à de nouvelles situations et la littérature de NVP doit être enrichi. Dans ce travail, nous proposons trois nouvelles extensions NVP compte tenu des questions importantes rencontrées par le NV: plusieurs soldes, variété de produits et d'assortiment ainsi que des problèmes de drop-shipping et de retour des produits qui sont liés à l'e-commerce. Notre travail ajoute de la valeur à partir des travails antérieurs dans plusieurs aspects: assouplissement des hypothèses, l'examen de nouvelles questions, de nouvelles formulations et de la méthodologie ainsi que des aperçus intéressants. Nous formulons les modèles et donner les conditions d'optimalité de la quantité de commande. Aperçus utiles sont fournis sur la base des études numériques.En particulier, pour faire face à surstock, nous présentons un modèle NVP avec le prix dépendant de la demande et de multiples soldes. Nous prouvons la concavité de l’espérance de profit sur la quantité avec les distributions générales de la demande. Le prix initial et les pourcentages de soldes sont également analysés. La variété de produit est traité dans un multi-produits Problème avec le transfert de la demande (les demandes de produits non inclus dans l'assortiment proposé dans le magasin sont en partie transférés aux produits conservés dans l'assortiment) et substitution de la demande entre les produits qui sont inclus dans l'assortiment, en faisant la détermination conjointe de décision optimale de l'assortiment et des quantités de commande pour les produits qui sont inclus dans l'assortiment, pour optimiser le profit total prévu. Pour e-commerce, nous considérons un NV qui gère à la fois un magasin physique et un canal de vente sur Internet qui est remplie par une option drop-shipping, ainsi que la possibilité de revendre les produits qui sont retournés par les consommateurs au cours de la saison de vente. La concavité de l’espérance profit est prouvée et différents résultats sont obtenus à partir d'une analyse numérique. / The NVP (News-Vendor Problem) has been continuously studied over the last decades for decision making in manufacturing and service industries. Although a lot of work has been done in the NVP area, interest on this topic does not decrease. As new trends emerge in business, e.g. international flow of products and e-commerce, retailers are facing new situations and the literature of NVP needs to be enriched. In this work, we propose three new NVP extensions considering important issues faced by the NV: multiple discounts, product variety and assortment as well as drop-shipping and product return problems that are related to e-commerce. Our work adds value from earlier achievements in several aspects: relaxation of assumptions, consideration of new issues, new formulations and methodology as well as interesting insights. We formulate the models and give the optimality conditions of the order quantity. Useful insights are provided based on numerical studies.In particular, for dealing with overstock, we present a NVP model with price-dependent demand and multiple discounts. We prove the concavity of the expected profit on order quantity under general demand distributions. The optimal initial price and discount scheme are also analyzed. The product variety is treated in a multi-product News-Vendor Problem with demand transfer (the demands of products not included in the assortment proposed in the store are partly transferred to products retained in the assortment) and demand substitution between products that are included in the assortment, by focusing on the joint determination of optimal product assortment decision and optimal order quantities for products that are included in the assortment to optimize the expected total profit. For e-commerce, we consider a NV managing both a physical store inventory and a sale channel on internet that is fulfilled by a drop-shipping option, as well as the possibility of reselling products that are returned by consumers during the selling season. The concavity of the expected profit is proven and various results are obtained from a numerical analysis.

The aim of the study is to further understand the factors influencing consumer behavior in the fast fashion segment. The study is done from a consumer perspective where 84 consumers were asked questions regarding their preferences, behaviors, and habits while shopping, and which aspects they are most keen about while visiting fast fashion stores. After the data was collected from the respondents it has been analyzed with SPSS to answer the two hypotheses, if price and assortment are essential factors for consumers in the fast fashion branch. Findings from the analysis made it clear that price is by far the most important factor for consumers while assortment is essential as well but not in comparison with price. Therefore, it is important for companies within the fast fashion segment to be aware of their competitors price levels to be able to stand out, create and obtain a competitive advantage and preserve or expand their market share. / Syftet med undersökningen är att skapa en ökad förståelse för faktorerna som påverkar konsumentbeteendet inom fast fashion branschen. Genom den ökade förståelsen är det möjligt för företag att utveckla sina kunskaper om sina kunder och på så vis utveckla deras lönsamhet och kundnöjdhet. Undersökningen grundar sig i ett konsumentperspektiv där 84 konsumenter svarade på en enkät som innehöll frågor om deras preferenser, beteenden och vanor vid köp av kläder från fast fashion butiker, online eller fysiskt i butik. Respondenternas svar analyserades därefter med hjälp av SPSS för att svara på arbetets två hypoteser, om pris och sortiment är två viktiga faktorer för konsumenter inom fast fashion branschen. Arbetet visade att pris är den faktor som flest konsumenter prioriterar när de köper kläder. Även sortiment är något som konsumenter prioriterar vid konsumtion, men förhållandevis lågt jämfört med pris. Det är därför viktigt för företag inom fast fashion branschen att vara medvetna om konkurrenternas prisnivå för att på så vis skapa och behålla marknadsandelar samt konkurrensfördelar.

Kläder i samma storlek från samma företag kan skilja sig radikalt mot varandra men det kan även skilja sig mellan olika företag. Som konsument kan du beställa samma storlek från två olika företag och motta produkter som skiljer sig stort i upplevd passform. Trots att flertal studier gjorts på storleksstrategin har vi inte kunnat hitta någon studie som kombinerar och ser på helheten av företags storleksstrategi. Därav är studiens syfte att undersöka svenska företags storleksstrategi inom deras damsortimentet och hur en förändrad strategi kan påverka företagets returer. Studien bidrar till en större förståelse för inköpare inom modeindustrin och om hur strategier gällande storleksurval och information till kund gällande storlekar kan komma att påverka företagets returer. Studien kommer också undersöka hur svenska företag storleksstrategier motsvarar kundernas förväntningar på klädernas passform och storlek. För att besvara studiens frågeställning genomfördes semistrukturerade intervjuer med tre svenska modeföretag, samt en en enkätstudie mot kvinnliga konsumenter mellan 20-84 års ålder. Detta för att få en syn på problemet ur både ett företagsperspektiv och ett konsumentperspektiv. De teman som undersökts är prover, måttlista, returandel, förbättrad passform och lönsamhet. Resultatet från fyra intervjuer och 96 enkätsvar visar på att det finns en dissonans mellan företags arbetssätt och konsumenters förväntningar på företagen. Möjlighet till att minska denna dissonans hade varit ifall företagen hade ändrat i sina storleksstrategier genom att alla utgår ifrån samma måttlista och storlekssystem. Vidare att företag implementerar sina mönsterkonstruktioner internt för att motverka variationer i passform på grund av varierande leverantörer. Genom att upprätthålla virtuella provrum för konsumenterna ger det dem chansen att testa plagg online innan köp, vilket hade kunnat eliminera många av de returer som på grund av att man beställer samma plagg i fler än en storlek. Således hade egna mönsterkonstruktioner resulterat i färre returer och påverkat lönsamheten positivt, då företagen hade kunnat erbjuda storlekar och passform som inte beror på val av leverantör. / Clothes of the same size and from the same company, can differ radically from each other. Likewise, the same size and fit can also differ between different companies. A consumer can order the same size and receive products that differ greatly in perceived and actual fit. Although there have been studies made on different parts of companies size strategy, there has not been any study that combines them and looks at the different strategies as a whole. The purpose of this study is therefore to examine the size strategies of Swedish fashion companies’ ladies assortment and whether a change in strategy would affect the returns. Furthermore, this includes whether companies’ size strategies correspond to the customers’ expectations on size and fit. The method was conducted by semi-structured interviews with three different Swedish fashion companies and by a quantitative survey-study towards female consumers above the age of 20. This was made in order to get a perspective on the different size strategies from both companies and consumers. The themes examined throughout this paper are samples, measurement charts, returns, consumers, improved fit and profitability. The result from the four interviews and the 96 survey answers shows that there exists a dissonance between the way companies work and customers’ expectations on sizes and fit that companies offer. Opportunity to reduce this dissonance would have been if all companies changed their size strategies and instead started using the same measurement list och size system. Furthermore, companies could implement their pattern design on the internet to avoid different variations in fit due to the use of different suppliers. Likewise, to maintain virtual test rooms for consumers gives them a chance to test a garment online before purchasing. By offering virtual testing rooms online, it would have been possible to avoid several of the returns that occur due to the need of ordering the same garment in different sizes. Creating their own patterns would result in fewer returns and thus a positive effect on profitability, as the companies should be able to offer sizes and fits that did not depend on their choice of supplier. The report is written in Swedish.

Submitted by Ronildo Vaz (ronildo-vaz@uol.com.br) on 2018-06-26T23:24:29Z No. of bitstreams: 1 DISSERTAÇÃO DE MESTRADO- RONILDO VAZ- 2018.pdf: 1657277 bytes, checksum: 79e4e031bd73a4da58863c90055ef1d8 (MD5) / Approved for entry into archive by Simone de Andrade Lopes Pires (simone.lopes@fgv.br) on 2018-06-28T16:19:28Z (GMT) No. of bitstreams: 1 DISSERTAÇÃO DE MESTRADO- RONILDO VAZ- 2018.pdf: 1657277 bytes, checksum: 79e4e031bd73a4da58863c90055ef1d8 (MD5) / Approved for entry into archive by Suzane Guimarães (suzane.guimaraes@fgv.br) on 2018-06-28T16:33:06Z (GMT) No. of bitstreams: 1 DISSERTAÇÃO DE MESTRADO- RONILDO VAZ- 2018.pdf: 1657277 bytes, checksum: 79e4e031bd73a4da58863c90055ef1d8 (MD5) / Made available in DSpace on 2018-06-28T16:33:06Z (GMT). No. of bitstreams: 1 DISSERTAÇÃO DE MESTRADO- RONILDO VAZ- 2018.pdf: 1657277 bytes, checksum: 79e4e031bd73a4da58863c90055ef1d8 (MD5) Previous issue date: 2018-05-30 / A partir dos fundamentos do gerenciamento por categorias, o objetivo do estudo foi identificar como o pequeno varejista pode buscar formas de melhorar as decisões sobre o sortimento e exposição de produtos tornando o negócio mais lucrativo e avaliar os impactos na percepção dos shoppers. A unidade de análise é um minimercado de dois checkouts com 66 metros quadrados de área de vendas na cidade de Florianópolis. O trabalho foi desenvolvido em duas etapas: na primeira etapa foram realizadas mudanças no sortimento e na forma de exposição na gôndola de seis categorias de produtos de higiene pessoal. Para isso, foi utilizado o método de pesquisa-ação que procura melhorar uma prática através da colaboração entre o pesquisador e sua unidade da análise, neste caso o pequeno varejo estudado. Para balizar as mudanças, foi feita uma revisão secundária de pesquisas sobre o comportamento dos shoppers, participação de mercado dos produtos, formas de segmentação e exposição das categorias, dados de vendas e margem e espaço na gôndola disponível para exposição das categorias de produtos. A partir das análises da primeira etapa foi possível observar o incremento das vendas e margem das categorias manipuladas. Na segunda etapa foram feitas observações diretas e entrevistas com os clientes e profissionais da empresa. Os objetivos desta etapa foram: identificar as políticas e os processos praticados pelo pequeno varejo sobre sortimento e exposição de produtos, se há suporte das indústrias e seus distribuidores sobre definição do sortimento e exposição de produtos e observar se houveram melhorias na percepção dos shoppers sobre as mudanças realizadas. Na perspectiva dos profissionais do pequeno varejo, não há suporte dos seus fornecedores para a definição do sortimento e exposição de produtos sendo ainda uma relação predominantemente transacional focada no sell in. As mudanças não melhoraram a percepção dos shoppers apontando um canal alternativo, farmácia, como a opção mais indicada como o local de compra das categorias de higiene pessoal, ao invés do pequeno do pequeno varejista estudado. / From the fundamentals of category management, the aim of the study was to identify how the small retailer can look for ways to improve product assortment and exposure decisions by making the business more profitable and assessing perceptual impacts on shoppers. The unit of analysis is a mini-market of two checkouts with 66 square meters of sales area in the city of Florianópolis. The work was carried out in two stages: in the first stage changes were made in the assortment and in the form of exposure in the shelf of six categories of personal hygiene products. For this, we used the action research method that seeks to improve a practice through the collaboration between the researcher and his unit of analysis, in this case the small retailer studied. To mark the changes, a second review of shopper behavior, market share of products, segmentation and exposure forms of categories, sales and margin datas and space in the shelf available for display of the product categories was made. From the analyzes of the first stage it was possible to observe the increase in sales and margin of the manipulated categories. In the second stage, direct observations and interviews with clients and professionals of the company were made. The objectives of this stage were: to identify the policies and processes practiced by small retailer on assortment and product exposition, if the industries and their distributors give support on assortment definition and product exposition, and to observe if there has been improvement in the perception of shoppers about changes made. From the perspective of small retail professionals, there is no support from their suppliers for assortment definition and product exposure, while a predominantly transactional relationship is focused on sell in. The changes did not improve shoppers' perception by pointing to an alternative channel, pharmacy, as the best choice as the place to buy personal hygiene categories, rather than the small retailer studied

Plus size är ett växande kundsegment som idag har blivit i stort sett negligerat av klädbranschen både nationellt och internationellt. Med ett begränsat utbud och brist på inspirerande butiksavdelningar har allt fler konsumenter slutat att handla i fysisk butik och istället övergått till att handla på nätet. Detta har inspirerat till en undersökning av hur svenska kvinnliga modemedvetna plus size konsumenter i olika åldrar upplever fysiska klädbutikers servicescape. I studien har en kvantitativ metod, surveyundersökning online, genomförts där bekvämlighetsurval använts som grund. 121 modemedvetna plus size kvinnor uttryckte sin åsikt angående sina upplevelser av fysiska butikers servicescape och hur produkterna upplevs. I enkäten gjordes en medveten uppdelning av frågorna gällande fysiska butiker, ena butikskonceptet har en specifik plus size avdelning och den andra har sitt plus size sortimentet integrerat med det övriga sortimentet i butiken. Efter genomförd deskriptiv och statistisk analys av det insamlade materialet har det kunnat fastställas att plus size konsumenter anser att det finns skillnader mellan butiker med enskild avdelning och butiker med integrerat sortiment. Den allmänna upplevelsen bland respondenterna var att servicescape genomförts bättre i butiker där plus size produkter är integrerade bland det övriga sortimentet. Utbudet av produkter i plus size upplevs vara begränsat. Det är därför svårt att avgöra hur servicescape påverkar uppfattningen av produkter. Dock uppfattas plus size avdelningars servicescape negativt och detta kan påverka konsumenters upplevelse av produkter och dess tillgänglighet. Studien har bidragit med nya insikter i hur det specifika kundsegmentet, plus size kvinnor, upplever servicescape. Vidare har studien bidragit till forskning gällande butiker med integrerat utbud då tidigare forskning inom detta område varit begränsat. / Plus size is a growing consumer segment that have become neglected in the clothing industry both nationally and internationally. With a limited supply and a lack of inspiring departments in store, more consumers have stopped shopping in physical stores and instead directed their shopping towards online retailers. These factors have inspired this study and the need to investigate how Swedish female fashion forward plus size consumers in different ages experience physical store environments in terms of servicescape. The study is based on a quantitative method where convenience sample was used. 121 female plus size consumers took part in an online survey to express their experiences of servicescape and how products are perceived in these environments. The survey was deliberately divided into two different parts where one part focused on stores that have a specific department for plus size clothing and the other where the plus size assortment was integrated with the other ranges in store. After conducted descriptive and statistical analysis of the compiled material, the study shows that female plus size consumers deem that there is a difference between the experienced servicescape of the two different types of store. The general conception among the respondents is that the stores where the plus size assortment is integrated have a better applied servicescape. The range of products in plus size was experienced to be limited. Because of this is has been hard to determine werther servicescape have a big impact on how products are perceived or not. However, since the study shows that plus size departments in terms of servicescape are perceived negatively, this may have an effect on how the products and its availability are perceived. The study has contributed with new insights into how the specific consumer segment, female plus size, experience servicescape. Furthermore, the study has contributed with new knowledge regarding the experience of stores with an integrated plus size assortment since this particular angle has been limited in earlier studies.

This diploma thesis deals with the current use of traditional folk culture in the form of souvenirs. These are tendencies that have accompanied traditional folk culture since its extinction in the natural environment. The work will focus on these manifestations in a selected part of Prague center. It maps the range of offer souvenirs and focuses on them in relation to three key groups. Sellers, tourists and residence of Prague. In conclusion, the work tries to address the issue in an applied way, by designing its own part of the concept of traditional folk souvenirs, which are inspired by regional specifics. From a theoretical point of view, the work pay attentetion to the very source of inspiration for this type of souvenirs, the theories that are associated with traditional folk souvenirs and a selected ethnographic region.

The correct classification of a logs assortment is crucial for the economic output within a fully mechanized timber harvest. This task is especially for unexperienced but also for professional machine operators mentally demanding. This paper presents a method towards an assistance system for machine operators for an automated log quality and assortment estimation. Therefore, machine vision methods for object detection are combined with machine learning approaches for estimating the logs weight based on a Convolutional Neural Network (CNN). Based on the dimensions oft he object ´log, a first categorisation into a specific assortment is done. By comparing the theoretical weight of a healthy log of such dimensions to the real weight estimated by the CNN-based crane scale, quality reducing properties such as beetle infestation or red rod can be detected. In such cases, the assistance system displays a visual warning to the operator to check the loaded log.

The short life cycles and highly variable demand in the fast fashion market causes various challenges in a retailer’s supply chain management processes. The essential task at hand is to provide the right product, at the right time, and at the right place. Due to this inherent difficulty, the bullwhip effect is a major issue in the fashion supply chain. To enhance customer satisfaction and increase the alignment between the supply and market place demand, companies have been pushed towards exploiting big data, supply chain analytics and AI techniques for better business decision making. One such critical but intrinsically complex decision is the development of a future apparel assortment; in particular defining its optimal breadth and depth. This thesis investigates how such AI techniques can be applied to develop a new assortment aligned with the future customer demands- and choice behavior. The research was conducted through firstly performing a qualitative case study at a fast fashion retailer. This explored the critical business decisions in the supply chain lacking AI support. The findings, revealing the assortment planning process as one such critical area, guided the second part of the thesis: a systematic literature review exploring the AI techniques used in this process in the retail - and fashion industry. An appropriate framework of planning a static apparel assortment in the fast fashion industry was developed and used as a guide throughout the study. The thesis discovered that there exists significant research in the field of applying AI techniques to generate and integrate knowledge about consumer demand- and choice behavior in the planning process of a future assortment. The main components to consider in this procedure is a) fashion forecasting, b) forecasting midterm demand, and c) forecasting product selection, incorporating the effects of substitution and complementarity at all times. This is believed to increase the alignment between supply and the marketplace demand, consequently reducing the bullwhip effect. The critical area for future research is how the discovered models are to be integrated in one singlemodel. Namely, simultaneously utilizing consumer choice behavior models and fashion forecasting to predict future demand of new items. Thus, the risk of suboptimization may be mitigated. / Modeindustrins korta produktlivscykler och högt varierande efterfrågan efter rådande trender skapar stora utmaningar i försörjningskedjan hos företag i branschen. Det essentiella målet för företagen är att tillhandahålla rätt produkt, vid rätt tidpunkt och på rätt plats. De komplexa karaktärsdragen i modeindustrin, där bland den fluktuerande efterfrågan, har gjort bullwhipeffekten till en stor utmaning i branschen. För att öka kundnöjdhet och anpassningen mellan marknadens utbud och efterfrågan har företag drivits mot utnyttjandet av big data i avsikt att förbättra kritisk affärsbeslutsfattning genom användandet av analytics och AI. Ett kritiskt ochkomplext beslut är utvecklingen av ett nytt produktsortiment, där definieringen av sortimentetsbredd och djup är särskilt viktigt. Denna uppsats undersöker hur AI-modeller kan tillämpas för att hjälpa företag inom modeindustrin i utvecklingen av nya sortiment anpassade efter kundens beräknade efterfrågan och val. Detta arbete inleddes med utförandet av en kvalitativ fallstudie hos en stor aktör verksam inom modeindustrin. Detta gjordes för att identifiera kritiska affärsbeslut i företagets försörjningskedja som saknade AI-stöd. Resultatet påvisade att sortimentsplanering var ett sådant kritiskt beslutsområde. Följaktligen utfördes en systematisk litteraturstudie i andra delen av arbetet i syfte att undersöka AI-modeller som appliceras i sortimentsplanerings-processen i såväl detaljhandeln som modebranschen. För att konceptualisera processen av att planera ett statiskt produktsortiment utvecklades ett ramverk som användes som en guide under hela arbetet. Studien visade att det finns betydande forskning inom tillämpningen av AI-modeller i syfte att planera ett optimalt sortiment efter konsumenternas efterfrågan. De huvudsakliga faktorerna att överväga innefattar prognostiseringen av efterfrågan, trender samt substitution- och komplementeffekter. Ett kritiskt område för framtida forskning är hur de upptäckta modellerna ska integreras i en enda modell som inkluderar dessa faktorer i ett tidigt såväl som sent skede av planeringen. Det som eftersträvas i en integrerad modell är att mildra risken av suboptimering som identifierats i nuvarande litteraturs angreppssätt.

An important goal of ecological studies is to identify and explain patterns or variation in species assemblages. Ecologists have discovered that global variation in the number of species in an assemblage relates strongly to climate, area, and topographic variability in terrestrial environments. Is the same true for other characteristics of species assemblages? The focus of this thesis is to determine whether species assemblage structure, defined primarily as the body mass frequency distributions and species abundance distributions relate in convergent ways to a set of a few environmental variables across broad spatial scales. First, I found that for mammals and trees most of their geographic variation across North and South America in assemblage structure is statistically related to temperature, precipitation, and habitat heterogeneity (e.g. different vegetation types) in convergent ways. I then examined bird assemblages across islands and continents. Despite the evolutionary and ecological differences between island and continental assemblages, I found that much of the variation in bird assemblage structure depends on temperature, precipitation, land area, and island isolation in congruent patterns in continent and island bird assemblages. Frank Preston modeled species richness based on the total number of individuals and the number of individuals of the rarest species. Building on Preston’s model, Chapter 2 hypothesized that gradients of diversity correlate with gradients in the number of individuals of the rarest species, which in turn are driven by gradients in temperature and precipitation. This hypothesis assumes that species abundance distributions relate to temperature and precipitation in similar ways anywhere in the world. I found that both the number of individuals of the rarest species (m) and the proportion of species represented by a single individual in samples of species assemblages (Φ) were strongly related to climate. Moreover, global variation in species richness was more strongly related to these measures of rarity than to climate. I propose that variation in the shape of the log-normal species abundance distribution is responsible for global gradients of species richness: rare species (reflected in m and Φ) persist better in benign climates. Even though body mass frequency distributions of assemblages show convergent patterns in relation to a set of a few environmental variables, the question remains as to what processes are responsible for creating the geographical variation in the body-size distribution of species. Several mechanisms (e.g. heat conservation and resource availability hypotheses) have been proposed to explain this variation. Chapter 5 tested and found no empirical support for the predictions derived from each of these mechanisms; I showed that species of all sizes occur across the entire temperature gradient. In conclusion, assemblage structure among various taxonomic groups across broad spatial scales relate in similar ways to a set of a few environmental variables, primarily mean annual temperature and mean annual precipitation. While the exact mechanisms are still unknown, I hypothesize several to explain the patterns of convergent assembly. Résumé Un but important de l'écologie est d'identifier et d'expliquer la variation de premier ordre dans les caractéristiques des assemblages d'espèces. Un des patrons ayant déjà été identifié par les écologistes, c'est que la variation mondiale de la richesse en espèces est liée à la variation du climat, de l'aire et de la topographie. Est-ce que d'autres caractéristiques des assemblages d'espèces peuvent être reliées à ces mêmes variables? Le but de cette thèse est de déterminer si la structure des assemblages d'espèces, ici définie comme la distribution des fréquences de masse corporelle ainsi que la distribution d'abondances des espèces, est reliée de manière convergente à un petit ensemble de variables environnementales, et ce, partout dans le monde. D'abord, j'ai déterminé que, pour les mammifères et les arbres, la majorité de la variation géographique dans la structure des assemblages d'espèces est reliée statistiquement à température, précipitation, et l’hétérogénéité du couvert végétal , et ce, de manière convergente pour l'Amérique du Nord et du Sud. Je me suis ensuite penché sur l'assemblage des oiseaux sur les îles et les continents. Malgré les larges différences évolutives et écologiques qui distinguent les îles des continents, je démontre que la majorité de la variation dans la structure des assemblages d'oiseaux dépend de la température, la précipitation, la superficie et l’isolation de façon congruente sur les îles et les continents. Frank Preston a modélisé la richesse en espèces d'une localité, basée sur le nombre total d'individus ainsi que le nombre d'individus de l’espèce la plus rare. En s'appuyant sur les modèles de Preston, Chapître 3 propose une nouvelle hypothèse voulant que les gradients de diversité dépendent des gradients du nombre d'individus de l’espèce la plus rare. Celle-ci dépend des gradients de température et de précipitation. Cette hypothèse repose sur le postulat que la distribution d’abondances des espèces dépend de la température et la précipitation, et ce, de la même manière n’importe où au monde. J’ai mis en évidence que le nombre d’individus de l’espèce la plus rare (m), ainsi que la proportion d’espèces représentées par un individu unique () dans des échantillons locaux étaient fortement reliés au climat. D’ailleurs, la variation globale de la richesse en espèces était plus fortement reliée à ces indices de rareté qu’au climat. Je propose que la variation dans la forme de la distribution log-normale d’abondances d’individus soit responsable des gradients mondiaux de richesse en espèces. En d’autres mots, les espèces rares (indiquées par m et ) persistent mieux dans des climats bénins. Malgré que la distribution des fréquences de masse corporelle des assemblages d'espèces soit liée de manière convergente à seulement quelques variables environnementales, la question demeure à savoir quels processus sont responsables des gradients géographiques de variation en masse corporelle des espèces. Plusieurs mécanismes ont été proposés pour expliquer cette variation. Dans Chapitre 5, j'ai testé les prédictions dérivées de chacun de ces mécanismes sans trouver de support empirique pour aucun. Je démontre aussi que des espèces de toutes tailles se retrouvent sur le gradient de température en entier. En conclusion, la structure des assemblages d'espèces, pour différents groupes taxonomiques et à travers le monde, est liée de façon similaire à un petit nombre de variables environnementales. Bien que les mécanismes soient encore inconnus, j'en propose plusieurs pouvant expliquer ces patrons d'assemblages convergents.

An important goal of ecological studies is to identify and explain patterns or variation in species assemblages. Ecologists have discovered that global variation in the number of species in an assemblage relates strongly to climate, area, and topographic variability in terrestrial environments. Is the same true for other characteristics of species assemblages? The focus of this thesis is to determine whether species assemblage structure, defined primarily as the body mass frequency distributions and species abundance distributions relate in convergent ways to a set of a few environmental variables across broad spatial scales. First, I found that for mammals and trees most of their geographic variation across North and South America in assemblage structure is statistically related to temperature, precipitation, and habitat heterogeneity (e.g. different vegetation types) in convergent ways. I then examined bird assemblages across islands and continents. Despite the evolutionary and ecological differences between island and continental assemblages, I found that much of the variation in bird assemblage structure depends on temperature, precipitation, land area, and island isolation in congruent patterns in continent and island bird assemblages. Frank Preston modeled species richness based on the total number of individuals and the number of individuals of the rarest species. Building on Preston’s model, Chapter 2 hypothesized that gradients of diversity correlate with gradients in the number of individuals of the rarest species, which in turn are driven by gradients in temperature and precipitation. This hypothesis assumes that species abundance distributions relate to temperature and precipitation in similar ways anywhere in the world. I found that both the number of individuals of the rarest species (m) and the proportion of species represented by a single individual in samples of species assemblages (Φ) were strongly related to climate. Moreover, global variation in species richness was more strongly related to these measures of rarity than to climate. I propose that variation in the shape of the log-normal species abundance distribution is responsible for global gradients of species richness: rare species (reflected in m and Φ) persist better in benign climates. Even though body mass frequency distributions of assemblages show convergent patterns in relation to a set of a few environmental variables, the question remains as to what processes are responsible for creating the geographical variation in the body-size distribution of species. Several mechanisms (e.g. heat conservation and resource availability hypotheses) have been proposed to explain this variation. Chapter 5 tested and found no empirical support for the predictions derived from each of these mechanisms; I showed that species of all sizes occur across the entire temperature gradient. In conclusion, assemblage structure among various taxonomic groups across broad spatial scales relate in similar ways to a set of a few environmental variables, primarily mean annual temperature and mean annual precipitation. While the exact mechanisms are still unknown, I hypothesize several to explain the patterns of convergent assembly. Résumé Un but important de l'écologie est d'identifier et d'expliquer la variation de premier ordre dans les caractéristiques des assemblages d'espèces. Un des patrons ayant déjà été identifié par les écologistes, c'est que la variation mondiale de la richesse en espèces est liée à la variation du climat, de l'aire et de la topographie. Est-ce que d'autres caractéristiques des assemblages d'espèces peuvent être reliées à ces mêmes variables? Le but de cette thèse est de déterminer si la structure des assemblages d'espèces, ici définie comme la distribution des fréquences de masse corporelle ainsi que la distribution d'abondances des espèces, est reliée de manière convergente à un petit ensemble de variables environnementales, et ce, partout dans le monde. D'abord, j'ai déterminé que, pour les mammifères et les arbres, la majorité de la variation géographique dans la structure des assemblages d'espèces est reliée statistiquement à température, précipitation, et l’hétérogénéité du couvert végétal , et ce, de manière convergente pour l'Amérique du Nord et du Sud. Je me suis ensuite penché sur l'assemblage des oiseaux sur les îles et les continents. Malgré les larges différences évolutives et écologiques qui distinguent les îles des continents, je démontre que la majorité de la variation dans la structure des assemblages d'oiseaux dépend de la température, la précipitation, la superficie et l’isolation de façon congruente sur les îles et les continents. Frank Preston a modélisé la richesse en espèces d'une localité, basée sur le nombre total d'individus ainsi que le nombre d'individus de l’espèce la plus rare. En s'appuyant sur les modèles de Preston, Chapître 3 propose une nouvelle hypothèse voulant que les gradients de diversité dépendent des gradients du nombre d'individus de l’espèce la plus rare. Celle-ci dépend des gradients de température et de précipitation. Cette hypothèse repose sur le postulat que la distribution d’abondances des espèces dépend de la température et la précipitation, et ce, de la même manière n’importe où au monde. J’ai mis en évidence que le nombre d’individus de l’espèce la plus rare (m), ainsi que la proportion d’espèces représentées par un individu unique () dans des échantillons locaux étaient fortement reliés au climat. D’ailleurs, la variation globale de la richesse en espèces était plus fortement reliée à ces indices de rareté qu’au climat. Je propose que la variation dans la forme de la distribution log-normale d’abondances d’individus soit responsable des gradients mondiaux de richesse en espèces. En d’autres mots, les espèces rares (indiquées par m et ) persistent mieux dans des climats bénins. Malgré que la distribution des fréquences de masse corporelle des assemblages d'espèces soit liée de manière convergente à seulement quelques variables environnementales, la question demeure à savoir quels processus sont responsables des gradients géographiques de variation en masse corporelle des espèces. Plusieurs mécanismes ont été proposés pour expliquer cette variation. Dans Chapitre 5, j'ai testé les prédictions dérivées de chacun de ces mécanismes sans trouver de support empirique pour aucun. Je démontre aussi que des espèces de toutes tailles se retrouvent sur le gradient de température en entier. En conclusion, la structure des assemblages d'espèces, pour différents groupes taxonomiques et à travers le monde, est liée de façon similaire à un petit nombre de variables environnementales. Bien que les mécanismes soient encore inconnus, j'en propose plusieurs pouvant expliquer ces patrons d'assemblages convergents.