Les radiations évolutives sont des phénomènes de diversification rapide, et une source majeure de la diversité biologique sur Terre. J'explore ici l'hypothèse selon laquelle les mécanismes écologiques et génétiques à la base des radiations évolutives structurent les patrons macroécologiques et macroévolutifs de diversité. Pour ce faire, j'analyse les prédictions de plusieurs modèles de radiation émergeant des dynamiques spatio-temporelles à l'échelle individuelle. Ces analyses montrent d'abord que la structuration spatiale est un facteur majeur de diversité et d'endémisme au sein des archipels océaniques, en raison d'interactions entre dispersion et spéciation allopatrique. L'intégration de la dynamique des paysages et des processus d'interactions compétitives révèle ensuite comment ces facteurs se combinent pour structurer la forme des arbres phylogénétiques, et notamment générer des arbres déséquilibrés et une décélération du tempo de branchement, souvent observés dans les phylogénies moléculaires. J'explore alors les mécanismes responsables de cette décélération. Je montre qu'elle reflète une diversité-dépendance négative du taux de spéciation, liée à une réduction de la persistance et différentiation écologique des nouvelles populations. Le taux d'extinction n'est lui pas influencé par la diversité, les extinctions étant ici surtout causées par une combinaison d'exclusion compétitive et d'hybridation d'espèces incipientes. Enfin, je mets en évidence l'importance, lors d'une crise d'extinction, de la topologie rangée des arbres phylogénétiques et de la distribution des extinctions sur les pertes de diversité phylogénétique, et donc sur le potentiel d'évolution future. / Evolutionary radiations are phenomena of rapid diversification, and one of the major sources of biodiversity on Earth. Here, I explore the hypothesis that ecological and genetic mechanisms underpinning evolutionary radiations structure macroecological and macroevolutionary patterns of diversity. To this end, I analyse the predictions of several models in which radiations emerge from spatio-temporal dynamics at the scale of the individual. These analyses first show that spatial structure is a major driver of diversity and endemism on oceanic archipelagos due to interactions between dispersal and allopatric speciation. Second, by integrating landscape dynamics and the processes of competitive interactions, I reveal how these factors combine to shape phylogenetic trees, and in particular to beget trees that are unbalanced and exhibit a deceleration in branching tempo, which is often observed on molecular phylogenies. I then explore the mechanisms responsible for this deceleration. I show that it reflects a negative diversity-dependence of the speciation rate, itself linked to a reduction in the persistence and ecological differentiation of new populations. The extinction rate is, on the other hand, uninfluenced by species diversity, extinctions being here mainly caused by a combinaison of competitive exclusion and hybridization of incipient species. Finally, I show that during mass extinctions the ranked topology of phylogenetic trees and the distribution of extinctions among the tips have a strong impact on the loss of phylogenetic diversity, and hence on the potential for future evolution.

Thesis (Ph. D.)--University of Chicago, Committee on Evolutionary Biology, August 2003. / Includes bibliographical references. Also available on the Internet.

Despite science education reform efforts stressing the importance of understanding evolution, many students receive little to no exposure to the most important unifying concept in biology. Since evolution is basic to the study of biology, its study should begin with the introduction of the life sciences to students in elementary school. However, many teachers lack sufficient evolutionary content knowledge, have limited acceptance of evolution, and have little confidence to effectively teach it. Better teacher preparation is needed to meet the challenges of ensuring students develop conceptual understanding of evolution. While research shows the general public typically accepts microevolution while rejecting macroevolution, few studies have focused on peoples’ understanding of macroevolution. Additionally, little research exists examining the effects of an intervention on elementary and middle school teachers’ acceptance, understanding, and teaching of macroevolution. Using a conceptual framework based on the Cognitive Reconstruction of Knowledge Model, this study reports the effects of a sustained professional development program on 4th through 8th grade teachers’ acceptance of evolution; understanding of macroevolution; and approach to teaching evolution in schools, awareness of challenges to teaching evolution, and pedagogical content knowledge about teaching macroevolution. This study also explores the relationship between teachers’ understanding of macroevolution and acceptance of evolution. Various data sources, including the Measurement of the Understanding of Macroevolution (Nadelson & Southerland, 2010), the Measure of the Acceptance of the Theory of Evolution (Rutledge & Warden, 1999), teacher interviews, and teacher workshop reflections, were used to answer the research questions. Results from the study revealed that after attending the professional development series, teachers’ understanding of macroevolution and acceptance of evolution significantly increased. Acceptance of evolution was positively correlated to understanding of macroevolution. Teachers’ prior understanding of macroevolution was a significant positive predictor of their subsequent acceptance of evolution. Teachers’ prior acceptance of evolution was a significant predictor of their understanding of macroevolution, but only after teachers participated in at least half of the sustained professional development. Finally, teachers demonstrated having increased macroevolutionary pedagogical content knowledge. This effect was strong in those teachers who were initially low acceptors of evolution. The significance of these findings is discussed. / text

The theory of “punctuated equilibrium” suggests that species evolve rapidly during or immediately upon speciation, “punctuating” long periods of little or no morphological evolution. Here I confirm that body size differences within clades of birds and mammals are best explained using a model of punctuated evolution. This allows me to suggest that rates of speciation and extinction are responsible for why there are more small mammals than large, as large mammals likely speciate and go extinct at a higher rate than small mammals, and hence undergo cladogenetic change more often. Likewise, mammals appear to evolve at a higher rate than birds, because mammals, as a whole, speciate and go extinct at a higher rate than birds. Furthermore I show that mass extinctions and competition, i.e. forms of natural selection, do not seem to explain differences in body size between species on a macroevolutionary scale. Taken together, these findings not only contradict the idea that apparently different rates of evolution are due to differential selection intensities, and emphasize the importance of the speciation process in evolution, but raise the intriguing question as to what limits evolution in established species. Here I suggest that phenotypic traits, dependent on one another for development and/or function may constrain evolution by exerting stabilizing selection from within the organism, as opposed to external environmental selection, which has been the main focus of evolutionary studies thus far. / Teorin om "punkterad jämvikt" säger att arter utvecklas snabbt under och omedelbart efter artbildning, vilket "punkterar" långa perioder med lite eller ingen morfologisk föränding. I den här avhandlingen visar jag att skillnader i kroppsstorlek inom klader (grupp med gemensam förfader) hos fåglar och däggdjur förklaras bäst när man använder en modell med punkterad evolution. Detta gör i sin tur att jag kan föreslå att hastigheten var med artbildning och utdöende sker, förklarar varför det finns fler små däggdjur än stora, eftersom stora däggdjur sannolikt bildar nya arter och dör ut med en högre hastighet än små däggdjur. Likaså förefaller däggdjur i sin helhet att evolvera med en högre hastighet än fåglar, detta eftersom däggdjur bildar nya arter och dör ut med en högre hastighet än fåglar. Dessutom visar jag att massutdöenden och konkurrens (naturlig selektion) inte verkar förklara skillnader mellan arter över makroevolutionära skalor (över geologisk tid). Sammantaget motsäger dessa resultat inte bara idén om att skenbart olika hastighet på evolution främst beror på skillnader i selektionstryck utan understryker också vikten av artbildningsprocessen som en viktig faktor som styr evolutionens hastighet. Dessutom leder dessa resultat till frågan om vad som begränsar evolutionen hos redan etablerade arter. Här föreslår jag att fenotypiska karaktärsdrag som är beroende av varandra för sin funktion och utveckling kan begränsa evolutionen genom att utöva stabiliserande selektion inifrån organismen, i motsats till selektion från den omgivande miljön vilket har varit fokus för de flesta evolutionära studier hittills.

The broad concept of 'biodiversity' can be roughly separated into two related components: trait diversity and species richness. Despite the fact that one or both of these types of biodiversity underlie much of ecology, evolution, and conservation, however, it remains largely unknown how traits and speciation dynamics can interact, particularly at a large scale. My thesis uses modern phylogenetic comparative methods and a new global database of avian morphological traits to quantify and predict the drivers of biodiversity across the world's birds, focusing particularly on the relative roles of ecological and social traits to understanding broad evolutionary patterns. In Chapter 2 I present a survey of avian functional traits, focusing on eight measurements of the beaks, wings, tails, and tarsi of 42,334 individuals representing 10,023 extant and recently extinct species. The global trait distribution of avian communities is consistent with a competition-based model of community assembly, and I find no evidence of environmental filtering at the biome level. The traits exhibited within avian orders tend to become more dissimilar as species richness increases, with the notable exception of the Passeriformes, an order containing around 60% of the total avian species richness but occupying a region of morphospace expected of a clade two orders of magnitude smaller. The Passeriformes also possess remarkable vocal morphology and behavior, and thus I spend the next three chapters of this thesis focused on the role of social processes in avian evolution. In Chapter 3, I use detailed morphological and vocal trait data from the suboscine family Furnariidae to demonstrate that social traits evolve faster and with less regularity than ecological traits. I then in Chapter 4 examine the social and ecological drivers of female song in birds, a widespread trait whose persistence challenges traditional sexual selection theory. I find that the separate drivers of male and female song can be explained by social selection theory, a framework which encompasses all social interactions above and beyond competition for mating opportunities. In Chapter 5 I apply this concept of social selection to macroevolutionary studies, using sex-specific song behaviors to separately investigate the roles of social and sexual selection on speciation and extinction rates. I demonstrate that lineages with male-only song (sexual selection) diversify faster than lineages with both male and female song (social selection). This result suggests that social selection theory may inform the controversial relationship between sexual selection and diversification. Finally, in Chapter 6 I look at the role of dispersal in modulating these speciation and extinction rates. Using data from the wing morphologies of 26,043 individuals from 6,028 species, I test the 'intermediate dispersal hypothesis', hitherto only examined at small scales, across the order Passeriformes, revealing that the highest rates of diversification are indeed found in lineages with an intermediate capacity for flight. When birds that defend year-round territories are considered separately from non-territorial birds, however, the intermediate dispersal hypothesis only holds for territorial birds, demonstrating the importance of considering the ecological context of traits in macroevolutionary studies. Together, my results present evidence that both social and ecological processes facilitate the generation and maintenance of biodiversity in birds.

No description available.

To understand how diversity varies through time and/or space we need to understand speciation and extinction dynamics, and ultimately which factors (biotic or abiotic) affect such dynamics. It has been argued that biological interactions play an important role on the diversification of organisms, but macroevolutionary studies have usually adopted a simple characterization of species interactions. On the other hand ecological studies usually focus on well-characterized interactions of very few species. A network approach can augment our understanding of the ecological roles played by different species but it still lacks an evolutionary perspective preventing us to fully understand how ecological interactions are assembled. Using the available phylogeny, dietary data for virtually all bird species (approximately 9965 species) and a large collection of frugivory net- works, we tested the effect of diet on the diversification of birds, and the relationship between ecological roles within interaction networks and diversification dynamics of frugivorous species. Lastly, using computational simulations, we assessed the per- formance of two state-of-the-art methods to estimate diversification rates using molecular phylogenies. We suggest that omnivory acts as macroevolutionary sink where its ephemeral nature is retrieved through transitions from other guilds rather than from omnivore speciation. We propose that these dynamics result from competition within and among dietary guilds, influenced by the deep-time availability and predictability of food resources. We also observed that in the temperate zone, lineages with high-paced evolutionary dynamics (e.g. higher turn- over rates) typically do not occupy central roles in frugivory net- works, and that these restrictions are modulated by water avail- ability/predictability. Lastly, we found that the two state-of-the art phylogenetic methods perform equally well in diversity de- cline scenarios when estimating current rates, but both fail to detect the true diversification trajectory when extinction rates vary in time. This dissertation contributes to the understanding of biotic and abiotic mechanisms driving both the diversification and the assembly of interaction networks, and also provides important information on the reliability of diversification rate estimates by current, widely used methods / Para entendermos como a biodiversidade varia no tempo e/ou no espaço precisamos entender a dinâmcia de especiação e extinção, e quais fatores (bióticos ou abióticos) afetam essa dinâmica. Acredita-se que as interações biológicas desempen- ham um papel importante na diversificação de organismos, porém estudos macroevolutivos usualmente adotam caracter- izações simples de interações entre espécies. Por outro lado, estudos ecológicos comumente focam na descrição detalhada de interações entre poucas espécies. Uma abordagem de re- des pode aumentar a compreensão dos papéis ecológicos de- sempenhados por diferentes espécies, mas a pouca ênfase em abordagens evolutivas em estudos de redes biológicas nos im- pedem de compreender completamente como essas redes são montadas. Usando a filogenia e dados de dieta disponíveis para virtualmente todas as espécies de aves (aprox. 9965 espécies), e uma grande coleção de redes de frugivoria, investigamos o efeito da dieta na diversificação de aves, e testamos a relação en- tre papéis ecológicos em redes de interação e a dinâmica da di- versificação de espécies frugívoras. Ainda, usando simulações computacionais, avaliamos a performance de dois métodos am- plamente utilizados para estimar taxas de diversificação usando filogenias moleculares. Sugerimos que onivoria atua como um ralo macroevolutivo, onde sua natureza efêmera é recuperada através de transições de outras guildas de dieta ao invés de através da especiação de espécies onívoras. Nós sugerimos que essa dinâmica resulta da competição intra- e entre guildas, in- fluenciada pela disponibilidade e previsibilidade de recursos em ampla escalas de tempo. Nós também observamos que em regiões temperadas, linhagens com uma dinâmica evolutiova mais rápida (maiores taxas de substituição de espécies) em geral não ocupam papéis centrais em redes de frugivoria, e que es- sas restrições são principalmente modificadas por disponibili- dade/previsibilidade hídricas. Por fim, observamos que ambos os métodos filogenéticos testados tem desempenho igualmente bom para estimar taxas atuais, porém ambos falham em detectar a trajetória da diversificação quando as taxas de extinção variam no tempo. Essa tese contribui para o conhecimento de mecanis- mos bióticos e abióticos que afetam tanto a diversificação quanto a montagem de redes de interação, e também provê informações importantes acerca da confiabilidade das estimativas de taxas de diversificação advindas dos métodos atuais amplamente utilizados

The effects of intrinsic traits on the diversification dynamics have been extensively investigated, with several traits being associated with increase in diversification. On the other hand, the possible negative effects of traits on the diversification of a lineage have been for the most part overlooked. Here we used both the fossil record and molecular data to study the diversification dynamics of Placentalia, focusing on the orders in decline of diversity, and investigated different mechanisms that might control the evolutionary success of the 21 placental orders. More specifically we: 1- determined which of the 21 orders of Placentalia are in decline of diversity (i.e., Decline model); 2- investigated whether the Decline model has a phylogenetic signal; 3- tested the hypothesis that the differences in body size are related to the Decline model; 4- tested the hypothesis that the orders in Decline have lower morphological disparity; 5- investigated whether the orders in decline of diversity, inferred from the fossil record, are the ones with higher extinction risk nowadays. Our analysis indicate that the majority of the orders of placental mammals have a pattern consistent with the Decline model and, although the Decline model is not equally distributed among the placental superorders, there was no significant phylogenetic signal for the orders in diversity decline. We found a positive correlation between the Decline model and the average body size which is in line with previous studies on body size evolution. We argue that such results suggest a complex evolutionary dynamics: larger body size appears to be an evolutionary attractor with lineages showing a tendency to increase in size, however, the increase in body size would be counterbalanced by a higher propensity to Decline. Moreover, we found a the negative correlation between the Decline model and morphological variation. We suggest that such results could indicate two possible scenario: (i) the low morphological variation would cause lineages to loose diversity; (ii) the low morphological variation would be the product of decrease in diversity through extinction selectivity. Finally, we found no correlation between the extinction risk of extant species and the deep time diversity decline, which suggests that the drivers of the current and the past Decline are not the same / O efeito de caracteres intrínsecos na dinâmica de diversificação foram extensamente investigados e diversos caracteres foram associados com aumentos na diversificação. Contudo, os possíveis efeitos negativos de um caractere sobre a diversificação de uma linhagem foram em grande parte ignorados. No presente trabalho integramos o registro fóssil com dados moleculares para estudar a dinâmica de diversificação de Placentalia, focando nas ordens em declínio de diversidade, e investigamos possíveis mecanismos responsáveis por gerar os padrões de diversificação encontrados. Mais especificamente nós: 1- determinamos quais das 21 ordens de Placentalia estão em declínio de diversidade (i.e., Declínio); 2- investigamos se o Declínio apresenta um sinal filogenético; 3- testamos a hipótese de que o tamanho do corpo está relacionado com o Declínio; 4- testamos a hipótese de que as ordens em Declínio possum menor disparidade morfológica; 5- investigamos se as ordens em Declínio, inferido a partir do registro fóssil, são as mesas com maior risco de extinção na atualidade. Nossas análises indicam que a maioria das ordens de mamíferos placentários apresentam um signal consistente com o Declínio e, embora o Declínio não esteja igualmente distribuído entre as superorderns de Placentalia, não há um signal filogenético significativo para as ordens em Declínio. Nossos resultados indicam uma correlação positiva entre o Declínio e o tamanho corporal médio de cada ordem que está de acordo com estudos prévios sobre evolução do tamanho do corpo. Argumentamos que estes resultados sugerem uma dinâmica de evolução complexa: tamanho corpóreo grande seria um atrator evolutivo que gera a tendência das linhagens aumentarem de tamanho, todavia, o aumento do tamanho do corpo seria contrabalançado pela maior susceptibilidade ao Declínio. Outrossim, encontramos uma correlação negativa entre o Declínio e a variação morfológica. Argumentamos que essa correlação poderia indicar dois possíveis cenários: (i) a baixa variação morfológica seria responsável pela redução no número de linhagens e tornaria as ordens mais susceptíveis ao declínio de diversidade; (ii) a baixa variação morfológica teria sido gerada pela diminuição da diversidade. Por último, o risco de extinção das espécies atuais não está correlacionado com o Declínio, o que sugere que os mecanismos responsáveis pelo Declínio no passado e no presente não são os mesmos.

No description available.

Body size is one of the most fundamental quantifiable traits of living or fossil organisms, and understanding it in various temporal and spatial contexts can offer key insights into the process of evolution. This volume examines body size of eukaryotes and its correlates in various temporal and spatial contexts in three distinct studies. The first study investigates the relationship between parasitism and body size of modern bivalve hosts. Individuals of Protothaca staminea were extensively parasitized (86%) by two types of trace-producing parasites. The only significant relationship between parasitism and body size was that spionid mudblister infested clams from one environment were slightly, yet significantly, smaller than their non-infested counterparts. The most obvious pattern regarding body size was that clams from a lagoon were significantly larger than clams from a tidal creek. This size discrepancy could be related to environmental stress, durophagous predators, differing hydrodynamic conditions, or the comparison of differing cohorts. Even though there was no discernible impact of trematode parasitism on bivalve body size, their traces were abundant and easy to identify. Investigators of body size in the fossil record should be aware of these organisms and their possible ramifications for body size studies. The second study, using Quaternary terrestrial gastropods from the Canary Islands, tests the hypothesis of limiting similarity, the idea that two closely related species will alter their size/morphology in order to minimize competition. By integrating amino acid geochronology, stable isotope estimates, and morphometric techniques I was able to more adequately test whether limiting similarity is an evolutionary process or a transient ecological phenomenon. The first prediction of limiting similarity, character displacement, was confirmed. The second prediction of limiting similarity, character release, was not confirmed. It appears that changing climate at the end of the Pleistocene may be responsible for the body size trends, but intraspecific competition likely played a secondary role in the evolution of body size of Theba. The third study addressed the history of body size and morphological disparity of the first 1.3 billion years of acritarch history. The results reject the idea that acritarch body size increased monotonically through the Proterozoic; in fact they displayed non-directional fluctuation. Acritarch body size decreased significantly following the first appearance of Ediacara organisms and gradually rose during the Cambrian. Morphological disparity increased a half billion years before the first taxonomic radiation. Morphological disparity decreased significantly during the snowball earth events and upon the first appearance of Ediacaran organisms suggesting multiple events of selective extinction in the Proterozoic biosphere. Disparity then increased in step with the diversification of acritarch and metazoans through the Cambrian suggesting ecological links between the two groups. Ecological processes, whether extrinsic abiotic processes or biotic interactions, influence the body size and evolution of organisms at wide range of spatial and temporal scales. / Ph. D.