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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Adaptation and Constraint in the Plant Reproductive Phase

Bolmgren, Kjell January 2004 (has links)
Conservatism is a central theme of organismic evolution. Related species share characteristics due to their common ancestry. Some concern have been raised among evolutionary biologists, whether such conservatism is an expression of natural selection or of a constrained ability to adapt. This thesis explores adaptations and constraints within the plant reproductive phase, particularly in relation to the evolution of fleshy fruit types (berries, drupes, etc.) and the seasonal timing of flowering and fruiting. The different studies were arranged along a hierarchy of scale, with general data sets sampled among seed plants at the global scale, through more specific analyses of character evolution within the genus Rhamnus s.l. L. (Rhamnaceae), to descriptive and experimental field studies in a local population of Frangula alnus (Rhamnaceae). Apart from the field study, this thesis is mainly based on comparative methods explicitly incorporating phylogenetic relationships. The comparative study of Rhamnus s.l. species included the reconstruction of phylogenetic hypotheses based on DNA sequences. Among geographically overlapping sister clades, biotic pollination was not correlated with higher species richness when compared to wind pollinated plants. Among woody plants, clades characterized by fleshy fruit types were more species rich than their dry-fruited sister clades, suggesting that the fleshy fruit is a key innovation in woody habitats. Moreover, evolution of fleshy fruits was correlated with a change to more closed (darker) habitats. An independent contrast study within Rhamnus s.l. documented allometric relations between plant and fruit size. As a phylogenetic constraint, allometric effects must be considered weak or non-existent, though, as they did not prevail among different subclades within Rhamnus s.l. Fruit size was correlated with seed size and seed number in F. alnus. This thesis suggests that frugivore selection on fleshy fruit may be important by constraining the upper limits of fruit size, when a plant lineage is colonizing (darker) habitats where larger seed size is adaptive. Phenological correlations with fruit set, dispersal, and seed size in F. alnus, suggested that the evolution of reproductive phenology is constrained by trade-offs and partial interdependences between flowering, fruiting, dispersal, and recruitment phases. Phylogenetic constraints on the evolution of phenology were indicated by a lack of correlation between flowering time and seasonal length within Rhamnus cathartica and F. alnus, respectively. On the other hand, flowering time was correlated with seasonal length among Rhamnus s.l. species. Phenological differences between biotically and wind pollinated angiosperms also suggested adaptive change in reproductive phenology. / Äpplet faller inte långt från trädet. Men varför? Den biologiska mångfalden präglas i stor utsträckning av fylogenetiskt bevarade karaktärsdrag; närbesläktade arter är lika. Det pågår en diskussion bland evolutionsbiologer om i vilken utsträckning denna konservatism är ett resultat av naturlig selektion eller av en begränsad anpassningsförmåga. Denna avhandling diskuterar begreppet evolutionära begränsningar i relation till den reproduktiva fasen hos växter. I fokus ligger särskilt evolutionen av bärliknande (endozoochora) frukter respektive evolutionen av säsongsmässiga mönster (fenologi) för blomning och fruktsättning. Avhandlingen är hierarkiskt organiserad så att olika delstudier gjordes på olika skalnivåer: fenologi- och fruktevolution analyserades för fröväxter respektive gömfröiga växter; inom brakvedssläktena Rhamnus och Frangula (Rhamnaceae); samt för en lokal population av brakved (Frangula alnus). Populationsstudien baserades på såväl experimentella som deskriptiva data, medan övriga studier i huvudsak genomfördes med fylogenetisk komparativ metodik baserade på litteraturdata. Som en del av de komparativa studierna rekonstruerades fylogenetiska hypoteser för Rhamnus s.l. utifrån DNA-sekvenser (ITS, trnL-F), vilka gav stöd för att Frangula och Rhamnus är monofyletiska systersläkten. I en biogeografiskt kontrollerad fylogenetisk kontrastanalys upptäcktes inga skillnader i artrikedom mellan djur- och vindpollinerade växter. Bärliknande frukter verkar dock vara en betydelsefull karaktär (key innovation) i skogsmiljöer. För det första var fylogenetiska klader med bärliknande frukter mer artrika än systerklader med torra frukter. Dessutom var uppkomster av bärliknande frukt korrelerad till habitat med mer sluten vegetation. En fylogenetisk kontrastanalys av allometriska effekter visade på en positiv korrelation mellan växtindividens och fruktens storlek inom Rhamnus s.l. Upprepade analyser av dessa allometriska samband i olika monofyletiska subklader inom Rhamnus s.l. indikerar dock att allometri, såsom evolutionär begränsning, är svag. I populationsstudien av F. alnus var fruktstorlek positivt korrelerad till såväl fröantal som frövikt. En generell hypotes utifrån denna avhandling blir därför att frugivorer (de djur som äter bären och därmed sprider växtens frön) utövar ett starkt selektionstryck på växter som koloniserar ett habitat där fröstorlek är adaptivt, eftersom fruktstorlek påverkar frugivorernas (ssk. fåglars) sätt att hantera frukten. Reproduktiv fenologi var korrelerad till fruktsättning, fröspridning och fröstorlek hos F. alnus. Detta stödjer tanken att evolutionen av blomnings- och fruktsättningstider begränsas av avvägningar (trade-offs) och partiella beroenden mellan blomning-, fruktsättnings-, spridnings och rekryteringsfaserna. Inomartsvariation i blomningstid för F. alnus respektive getapel (Rhamnus cathartica) över en nordeuropeisk latitudinell transekt var inte korrelerad till säsongslängd, vilket antyder att utvecklingen av blomningstider är evolutionärt begränsad. Å andra sidan påvisades en sådan korrelation mellan blomningstid och säsongslängd i en mellanartsstudie inom Rhamnus s.l. Den fylogenetiska kontrastanalysen mellan djur- och vindpollinerade växter visade också på adaptiva skillnader i fenologi. Blomningstiderna inom en klad med biotiskt pollinerade arter var mer åtskilda än inom den vindpollinerade systerkladen, och den välkända iakttagelsen att vindpollinerade träd blommor tidigare på säsongen fick även stöd i ett fylogenetiskt komparativt perspektiv.
22

Ecologia geográfica e evolução de quelônios continentais / Geographical ecology and evolution of continental turtles

Rodrigues, João Fabrício Mota 03 May 2017 (has links)
Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2018-07-12T20:09:09Z No. of bitstreams: 2 Tese - João Fabrício Mota Rodrigues - 2017.pdf: 7026938 bytes, checksum: bb5eb1fc81f363b414aa3c9e80fb3429 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-07-13T10:42:29Z (GMT) No. of bitstreams: 2 Tese - João Fabrício Mota Rodrigues - 2017.pdf: 7026938 bytes, checksum: bb5eb1fc81f363b414aa3c9e80fb3429 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-07-13T10:42:30Z (GMT). No. of bitstreams: 2 Tese - João Fabrício Mota Rodrigues - 2017.pdf: 7026938 bytes, checksum: bb5eb1fc81f363b414aa3c9e80fb3429 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-05-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Understanding the processes that shape the current distribution patterns of species is one of the main goals of Ecology. In this thesis, we aimed to understand which factors are related to the distribution of the turtle diversity, a group of ectothermic animals whose diversity patterns are still little known, over time and space. To that end, we used distribution data from continental chelonian species, as well as life history information (habitat type and body size), and reconstructed a phylogenetic hypothesis for the group using molecular data. Turtles had a burst of lineage diversification during the irradiation of the Emydidae family, which is probably linked to an event of ecological opportunity. In addition, aquatic animals had higher rates of diversification than terrestrial animals, which helps to explain the current greater diversity of aquatic animals. Turtle richness distribution along the continents is mainly influenced by climatic variables such as temperature and precipitation, but the time when lineages first colonized the continental regions also influences this pattern. Beta diversity among chelonian communities is mainly influenced by the geographical distance between communities, and communities from different biogeographic realms are structured by different drivers. Finally, body size diversity of turtles is also influenced by temperature, and small animals are more common in cold areas. / Compreender os processos responsáveis pelos padrões de distribuição atuais das espécies é um dos principais objetivos da Ecologia. Nesta tese, visamos entender quais fatores estão relacionados à distribuição da diversidade de quelônios, grupo de animais ectotérmicos cujos padrões de diversidade ainda são pouco conhecidos, ao longo do tempo e do espaço. Para esse fim, usamos dados de mapas de distribuição das espécies de quelônios continentais, além de informações de história de vida (tipo de hábitat e tamanho corporal), e reconstruímos uma hipótese filogenética para o grupo usando dados moleculares. O grupo dos quelônios apresentou uma explosão de diversificação durante a irradiação da família Emydidae, o que está provavelmente ligado a um evento de oportunidade ecológica. Além disso, animais aquáticos apresentaram taxas de diversificação mais elevadas que os animais terrestres, o que ajuda a explicar a maior diversidade de animais aquáticos atuais. A distribuição da riqueza de quelônios ao longo dos continentes é influenciada principalmente por variáveis climáticas tais como temperatura e precipitação, porém o intervalo de tempo desde o qual as áreas foram colonizadas também influencia nesse padrão. A diversidade beta entre as comunidades de quelônios é influenciada principalmente pela distância geográfica entre as comunidades, e comunidades de diferentes de domínios biogeográficos são estruturadas de modo diferenciado. Finalmente, a diversidade de tamanhos corporais dos quelônios também é influenciada pela temperatura, de modo que animais menores são mais comuns em áreas mais frias.

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