Sexo, herbívoros e a evolução das flores
Parasites represent a strong evolutionary force driving the evolution and maintenance of sex in different organisms. Species with a higher range of parasites should invest more in outcrossing and show more developed secondary sexual characters. In the last decades, many studies found support for...
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| Formato: | doctoralThesis |
| Idioma: | por |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/26231 |
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| Resumo: | Parasites represent a strong evolutionary force driving the evolution and maintenance of sex in
different organisms. Species with a higher range of parasites should invest more in outcrossing and
show more developed secondary sexual characters. In the last decades, many studies found support
for this theory in different groups of animals. Nonetheless, a more general test of this theory to
plants still poorly explored. Angiosperms show the most diverse range of reproductive strategies
among organisms, representing an interesting model for the study of evolutionary forces shaping
reproductive strategies. Sexual reproduction in angiosperms happens in flowers which can be
divided into four basic components: androecium (male function); gynoecium (female function);
corolla (pollinators attraction) and calyx (ovary defense). Surprisingly, comparative studies
evaluating resource partition between these flower components remain overlooked. The study of
flower allometry at a global scale offers great potential to unveil new macro-evolutionary patterns
in plant sex strategy. This thesis is organized in four chapters that investigate patterns of sex
allocation in angiosperms and the role of herbivores in the evolution of flower sexual strategies. In
the first chapter, flower biomass data was collected across four continents (South America, North
America, Europe and Oceania) to test the existence of a general allometric pattern in flower sex
allocation of angiosperms. It was shown that resource allocation to flowers follows a general
allometric rule in which species with large flowers invest more in the male and petals components.
In the second chapter, I tested the hypothesis that a higher pressure of herbivores at the
evolutionary scale favors the evolution of reproductive strategies with higher investment in
outcrossing. These results provide strong evidence that the parasite-mediated sex evolution theory
(“Red Queen Hypothesis”) also applies to the plant kingdom. In the third chapter, It was
estimated the stoichiometric cost of flowers and leaves for 56 Angiosperm species from the
european flora. Its demonstrated that flowers are costly structures, representing a honest signal of
quality in the competition for pollinators (“Zahavi’s handicap”). Flowers are phosphorus-rich
organs and have a distinct stoichiometric signature showing much higher P:C and P:N ratios than
leaves. In the fourth chapter, I present the sensiPhy software which was developed (R package) to
perform sensitivity analyses considering multiple types of uncertainties in phylogenetic comparative
methods (phylogenetic, intra-specific and sampling uncertainty). With this thesis, I expect to
contribute with a more solid and general understanding of the factors driving the evolution of plant
sexual strategies at the macroevolutionary scale. |
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