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Evolution of the vascular system in lineages that contain lianas

Texto completo
Autor(es):
Marcelo Rodrigo Pace
Número total de Autores: 1
Tipo de documento: Tese de Doutorado
Imprenta: São Paulo.
Instituição: Universidade de São Paulo (USP). Instituto de Biociências
Data de defesa:
Membros da banca:
Veronica Angyalossy; Carmen Regina Marcati; Anselmo Nogueira; Jose Rubens Pirani; Neusa Tamaio
Orientador: Veronica Angyalossy
Resumo

The vascular system of lianas, especially the xylem, has been repeatedly been shown to be different, with lianas having a set of features shared among even distantly related lineages, such as the presence of cambial variants, wide and long vessels, more abundant axial parenchyma, frequently non−lignified, taller and wider rays, which are generally heterocellular. In spite of this amount of knowledge, few works have investigated the impact for the vascular system of the evolution of this habit within lineages whose ancestors are not lianas, but self-supporting plants. Therefore, in this dissertation we explored wood, phloem and overall stem−anatomy evolution in lineages that contain lianas and self−supporting plants, using well−supported phylogenies and detailed anatomical investigations. Within Bignoniaceae (Lamiales), we thoroughly investigated the wood anatomy, delimiting character states and mapping them onto the last phylogeny for the group, encountering that eco−physiological and habit transition were the main drivers of modifications in the wood anatomy in the family. Ring−porous and semi−ring porous woods and helical thickening was found in plants either growing in higher latitudes or with marked seasonal water regimes, and septate fibres correlated with scanty axial parenchyma, which are eco−physiological drivers. Evolution of lianas, in turn, drove an increase in vessel diameter, wide vessels accompanied by very narrow ones, presence of perforated ray cells, scanty axial parenchyma and cambial variants. Despite the great wood anatomical diversity within the family, major clades have quite predictive wood anatomy and 9 possible anatomical synapomorphies were raised in this work to clades previously delimitated exclusively by molecular characters. Within the tracheophytes, we investigated 26 phylogenetically controlled pairs of lianas and their self−supporting relatives within all major lineages of tracheophytes (except lycophytes), in order to seek characters evolving in correlation with the lianescent habit. We found that the sieve elements and sieve pores were always wider in the lianas, and that the rays were always taller. However, all the main characters of the phloem of the lianas remained conserved with that of their self−supporting relatives. This evidenced that although a more efficient photosynthetic conductive system evolved in the phloem of lianas, overall anatomy conserved a high phylogenetic signal. Within Malpighiaceae, lianas are abundant and many cambial variants are present. However, nothing was known regarding how many types of cambial variants there were in the family and how they were distributed. We were able to delimit 6 different types of cambial variants that evolved at least 8 times independently in the family, which ancestrally lacks a cambial variant. Many of these types share common stages of development and some variants that are anatomically very similar derive from different ontogenetic trajectories. Within the genera, the variants are conserved, and even between sister groups in the new and old world, evidencing that cambial variants may be a good indicator of relationships within the family. Overall, we conclude that lianas greatly impact the evolution of the vascular system in the lineages where they have evolved, and these modifications normally result in a more efficient water and photosynthates conduction system and an increased flexibility for climbing. (AU)

Processo FAPESP: 12/01099-8 - Ontogenia, filogenia e evolução do sistema vascular de lianas
Beneficiário:Marcelo Rodrigo Pace
Linha de fomento: Bolsas no Brasil - Doutorado