Evolução de estratégias reprodutivas em melastomataceae

Abstract

In the plant reproduction cycle, there are two transport events in which vectors participate: pollination, when pollen grains dislocate between anthers and stigmas, and offspring dispersal when whole fruits or seeds are removed from their origin. Therefore, reproductive traits such as floral size and color, as well as the fruit constitution can evolve correlatedly, because they affect the attractiveness to vectors. Hence, this establishes different strategies, resulting from the attendance of one of these trends - a trade-off situation. We chose as a model the Melastomataceae family, one of the most diverse lineages among the angiosperms, that has both species with small and white flowers and species with large and colorful flowers, wherein clades distinguishable by the presence of fleshy or dry fruits, in Miconieae and Melastomateae, in that order. In this work, we aim to comprehend how the floral traits and type of fruit evolved, and how the evolution of Melastomataceae is correlated through comparative phylogenetic methods. It is expected that the evolution of large and colorful flowers is linked to dry fruits, whereas small and white flowers are associated with fleshy fruits. We have used data mining to obtain values for these reproductive attributes from papers and updated a pre-existing database. From these data, a reconstruction of the evolutionary history of flower size and color was made for Melastomataceae. Different petal size evolutionary scenarios, combined with the evolutionary history of color and fruit type in different evolutionary regimes were constructed, to investigate the correlation between the attributes. In the evolution of Melastomataceae, we infer that floral size is a labile trait, with the frequent increase, decrease, and reversals in its phylogeny, where petal size varies up to 2 orders of magnitude. We estimate that most flower color transitions occurred from white to colored. The best scenarios of correlated evolution were the one that ties the evolution of flower size to flower color and fruit type, followed by the other that considers only flower color is correlated to flower size, which suggests color as a strongly correlated attribute. to flower size. The optimal size estimated for flowers was greater for those colored with dry fruits, and the smallest for white flowers and fleshy fruits. The lability and correlated evolution between flower size and color and fruit type support the hypothesis of evolution of reproductive strategies in Melastomataceae: species with large and colorful flowers promote plant movement in the gametophytic phase, develop into dried fruits with local dispersion; and species with white and tiny flowers evolved correlated with fleshy fruits, favoring movement of the sporophyte. As expected, in Melastomataceae, there are either plants that invest more in attracting and rewarding pollinators or plants that invest more in attracting and rewarding dispersers.