Diversidade de frutos em Myrtaceae: hipóteses ecológicas e evolutivas para o sucesso desta família neotrópico

Abstract

Fleshy fruits are the link between fauna and flora. They serve as a resource for fauna, while at the same time favouring the colonisation of plant species. Selective pressures in plant-animal interactions can shape fruit and seed characters and have the potential to explain current species diversity. In this dissertation, I used Myrtaceae, one of the most species-rich families in the tropics, as a model to test the effect of plant and fruit characters on the family's speciation rates. Thus, in chapter one I expanded the morphological database of Myrtaceae fruits and seeds, resulting in data for 956 species and adding new variables on display, plant height and life habit. Myrtaceae showed wide morphological variation, with large fruits with several small seeds or small fruits with few small seeds. Black colouring is present in half of the species in the database, occurring in 56.8%, followed by yellow (17.4%) and red (17.4%). Orange, green, brown and grey are less common in the fruits of the Myrteae tribe (8.4%). In chapter two, using the data from chapter one, I tested the relationship between fruit and seed size, seed number, fruit colour and plant height and quantified the influence of these characters on speciation rates in Neotropical Myrtaceae. Only fruit diameter was able to predict speciation rates, i.e. small fruit sizes have high speciation rates. Since fruit diameter is a limiting factor for dispersal, it is expected that this morphology will be selected over time, but contrary to expectations, the other traits are not associated with speciation in the Myrteae tribe, indicating that other abiotic and biotic factors shape current species diversity. In Chapter 3, I tested the visual-attractiveness hypothesis, which predicts that fruits at an intermediate stage of ripeness and with conspicuous colouring increase the attractiveness of the canopy and have an earlier germination capacity. The multicoloured display proved to be more attractive when removed than the unicoloured display, but germination was independent of the type of display of the species, i.e. the seeds were able to germinate at all stages of ripeness. The results found contribute to advancing the understanding of fruit and seed morphological patterns linked to dispersal and their role in the diversity of the Myrtaceae family.