Filogenia molecular, biogeografia e dinâmica populacional de anfípodos de água doce (Crustacea) da América do Sul

Abstract

Freshwater ecosystems are considered the most threatened environments on the planet. Several freshwater species are becoming extinct before being described and the situation is even worse for invertebrates, such as the amphipod crustaceans Hyalella. The existence of cryptic species of Hyalella difficult the development of studies about these animals, as well as the creation of conservation policies addressed to them. Studying the ecology and the molecular phylogeny of Hyalella will aid to understand its diversity and geographic distribution, in the delimitation of its species, in the evolutionary relationships within the genus and on the estimate of their actual threat situation. Thus, this thesis was performed with the aim of know the molecular phylogeny, the biogeography and some population aspects of Hyalella in South America. The first chapter presents a literature revision about the topic studied, as well as the aims and hypothesis of the author. The second chapter studied the molecular phylogeny of the genus and its biogeographic history in South America. For this, one nuclear gene (H3) and two mitochondrial (16S and 12S) were partially sequenced and the relationships of the species were elucidated by Maximum Likelihood and Bayesian Inference analyzes. An impressive number of 20 new species was found, as well as the existence of a species complex. The subgenus of Hyalella did not form a monophyletic group and the genus has a origin probable in Eocene, with a peak of diversification in Miocene. The third chapter presents the study of the population aspects of four species of Hyalella in Brazil, from different latitudes and biomes. Populations were sampled in two seasons of 2012. In general, the reproduction of the species closer to the tropics was continuous throughout the year and in species from high latitudes the reproduction was seasonal. Body size of individuals in high latitudes is larger than individuals of lower latitudes. Moreover, sexual maturity of the species closer to tropics is reached at smaller body sizes. The fecundity of the species is apparently more related to the female's body size than to the climate and latitude. This thesis is the first study that uses molecular techniques in order to understand the evolutionary relationships of Hyalella in South America and performs the comparison of population aspects of geographically distant species. Molecular phylogeny and ecological information of the genus obtained from this thesis will aid in the conservation of freshwater ecosystems in South America, as these organisms are endemic and bioindicators of water quality.