Problemas taxonômicos da família Threskiornithidae: filogenia molecular e o caso de Eudocimus
Malaver, Jorge Luis Ramirez
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The family Threskiornithidae includes 13 genera and 32 species, but the relationships among genera, species or subspecies have been little studied. This family is traditionally divided into two subfamilies: Plataleinae and Threskiornithinae. One of the more interesting taxonomical questions within this group is the case of the species Eudocimus ruber and Eudocimus albus. They are usually considered as separate species, but they show similar behavior and there are also records of hybridization in nature. This study aims to reconstruct the phylogenetic relationships within the family Threskiornithidae as well as assess the level of genetic differentiation between Eudocimus albus and E. rubber, using mitochondrial and nuclear gene sequences. DNA was extracted from blood and tissue samples from 13 species of Threskiornithidae (seven genera) and two outgroups. For the Eudocimus study were extracted 10 individuals of each species. We sequenced the 16S rRNA and the intron 7 of β- Fibrinogen for all species. For Eudocimus Cytochrome B, Cytochrome Oxidase I, intron 11 of Glyceraldehyde-3-Phosphate Desidrogenase, intron 4 of the Myelin Proteolipid Protein and intron 2 of Myoglobin were also sequenced. Sequences for other five species of the family were obtained from GenBank. Phylogenetic trees were constructed using Neighbor-Joining, Maximum Parsimony, Maximum Likelihood, Bayesian inference and Bayesian inference of species tree. Networks and genetic distances were determined for Eudocimus haplotypes. Several approaches for species delimitation using multilocus data were applied. All analyses strongly supported the family Threskiornithidae (18 species) as a monophyletic group. However, the current classification of two subfamilies was not supported by our data: Plataleinae formed a monophyletic group, but nested within Threskiornithinae (a paraphyletic group). Tests of monophyly rejected the hypothesis of monophyly of Threskiornithinae. The family Threskiornithidae also showed a division into two groups: one with only genera endemic to the American continent (Theristicus and Eudocimus) and another with the remaining species. Within the latter clade, species of genus Plegadis are observed in a basal position, while subfamily Plataleinae was grouped with the remaining species. This pattern of species distribution suggests an initial Gondwana division and subsequent colonization by species from the Old to the New World. The divergence within the family was estimated at 35-40 million years, which is before the separation between America and Antarctica. Mitochondrial genetic analysis showed Eudocimus species as two different lineages. Multilocus analysis based on nuclear genes revealed a strong signal of speciation despite the polyphyly found in three of the four markers.