Hybridisierung und Verwandtschaftsgrade innerhalb der Anatidae - eine systematische und evolutionstheoretische Betrachtung

From literature, 418 speciesoverlapping hybrids are summarized for the family of Anatidae, observed between 126 species of the family which covers 149 species. 52 % of the hybrids overlap different genera, 48 % are reported to occur between species of the same genera. 31 % of the hybrids connect different tribes and 20 % of the hybrids are found to be fertile. Some hybrids show morphological and ethological features which are not found in the parents. These features could be observed in other species of the family. Some reports are summarized, describing hybrids which are very similar to a third species. Ethological and morphological peculiarities occuring in quite different species of the Anatidae are placed together. On the other hand, so-called aberrant types can not be placed in a distinct tribe due to their features of different tribes. These findings, well documented in literature, are discussed with respect to a common ancestor of the Anatidae. According to the hypothesis favoured in this paper, the common ancestor can not be described as a primitive form. It seems opportune to consider this common ancestor as an unspecialized duck, the features of which are developed in the ducks observed today in different ways. It is likely that the formation of the 149 species of the Anatidae from this ancestor is explainable by already known microevolutionary processes. The data discussed in this communication show that the Anatidae form a tight closed group, genetically and morphologically strictly separated from other birds. It is suggested to take into consideration these facts of the case in the systematic treatment of the family by describing the Anatidae as a basic type.