Therefore, the results point to Schmidtea as a low diversifying genus and to S. mediterranea as an old species compared to others in the same area, even within the Tricladida.
This seems to be the case here, where no hybrids are known among the older taxa in the "primitive genera" (Figs. 1, 3), and hybridization is restricted to the three most recently diversified groups: genus Eueides, the erato-sara-sapho group and the melpomene-cydno-silvaniform group within the genus Heliconius.
Such behavioural processes could also provide a mechanistic perspective for frequently-detected asymmetrical introgression patterns in the largely allopatrically diversifying Microtus genus and other rapidly speciating rodents.
Using fossil calibration in a coalescent framework we estimated that the genus diversified in the second half of the Miocene, coinciding with marine introgressions.
Host-plant associations are highly diversified in the genus Brachycaudus.
However, little is known about the process by which the genus diversified or the factors that drove its speciation.
Gene gain/loss analysis revealed a dynamic pattern of genome evolution characterized by an initial period of gene gain followed by a period of loss, as the major groups within the genus diversified.
First, although the genus diversified recently (4 5 Ma Mattheeetet al. 2004), over 30 different species are currently classified, which colonized the entire globe and are well adapted to contrasting environments (Alves and Hackländer 2008).
During their expansion into Asia in the late Miocene, the genus diversified into various species groups and species that have been defined by morphological, behavioral and molecular characters, and by their geographic distribution [ 2- 9].
Abundant fossils (15 fossil species) of this genus in Europe [ 42] suggested that the genus had diversified widely in this region adapting to wet swamps in the Late Cretaceous [ 66].
