"No, the fact that Pseudacris (including crucifer and regilla) form their own exclusive branch in all analyses (including Maxson and Wilson's), something that you acknowledge above, means that they share a more recent common ancestor exclusive of the one uniting all Hyla."



You would be correct if new species evolve at regular and short intervals. It is true that the node from which Hyla regilla, Hyla crucifer and Pseudacris branch off does not coincide exactly with the node from which Hyla arborea and Hyla eximia/chrysoscelis branched off. The immunological distance between those two nodes, however, is short. In 1974, Maxson and Wilson thought that Hyla eximia is only convergently similar to Hyla regilla morphologically because these two are separated by a surprising amount of immunological distance. In 1975 they probably rethought their hypothesis after they found that these two also shared a common ancestor with Hyla arborea, which is also similar morphologically to Hyla regilla and Hyla eximia. Hyla regilla, Hyla arborea and Hyla eximia are almost certainly morphologically conservative species that resemble each other because they have changed little and because they resemble their common ancestor. That common ancestor, which is also the ancestor of all holarctic hylids is most likely Hyla eximia, given its morphology and biogeography. Evolutionary stasis, which is probable in a morphologically conservative lineage, may have kept Hyla eximia unchanged even though numerous species have budded off of it. The species from which all holarctic hylids evolved is probably the same species as the one from which Hyla regilla, Hyla crucifer and Pseudacris evolved.



"Look at taxon sampling in Moriarty and Canatella relative to Maxson and Wilson. That is the reason you "H. crucifer" is sister to Pseudacris, not nested within."



I disagree. It is instead the choice of outgroup species which accounts for the anomalies one sees in Moriarty and Canatella's ML and MP trees. Both trees surprisingly show H. chrysoscelis more basal to Hyla eximia. As I pointed out above, Hyla eximia is most likely the ancestor of all holarctic hylids (judging from biogeography and morphology) and it is also morphologically conservative (as I explained above). If Hyla chrysoscelis is more basal, that means Hyl eximia probably evolved from a Hyla chrysoscelis morphotype. But since there are several species that are morphologically similar to Hyla eximia in Mexico (namely members of the Hyla eximia group as defined by Duellman), Moriarty and Cannatella's tree would require these species (which are morphologically close to Hyla eximia) to have evolved convergently to resemble Hyla eximia, or it would require Hyla chrysoscelis to have evolved from an ancestor that looked like Hyla eximia, and then Hyla eximia would evolve by undergoing a reversal from a H. chrysoscelis-like ancestor. In other words, in order to embrace Moriarty and Cannatella's tree topology, one has to invoke multiple unparsimonious scenarios, not only in the evolution of toe pads but also in the evolution of the Hyla eximia morphotype. Personally I would not invoke such a large number of ad hoc hypotheses in order to embrace Moriarty and Cannatella's phylogeny, nor would I embrace their classification since it is both heterogeneous and probably unstable due to the possibility that the inclusion of Hyla arborea in their "Pseudacris" is unavoidable.

[ Reply To This Message ] [ Subscribe to this Thread ] [ Show Entire Thread ]