Evolutionary relationships of the discoglossoid frogs - osteological evidence
The discoglossoid Frogs (Discoglossidae and Leiopelmatidae) are
generally considered to be the most primitive of the living frogs.
Previous authors have grouped them on the basis of common possession
of a limited number of primitive features of little phylogenetic significance,
leaving the question of intra-discoglossoid relationships uncertain.
The present study is a re-examination df the supraspecific relationships
in the superfamily using computer-aided cladistic analyses of a large set
of osteological data - specifically 95 characters (153 binary characters)
in 21 modern discoglossoid taxa. Where possible, characters are assigned
a polarity, principally using urodeles as the outgroup. Evolutionary
relationships are inferred from the congruence of cladograms generated
from compatibility and parsimony analyses of the data set.
In an introductory section, modern approaches to systematic analysis
and classification are reviewed and a justification for the chosen method
is provided. The concepts of natural taxa and natural classifications are
discussed, criteria for hypothesizing character polarities and accounts of
compatibility and parsimony analysis methods are given •
•A. remarkable degree of congruence' between the cladograms produced from
a Le Quesne compatibility analysis and a Wagner parsimony analysis is evident.
(a) The leiopelmatid genera Ascaphus and Leiopelma are a sister pair but
are probably only weakly related.
(b) The modern DiBcoglossidae is a monophyletic group in which Alytes
is sister to Bombina + Barbourula + Discoglossus.
(c)Discoglossus is sister to Bombina + Barbourula.
(d)Bombina and Barbourula are a sister pair.
(e)All the discoglossoid genera are monophyletic.
(f)Bombina comprises two species groups: small (B. bombina - B variegata
- B orientalis) and large species (B maxima and B microdeladigitora).
Comparisons are made with previous work and an overview hypothesis of
the historical zoogeography of the discoglossoid frogs is presented.