Phylogenetic studies
Cladistic analyses of notothenioids have been undertaken
by Iwami24and Eastmans. A convincing sistergroup for
notothenioids has yet to be identified among Perciformes
(see discussion in Ref. 8) and consequently the Bovichtidae
have been used as a functional outgroup. The presently accepted
cladogram is shown
in Fig. 2, and this has been
used as the best working hypothesis
for the evolutionary
relationships among notothenioid
fishes. Karyotype
analysis has been confined
largely to the Nototheniidae
and Channichthyidae, and
largely supports the proposed
relationships of nototheniid
subfamilieszs.
An area cladogram may
be produced by mapping
broad geographic distributions
onto the terminal taxa
produced by cladistic analysis
(Fig. 2). This procedure
is a valuable broad-brush
approach to understanding
patterns of evolutionary dispersal
and vicariance, and
invokes the fewest assumptionss.
The area cladogram
suggests that the ancestral
notothenioid stock, probably
located in the Weddellian
province of Gondwana, split
initially into two clades: (1) the
bovichtids and (2) all other
notothenioids. More-detailed
analysis of area cladograms
for higher taxonomic levels
suggests that most of the
diversification of Antarctic