78
A. R. MAIN
which have persistad to the present. Those species whose speciation
can be attributed to the Pleistocene are restricted to (a) species which
extendeC their range when sea level fell, e.g. crossed from New Guinea
to Australia (Straughan and Main, 1966) or crossed between Australia
and Tasmania (Moore, 1954; Littlejohn and Martin, 1964); (b) forms
which croesed from eastern to western Australia when conditions were
moister than at present, i.e. during Pluvials of the Pleistocene (Main
et aZ., 1958; Littlejohn, 1961). Judging from the biology of the forms
involved it seems that the connections between Australia and New
Guinea, and Australia and Taamania, were very wet. On the other
hand the connections between eastern and western Australia were much
more diverse as can be appreciated by discussing the fauna of southwestern Australia.
I n the lower southern part of Western Australia there are 26 species
in 8 genera (Main, 1965a). When the 26 species are tabulated to show
affinities with eastern Australia (Table VII) a quite remarkable state of
affairs is revealed.
Three genera (Limnodynaetee, Metacrinia, Hyobatrachw) are represented by sing1e”species. The first of these (Limnodynaetee) is one of a
species pair and the other two are unrepresented in eeatern Australia.
Five genera (Hyla, Neobatrachw , Heleiqorus , Crinia, Peeudqhryne)
are reprmented by three or more species and in each 0888 there are one
or more species pairs between eastern and western Australia. The
genus H y b is a relatively simple case - Hyla m r e i in the west and
H y b aurea in the east are a species pair; H. cyclorhynchw is morphologically and reproductively distinct from H . w e i . Hyla adelaa&e
is unliko other members of the genus.
The lasge number of species in Neobatrachw, Heleiand Crinia
is quite unexpected in view of the complete absence, in southern
Western Australia, of physical barriera of any sort which might be
expected to isolate populations and so permit speciation. This observation forced consideration of a number of hypothema, the most plausible
of which envisaged Western Australia as a peninsula from which the
fauna of south-eastern Australia is now isolated by desert but into
which components of the south-eastern fauna could migrate when the
intervening country was less arid than it is now.
The hypothesis is as follows: in Western Australia, a Tertiary wetland adapted fauna persisted throughout the Pleistocene (Table VII).
Into this fauna, eastern elements were introduoed on three occasions
during the Pleistocene at times of wetter climate. At the time of the
most recent connection and during one of the earlier connections, the
climate was only wet enough for frogs from seasonally-arid environments to invade. However, during one of the periods of wetter climate,
A. R. MAIN
which have persistad to the present. Those species whose speciation
can be attributed to the Pleistocene are restricted to (a) species which
extendeC their range when sea level fell, e.g. crossed from New Guinea
to Australia (Straughan and Main, 1966) or crossed between Australia
and Tasmania (Moore, 1954; Littlejohn and Martin, 1964); (b) forms
which croesed from eastern to western Australia when conditions were
moister than at present, i.e. during Pluvials of the Pleistocene (Main
et aZ., 1958; Littlejohn, 1961). Judging from the biology of the forms
involved it seems that the connections between Australia and New
Guinea, and Australia and Taamania, were very wet. On the other
hand the connections between eastern and western Australia were much
more diverse as can be appreciated by discussing the fauna of southwestern Australia.
I n the lower southern part of Western Australia there are 26 species
in 8 genera (Main, 1965a). When the 26 species are tabulated to show
affinities with eastern Australia (Table VII) a quite remarkable state of
affairs is revealed.
Three genera (Limnodynaetee, Metacrinia, Hyobatrachw) are represented by sing1e”species. The first of these (Limnodynaetee) is one of a
species pair and the other two are unrepresented in eeatern Australia.
Five genera (Hyla, Neobatrachw , Heleiqorus , Crinia, Peeudqhryne)
are reprmented by three or more species and in each 0888 there are one
or more species pairs between eastern and western Australia. The
genus H y b is a relatively simple case - Hyla m r e i in the west and
H y b aurea in the east are a species pair; H. cyclorhynchw is morphologically and reproductively distinct from H . w e i . Hyla adelaa&e
is unliko other members of the genus.
The lasge number of species in Neobatrachw, Heleiand Crinia
is quite unexpected in view of the complete absence, in southern
Western Australia, of physical barriera of any sort which might be
expected to isolate populations and so permit speciation. This observation forced consideration of a number of hypothema, the most plausible
of which envisaged Western Australia as a peninsula from which the
fauna of south-eastern Australia is now isolated by desert but into
which components of the south-eastern fauna could migrate when the
intervening country was less arid than it is now.
The hypothesis is as follows: in Western Australia, a Tertiary wetland adapted fauna persisted throughout the Pleistocene (Table VII).
Into this fauna, eastern elements were introduoed on three occasions
during the Pleistocene at times of wetter climate. At the time of the
most recent connection and during one of the earlier connections, the
climate was only wet enough for frogs from seasonally-arid environments to invade. However, during one of the periods of wetter climate,