ECOLOOY, SYSTEMATICS AND EVOLUTION OF AUSTRALLAN FROGS 77
of the New Guinea frogs, e.g. R a w , N y d h y 8 k 8 , S p h e q h r y n e and
Caphixalus in Queensland where they are restricted to the northern
rain forests. The Queensland rain foreats a m peculiarly dependent on
omgraphic effects for the high rainfall neoessary for their establishment. The northern rain foreats have many New Guinea a 5 i t i e s and
are separated by a wide belt of lov dry country from the southern rain
forests. The invasion of New Guinea forms appeers as a consequence of
the lower eea level of the Pleistocene which led to repeated connections
between Australia and New Guinea (Tate, 1962). $t the times of
lowered sea level, New Guinea forms apparently extended to the
southern limit of environment suitable for the establishment of rain
forest ecosys tems .
New Guinea forms of the families Ranidae and Microhylidae and the
hylid genus Nyctimystee, all otherwise exotic to Australia, reach the
region of the Atherton Tableland where they co-exist in diverse situations, with typical Australian forms such as Tazldactylue, khriodus
and Mixophyee which are also found again in the rain forest to the south
of the dry belt already referred to. It is conceivable that aridity has
caused the contraction of the most expanded range of the New Guinea
frog fauna but it seems unlikely that the fauna ever crossed the low
dry country to the south of the Atherton Tableland (especially well
developed between Townsville and Rockhampton) because, had they
reached the southern locality, some species would surely have persisted
and in this well-studied area none of the New Guinea frogs have been
found. Consequently it follows that forms which are common to both
sides of the dry belt (Mixophyee, Lechriodus, Taudaetylus) passed across
before it developed, while those extending only to the southern margin of
the northern forest must have arrived after the dry barrier had formed.
A plausible interpretation of the several sympatric species of the two
microhylids C o p h i d u s and Sphensphryne in North Queensland is that
they represent repeated Pleistocene invaaions from New Guinea at
times when this island waa connected to Australia across Torrea Strait.
That these species have not crossed to the south implies that the dry
belt pomisted from the time of their first presence in Australia to the
present, i.e. Pleistocene time. Conversely those genera which have
species each side of the barrier, e.g. Mixophyee, LechriaEus, Taudmtylus,
must, have been continuous at some time prior to the development of
the dry belt. If the dry belt is Pleistocene in age, then the former continuous distribution of Nixophyee, LechriaEua and Tazrdactylus must
represent a Tertiary phenomena (Pliocene being the latest possible time
of connection).
In the light of this interpretation it would seem that all the mountain
or forest dwelling species of leptodactylids represent Tertiary species
of the New Guinea frogs, e.g. R a w , N y d h y 8 k 8 , S p h e q h r y n e and
Caphixalus in Queensland where they are restricted to the northern
rain forests. The Queensland rain foreats a m peculiarly dependent on
omgraphic effects for the high rainfall neoessary for their establishment. The northern rain foreats have many New Guinea a 5 i t i e s and
are separated by a wide belt of lov dry country from the southern rain
forests. The invasion of New Guinea forms appeers as a consequence of
the lower eea level of the Pleistocene which led to repeated connections
between Australia and New Guinea (Tate, 1962). $t the times of
lowered sea level, New Guinea forms apparently extended to the
southern limit of environment suitable for the establishment of rain
forest ecosys tems .
New Guinea forms of the families Ranidae and Microhylidae and the
hylid genus Nyctimystee, all otherwise exotic to Australia, reach the
region of the Atherton Tableland where they co-exist in diverse situations, with typical Australian forms such as Tazldactylue, khriodus
and Mixophyee which are also found again in the rain forest to the south
of the dry belt already referred to. It is conceivable that aridity has
caused the contraction of the most expanded range of the New Guinea
frog fauna but it seems unlikely that the fauna ever crossed the low
dry country to the south of the Atherton Tableland (especially well
developed between Townsville and Rockhampton) because, had they
reached the southern locality, some species would surely have persisted
and in this well-studied area none of the New Guinea frogs have been
found. Consequently it follows that forms which are common to both
sides of the dry belt (Mixophyee, Lechriodus, Taudaetylus) passed across
before it developed, while those extending only to the southern margin of
the northern forest must have arrived after the dry barrier had formed.
A plausible interpretation of the several sympatric species of the two
microhylids C o p h i d u s and Sphensphryne in North Queensland is that
they represent repeated Pleistocene invaaions from New Guinea at
times when this island waa connected to Australia across Torrea Strait.
That these species have not crossed to the south implies that the dry
belt pomisted from the time of their first presence in Australia to the
present, i.e. Pleistocene time. Conversely those genera which have
species each side of the barrier, e.g. Mixophyee, LechriaEus, Taudmtylus,
must, have been continuous at some time prior to the development of
the dry belt. If the dry belt is Pleistocene in age, then the former continuous distribution of Nixophyee, LechriaEua and Tazrdactylus must
represent a Tertiary phenomena (Pliocene being the latest possible time
of connection).
In the light of this interpretation it would seem that all the mountain
or forest dwelling species of leptodactylids represent Tertiary species