ECOLOQY, SYSTEMATICS AND EVOLUTION OF AUSTRAUAN FROW 51
Althoagh the terntrial oviposition and embryonic development of
species of Heleiopmu and Peeduphryw is inappropriate for life in the
desert it is of advantage in the seaeonally arid, winter rainfall, situations characteristic of the geographic region in which they occur. The
advantage appears to have wveral ctepects: (a) the terrestrial embryonio
development can proceed before sufficient rain has fallen for ponds to
fill. Coneequently when the ponds do fill, the hatching larvae of them
species can feed and grow for some time without inter-species competition for food. (b) The larvae do not have to hatch as mon aa embryonic derelopment is completed but may delay hatching for many weeks
until the ponds fill and flood the eggs, so they are in a position to take
immediate advantage of water when it is abundant enough to form
ponds. (c) Pseudophyne species particularly, by spending the 6-8 days
of larval life out of water, are able to occupy ephemeral ponds which
would ody support aquatic development for about 40 days and such a
short period would be too brief if both embryonic and larval life were
aquatic.
Species such as Metacrinia nichollei, Crinia rmea and CrinM lutea
which lack aquatic stages during larval life occur in high rainfall arewhere water is not in short supply. However, these are found in eucalypt
foreat where fast flowing streams are common but ponds rare and
terntrial development is most readily interpreted as an adaptation of
a small frog whose larvae survive best if they avoid life in the running
water of streams.
"he most extreme case of terrestrial development is provided by
Crinia d/crZingtoni Loveridge in which the oomplete larval life is spent
in dorsal brood pouches of the male (Straughan and Main, 1900). The
advantage of this type of larval development is unclear. The frog occurs
in mossy cloud forest in mountain situations about 4000 ft in elevation.
All streams in these places are fast flowing torrents and the common
stream tadpoles are the large larvae of Mixophyes. The appearance of
such streams suggests that they would be unsuited for small tadpoles.
However, carrying larvae on the back of the male seems to be an
unnecessarily extreme response unless predators preclude termtrial
development.
D. WATER ECONOMY IN ADULTS
Frogs are unable to control the loss of water through the skin, yet
even when water is present in ponds many species do not remain after
egg 1ayir.g. Indeed all species of Heleioporus never enter water at all
after they have metamorphosed. Thus all epecies which occupy desert
habitate, and many which are found in aeamndy arid situations, are
in danger of death from desiccation. In an atmosphere with a relative
Althoagh the terntrial oviposition and embryonic development of
species of Heleiopmu and Peeduphryw is inappropriate for life in the
desert it is of advantage in the seaeonally arid, winter rainfall, situations characteristic of the geographic region in which they occur. The
advantage appears to have wveral ctepects: (a) the terrestrial embryonio
development can proceed before sufficient rain has fallen for ponds to
fill. Coneequently when the ponds do fill, the hatching larvae of them
species can feed and grow for some time without inter-species competition for food. (b) The larvae do not have to hatch as mon aa embryonic derelopment is completed but may delay hatching for many weeks
until the ponds fill and flood the eggs, so they are in a position to take
immediate advantage of water when it is abundant enough to form
ponds. (c) Pseudophyne species particularly, by spending the 6-8 days
of larval life out of water, are able to occupy ephemeral ponds which
would ody support aquatic development for about 40 days and such a
short period would be too brief if both embryonic and larval life were
aquatic.
Species such as Metacrinia nichollei, Crinia rmea and CrinM lutea
which lack aquatic stages during larval life occur in high rainfall arewhere water is not in short supply. However, these are found in eucalypt
foreat where fast flowing streams are common but ponds rare and
terntrial development is most readily interpreted as an adaptation of
a small frog whose larvae survive best if they avoid life in the running
water of streams.
"he most extreme case of terrestrial development is provided by
Crinia d/crZingtoni Loveridge in which the oomplete larval life is spent
in dorsal brood pouches of the male (Straughan and Main, 1900). The
advantage of this type of larval development is unclear. The frog occurs
in mossy cloud forest in mountain situations about 4000 ft in elevation.
All streams in these places are fast flowing torrents and the common
stream tadpoles are the large larvae of Mixophyes. The appearance of
such streams suggests that they would be unsuited for small tadpoles.
However, carrying larvae on the back of the male seems to be an
unnecessarily extreme response unless predators preclude termtrial
development.
D. WATER ECONOMY IN ADULTS
Frogs are unable to control the loss of water through the skin, yet
even when water is present in ponds many species do not remain after
egg 1ayir.g. Indeed all species of Heleioporus never enter water at all
after they have metamorphosed. Thus all epecies which occupy desert
habitate, and many which are found in aeamndy arid situations, are
in danger of death from desiccation. In an atmosphere with a relative