In just the last fifteen years, field
surveys have led to the discovery
of five Phyllurus geckos –
P. ossa, P. isis, P. chamionae,
P. amnicola, and P. gulbaru – all
of which, incidentally, have a
highly-localized distribution. In
2008, two new Saltuarius species
were described (S. moritzi and
S. katae). And in 2013, another
new species of Saltuarius was
described. Hailing from the
Melville Range on Cape Melville,
a rainforest outlier on Cape York
Peninsula, and dubbed Saltuarius
eximius, this spectacular new
leaf-tailed gecko is highly distinct
from its congeners in multiple
aspects of its morphology.
Compared with other Saltuarius,
S. eximius has relatively longer
limbs, a longer, more slender and
narrower body, a narrower neck,
and a relatively small head.
Unlike all other species, its large
eyes (large even for geckos)
have grey irises rather than being
patterned. It has a large tail with
a short, attenuated tip. Saltuarius
eximius is highly localized to
boulder habitat in upland rainfor-
est, and the species’ elongate
body and large eyes are likely
adaptations to this niche. Being
another narrow-range endemic, it
is also of high conservation
concern.
Ironically, although climate
change was originally an
instrument in the isolation and
diversification of our leaf-tailed
geckos, it also looms as a key
threatening process. As indicated
by the disjunct distributions,
together with phylogeographic
evidence, it is clear that leaf-
tailed geckos are strongly associ-
ated with rainforest habitat, and
that their powers of dispersal are
limited. Under climate change,
rainforest biomes are projected to
change in location. Because
geckos are limited in their mobil-
ity, they may be unable to
migrate to keep pace with the
changing distribution of their
habitat. The extent of rainforest
habitat is also predicted to
change, with a 1 o C rise in
temperature estimated to result in
a 50% decline in the amount of
highland rainforest, such as that
which O. occultus, S. cornutus
and S. swaini inhabit. In this way,
livestock agriculture represents a
potential double whammy for leaf
-tailed geckos: firstly through
habitat destruction for pasture;
and secondly by being one of the
greatest contributing factors to
greenhouse gas emissions that
are causing global warming and
climate change.
The small, restricted populations
of leaf-tailed geckos also make
them more prone to extinction
through intrinsic genetic factors.
Indeed, genetic analysis has
found that some species, in
particular S. swaini, exhibit very
limited genetic variation between
localities. This may indicate that
the populations are inbred, which
can result in reduced survival and
reproduction through inbreeding
depression. Low levels of genetic
diversity also mean there is
limited genetic variation for
natural selection to act upon in
response to factors such as
climate change, meaning there is
limited potential for the species to
adapt as the environment
changes.
Leaf-tailed geckos are arguably
amongst Australia’s most impres-
sive herps, and have acquired
elaborate and eccentric niche
adaptations. But the geckos have
become intrinsically linked to their
patchwork of rainforest environs.
Being narrow-range endemics, it
is crucial that their habitat is
preserved and enhanced if we
are to save these wonders of
evolution.
Saltuarius cornutus.
Image by Michael Cermak.