Short-nosed bandicoots, Isoodon, have undergone marked
range contractions since European colonisation of Australia and are currently
divided into many subspecies, the validity of which is debated. Discriminant
function analysis of morphology and a phylogeny of
Isoodon based on mtDNA control region sequences indicate
a clear split between two of the three recognised species,
I. macrourus and
I. obesulus/auratus. However, while all previously
recognised taxa within the I. obesulus/auratus group
are morphologically distinct,I. auratus and
I. obesulus are not phylogenetically distinct for mtDNA.
The genetic divergence between I. obesulus and
I. auratus (2.6%) is similar to that found among
geographic isolates of the former (I. o. obesulus and
I. o. peninsulae: 2.7%). Further, the divergence
between geographically close populations of two different species
(I. o. obesulus from Western Australia and
I. a. barrowensis: 1.2%) is smaller than that
among subspecies within I. auratus
(I. a. barrowensisand I. auratus
from northern Western Australia: 1.7%). A newly discovered population
of Isoodon in the Lamb Range, far north Queensland,
sympatric with a population ofI. m. torosus, is shown to
represent a range extension of I. o. peninsulae (350
km). It seems plausible that what is currently considered as two species,
I. obesulus and I. auratus, was
once one continuous species now represented by isolated populations that have
diverged morphologically as a consequence of adaptation to the diverse
environments that occur throughout their range. The taxonomy of these
populations is discussed in relation to their morphological distinctiveness
and genetic similarity.
Phylogeographic population structure of great reed warblers: an analysis of mtDNA control region sequences
