Hello Bioacoustics-L,
The following article appears in the latest Journal of Mammalogy.
Members of this list can download a copy at
http://www.uvm.edu/~bmitchel/Bioacoustics.html.
Armstrong, Kyle N., and Roger B. Coles. 2007. Echolocation call
frequency differences between geographic isolates of Rhinonicteris
aurantia (Chiriptera: Hipposideridae): Implications of nasal chamber
size. Journal of Mammalogy 88(1):94-104.
ABSTRACT:
Most previous studies considering intraspecific differences in bat
echolocation call frequency among geographic groups have related this to
morphological features not directly involved in producing the
characteristics of the emitted signal. We related a pattern of
intraspecific call differences to the size of nasal chambers (estimated
from radiographs of museum specimens), expecting chamber dimensions to
be functionally coupled with the sound source. Such a relationship is
potentially informative in the context of competing hypotheses that
account for call frequency differences. Allopatry has been a precursor
to differences in echolocation call frequency between isolated
populations of the Australian endemic orange leaf-nosed bat
(Rhinonicteris aurantia (Gray, 1845); Pilbara isolate: 120.99 +/- 1.91
kHz; compared with Kimberley region: 114.65 +/- 1.98 kHz and Northern
Territory: 114.62 +/- 2.10 kHz). Correlations with morphological
features not directly involved in signal production or modification were
either moderate (nose-leaf width) or absent (forearm length). Overall
nasal volume was shown to be relatively smaller in the Pilbara
population, which had higher average call frequency. This relationship
was expected given the suggested function of nasal chambers in impedance
matching. The finding is significant because nasal chamber size was the
only character observed to vary in a species that was otherwise
conserved morphologically, suggesting adaptation and not a simple
scaling relationship with body size that might be more indicative of
drift. We consider that the combination of patterns from echolocation
call frequency and associated morphological features, as well as neutral
DNA markers, provide adequate support for recognition of the separate
populations of R. aurantia for conservation, according to more recent
concepts that consider ecological as well as genetic characters when
allocating groups to evolutionarily significant units.
|