Song variation and habitat structure in the Golden Bowerbird
F. J. Kroon A , B and D. A. Westcott A
A CSIRO Sustainable Ecosystems and Rainforest CRC, Tropical Forest
Research Centre, PO Box 780, Atherton, Qld 4883, Australia.
B Corresponding author. Email:
Abstract
Variation is a commonly reported feature of the signals of many animal
species. One hypothesis that seeks to explain this variation, the
Acoustic Adaptation Hypothesis, suggests that selection should shape the
structure of long-distance signals to maximise their transmission
through different habitats. One prediction of this hypothesis is that
signals will be designed such that within local habitats, local dialects
will experience less degradation during transmission than will foreign
dialects. We tested this prediction as part of a study of geographical
variation in the song of the Golden Bowerbird (Prionodura newtoniana).
Our aim was to evaluate the significance of local habitat structure in
selection for divergent song in this species. We played both local and
foreign dialects at four locations and re-recorded the song at 2 m and
50 m distance from the speaker. Song degraded differentially at the four
locations, indicating the existence of different acoustic environments.
However, songs that exhibited the least degradation did not originate
from the locations that induced the greatest degradation. Most
significantly, in local habitats, local dialects suffered similar levels
of degradation to foreign dialects. These results suggest that local
habitat structure has relatively little effect on the design of acoustic
signal in the Golden Bowerbird at the individual level. While efficiency
of transmission may influence signal design on evolutionary time-frames,
conflicting social and ecological pressures probably act to reduce its
importance in ecological time-frames.
Emu 106(4) 263-272
Submitted: 5 October 2005 Accepted: 7 September 2006 Published: 19
October 2006
Full text DOI: 10.1071/MU05052
Evolution of hearing in moths: the ears of Oenosandra boisduvalii
(Noctuoidea : Oenosandridae)
James H. Fullard
Department of Biology, University of Toronto at Mississauga, 3359
Mississauga Road North, Mississauga, Ontario, Canada L5L 1C6. Email:
Abstract
The ears of Oenosandra boisduvalii (Oenosandridae), as a representative
of this heretofore unstudied family of moths, were
electrophysiologically examined from specimens captured in South
Australia. Male and female moths possess ears with two auditory receptor
neurons that are similarly sensitive and tuned to the frequencies
emitted by sympatric bats, suggesting that both sexes face equal
predation pressures from aerially foraging bats. The two-celled ear of
this moth supports the independence of the Oenosandridae from its
previous affiliation with the Notodontidae, whose single auditory neuron
remains a unique character within the Noctuoidea. The general
insensitivity of its ear, however, resembles that of the notodontid moth
and is surprising considering the diversity of insectivorous bats that
forms its predation potential.
Australian Journal of Zoology 54(1) 51-56
Submitted: 4 November 2005 Accepted: 12 January 2006 Published: 23 March
2006
Full text DOI: 10.1071/ZO05066
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