Neural evolution in the bat-free habitat of Tahiti: partial regression in an anti-predator auditory system |
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Authors: | Fullard James H Ratcliffe John M ter Hofstede Hannah |
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Affiliation: | Department of Biology, University of Toronto at Mississauga, Mississauga, Ontario, Canada L5L 1C6. jfullard@utm.utoronto.ca |
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Abstract: | Noctuid moths endemic to the mountains of Tahiti have evolved in an environment without bats and these insects have lost a defensive behaviour against these predators, the acoustic startle response (ASR). The ASR in noctuid moths is presumed to be activated by a single auditory receptor neuron (A2 cell) and we report that while this cell still exists in endemic species and possesses similar sensitivity thresholds compared to the A2 cell of recently introduced species, it exhibits reduced firing activity to ASR-evoking sounds. This partial neural regression suggests that the evolutionary disappearance of the ASR in these insects is incomplete and that sensoribehavioural integration decays gradually following the removal of stabilizing selective forces. |
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Keywords: | moths evolution neuroethology regression auditory ecology predator release |
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