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Fluctuating asymmetry, call structure and the risk of attack from phonotactic parasitoids in the bushcricket Sciarasaga quadrata (Orthoptera: Tettigoniidae)

journal contribution
posted on 2023-05-16, 11:04 authored by Hunt, J, Geoff AllenGeoff Allen
The acoustically orienting parasitoid Homotrixa alleni (Diptera: Tachinidae) is a significant mortality factor of calling male Sciarasaga quadrata (Orthoptera: Tettigoniidae), with less than 10% of males escaping parasitism within the duration of the calling season. This study examined fluctuating asymmetry (FA) (small, random deviations from perfect symmetry) in five morphological traits in S. quadrata and its relation to the survival of calling males in the field. A significant relationship was demonstrated in only a single trait; across three consecutive field seasons and among each of the collections per season, parasitised males were shown to have significantly more asymmetric hind tibia than unparasitised males. Since the morphological development of males is complete prior to parasitoid attack, this relationship is not caused by the activities of the parasitoid. Further experimentation revealed that there was no relationship between the level of FA in the hind tibia and the success of parasitism, with males artificially parasitised in the laboratory showing no difference in FA from those where parasitism was unsuccessful. Instead, FA was shown to be negatively related to chirp length, an aspect of call structure that significantly affects the survival of calling males under parasitism risk in the field. We explore the possible reasons why more asymmetric males produce calls of shorter chirp length and hypothesise that the difference in hind tibia asymmetry seen between parasitised and unparasitised males in the field is related to host location in H. alleni rather than the inability of S. quadrata to defend itself against parasitoid attack.

History

Publication title

Oecologia

Volume

116

Pagination

356-364

ISSN

0029-8549

Department/School

Tasmanian Institute of Agriculture (TIA)

Publisher

Springer-Verlag

Place of publication

175 Fifth Ave, New York, USA, Ny, 10010

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the environmental sciences

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