Call structure variability and field survival among bushcrickets exposed to phonotactic parasitoids

Allen, GR

Gr. Allen, Call structure variability and field survival among bushcrickets exposed to phonotactic parasitoids, ETHOLOGY, 106(5), 2000, pp. 409-423

48

INGLESE

Article

Animal Sciences","Neurosciences & Behavoir

ETHOLOGY

0179-1613 → ACNP

106

5

2000

409 - 423

ISI

0179-1613(200005)106:5<409:CSVAFS>2.0.ZU;2-B

Calling adult males of the univoltine bushcricket Sciarasaga quadrata are s ubject to significant mortality from the phonotactic parasitoid fly Homotri xa alleni. These flies kill their host within 14d and act as a constant 'fi lter' on the survival of male bushcrickets. In this study, I investigate bo th short-term and lifetime variability in male call structure and compare t he call properties of collections of males made over a 3-mo calling season to establish whether there are any significant differences in the call prop erties of males surviving the length of the calling season. Call frequency, chirp length, interchirp length, chirp rate, file teeth used to make a chi rp and duty cycle all showed good differentiation among males and significa nt repeatability: (1) within a calling bout (0.57-0.88), (2) between succes sive nights (0.27-0.83), and (3) over a male's lifetime (0.15-0.43). Freque ncy and to a lesser extent chirp length showed low variability within and a mong males whereas interchirp length was the most flexible and dynamic call property. As males aged, chirp length, which is produced by one wing closu re, and its correlate, teeth per chirp, significantly increased and chirp r ate significantly decreased. Over the calling season chirp length and teeth per chirp showed strong directional shifts. Shorter chirp males were lost from the calling population, indicating that flies may use chirp length as a cue in host location. The implications of this result are discussed in re lation to the reproductive fitness of male S. quadrata and within the conte xt of host location and sensory bias in phontotactic parasitoids.