Two matched filters and the evolution of mating signals in four species of cricket

Kostarakos Konstantinos, Hennig, Römer, Römer Heiner

Description

Male field crickets produce pure-tone calling songs to attract females. Receivers are expected to have evolved a "matched filter" in the form of a tuned sensitivity for this frequency. In addition, the peripheral directionality of field crickets is sharply tuned as a result of a pressure difference receiver. We studied both forms of tuning in the same individuals of four species of cricket, where Gryllus bimaculatus and G. campestris are largely allopatric, whereas Teleogryllus oceanicus and T. commodus occur also sympatrically. Results The sharpness of the sensitivity filter is highest for T. commodus , which also exhibits low interindividual variability. Individual receivers may also vary strongly in the best frequency for directional hearing. In G. campestris , such best frequencies occur even at frequencies outside the range of carrier frequencies of males. Contrary to the predictions from the "matched filter hypothesis", in three of the four species the frequency optima of the two involved filters are not matched to each other, and the mismatch can amount to 1.2 kHz. The mean carrier frequency of the male population is between the frequency optima of both filters in three species. Only in T. commodus we found a match between both filters and the male carrier frequency. Conclusion Our results show that a mismatch between the sensitivity and directionality tuning is not uncommon in crickets, and an observed match ( T. commodus ) appears to be the exception rather than the rule. The data suggests that independent variation of both filters is possible. During evolution each sensory task may have been driven by independent constraints, and may have evolved towards its own respective optimum.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2009
• Nombre de lectures: 4
• Langue: English

Extrait

Frontiers in Zoology

Research Two matched filters and the evolution of mating signals in four species of cricket 1 2 1 Konstantinos Kostarakos , Matthias R Hennig and Heiner Römer*

BioMedCentral

Open Access

1 2 Address: Zoology, KarlFranzensUniversity, 8010 Graz, Austria and Department of Biology, HumboldtUniversität zu Berlin, 10115 Berlin, Germany Email: Konstantinos Kostarakos  [e-mail]; Matthias R Hennig  [e-mail]berlin.de; Heiner Römer*  heinrich.roemer@unigraz.at * Corresponding author

Published: 28 September 2009 Received: 30 July 2009 Accepted: 28 September 2009 Frontiers in Zoology2009,6:22 doi:10.1186/17429994622 This article is available from: http://www.frontiersinzoology.com/content/6/1/22 © 2009 Kostarakos et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract Background:Male field crickets produce puretone calling songs to attract females. Receivers are expected to have evolved a "matched filter" in the form of a tuned sensitivity for this frequency. In addition, the peripheral directionality of field crickets is sharply tuned as a result of a pressure difference receiver. We studied both forms of tuning in the same individuals of four species of cricket, whereGryllus bimaculatusandG. campestrisare largely allopatric, whereasTeleogryllus oceanicusandT. commodusoccur also sympatrically.

Results:The sharpness of the sensitivity filter is highest forT. commodus, which also exhibits low interindividual variability. Individual receivers may also vary strongly in the best frequency for directional hearing. InG. campestris, such best frequencies occur even at frequencies outside the range of carrier frequencies of males. Contrary to the predictions from the "matched filter hypothesis", in three of the four species the frequency optima of the two involved filters are not matched to each other, and the mismatch can amount to 1.2 kHz. The mean carrier frequency of the male population is between the frequency optima of both filters in three species. Only inT. commoduswe found a match between both filters and the male carrier frequency.

Conclusion:Our results show that a mismatch between the sensitivity and directionality tuning is not uncommon in crickets, and an observed match (T. commodus) appears to be the exception rather than the rule. The data suggests that independent variation of both filters is possible. During evolution each sensory task may have been driven by independent constraints, and may have evolved towards its own respective optimum.

Background Sensory pathways serve to extract information from the physical environment. On this basis an organism may choose an appropriate behavioural action that ultimately maximizes its fitness. Sensory systems and their underly ing neuronal processing capacity are therefore  in a gen eral sense  tuned to the relevant physical environment [1]

and may be aided by rather peripheral 'matched filters' that relax the nervous system from computational strain [2]. If matched filters and sensory pathways are involved in signal processing in communication systems, a close and specific match between the physical properties of the sender's signal and the receiver's filter are expected, because it enables reproductive isolation by facilitating

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