TY  - THES
T1  - The evolution of complex courtship songs in the genus Stenobothrus Fischer, 1853 (Orthoptera, Caelifera, Gomphocerinae)
A1  - Berger,Dirk
Y1  - 2008/08/06
N2  - Gomphocerine grasshoppers produce complex songs by rubbing the hind legs against the fore wings. The songs produced by the males serve exclusively for intra-specific communication and are subject of a strong pressure of sexual selection. Acoustic communication plays an important role in pre-mating reproductive isolation between closely related grasshopper species and the species-specific songs are probably the most important reproductive isolation mechanism. The aim of this study was to understand how new and complex song pattern in grasshoppers evolve. I choose the genus Stenobothrus as study object, since different species of this genus produce songs that range from rather simple songs to highly complex song repertoires.

In the first part of the thesis the calling songs, courtship songs, song production and the courtship behaviour of 25 species form 65 European and Anatolian populations were described. In addition four Omocestus species were included because prior studies revealed that they have a common ancestor with some Stenobothrus-species. The distribution, acoustic differentiation between species and populations are illustrated and time periods in which modifications of the communication system might have evolved are discussed on the basis of biogeographic and geo-morphological information.

In the second part the characters of song and stridulatory leg movement patterns were coded in a numerical character matrix and analysed in combination with morphological data using parsimony algorithms. Especially the analyses of song and song production gave valuable information about species relationships, which could not yet been resolved by morphological investigations. The results of the phylogenetic reconstruction are discussed in comparison to present taxonomical work.

On the basis of the phylogenetic reconstruction the origin and genesis of complex communication signals are discussed. In the plesiomorphic stage calling and courtship songs consist of simple structured phrases and pauses only differing in duration. Highly complex courtship song repertoires evolved, if males combined different song elements and if visual elements were added during courtship. In lineage A (S. stigmaticus-group) a one legged post-phrase is added to a simple courtship song phrase, which resembles widely the calling song. The members of the species groups of S. nigromaculatus, S. fischeri, S. grammicus and S. eurasius reach higher levels of acoustic complexity. They produce multi-component courtship repertoires consisting of more than two song elements and optical elements, whereas the calling song remains simple, i.e. it consists of a single song element. Within the S. rubicundulus-group the courtship repertoire consists of a single long-lasting succession of different song elements. Within this group song elements were reduced in several species and phrase structure is lost in most species. In general, many courtship elements of multimodal courtship repertoires originate from plesiomorphic song pattern. Therefore, new acoustic signals that might isolate populations ethologically in rather short periods probably evolved by small modifications in leg coordination or accentuation. Subsequent questions about the function of single courtship components are discussed on the basis of their structure, derivation and topography within the complex courtship arrangement.
KW  - Evolution
KW  - Phylogenie
KW  - Heuschrecken
KW  - Bioakustik
KW  - Biogeographie
CY  - Erlangen
PB  - Universitätsbibliothek der Universität Erlangen-Nürnberg
AD  - Universitätsstraße. 4, 91054 Erlangen
L2  - http://www.opus.ub.uni-erlangen.de/opus/volltexte/2008/1044
ER  -