Zugl.: Wuppertal, Univ., Diss., 2005

Universiẗat, Diss., 1986--Hannover.

Zugl.: Zürich, Univ., Diss., 2004

Konstanz, Univ., Diss., 2002.

Zugl.: Wuppertal, Univ., Diss., 2005

Univ., Diplomarbeit, 2006--Frankfurt (Main)

Natural populations exhibit a non-random mating behavior and it is assumed that mate preferences causing the non-random mating behavior play a role in sympatric speciation. In my thesis, I have proposed a new model of a mate preference that is based on ecological performance and I have named it fitness-based mating. Individuals that express this mate preference choose primarily fit partners. Fitness-based mating is modelled for haploid, diallelic populations. Individuals are distributed across two niches, and genomes are simplified to two loci. The first locus is subject to natural selection, and the second-locus genotype gives the strength of the mate preference. The population is separated into females and males, among which only females exhibit the mate preference. Ecological selection acts on both sexes alike. With the model I have investigated how female choosiness based on direct advantages offered by their partners can cause and maintain a polymorphic population. Fitness-based mating is an evolutionary successful mating strategy. It spreads in a population due to its amplifying effect on the reproductive success and on the attractiveness of its carriers. A polymorphism arises naturally in the model. The emergence of a stable polymorphism of traits underlying ecological selection is of special interest, because a polymorphism can be a precursor of speciation.

Natural populations exhibit a non-random mating behavior and it is assumed that mate preferences causing the non-random mating behavior play a role in sympatric speciation. In my thesis, I have proposed a new model of a mate preference that is based on ecological performance and I have named it fitness-based mating. Individuals that express this mate preference choose primarily fit partners. Fitness-based mating is modelled for haploid, diallelic populations. Individuals are distributed across two niches, and genomes are simplified to two loci. The first locus is subject to natural selection, and the second-locus genotype gives the strength of the mate preference. The population is separated into females and males, among which only females exhibit the mate preference. Ecological selection acts on both sexes alike. With the model I have investigated how female choosiness based on direct advantages offered by their partners can cause and maintain a polymorphic population. Fitness-based mating is an evolutionary successful mating strategy. It spreads in a population due to its amplifying effect on the reproductive success and on the attractiveness of its carriers. A polymorphism arises naturally in the model. The emergence of a stable polymorphism of traits underlying ecological selection is of special interest, because a polymorphism can be a precursor of speciation.

Zugl.: Bremen, Universiẗat, Diss., 2003.

Die Heuschreckenart Chorthippus biguttulus (Orthoptera: Acrididae) ist ein Modellorganismus für akustische Kommunikation. Die Männchen stridulieren durch Reiben des Hinterbeins gegen eine Flügelvene. Diese Dieser Gesang bietet Weibchen Informationen über Artzugehörigkeit, Geschlecht und u.U. die Qualität. Rezeptive Weibchen antworten auf arteigene und attraktive Gesänge. Ich untersuchte, welche Informationen der Männchengesang enthält, wie diese sich in Gesangsparametern manifestieren und welche Informationen rezipiert werden. Ich untersuchte Abhängigkeiten zwischen Gesang und Temperatur, Alter, Morphologie und Immunkompetenz. Ebenfalls testete ich auf eine Infektion mit Wolbachia sp.. Mit Playback-Versuchen wurde die Präferenz der Weibchen getestet. Der Sexualdimorphismus, Populationsunterschiede und Unterschiede zwischen Freiland- und F1-Populationen wurden untersucht. Es konnte gezeigt werden, dass die Männchengesänge in geringem Maße altersabhängig waren während sie Temperatur den Gesang stark beeinflusst. Länger andauernde Nymphenphasen induzierten veränderte Gesangsmerkmale. Größere und schwerere Beine korrelierten mit dem Onsetsowie der Versdauer und der Pausendauer. Die Phasenverschiebung der Hinterbeine hing stark mit der Störpausentiefe und der Thoraxbreite zusammen. Die Werte der Immunkompetenz korrelierten positiv mit dem Onset des Gesangs des jeweiligen Männchens sowie der Femurlänge. Die Weibchen bevorzugten Männchengesänge, die tiefe Offsets, lange Periode, bzw. Silben, geringe Störpausen und besonders lange Versdauern aufwiesen. Die Tiere zeigten einen hohen Grad an Sexualdimorphismus in Morphologie und Gesang. Ebenfalls waren starke Unterschiede in fast allen untersuchten Morphologiemerkmalen und den meisten Gesangsparametern verschiedener Populationen von Männchen festzustellen, wobei die Weibchenpräferenzen ähnlich waren und der artspezifische Parameter, das Silben-Pausen-Verhältnis, sich nicht unterschied. / The grasshopper Chorthippus biguttulus (Orthoptera: Acrididae) is a model organism for acoustic communication. The males stridulate by rubbing the hind legs against their forewings. The "song" is species-specific and contains information about the gender and perhaps about the quality. Receptive females answer by singing, if the male song is attractive. I worked on the question, which information about the male is in the song, which song parameters contain the information and which of these information is received by the females. I tested correlations between the song parameters and temperature, age, morphology and immunocompetence and I tested for an infection with Wolbachia sp.. The females’ preferences on male songs were tested with playback-experiments. I investigated the sexual size dimorphism and behavioral differences and the differences in these parameters of animals of different sites in Germany and of laboratory and field animals. The male songs were on a small scale age-dependent. Temporal parameters) depended very much from the temperature and decrease with higher temperatures. The developmental time correlated with the duration of the syllables, the onset variances and the gaps in the syllable. Males with longer and heavier legs produced higher onset, longer verses and longer pauses. The gaps in the syllable amplitude and the width of the thorax correlated with the phase shifting of the hind legs. The immunocompetence rate was positively correlated with the onset and the length of the femur. Females preferred male songs, which contained deep offsets, long periods (syllables), small gaps and long verse durations. The species showed a high degree on sexual dimorphism in morphology and the song parameters. The animals of different populations differed significantly in almost every morphology parameter and a lot of song parameters, while the syllable-to-pause-ration (species-specific) was constant. The females preference of the different sites were similar.