2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

����102 Christian Sturmbauer
Genetic differentiation in relation to body shape change in sympatric and nonsympatric
Tropheus populations of Lake Tanganyika
Authors: Christian Sturmbauer 1 , Michaela Kerschbaumer 1 , Philipp Mitteröcker 1 , Nina
Znidaric 1 , Christine Börger 1 , Immanuel Karner 1
Affiliation: 1 Department of Zoology, University of Graz, Austria
Allopatric speciation often yields ecologically equivalent sister species, so that
secondary admixis of such species pairs must enforce competition and possibly
character displacement. This scenario is difficult to study in complex species
communities. The rocky shores of Lake Tanganyika are populated by about 120
distinct populations of the cichlid fish genus Tropheus, some of which live in
sympatry. We utilized the partial natural co-occurrence of Tropheus moorii ‘Kaiser’
and ‘Kirschfleck’ with Tropheus polli at the central eastern coast. When alone
Tropheus occupies a relatively broad depth zone but in sympatry fish segregate by
water depth. In a previous study we demonstrated via standardized pond breeding
experiments that the observed diffenences between sym- and non-sympatrically
living Tropheus ‘Kaiser’ have a genetic basis despite large-scale phenotypic plasticity.
Using geometric morphometrics and neutral genetic markers, we investigated
whether the sympatric populations differ consistently in body shape from their nonsympatric
allies and if differences are likely to result from adaptation. We found
significant differences in mean shape between non-sympatric and sympatric
populations, whereas all sympatric populations of both color morphs clustered
together in shape space. Sympatric populations had a relatively smaller head, smaller
eyes, and a more anterior insertion of the pectoral fin than non-sympatric
populations. Genetically, however, non-sympatric and sympatric ‘Kaiser’ populations
clustered together to the exclusion of T. ‘Kirschfleck’. Genetic distances, but not
morphological distances, were correlated with geographic distances. Within- and
between-population covariance matrices for Tropheus moorii populations clearly
deviated from proportionality. It is thus likely that divergent natural selection on
body shape acts on both phenotypic plasticity and genetically-based traits. The
pattern observed in five sympatric populations is consistent with character
displacement.
����103 Meike Teschke
An evolutionary perspective on MHC sequence diversity
Authors: Meike Teschke 1 , Inka Montero 1
Affiliation: 1 Max Planck Institute for Evolutionary Biology
The Major Histocompatibility Complex, a genomic region harboring genes with key
roles in the immune system of all jawed vertebrates, is known for its extraordinary
polymorphism and heterozygosity. Despite decades of intense empirical and
theoretical research, the evolutionary mechanisms of the origin and the long
preservation of polymorphism are not fully understood. Several authors suggest the
solution in a combination of different selective forces like balancing selection,
heterozygote advantage and frequency dependent selection. However, the majority
of empirical studies harbor caveats in either sample and/or locus selection or in data
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