2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

�67 Martin Plath A 703 / 15:00
Gradient evolution of body coloration in surface- and cave-dwelling Poecilia
mexicana and the role of phenotype-assortative female mate choice
Authors: Martin Plath 1 , David Bierbach 1
Affiliation: 1 Johann-Wolfgang-Goethe University of Frankfurt am Main, Evolutionary
Ecology Group
Ecological speciation assumes reproductive isolation to be the product of ecologically
based divergent selection. Beside natural selection (e.g., via H2S-toxicity, darkness or
predation), female mate choice in favour of males from their own, locally adapted
population (phenotype-assortative mating) is thought to play a key role in promoting
reproductive isolation among populations from ecologically different habitat types.
Using the neotropical fish Poecilia mexicana from a system that has been described
to undergo incipient ecological speciation in adjacent, but ecologically starkly
divergent habitats characterized by the presence or absence of two environmental
stressors (toxic H2S and darkness in cave habitats), we show (1) a gradual change in
male and female body coloration along the ecological gradient of light/ darkness,
including a reduction of male ornaments that are under both inter- and intra-sexual
selection in surface populations. (2) In dichotomous choice tests using videoanimated
stimuli we found surface females to have a strong preference for males
from their own population over the cave phenotype. (3) In another experiment we
asked whether morphological and/or behavioural differences between surface and
cave ecotypes translate into female mate choice for the resident male phenotype in
cave females, too. When investigating the choices of female cave fish on site (i.e. in
darkness, using infrared observation techniques), however, females preferred to
associate with surface males rather than size-matched cave fish males, likely
reflecting the female predilection for better-nourished (in this case: surface) males
described beforehand. Hence, divergent selection of body coloration indeed
translates into phenotype-assortative mating in the surface ecotype, thereby
promoting reproductive isolation by selecting against potential migrant males.
Female cave fish, by contrast, do not have such a preference, identifying natural
selection against migrants imposed by the cave environment as the major driver of
the observed divergence.
�68 Anne Weeda A 703 / 15:15
Diploid males - the unknown sex: A study on mating behaviour and fertility of
diploid Bracon brevicornis males
Authors: Anne C. Weeda 1 , Andra Thiel 1 , Thomas S. Hoffmeister 1
Affiliation: 1 University of Bremen
While females in the Hymenoptera (ants, bees and wasps) develop from diploid
fertilized eggs, males normally derive from unfertilized eggs and are thus haploid.
Diploid males however, may arise whenever a female mates with a male who carries
a sex allele matching one of her own. What are the consequences of diploid males
within a population? Given they cannot sire offspring, they pose a twofold load: first,
their production is a waste of resources, since they represent zero fitness individuals;
second, they constrain the females they mate with to produce only sons and thus
90