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Free keywords:
urban ecology; host-parasite interactions ; Melanin-based coloration ; avian malaria; feral pigeon
Abstract:
Urbanization is a major challenge for biodiversity
conservation, yet the evolutionary processes taking
place in urbanized areas remain poorly known. Human
activities in cities set new selective forces in motion which
need to be investigated to predict the evolutionary
responses of animal species living in urban areas. In this
study, we investigated the role of urbanization and parasites
in the maintenance of melanin-based color polymorphism
in the feral pigeon Columba livia. Using a
correlative approach, we tested whether differently colored
genotypes displayed alternative phenotypic responses to
urbanization, by comparing body condition, blood parasite
prevalence and parasite load between colored morphs
along an urbanization gradient. Body condition did not
vary with urbanization, but paler individuals had a higher
body condition than darker individuals. Moreover, paler
morphs were less often parasitized than darker morphs in
moderately urbanized habitats, but their parasite prevalence
increased with urbanization. In contrast, darker
morphs had similar parasite prevalence along the urbanization
gradient. This suggests that paler morphs did better
than darker morphs in moderately urbanized environments
but were negatively affected by increasing urbanization,
while darker morphs performed equally in all environments.
Thus, differently colored individuals were distributed
non-randomly across the urban habitat and suffered
different parasite risk according to their location (a geneby-
environment interaction). This suggests that melaninbased
coloration might reflect alternative strategies to cope
with urbanization via different exposure or susceptibility to
parasites. Spatial variability of parasite pressures linked
with urbanization may, thus, play a central role in the
maintenance of plumage color polymorphism in this urban
species.
