Résumé
Parasites may have strong eco-evolutionary interactions with their hosts.
Consequently, they may contribute to host diversification. The radiation
of cichlid fish in Lake Victoria provides a good model to study the role
of parasites in the early stages of speciation. We investigated patterns
of macroparasite infection in a community of 17 sympatric cichlids from a
recent radiation and 2 older species from 2 non-radiating lineages, to
explore the opportunity for parasite-mediated speciation. Host species had
different parasite infection profiles, which were only partially explained
by ecological factors (diet, water depth). This may indicate that
differences in infection are not simply the result of differences in
exposure, but that hosts evolved species-specific resistance, consistent
with parasite-mediated divergent selection. Infection was similar between
sampling years, indicating that the direction of parasite-mediated
selection is stable through time. We morphologically identified 6
Cichlidogyrus species, a gill parasite that is considered a good candidate
for driving parasite-mediated speciation, because it is host
species-specific and has radiated elsewhere in Africa. Species composition
of Cichlidogyrus infection was similar among the most closely related host
species (members of the Lake Victoria radiation), but two more distantly
related species (belonging to non-radiating sister lineages) showed
distinct infection profiles. This is inconsistent with a role for
Cichlidogyrus in the early stages of divergence. To conclude, we find
significant interspecific variation in parasite infection profiles, which
is temporally consistent. We found no evidence that Cichlidogyrus-mediated
selection contributes to the early stages of speciation. Instead, our
findings indicate that species differences in infection accumulate after
speciation.