In temperate regions, many vector-borne parasites maximise their transmission prospects by adjusting
reproduction to seasonal cycles of host susceptibility and vector availability. Nevertheless, in these
regions there are areas where environmental conditions are favourable throughout the year, so that parasites
could benefit from a year-round transmission strategy. We analysed how different transmission
strategies (strict summer transmission, extended summer transmission – including spring and autumn,
and year round transmission) have evolved among the different genetic lineages of Haemoproteus parabelopolskyi,
an avian blood-borne parasite shared by three sibling species of passerine hosts. Our results
indicate that the ancestral state of this clade of parasites had a strict summer transmission with the
blackcap (Sylvia atricapilla) as the host. Other transmission strategies and switches to the other host species
(Sylvia abyssinica and Sylvia borin) evolved recently, several times, independently. This suggests that,
although year-round transmission is ecologically successful at present, seasonal transmission may have
become more stable over evolutionary time. Switches from strict summer to an extended or year-round
transmission strategy could have ecological consequences, if they promote the spread of parasites into
more distant regions, transported by the migrating bird hosts. Therefore, a deeper knowledge of how different
parasite transmission strategies are structured among birds in temperate areas is essential for
understanding how disease emergence risks may develop in the future.
2015 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.