Editor´s Choice: Avian malaria is associated with increased reproductive investment
Submitted by avianbiology on 7 May 2014.
High quality individuals or Terminal investment?
Avian malaria parasites, e.g. Haemoproteus and Plasmodium, are commonly found in many bird species. Studies aiming at estimating these parasites’ fitness effects have typically either found no effect or a negative effect on reproductive success and/or survival. In a most interesting recent paper in J. Avian Biol., Podmokła and colleagues set out to investigate the effects of these parasites in an experimental system where blue tit parental effort was manipulated by enlarging some broods. Surprisingly, when blue tit parents were working hard feeding enlarged broods, they produced larger offspring with a better immune response if both members of the pair were infected with these parasites compared to uninfected pairs. Thus, these infected pairs seem to have a higher reproductive success than uninfected pairs. The authors offer two different explanations for this contra intuitive result. Only individuals of the highest quality may be able to survive the first acute stage of the infection. Later, when at the chronic stage of the infection, these surviving individuals may be of superior quality enabling them to invest more resources into feeding young. Alternatively, infected parents may do a last heavy investment in reproduction (terminal investment), with a predicted great reduction in later survival.
Jan-Åke Nilsson, Editor in Chief
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