Data from: Haemosporidian infection and co-infection affect host survival and reproduction in wild populations of great tits

Theoretical studies predict that parasitic infection may impact host
longevity and ultimately modify the trade-off between reproduction and
survival. Indeed, a host may adjust its energy allocation in current
reproduction to balance the negative effects of parasitism on its survival
prospects. However, very few empirical studies tested this prediction.
Avian haemosporidian parasites provide an excellent opportunity to assess
the influence of parasitic infection on both host survival and
reproduction. They are represented by three main genera (Plasmodium,
Haemoproteus and Leucocytozoon) and are highly prevalent in many bird
populations. Here we provide the first known long-term field study (12
years) to explore the effects of haemosporidian parasite infection and
co-infection on fitness in two populations of great tits (Parus major),
using a multistate modelling framework. We found that while co-infection
decreased survival probability, both infection and co-infection increased
reproductive success. This study provides evidence that co-infections can
be more virulent than single infections. It also provides support for the
life-history theory which predicts that reproductive effort can be
adjusted to balance one’s fitness when survival prospects are challenged.

理论研究预测，寄生虫感染可能影响宿主寿命，并最终改变繁殖与生存之间的权衡关系。事实上，宿主可能会调整当前繁殖过程中的能量分配，以平衡寄生虫感染对其生存前景的负面影响。然而，验证这一预测的实证研究却寥寥无几。鸟类血孢子虫寄生虫为评估寄生虫感染对宿主生存与繁殖的影响提供了绝佳机会。它们主要由三个属构成（疟原虫属Plasmodium、血变形虫属Haemoproteus、白细胞虫属Leucocytozoon），且在许多鸟类种群中高度流行。在此，我们首次报道了一项为期12年的长期野外研究——该研究采用多状态建模框架，探究了血孢子虫感染及共感染对两个大山雀（Parus major）种群适合度的影响。研究发现，尽管共感染降低了生存概率，但无论是单一感染还是共感染均能提高繁殖成功率。本研究不仅证明共感染的致病性可能强于单一感染，还为生活史理论提供了支持：该理论预测，当生存前景受到挑战时，生物可通过调整繁殖投入来平衡自身适合度。