Maternal effects, malaria infections and the badge size of the house sparrow

Abstract

Background: The evolution of sexual signals is not only determined by immediate sexual selection but also by selection arising from the environment and the interaction with developmental effects. In this study we aimed to investigate how the badge size of male house sparrows (Passer domesticus) is correlated to avian malaria infections as well as to prenatal testosterone exposure, measured as the 2D:4D digit ratio. The rationale behind this study is that the immunosuppressive effect of maternal testosterone deposition combined with the fitness cost imposed by parasites may cause important trade-offs to the development of secondary sexual signals. Methods:Assuming that vector abundance is a key variable associated with infection risk by avian malaria, we caught adult male sparrows from eight different populations in the Camargue, France, four of which were located in a vector-controlled area, and the other four in an untreated area. For each bird we measured its badge size, digit ratio and took blood to determine its infections status. We used PCR to identify the malaria parasite species and strain that caused the infection.Results: Contrary to our expectation, prevalence of disease did not differ across the vector-treatment regions, with around 80 % of birds being infected in both areas, and those infections were caused largely by a single strain, Plasmodium relictum SGS1. Although infected birds had a badge size not significantly different from uninfected males, there was a condition-dependent association between badge size, infection status and maternal testosterone deposition. Conclusions:This study illustrates that the complexity of temporal and ecological dimensions makes the relationships between disease, testosterone-related traits and secondary sexual signals that have been previously reported less general than thought.

Diversity, prevalence and host specificity of avian parasites in southern Tunisian oases

“…In sparrows, we detected higher parasite diversity, with five lineages of Plasmodium and five lineages of Haemoproteus. This result is similar to those found in other sparrow populations in another part of the world (Marzal et al 2011; Birget and Larcombe, 2015; Coon et al 2016). Haemoproteus lineages were rather specific to the genus Passer , while Plasmodium lineages were highly generalist, which confirms the general pattern of host specificity of these two genera, Haemoproteus found repeatedly to be more specialist than Plasmodium (Clark and Clegg, 2017; Loiseau et al 2017).…”

Nowhere to escape: the cross‐age avian haemosporidian exposure of migrants in northeast China

“…The development of the immune organ, which is critical for defending against parasite infections, depends largely on maternal conditions (Harrison et al 2011). Compared with Japanese tit, the energy cost for yellow‐rumped flycatcher during an extra life‐stage of migration may lead to a worse physiological state upon arrival at the breeding grounds (Harrison et al 2011), and the maternal condition can directly influence the performance of offspring (Badyaev and Uller 2009, Birget and Larcombe 2015). Additionally, infected mothers may transfer less immunoglobulins to their eggs, result in a weak immune system in their nestlings, and therefore low parasite resistance (Norris and Evans 2000).…”

“…If we observe the opposite pattern, it would indicate that the 'migratory escape' hypothesis is more pronounced. Moreover, as migration would cost lots of energy, during breeding seasons migratory species may suffer a worse body condition compared to resident birds, thus, offspring may be weaker and more susceptible to parasite infection (Birget and Larcombe 2015). In this case, nestlings of migratory birds may present a higher prevalence of infection than resident species, a similar pattern as in adults.…”