Malaria infections reinforce competitive asymmetry between two Ficedula flycatchers in a recent contact zone

Abstract

Parasites may influence the outcome of interspecific competition between closely related host species through lower parasite virulence in the host with which they share the longer evolutionary history. We tested this idea by comparing the prevalence of avian malaria (Haemosporidia) lineages and their association with survival in pied and collared flycatchers (Ficedula hypoleuca and F. albicollis) breeding in a recent contact zone on the Swedish island of Öland. A nested PCR protocol amplifying haemosporidian fragments of mtDNA was used to screen the presence of malaria lineages in 1048 blood samples collected during 6 years. Competitively inferior pied flycatchers had a higher prevalence of blood parasites, including the lineages that were shared between the two flycatcher species. Multistate mark-recapture models revealed a lower survival of infected versus uninfected female pied flycatchers, while no such effects were detected in male pied flycatchers or in collared flycatchers of either sex. Our results show that a comparatively new host, the collared flycatcher, appears to be less susceptible to a local northern European malarial lineage where the collared flycatchers have recently expanded their distribution. Pied flycatchers experience strong reproductive interference from collared flycatchers, and the additional impact of species-specific blood parasite effects adds to this competitive exclusion. These results support the idea that parasites can strongly influence the outcome of interspecific competition between closely related host species, but that the invading species need not necessarily be more susceptible to local parasites.

Effect of haemosporidian infections on host survival and recapture rate in the blue tit

“…We did not find any support for the effect of the analysed predictors (sex, age and time) on transition rates between infection states (Table ). This result stays in line with a study on flycatchers (Kulma et al ). However, some other factors, such as spatial patterns (Lachish et al ), which were not taken into account in our analyses, may be associated with differential probability of transition between states.…”

Malaria-Infected Female Collared Flycatchers (Ficedula albicollis) Do Not Pay the Cost of Late Breeding

“…uninfected individuals do best because they are in better shape and can bring more food) and the pattern late in the season would reflect variation in allocation (infected individuals do best because they allocate more resources to current reproduction and work harder). However, infected females do not have a lower survival than their uninfected counterparts in our population [45], so they do not have lower prospects of future breeding, which rejects the core assumption of the terminal investment hypothesis.…”

Generalist haemosporidian parasites are better adapted to a subset of host species in a multiple host community

“…Considering that main hosts should be able to provide a stable reservoir for persistence and transmission (Moens et al., ), it is unlikely that generalist parasites can use locally rare species as their main hosts. In a previous study carried out elsewhere in northern Europe (Kulma, Low, Bensch, & Qvarnstrom, ), PHSIB1 was frequently detected (prevalence >20%) in both collared and pied flycatchers ( Ficedula albicollis and F. hypoleuca ), but only the latter occasionally breed in our study area. Thus, the main host species of PHSIB1 may not be present in our sampling community.…”