Factors affecting the distribution of haemosporidian parasites within an oceanic island

Abstract

20Understanding how different ecological and evolutionary processes influence the distribution of 21 pathogens within the environment is important from many perspectives, including for wildlife 22 epidemiology, evolutionary ecology and conservation. The simultaneous use of ecological and 23 evolutionary frameworks together can enhance our conceptual understanding of host-parasite 24 interactions, however such studies are rare in the wild. Using samples from 12 bird species caught 25 across all habitats existing on an oceanic island, we evaluated how environmental variables, parasites 26 host specificity, and parasite phylogenetic relationships determine the distribution and prevalence of 27 haemosporidians (Haemoproteus, Plasmodium and Leucocytozoon) in the wild living avifauna. 28Differences were found in the prevalence of Plasmodium, but not Leucocytozoon, strains between 29 habitats. The warmest temperature best predicted Plasmodium prevalence in the low altitude habitats, 30 which had the highest incidence of Plasmodium. The prevalence of Leucocytozoon lineages was 31 associated with natural factors, i.e. rainfall, temperature and habitat, but the two most important 32 predictors (from model averaging) for models of Leucocytozoon were anthropogenic: poultry farms 33 and distance to a water reservoir. We found no relationship between local (Tenerife) versus global 34 host range indexes (which assess the diversity of hosts that a parasite is observed to infect), thus 35 global generalist lineages do not behave in the same way on Tenerife (i.e. they infected less avian 36 hosts than was expected). Phylogenetic analysis revealed that the most abundant haemosporidians on 37Tenerife grouped with lineages found in African host species. Our data indicate that climatic and 38 anthropogenic factors, plus proximity to the African mainland, are the main factors influencing the 39 presence and distribution of avian haemosporidians on Tenerife. Future climate projections for the 40 archipelago foresee significant temperature increases, which would, given our results, increase rates 41 of Plasmodium infection in bird species in all habitats. Such patterns could be of concern if they 42 increase mortality rates in the unique avifauna of these islands. 43 44

Host species, and not environment, predicts variation in blood parasite prevalence, distribution, and diversity along a humidity gradient in northern South America

“…We found, however, that the proportion of individuals infected was similar between wet and dry seasons, suggesting little influence of seasonality on prevalence patterns. Likewise, although temperature has been shown to be an important predictor of prevalence across environmental gradients (Padilla et al., ; Zamora‐Vilchis, Williams, & Johnson, ), the lack of significant variation in temperature across the Magdalena River Valley (Appendix ) suggests that, at least at the spatial scale of our study, temperature likely has similar effects on infection probability across the Magdalena River Valley. However, we acknowledge that complex interactions among temperature, water availability, and vector abundance at local scales might partly explain variability in haemosporidian prevalence in birds.…”

“…We found, however, that the proportion of individuals infected was similar between wet and dry seasons, suggesting little influence of seasonality on prevalence patterns. Likewise, although temperature has been shown to be an important predictor of prevalence across environmental gradients (Padilla et al, 2017;Zamora-Vilchis, Williams, & Johnson, 2012), the lack of significant variation in temperature across the Magdalena River…”

“…Environmental factors are known to play a fundamental role in bird-haemosporidian interactions (Loiseau et al, 2010;Sehgal, 2015). In particular, water availability is likely a key determinant of infection patterns in haemosporidians because it is critical for the development of vector larvae (Krama et al, 2015;Loaiza & Miller, 2013;Okanga, Cumming, & Hockey, 2013;Padilla, Illera, Gonzalez-Quevedo, Villalba, & Richardson, 2017). Accordingly, the geographic distribution, transmission, and prevalence of haemosporidians are often predicted by variation in water availability over time (Cornuault et al, 2013; Hernández-Lara, González-García, & Santiago-Alarcon, 2017) and space (Coon & Martin, 2013;Gonzalez-Quevedo, Davies, & Richardson, 2014;Svensson & Ricklefs, 2009;Wood et al, 2007).…”

Adaptive landscape genetics and malaria across divergent island bird populations

“…In earlier years, approximately half of the samples were collected from the high‐altitude (>2,000 m above sea level) plateau of El Teide. Malaria has not been found in Berthelot's pipits in this location (González‐Quevedo et al, ; Illera et al, ; Spurgin et al, ), although a survey of passerine communities on Tenerife found malaria at low frequency in high‐altitude habitats (Padilla et al, ). The relationship seen in 2011 between TLR4_P1 and infection may be masked in other sampling years by the increase in uninfected individuals from areas of low malaria abundance.…”

Louse flies of Eleonora’s falcons that also feed on their prey are evolutionary dead‐end hosts for blood parasites

“…Because of the generally low prevalence and diversity of the hemosporidian parasites on islands (Hellgren, Križanauskienė, Hasselquist, & Bensch, ; Martínez‐de la Puente et al, ; Padilla, Illera, Gonzalez‐Quevedo, Villalba, & Richardson, ; Pérez‐Rodríguez, Ramírez, Richardson, & Pérez‐Tris, ; Sari, Klompen, & Parker, ) and the presence of only one potential vector species on the island, we expected to find an essentially simple host‐vector‐parasite system. However, we found that the opportunistic feeding behavior of louse flies resulted in an unexpected massive transmission of haemosporidians from kills to falcons’ louse flies.…”