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Avian haemosporidian parasites are particularly diverse and widespread. To date, more than 3,000 distinct cytochrome b lineages have been recorded, of which some present extremely wide geographical distributions, even including multiple continents. Whether these isolates represent one or several cryptic species remains unknown. Here we carried out a case study of SISKIN1, a common haemosporidian parasite lineage belonging to the morphologically described species Haemoproteus tartakovskyi . To shed light on its evolutionary origin, we investigated the divergence between SISKIN1 isolates obtained from siskins and redpolls in Europe (Russia and Sweden) and house finches in North America (Mexico). First, we used sequence capture of a small data set (2 Russian isolates and 1 Mexican isolate) to investigate the genetic structure based on the full-length mitochondrial genome and ∼1,000 genes. The mitochondrial genomes of Russian isolates were identical with each other but differed from the Mexican one at 6 positions. The nuclear divergence between Russian and Mexican isolates was on average 2.8%, close to what has been observed between 2 species of malaria parasites that respectively infect humans ( Plasmodium falciparum ) and gorillas ( Plasmodium praefalciparum ). Second, we used the expanded data set (15 samples in total) to investigate the genetic structure in 3 genes known to be involved in host invasion. The European isolates were identical across all sequenced genes, whereas the Mexican isolates were highly diverse. The lack of shared alleles between European and Mexican populations suggests that they might have diverged in isolation without gene flow. From the MalAvi database we examined the lineages most similar to the SISKIN1 barcode fragment (part of the cyt b gene) and found that most of them had been recorded in North and South America. This suggests that the lineage SISKIN1 originated in North America and subsequently spread to Europe. Our analyses support that the cyt b gene barcoding region is a useful marker for identification of avian haemosporidian lineages that can classify them into clusters of closely related parasites, but to further investigate species limits and evolutionary history, molecular data from multiple faster-evolving genes are required.

To date it is not well-understood how seasonality and human-induced habitat change may affect haemosporidian prevalence and parasitaemia in bird hosts in dryland habitats. We compared haemosporidian prevalence and parasitaemia between habitat types, including Yucca-dominated scrublands (closed habitat) and creosotebush scrublands (open habitat), and between seasons, including non-breeding (dry) and breeding (wet) in the Black-throated sparrow (Amphispiza bilineata) at semi-arid scrublands of Central Mexico. This bird species has different habitat preferences in comparison to other, previously studied species in the region; it shows higher abundances in open than in closed habitats and avoids urban areas. Overall haemosporidian prevalence was 22.1%. Prevalence and parasitaemia were higher for Haemoproteus sp. (Parahaemoproteus sp.) than Plasmodium. Variation in haemoparasitism was not associated with habitat type. This response differs from the previously recorded response in other bird species in the region for which haemoparasitism increases with increasing habitat degradation. Seasonality seems to be the most important driver of parasite infection for this sparrow as prevalence and parasitaemia were higher during the breeding than the non-breeding season. Two new lineages of Haemoproteus sp. that had not been reported before in any avian species were found through molecular diagnosis. A high diversity of haemosporidian lineages is shared among sites. More study is needed to understand the mechanisms that associate parasitaemia, prevalence, and specific environmental factors.

Background: Studies of avian haemosporidians allow understanding how these parasites affect wild bird populations, and if their presence is related to factors such as habitat loss, degradation and fragmentation, and climate change. Considering the importance of the highland Plateau of Mexico as part of the North American bird migratory route and as a region containing important habitat for numerous bird species, the purpose of this study was to document haemosporidian species richness and how habitat degradation, bird body condition, and distance from water sources correlate with bird parasitemia., Methods: We assessed the presence of avian haemosporidians in three resident bird species through microscopy and PCR amplification of a fragment of the haemosporidian cytochrome b gene. Average parasitemia was estimated in each species, and its relationship with habitat degradation through grazing, bird body condition and distance from water bodies was assessed., Results: High levels of parasitemia were recorded in two of the three bird species included in this study. Four lineages of haemosporidians were identified in the study area with nearly 50 % prevalence. Areas with highly degraded shrublands and villages showed higher parasitemia relative to areas with moderately degraded shrublands. No strong relationship between parasitemia and distance from water bodies was observed. There were no significant differences in prevalence and parasitemia between the two bird species infected with the parasites. Two of the sequences obtained from the fragments of the parasite's cytochrome b gene represent a lineage that had not been previously reported., Conclusions: Haemosporidian diversity in arid zones of the Mexican highland plateau is high. Shrubland habitat degradation associated to the establishment of small villages, as well as tree extraction and overgrazing in the surroundings of these villages, significantly enhances parasitemia of birds by haemosporidians.