The distribution of avian haemosporidians of the genus Leucocytozoon in the Neotropics remains poorly understood. Recent studies confirmed their presence in the region using molecular techniques alone, but evidence for gametocytes and data on putative competent hosts for Leucocytozoon are still lacking outside highland areas. We combined morphological and molecular data to characterize a new Leucocytozoon species infecting a non-migratory red-legged seriema (Cariama cristata), the first report of a competent host for Leucocytozoon in Brazil. Leucocytozoon cariamae n. sp. is distinguished from the Leucocytozoon fringillinarum group by its microgametocytes that are not strongly appressed to the host cell nucleus. The bird studied was coinfected with Haemoproteus pulcher, and we present a Bayesian phylogenetic analysis based on nearly complete mitochondrial genomes of these 2 parasites. Leucocytozoon cariamae n. sp. morphology is consistent with our phylogenetic analysis indicating that it does not share a recent common ancestor with the L. fringillinarum group. Haemoproteus pulcher and Haemoproteus catharti form a monophyletic group with Haemocystidium parasites of Reptilia, supporting the polyphyly of the genus Haemoproteus. We also discussed the hypothesis that H. pulcher and H. catharti may be avian Haemocystidium, highlighting the need to study non-passerine parasites to untangle the systematics of Haemosporida.

Parasites display various degrees of host specificity, reflecting different coevolutionary histories with their hosts. Avian hosts follow multiple migration patterns representing short but also long distances. As parasites infecting migratory birds are subjected to multiple environmental and biotic changes through their flyways, migration may disrupt or strengthen cophylogenetic congruence between hosts and parasites. On the one hand, parasites might adapt to a single migratory host, evolving to cope with the specific challenges associated with the multiple habitats occupied by the host. On the other, as migrants can introduce parasites into new habitats, higher rates of host switching could also disrupt cophylogenetic patterns. We analysed whether migratory behaviour shapes avian haemosporidian parasite–host cophylogenetic congruence by testing if contributions of host–parasite links to overall congruence differ among resident and short-, variable- and long-distance migrants globally and within South America only. On both scales, we found significant overall cophylogenetic congruence by testing whether overall congruence differed between haemosporidian lineages and bird species. However, we found no difference in contribution towards congruence among links involving resident vs migratory hosts in both models. Thus, migratory behaviour neither weakens nor strengthens bird–haemosporidian cophylogenetic congruence, suggesting that other avian host traits are more influential in generating phylogenetic congruence in this host–parasite system.

The blackcap (Sylvia atricapilla) is a common Palearctic migratory warbler, and haemosporidian parasites are common in this species. However, genetic and phenotypic diversity of haemosporidians in warblers has been insufficiently investigated and poorly linked. We addressed this issue by combining molecular and microscopy data for detection of pigment-forming haemosporidians of the genera Haemoproteus and Plasmodium. Blood samples from 498 blackcaps were collected at 7 different sites in Europe and investigated for these parasites by polymerase chain reaction (PCR)-based techniques and microscopic examination. In all, 56% of the birds were infected by at least 1 out of 25 distinct mitochondrial cytochrome b (cyt b) gene lineages of these haemosporidians. It is concluded that the blackcap is infected not only with blackcap specific haemosporidians, but also with Haemoproteus majoris, which is a host generalist and common in birds belonging to the Paridae. Haemoproteus pallidulus sp. nov. is described based on morphology of its blood stages and segments of the cyt b and dihydrofolate reductase/thymidylate synthase (DHFR-TS) genes. This study provides evidence that genetic diversity of haemosporidian parasites might be positively correlated with migratory strategies of their avian hosts; it also contributes to the value of both microscopy and molecular diagnostics of avian blood parasites.

Common bird species were screened during May and June 2007 on Barbados for haemosporidian parasites (Haemosporida) of the genera Haemoproteus and Plasmodium to determine whether the low parasite diversity reported in previous studies might have reflected limited sampling. PCR screening and DNA sequencing revealed a single predominant lineage of Haemoproteus identified as H. coatneyi. Sixty-two out of 257 birds were infected with Haemoproteus spp. on Barbados in 2007. Fifty-nine of the infections were identified as H. coatneyi (lineage HC), the only lineage recovered in the previous study in 1993. Two of the infections recovered from the bananaquit (Coereba flaveola) were identified as Haemoproteus spp. (lineage HD), which is the prevalent haemosporidian parasite in C. flaveola on Grenada. We discuss the possibility of infrequent colonization events and absence of vectors as explanations for Barbados's low avian haemosporidian diversity. In our study, the parasites were absent from the southeast of the island, whereas they were abundant in several host species in the northwest. Accordingly, environmental and host population genetic differences were also investigated between the areas with and without parasites. No host genetic differences were found between the parasite-free and the parasite-afflicted regions. However, the parasite-free region is slightly warmer and drier, and it supports less vegetation than the parasite-afflicted region. The influence that this harsher environment may have on vector survival is discussed.