Phylogenetic relationships of haemosporidian parasites in New World Columbiformes, with emphasis on the endemic Galapagos dove

Abstract

DNA-sequence analyses of avian haemosporidian parasites, primarily of passerine birds, have described the phylogenetic relationships of major groups of these parasites, which are in general agreement with morphological taxonomy. However, less attention has been paid to haemosporidian parasites of non-passerine birds despite morphological and DNA-sequence evidence for unique clades of parasites in these birds. Detection of haemosporidian parasites in the Galapagos archipelago has raised conservation concerns and prompted us to characterise the origins and diversity of these parasites in the Galapagos dove (Zenaida galapagoensis). We used partial mitochondrial cytochrome b (cyt b) and apicoplast caseinolytic protease C (ClpC) genes to develop a phylogenetic hypothesis of relationships of haemosporidian parasites infecting New World Columbiformes, paying special attention to those parasites infecting the endemic Galapagos dove. We identified a well-supported and diverse monophyletic clade of haemosporidian parasites unique to Columbiformes, which belong to the sub-genus Haemoproteus (Haemoproteus). This is a sister clade to all the Haemoproteus (Parahaemoproteus) and Plasmodium parasites so far identified from birds as well as the Plasmodium parasites of mammals and reptiles. Our data suggest that the diverse Haemoproteus parasites observed in Galapagos doves are not endemic to the archipelago and likely represent multiple recent introductions.

Introduction

Haemosporidian parasites are vector-born parasites in the order Haemosporida (Phylum Apicomplexa) that are commonly found in reptiles, birds and mammals (Valkiūnas, 2005). Avian haemosporidian parasites have a cosmopolitan distribution and are divided into four genera: Plasmodium, Haemoproteus, Fallisia and Leucocytozoon (Atkinson and van Riper, 1991, Atkinson, 1991, Valkiūnas, 2005). Only recently have evolutionary biologists and ecologists applied molecular approaches to study this group of parasites in free-ranging hosts (e.g., see Schall and Marghoob, 1995, Schall and Pearson, 2000, Salkeld and Schwarzkopf, 2005 for lizards; and Bensch et al., 2000, Ricklefs and Fallon, 2002, Fallon et al., 2003, Fallon et al., 2004, Fallon et al., 2005, Pérez-Tris and Bensch, 2005, Valkiūnas, 2005, Hellgren et al., 2007a for birds). These studies have revealed that the diversity of parasite DNA lineages greatly surpasses the number of named species based on morphological characters (Ricklefs and Fallon, 2002, Križanauskienė et al., 2006, Martinsen et al., 2006, Hellgren et al., 2007a).

Phylogenetic studies of avian haemosporidian parasites, mostly based on mitochondrial (mtDNA) cytochrome b (cyt b), have identified many parasite lineages of the genera Plasmodium and Haemoproteus infecting passerine birds (Perkins and Schall, 2002, Ricklefs and Fallon, 2002, Martinsen et al., 2008); however, few studies have specifically addressed the haemosporidian parasites of non-passerine birds. Traditional taxonomy based on morphological characters places Haemoproteus parasites that infect Columbiformes in the sub-genus Haemoproteus, whereas all other Haemoproteus parasites belong to the sub-genus Parahaemoproteus (Valkiūnas, 2005). Sequence (mtDNA cyt b and cytochrome c oxidase subunit I (COI), apicoplast caseinolytic protease C (ClpC) and nuclear adenylosuccinate lyase (asl), genes) have verified the phylogenetic position of the sub-genus Haemoproteus (Haemoproteus) clade as sister to the sub-genus Haemoproteus (Parahaemoproteus) and the genus Plasmodium (Martinsen et al., 2008); however, that study only included three samples from domestic pigeons (Columba livia), which represent one morphological species of parasite (Haemoproteus columbae). Thus, sampling of haemosporidian parasites from pigeons and doves, as well as from other non-passerine birds, has been rather limited in phylogenetic analyses. Wide geographical sampling of blood parasites infecting non-passerine birds will certainly provide a refinement of the taxonomy and systematics of the order Haemosporida.

Traditional taxonomy recognises 19 morphological species of haemosporidian parasites infecting Columbiformes (Bennett and Peirce, 1990, Valkiūnas, 2005). Of these, six belong to the genus Haemoproteus, 11 to Plasmodium, one to Fallisia and one to Leucocytozoon (Valkiūnas, 2005). H. columbae, H. sacharovi, H. palumbis, H. turtur, Plasmodium gabaldoni, P. columbae, Fallisia neotropicalis and Leucocytozoon marchouxi have been described from bird species of the family Columbidae (Valkiūnas, 2005). The other two Hemoproteus parasites (H. krylovi and H. pteroclis) that infect pigeons and doves have been described from the bird family Pteroclididae. The remaining parasites infecting pigeons and doves have been described from birds belonging to the families Passeridae, Turdidae, Hirundinidae, Phasianidae, Mimidae and Psittacidae (Valkiūnas, 2005). The vertebrate hosts of the present study belong to the family Columbidae, sub-family Columbinae, with approximately 60 species recognised across the American continent (Baptista et al., 1997). The endemic Galapagos dove (Zenaida galapagoensis) belongs to a genus comprising seven species, within which its sister species is the widespread South American eared dove (Z. auriculata) (Johnson and Clayton, 2000).

The study of avian haemosporidian parasites has contributed to understanding emerging infectious diseases in novel hosts (e.g., Mackenzie et al., 2004, Kilpatrick et al., 2006, Jourdain et al., 2007). Because millions of migratory birds travel enormous distances, they potentially can transmit parasites between distant geographical locations, even between continents (e.g., Waldeström et al., 2002, Ricklefs et al., 2005, Pérez-Tris and Bensch, 2005, Fallon et al., 2006, Svensson et al., 2007; but see Hellgren et al., 2007b). In addition, many avian haemosporidian parasites are able to infect species from different bird families (Ricklefs and Fallon, 2002, Ricklefs et al., 2004, Križanauskienė et al., 2006; but see Iezhova et al., 2005).

Introduced avian diseases are a concern for the conservation of endemic species in the Galapagos archipelago (Padilla et al., 2004, Parker et al., 2006). Recently, we have detected high prevalence (>80%) and infection intensities of Haemoproteus spp. in endemic Galápagos doves from eight different islands of the archipelago (Padilla et al., 2004, Santiago-Alarcon et al., 2008). We suspected that these haemosporidian parasites might have arrived in the Galapagos recently, perhaps via introduced domestic pigeons, which were repeatedly brought to the islands during the last century (Harmon et al., 1987, Padilla et al., 2004). An extermination program removed the last remaining domestic pigeons from the Galapagos in 2002, leaving the endemic Galapagos dove as the only columbiform species inhabiting the archipelago.

Until now, no attempt has been made to characterise the diversity of columbiform haemosporidian parasites using molecular methods. In this study, we provide a comprehensive phylogenetic analysis of columbiform haemosporidian parasites using partial mtDNA cyt b and ClpC genes. We also characterise the haplotype diversity of haemosporidian parasites of Galapagos doves in relation to parasite lineages obtained from doves across Latin America.