Within-Host Speciation of Malaria Parasites

Javier Pérez-Tris,Jon Fjeldså,Jonas Waldenström,Asta Križanauskienė,Dennis Hasselquist,Olof Hellgren,Camille Bonneaud,Staffan Bensch,Jean Secondi,Angus Buckling

doi:10.1371/journal.pone.0000235

Abstract

BackgroundSympatric speciation—the divergence of populations into new species in absence of geographic barriers to hybridization—is the most debated mode of diversification of life forms. Parasitic organisms are prominent models for sympatric speciation, because they may colonise new hosts within the same geographic area and diverge through host specialization. However, it has been argued that this mode of parasite divergence is not strict sympatric speciation, because host shifts likely cause the sudden effective isolation of parasites, particularly if these are transmitted by vectors and therefore cannot select their hosts. Strict sympatric speciation would involve parasite lineages diverging within a single host species, without any population subdivision.Methodology/Principal FindingsHere we report a case of extraordinary divergence of sympatric, ecologically distinct, and reproductively isolated malaria parasites within a single avian host species, which apparently occurred without historical or extant subdivision of parasite or host populations.Conclusions/SignificanceThis discovery of within-host speciation changes our current view on the diversification potential of malaria parasites, because neither geographic isolation of host populations nor colonization of new host species are any longer necessary conditions to the formation of new parasite species.

Highlights

Malaria parasites comprise a diverse group of protozoans that infect reptiles, mammals and birds, and that are transmitted through the bite of different families of blood-feeding insect vectors [1,2]
Speciation in malaria parasites is known to follow from the subdivision of parasite populations in discrete habitats, such as different geographic regions in which host populations become isolated, or different host species accidentally colonised with the assistance of vectors [4,5]
We sequenced part of the mitochondrial cytochrome b gene of malaria parasites found in European passerine birds to broadly investigate the phylogenetic diversity of this group of organisms

Summary

Introduction

Malaria parasites comprise a diverse group of protozoans that infect reptiles, mammals and birds, and that are transmitted through the bite of different families of blood-feeding insect vectors [1,2]. Speciation in malaria parasites is known to follow from the subdivision of parasite populations in discrete habitats, such as different geographic regions in which host populations become isolated, or different host species accidentally colonised with the assistance of vectors [4,5]. Such findings fit to the expectations of usual modes of allopatric and sympatric speciation, respectively, which have been proposed for parasitic organisms [6,7,8,9]. This discovery of within-host speciation changes our current view on the diversification potential of malaria parasites, because neither geographic isolation of host populations nor colonization of new host species are any longer necessary conditions to the formation of new parasite species

Methods

Results

Conclusion