What Do <i>Pneumocystis</i> Organisms Tell Us about the Phylogeography of Their Hosts? The Case of the Woodmouse <i>Apodemus sylvaticus</i> in Continental Europe and Western Mediterranean Islands

<div><p><i>Pneumocystis</i> fungi represent a highly diversified biological group with numerous species, which display a strong host-specificity suggesting a long co-speciation process. In the present study, the presence and genetic diversity of <i>Pneumocystis</i> organisms was investigated in 203 lung samples from woodmice (<i>Apodemus sylvaticus</i>) collected on western continental Europe and Mediterranean islands. The presence of <i>Pneumocystis</i> DNA was assessed by nested PCR at both large and small mitochondrial subunit (mtLSU and mtSSU) rRNA loci. Direct sequencing of nested PCR products demonstrated a very high variability among woodmouse-derived <i>Pneumocystis </i>organisms with a total number of 30 distinct combined mtLSU and mtSSU sequence types. However, the genetic divergence among these sequence types was very low (up to 3.87%) and the presence of several <i>Pneumocystis</i> species within <i>Apodemus sylvaticus</i> was considered unlikely. The analysis of the genetic structure of woodmouse-derived <i>Pneumocystis</i> revealed two distinct groups. The first one comprised <i>Pneumocystis</i> from woodmice collected in continental Spain, France and Balearic islands. The second one included <i>Pneumocystis</i> from woodmice collected in continental Italy, Corsica and Sicily. These two genetic groups were in accordance with the two lineages currently described within the host species <i>Apodemus sylvaticus</i>. <i>Pneumocystis</i> organisms are emerging as powerful tools for phylogeographic studies in mammals.</p>