The evolutionary history of parasitic sucking lice and their rodent hosts: A case of evolutionary co-divergences

Parasites are often dependent on their hosts for survival and dispersal and this led to a hypothesis that the evolution of obligate permanent host-specific parasites specifically will show phylogenetic congruence with their hosts. To investigate the factors influencing parasite evolution, mitochondrial- and nuclear DNA sequence data were used to test for genetic co-divergences between Hoplopleura and Polyplax lice occurring on four rodent taxa associated with the Aethomys/Micaelamys rodent complex. Mitochondrial DNA haplotype networks drawn from 24 rodents and 74 obligate permanent lice supported the existence of at least eight genetically distinct parasite lineages. Bayesian and maximum likelihood analyses showed considerable congruence between the phylogenies of the parasites and their hosts, and these finding were also partly supported in a fair amount of overlap in the timing of divergences. Jane co-phylogenetic reconstructions illustrated that co-divergences are the most parsimonious solution to explain the evolution within Polyplax, and also within Hoplopleura. Based on mitochondrial DNA cytochrome oxidase subunit I sequence distances of >13% between strongly supported monophyletic parasite lineages, coupled to some unique morphological features detected for both lice taxa occurring on Micaelamys granti, we propose that the taxonomy of Polyplax and Hoplopleura studied herein is in need of revision. In addition, our findings provide examples of perfect topological co-divergence between parasites and their hosts, and in doing so also provide circumstantial evidence for co-evolution between these permanent host-specific parasites and their hosts. We argue that the signal of co-divergence is partly enforced by limited opportunities for host switching events across the landscape.