Unravelling the evolution of the head lice and body lice of humans
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Recent studies of mitochondrial genes of the head and body lice of humans indicate that present-day lice comprise two lineages that diverged before the evolution of modern humans. To test if this was a locus-specific phenomenon, we studied two nuclear genes, elongation factor-1α (EF-1α) and small subunit ribosomal RNA (ssu rRNA). Our ssu rRNA phylogeny was concordant with the phylogenies from mitochondrial genes, but the EF-1α phylogeny was not concordant either with the mitochondrial phylogenies or with the ssu rRNA phylogeny. So both nuclear (ssu rRNA) and mitochondrial data indicate that there are two lineages of lice: one lineage with head lice only (H-only lineage) the other lineage with head and body lice (H+B lineage). Thus, body lice apparently evolved from just one of the two main lineages of lice. However, the date of divergence and geographical origins of the two lineages are controversial. Kittler et al. (Curr Biol 13:1414–1417, 2003; Curr Biol 14:2309, 2004) proposed that these two lineages diverged 0.77 mya, whereas Reed et al. (PLoS Biol 2:e340, 2004) proposed that they diverged 1.18 mya and suggested that one of the lineages, the H-only lineage, evolved in the New World on Homo erectus. We discuss this hypothesis in light of our results from ssu rRNA.
KeywordsPediculus humanus capitis Phthiraptera Small subunit ribosomal RNA Phylogeny
We thank the following people who collected and/or donated the lice used in this study: Debby Cox, for P. schaeffi (B1387); Maryam Ashrafi, Julio V. Barbosa, L. Breen, Wen Chao, Yin Hong, Arezki Izri, Kosta Mumcuoglu, James Opiyo Ochanda, Ricardo Palma, Renfu Shao, Rick Speare, Cheryl Thomas, Claudia Vassena, Helen Weld and Xiaoye Yang. Dr. Bruce Hayes, Patan Hospital, Kathmandu, Nepal, and Mr. Shree Poudel, Department of Science, Janapriya Multiple Campus, Pokhara, Nepal, who helped SCB collect lice in Nepal. We also thank Anna Murrell for preliminary molecular clock analyses of ssu rRNA data.