title: Global divergence of the human follicle mite Demodex folliculorum: Persistent associations between host ancestry and mite lineages.
abstract: Microscopic mites of the genus Demodex live within the hair follicles of mammals and are ubiquitous symbionts of humans, but little molecular work has been done to understand their genetic diversity or transmission. Here we sampled mite DNA from 70 human hosts of diverse geographic ancestries and analyzed 241 sequences from the mitochondrial genome of the species Demodex folliculorum. Phylogenetic analyses recovered multiple deep lineages including a globally distributed lineage common among hosts of European ancestry and three lineages that primarily include hosts of Asian, African, and Latin American ancestry. To a great extent, the ancestral geography of hosts predicted the lineages of mites found on them; 27% of the total molecular variance segregated according to the regional ancestries of hosts. We found that D. folliculorum populations are stable on an individual over the course of years and that some Asian and African American hosts maintain specific mite lineages over the course of years or generations outside their geographic region of birth or ancestry. D. folliculorum haplotypes were much more likely to be shared within families and between spouses than between unrelated individuals, indicating that transmission requires close contact. Dating analyses indicated that D. folliculorum origins may predate modern humans. Overall, D. folliculorum evolution reflects ancient human population divergences, is consistent with an out-of-Africa dispersal hypothesis, and presents an excellent model system for further understanding the history of human movement.
authors.affiliation: Department of Biology, Bowdoin College, Brunswick, ME 04011; mpalopol@bowdoin.edu.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Palopoli
authors.affiliation: North Carolina Museum of Natural Sciences, Raleigh, NC 27601; Department of Applied Ecology, North Carolina State University, Raleigh, NC 27695;
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Fergus
authors.affiliation: Department of Biology, Bowdoin College, Brunswick, ME 04011;
authors.forename: Samuel
authors.initials: S
authors.lastname: Minot
authors.affiliation: Department of Biology, Bowdoin College, Brunswick, ME 04011;
authors.forename: Dorothy T
authors.initials: DT
authors.lastname: Pei
authors.affiliation: Center for Comparative Genomics, California Academy of Sciences, San Francisco, CA 94118;
authors.forename: W Brian
authors.initials: WB
authors.lastname: Simison
authors.affiliation: Center for Comparative Genomics, California Academy of Sciences, San Francisco, CA 94118; Department of Biochemistry, Genetics and Immunology, University of Vigo, 36310 Vigo, Spain;
authors.forename: Iria
authors.initials: I
authors.lastname: Fernandez-Silva
authors.affiliation: Department of Applied Ecology, North Carolina State University, Raleigh, NC 27695; Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC 27695;
authors.forename: Megan S
authors.initials: MS
authors.lastname: Thoemmes
authors.affiliation: Department of Applied Ecology, North Carolina State University, Raleigh, NC 27695; Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, 2100 Copenhagen Ø, Denmark.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Dunn
authors.affiliation: Center for Comparative Genomics, California Academy of Sciences, San Francisco, CA 94118;
authors.forename: Michelle
authors.initials: M
authors.lastname: Trautwein
mesh_terms: D000349:Africa; D000818:Animals; D001208:Asia; D001315:Australia; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics; D005060:Europe; D014644:Genetic Variation; D054629:Genome, Mitochondrial / Q000235:genetics; D005843:Geography; D018859:Hair Follicle / Q000469:parasitology*; D006239:Haplotypes; D058507:Host Specificity; D006801:Humans; D007843:Latin America; D008925:Mites / Q000145:classification / Q000235:genetics* / Q000502:physiology*; D009656:North America; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV
keywords: Demodex; coevolution; phylogeography; symbiosis