The diversity and evolutionary relationships of ticks and tick-borne bacteria in China

Phylogenetic tree of tick and tick-associated bacteria in this study. We collected more than 20,000 contemporary and historical
(up to 60 years of preservation) tick samples representing a wide range of tick
biodiversity across diverse geographic regions in China. Metagenomic sequencing
was performed on individual ticks to obtain the complete or near-complete
mitochondrial (mt) genome sequences from 46 tick species, among which mitochondrial
genomes were revealed for the first time for 23 species. These new mt genomes
data greatly expanded the diversity of many tick groups and revealed five
cryptic species. Utilizing the same metagenomic sequence data we identified
divergent and abundant bacteria in <i>Haemaphysalis</i>,
<i>Ixodes</i>, <i>Dermacentor</i> and <i>Carios </i>ticks,
including nine species of pathogenetic bacteria and potentially new species
within the genus <i>Borrelia</i>. We also
used these data to explore the evolutionary relationship between ticks and
their associated bacteria, revealing a pattern of long-term co-divergence
relationship between ticks and <i>Rickettsia</i>
and <i>Coxiella </i>bacteria.