Multi-locus sequence typing of Ixodes ricinus and its symbiont Candidatus Midichloria mitochondrii across Europe reveals evidence of local co-cladogenesis in Scotland

Al-Khafaji, A. M. et al. (2019) Multi-locus sequence typing of Ixodes ricinus and its symbiont Candidatus Midichloria mitochondrii across Europe reveals evidence of local co-cladogenesis in Scotland. Ticks and Tick-borne Diseases, 10(1), pp. 52-62. (doi: 10.1016/j.ttbdis.2018.08.016) (PMID:30197267)

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Ticks have relatively complex microbiomes, but only a small proportion of the bacterial symbionts recorded from ticks are vertically transmitted. Moreover, co-cladogenesis between ticks and their symbionts, indicating an intimate relationship over evolutionary history driven by a mutualistic association, is the exception rather than the rule. One of the most widespread tick symbionts is Candidatus Midichloria, which has been detected in all of the major tick genera of medical and veterinary importance. In some species of Ixodes, such as the sheep tick Ixodes ricinus (infected with Candidatus Midichloria mitochondrii), the symbiont is fixed in wild adult female ticks, suggesting an obligate mutualism. However, almost no information is available on genetic variation in Candidatus M. mitochondrii or possible co-cladogenesis with its host across its geographic range. Here, we report the first survey of Candidatus M. mitochondrii in I. ricinus in Great Britain and a multi-locus sequence typing (MLST) analysis of tick and symbiont between British ticks and those collected in continental Europe. We show that while the prevalence of the symbiont in nymphs collected in England is similar to that reported from the continent, a higher prevalence in nymphs and adult males is apparent in Wales. In general, Candidatus M. mitochondrii exhibits very low levels of sequence diversity, although a consistent signal of host-symbiont coevolution was apparent in Scotland. Moreover, the tick MLST scheme revealed that Scottish specimens form a clade that is partially separated from other British ticks, with almost no contribution of continental sequence types in this north-westerly border of the tick’s natural range. The low diversity of Candidatus M. mitochondrii, in contrast with previously reported high rates of polymorphism in I. ricinus mitogenomes, suggests that the symbiont may have swept across Europe recently via a horizontal, rather than vertical, transmission route.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Gilbert, Dr Lucy
Authors: Al-Khafaji, A. M., Clegg, S. R., Pinder, A. C., Luu, L., Hansford, K. M., Seelig, F., Dinnis, R. E., Margos, G., Medlock, J. M., Feil, E. J., Darby, A. C., McGarry, J. W., Gilbert, L., Plantard, O., Sassera, D., and Makepeace, B. L.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:Ticks and Tick-borne Diseases
ISSN (Online):1877-9603
Published Online:31 August 2018
Copyright Holders:Copyright © 2018 Elsevier GmbH.
First Published:First published in Ticks and Tick-borne Diseases 10(1):52-62
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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