Dataset Information

Genetic Melting Pot in Blacklegged Ticks at the Northern Edge of their Expansion Front.

ABSTRACT: Blacklegged ticks (Ixodes scapularis) are considered to be the main vector of Lyme disease in eastern North America. They may parasitize a wide range of bird and mammal hosts. Northward dispersal of blacklegged ticks has been attributed largely to movement of hosts to areas outside of the current range of the tick, in conjunction with climate change. To better understand the drivers of range expansion in the blacklegged tick, we need investigations of the genetic connectivity and differentiation of tick populations at a fine spatial scale using appropriate markers. In this study, we investigated genetic connectivity and differentiation in blacklegged ticks, in an area of putatively recent advance in Ontario and Quebec, Canada, using microsatellite markers. Our findings suggest patchy differentiation of alleles, no spatial pattern of genetic structure, and genetic subdivision within sites, which are consistent with the very limited evidence available near the leading edge of range expansion of blacklegged ticks into Canada. These findings are consistent with the prevailing hypothesis, drawn from a variety of fields of study, suggesting that migratory birds from a variety of regions may be bringing hitchhiking ticks northward into Canada.

SUBMITTER: Talbot B

PROVIDER: S-EPMC7423068 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Genetic Melting Pot in Blacklegged Ticks at the Northern Edge of their Expansion Front.

Talbot Benoit B Leighton Patrick A PA Kulkarni Manisha A MA

The Journal of heredity 20200801 4

Blacklegged ticks (Ixodes scapularis) are considered to be the main vector of Lyme disease in eastern North America. They may parasitize a wide range of bird and mammal hosts. Northward dispersal of blacklegged ticks has been attributed largely to movement of hosts to areas outside of the current range of the tick, in conjunction with climate change. To better understand the drivers of range expansion in the blacklegged tick, we need investigations of the genetic connectivity and differentiation ...[more]

PMID: 32609830

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Project description:Lyme disease is a major vector-borne bacterial disease in the USA. The disease is caused by Borrelia burgdorferi, and transmitted among hosts and humans, primarily by blacklegged ticks (Ixodes scapularis). The ~25 B. burgdorferi genotypes, based on genotypic variation of their outer surface protein C (ospC), can be phenotypically separated as strains that primarily cause human diseases-human invasive strains (HIS)-or those that rarely do. Additionally, the genotypes are non-randomly associated with host species. The goal of this study was to examine the extent to which phenotypic outcomes of B. burgdorferi could be explained by the host communities fed upon by blacklegged ticks. In 2006 and 2009, we determined the host community composition based on abundance estimates of the vertebrate hosts, and collected host-seeking nymphal ticks in 2007 and 2010 to determine the ospC genotypes within infected ticks. We regressed instances of B. burgdorferi phenotypes on site-specific characteristics of host communities by constructing Bayesian hierarchical models that properly handled missing data. The models provided quantitative support for the relevance of host composition on Lyme disease risk pertaining to B. burgdorferi prevalence (i.e. overall nymphal infection prevalence, or NIPAll) and HIS prevalence among the infected ticks (NIPHIS). In each year, NIPAll and NIPHIS was found to be associated with host relative abundances and diversity. For mice and chipmunks, the association with NIPAll was positive, but tended to be negative with NIPHIS in both years. However, the direction of association between shrew relative abundance with NIPAll or NIPHIS differed across the two years. And, diversity (H') had a negative association with NIPAll, but positive association with NIPHIS in both years. Our analyses highlight that the relationships between the relative abundances of three primary hosts and the community diversity with NIPAll, and NIPHIS, are variable in time and space, and that disease risk inference, based on the role of host community, changes when we examine risk overall or at the phenotypic level. Our discussion focuses on the observed relationships between prevalence and host community characteristics and how they substantiate the ecological understanding of phenotypic Lyme disease risk.

Project description:Due to their strategic geographic location between three different continents, Sicily and Southern Italy have long represented a major Mediterranean crossroad where different peoples and cultures came together over time. However, its multi-layered history of migration pathways and cultural exchanges, has made the reconstruction of its genetic history and population structure extremely controversial and widely debated. To address this debate, we surveyed the genetic variability of 326 accurately selected individuals from 8 different provinces of Sicily and Southern Italy, through a comprehensive evaluation of both Y-chromosome and mtDNA genomes. The main goal was to investigate the structuring of maternal and paternal genetic pools within Sicily and Southern Italy, and to examine their degrees of interaction with other Mediterranean populations. Our findings show high levels of within-population variability, coupled with the lack of significant genetic sub-structures both within Sicily, as well as between Sicily and Southern Italy. When Sicilian and Southern Italian populations were contextualized within the Euro-Mediterranean genetic space, we observed different historical dynamics for maternal and paternal inheritances. Y-chromosome results highlight a significant genetic differentiation between the North-Western and South-Eastern part of the Mediterranean, the Italian Peninsula occupying an intermediate position therein. In particular, Sicily and Southern Italy reveal a shared paternal genetic background with the Balkan Peninsula and the time estimates of main Y-chromosome lineages signal paternal genetic traces of Neolithic and post-Neolithic migration events. On the contrary, despite showing some correspondence with its paternal counterpart, mtDNA reveals a substantially homogeneous genetic landscape, which may reflect older population events or different demographic dynamics between males and females. Overall, both uniparental genetic structures and TMRCA estimates confirm the role of Sicily and Southern Italy as an ancient Mediterranean melting pot for genes and cultures.

Dataset Information

Genetic Melting Pot in Blacklegged Ticks at the Northern Edge of their Expansion Front.

Publications

Genetic Melting Pot in Blacklegged Ticks at the Northern Edge of their Expansion Front.

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