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Research
Kozo Watanabe
Ehime University
Corresponding Author
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Background
Ixodid tick species such as Ixodes ovatus and Haemaphysalis flava function as important vectors of tick-borne diseases in Japan. The study of the genetic patterns of tick populations can reveal information regarding the spread of tick-borne disease. We hypothesized that I. ovatus and H. flava have different population genetic structure because of their host mobility in different tick life stages despite sharing of hosts.
Methods
Samples (n = 1 to 77) were collected in 29 (I. ovatus) and 17 (H. flava) sampling locations across Niigata. In this study, we used genetic structure at two mitochondrial loci (cox1, 16S rRNA gene) to infer gene flow patterns of I. ovatus and H. flava from Niigata Prefecture, Japan.
Results
For I. ovatus, pairwise FST and analysis of molecular variance (AMOVA) analyses of cox1 sequences indicated significant among-population differentiation. This was in contrast to H. flava, for which there were only two cases of significant pairwise differentiation and no overall structure. A Mantel test revealed isolation by distance and there was positive spatial autocorrelation of haplotypes in I. ovatus cox1 and 16S sequences, but non-significant results were observed in H. flava in both markers. We found three genetic groups (China 1, China 2 and Japan) in the cox1 I. ovatus tree. Newly sampled I. ovatus grouped together with a published I. ovatus sequence from northern Japan and were distinct from two other I. ovatus groups that were reported from southern China.
Conclusions
The three genetic groups in our data set suggest the potential for cryptic species within the lineage. While many factors can potentially account for the observed differences in genetic structure, including population persistence and large-scale patterns of range expansion, we propose that differences in the mobility of hosts of tick immature stages (small mammals in I. ovatus; birds in H. flava) may be driving the observed patterns.
Keywords
gene flow, host mobility, Mantel test, Spatial autocorrelation, cryptic species
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This is a preprint. It has not completed peer review.
Research
Kozo Watanabe
Ehime University
Corresponding Author
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
History
CURRENT STATUS: Posted
Version 1
Posted 11 Dec, 2019
No community comments so far
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Parasitology
License:
This work is licensed under a CC BY 4.0 License. Read Full License
Background
Ixodid tick species such as Ixodes ovatus and Haemaphysalis flava function as important vectors of tick-borne diseases in Japan. The study of the genetic patterns of tick populations can reveal information regarding the spread of tick-borne disease. We hypothesized that I. ovatus and H. flava have different population genetic structure because of their host mobility in different tick life stages despite sharing of hosts.
Methods
Samples (n = 1 to 77) were collected in 29 (I. ovatus) and 17 (H. flava) sampling locations across Niigata. In this study, we used genetic structure at two mitochondrial loci (cox1, 16S rRNA gene) to infer gene flow patterns of I. ovatus and H. flava from Niigata Prefecture, Japan.
Results
For I. ovatus, pairwise FST and analysis of molecular variance (AMOVA) analyses of cox1 sequences indicated significant among-population differentiation. This was in contrast to H. flava, for which there were only two cases of significant pairwise differentiation and no overall structure. A Mantel test revealed isolation by distance and there was positive spatial autocorrelation of haplotypes in I. ovatus cox1 and 16S sequences, but non-significant results were observed in H. flava in both markers. We found three genetic groups (China 1, China 2 and Japan) in the cox1 I. ovatus tree. Newly sampled I. ovatus grouped together with a published I. ovatus sequence from northern Japan and were distinct from two other I. ovatus groups that were reported from southern China.
Conclusions
The three genetic groups in our data set suggest the potential for cryptic species within the lineage. While many factors can potentially account for the observed differences in genetic structure, including population persistence and large-scale patterns of range expansion, we propose that differences in the mobility of hosts of tick immature stages (small mammals in I. ovatus; birds in H. flava) may be driving the observed patterns.
Figure 1
Figure 2
Figure 3
Figure 4
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