Rosa F, Caeiro M F, Carvalho M, Dias D, Pina-Martins F
Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017, Lisbon, Portugal.
Centre for Ecology, Evolution and Environmental Changes (CE3C) & CHANGE - Global Change and Sustainability Institute, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016, Lisbon, Portugal.
Parasitol Res. 2025 Sep 18;124(9):105. doi: 10.1007/s00436-025-08550-9.
Rhipicephalus sanguineus is a tick species characterized by high intraspecific variability, even among populations occupying the same habitats. This study investigated whether two distinct phenotypes of R. sanguineus, collected from four geographically separated regions, are associated with specific nucleotide polymorphisms in the mitochondrial cox1 and 16S rRNA gene regions-markers commonly employed in phylogenetic analyses. Morphometric analysis based on established criteria clearly distinguished two morphotypes-Morphotype 1 and Morphotype 2-with statistically significant differences. This morphological differentiation was supported by phylogenetic and genetic divergence analyses, primarily based on mitochondrial cox1 sequences, which revealed six polymorphic sites within the analyzed fragment. Among the identified haplotypes, two-Haplotype 2a and Haplotype 2b-were consistently associated with Morphotype 2. This genetic segregation was confirmed in extended analyses including reference isolates (morphologically and/or genetically defined either as R. sanguineus or R. hibericus). These analyses also demonstrated a close phylogenetic relationship between Morphotype 1 and the R. sanguineus neotype, as well as between R. hibericus and both morphotypes. Although the 16S rRNA marker exhibited lower resolution, it still effectively distinguished the two morphotypes and corroborated the haplotype assignments established by the cox1 phylogeny. The observed genetic divergence (p-distance of 1% in cox1 gene) and the phylogenetic relationship between R. sanguineus and R. hibericus confirmed that R. sanguineus is a polymorphic species, with well-defined haplo-morphotypes, and that R. hibericus is not genetically distinguishable from R. sanguineus.
血红扇头蜱是一种具有高度种内变异性的蜱种，即使在占据相同栖息地的种群之间也是如此。本研究调查了从四个地理上分离的区域采集的两种不同表型的血红扇头蜱，是否与线粒体细胞色素氧化酶亚基1（cox1）和16S核糖体RNA（rRNA）基因区域中的特定核苷酸多态性相关，这两个区域是系统发育分析中常用的标记。基于既定标准的形态测量分析清楚地区分了两种形态型——形态型1和形态型2——具有统计学上的显著差异。这种形态分化得到了系统发育和遗传分化分析的支持，主要基于线粒体cox1序列，该序列在分析片段内揭示了六个多态性位点。在鉴定出的单倍型中，两种——单倍型2a和单倍型2b——始终与形态型2相关。在包括参考分离株（在形态上和/或遗传上定义为血红扇头蜱或希伯里克扇头蜱）的扩展分析中证实了这种遗传分离。这些分析还表明形态型1与血红扇头蜱新模式之间以及希伯里克扇头蜱与两种形态型之间存在密切的系统发育关系。尽管16S rRNA标记的分辨率较低，但它仍然有效地区分了两种形态型，并证实了由cox1系统发育建立的单倍型分配。观察到的遗传分化（cox1基因的p距离为1%）以及血红扇头蜱和希伯里克扇头蜱之间的系统发育关系证实，血红扇头蜱是一个多态性物种，具有明确的单倍型-形态型，并且希伯里克扇头蜱在遗传上与血红扇头蜱无法区分。
