Globally spreading ticks evolved asexual reproduction multiple times
The Asian longhorned tick, Haemaphysalis longicornis, spreads serious pathogens, including severe fever with thrombocytopenia syndrome (SFTS) virus, Rickettsia and Theileria, and its bite can cause a meat allergy in humans. Once confined to Japan, South Korea, North Korea, China and Russia, the ticks have expanded across Oceania, and in 2017, they were detected in the United States. Perhaps…
The Asian longhorned tick, Haemaphysalis longicornis, has rapidly spread across the globe, carrying serious pathogens like the SFTS virus and causing meat allergies in humans. Native to East Asia, the tick has now established populations in Oceania and the United States. Scientists believe this rapid expansion may be due to the tick's unique ability to reproduce asexually, a process called parthenogenesis.
Only female ticks are capable of this form of reproduction, and they have been found outside their native range in places like Fiji, New Caledonia, and Australia. Researchers analyzed the genetic makeup of both native Japanese and introduced Oceanian populations using complete mitogenomes and genome-wide single-nucleotide polymorphisms (SNPs).
Initially, the genetic data suggested that a parthenogenetic branch had spread worldwide, but the presence of male ticks added complexity to the picture. Further analysis revealed that gene flow existed between sexual and parthenogenetic lineages, indicating that parthenogenesis evolved multiple times independently. This repeated evolution of asexual reproduction may help explain the tick's ability to rapidly colonize new areas and spread pathogens globally.
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