Equus roundworms (Parascaris spp.) are undergoing divergence due to
natural and anthropogenic factors
Abstract
The evolution of parasites is often directly affected by the host’s
environment or behavior. Studies on the evolution of the same parasites
in different hosts are extremely attractive and highly relevant to our
understanding of divergence and speciation. Here we analyzed the genetic
variation of Equus roundworm populations in different hosts (horses,
zebras and donkeys), and presented the first molecular evidence of
divergence in Equus roundworms (Parascaris univalens). At the genetic
level, Equus roundworms were mainly separated into two clades
(Horse-derived and Zebra & Donkey-derived). This divergence began at
600-1500 years ago, which interestingly coincided with the domestication
history of horses. We found that compared with horse-derived roundworms,
most of the key enzymes related to glycolysis were under strong positive
selection in zebra & donkey-derived roundworms, indicating that the
evolution of the metabolic level was one of the main reasons for the
divergence. In addition, we conducted a selective scan of
resistance-related genes and found that the three populations were under
different degrees of selection. This prompted us to pay attention to the
possible impact of drugs on divergence, not just the drug resistance.
This work supports that divergence or speciation is a continuous and
dynamic process, and continuous monitoring of environmental factors is
conducive to further understanding the adaptive evolution of roundworms.