Molecular phylogenetics and species-level systematics of Baylisascaris

Abstract

Nucleotide sequences representing nine genes and five presumptive genetic loci were used to infer phylogenetic relationships among seven Baylisascaris species, including one species with no previously available molecular data. These genes were used to test the species status of B. procyonis and B. columnaris using a coalescent approach. Phylogenetic analysis based on combined analysis of sequence data strongly supported monophyly of the genus and separated the species into two main clades. Clade 1 included B. procyonis, B. columnaris, and B. devosi, species hosted by musteloid carnivores. Clade 2 included B. transfuga and B. schroederi from ursids, B. ailuri, a species from the red panda (a musteloid), and B. tasmaniensis from a marsupial. Within clade 2, geographic isolates of B. transfuga, B. schroederi (from giant panda), and B. ailuri formed a strongly supported clade. In certain analyses (e.g., some single genes), B. tasmaniensis was sister to all other Baylisascaris species rather than sister to the species from ursids and red panda. Using one combination of priors corresponding to moderate population size and shallow genetic divergence, the multispecies coalescent analysis of B. procyonis and B. columnaris yielded moderate support (posterior probability 0.91) for these taxa as separate species. However, other prior combinations yielded weak or no support for delimiting these taxa as separate species. Similarly, tree topologies constrained to represent reciprocal monophyly of B. columnaris and B. procyonis individuals (topologies consistent with separate species) were significantly worse in some cases, but not others, depending on the dataset analyzed. An expanded analysis of SNPs and other genetic markers that were previously suggested to distinguish between individuals of B. procyonis and B. columnaris was made by characterization of additional individual nematodes. The results suggest that many of these SNPs do not represent fixed differences between nematodes derived from raccoon and skunk hosts.

The morphological and molecular characterization of Baylisascaris devosi Sprent, 1952 (Ascaridoidea, Nematoda), collected from Pine marten (Martes martes) in Iran

“…Due to the high level of divergence in the Cox1 gene, it is appropriate to consider it for phylogenetic and taxonomic studies of genus Baylisascaris . The results of some studies confirmed that mitochondrial genes are suitable markers for phylogenetic relationships and evolutionary biological aspects within the genus Baylisascaris [ 24 , 26 , 27 ].…”

“…DNA sequence-based methods have been widely applied over recent years for species identification, classification and evaluation of phylogenetic relationships among ascarid nematodes [ 24 , 25 ]. Morphological differences between Baylisascaris species are not so clear; therefore, utilization of the sequence data will be helpful in this aspect.…”

“…This nematode lives in the small intestine of carnivorous mammals such as different species of marten and the third-stage larvae present in the cervical and thoracic musculature of paratenic hosts such as rodents and birds [ 1 , 2 , 5 ]. Human is the accidental host of B. devosi , and baylisascariasis in human can be caused by this nematode, but the clinical diagnosis of the disease is based on the serological tests, and these tests cannot discriminate among Baylisascaris species [ 24 , 28 ]. Until now, none of the Baylisascaris species have been reported from Iran, and to our knowledge this study also is the first report of B. devosi isolated from the Pine marten.…”

“…no. Cox1 Location References B. devosi Martes martes MN960313 MN960312 MN961617 Iran Current study B. devosi Pekania pennanti MG937776 MH030598 MH795151 Canada [ 24 ] B. devosi Martes zibellina KY465564 KY465505 KX646394 Russia [ 9 ] B. procyonis Procyon lotor MG937774 and MG937775 MH030597 – USA [ 24 ] B. procyonis Procyon lotor AY821774 – – USA [ 30 ] B. procyonis Procyon lotor – JQ403615 – Norway [ 31 ] B. procyonis Procyon lotor – MH030597 – USA [ 32 ] B. procyonis Procyon lotor – – KJ69855...…”

Nematodes from the Tasmanian devil (Sarcophilus harrisii(Boitard)), with the description ofSarcophiloxyuris longusn. gen. and n. sp. (Oxyuridae)

“…Of the nematode specimens collected, the majority were determined to be B. tasmaniensis based on morphological and molecular analysis. Molecular sequences obtained in this study (GenBank sequences MW063459-MW063468) were a 100% match to a specimen of B. tasmaniensis (GenBank sequence MH030603; Camp et al, 2018) and clustered with B. tasmaniensis with 100% branch support (fig. 1; table 3).…”