Molecular Characterization and Haplotype Diversity of Aporcelaimellus obtusicaudatus (Bastian, 1865) Altherr, 1968 (Dorylaimida, Aporcelaimidae) from India.

Aporcelaimellus obtusicaudatus was recovered from mustard and sugarcane fields of Uttar Pradesh and Uttarakhand, India. The present species was identified through morphology, molecular and phylogenetic analysis. The Indian populations are characterized by having females with a body length (1.7–3.4 mm), lip region (4.9–8.8 µm), Amphids 6–9 µm, odontostyle length (15.7–26.4 µm), neck length (374.6–745.1 µm), pharyngeal expansion occupying 45–60% of neck length, simple uterus (67.4–124.3 µm), V = 49.1–58.7, female tail (32–44.9 µm, c = 41.1–105, c' = 0.5–1.3) with short, conoid, rounded terminus to convex conical. The molecular phylogenetic analysis based on 18S and 28S rDNA revealed A. obtusicaudatus as a paraphyly. The present populations of Indian A. obtusicaudatus (OM269524; OP020675) placed close to deposited Indian sequence (OP048816; OP048823) and Slovakian populations of A. obtusicaudatus (MH206119). The result of 28S rDNA phylogeny showed that the present population (OM258706) placed close to other populations of the same species from India (OM418794) with 0.55 posterior probability supports. The haplotype analysis based on 28S rDNA revealed 6 haplotypes, which displayed low nucleotide (π = 0.013) diversity. In contrast, haplotype diversity (Hd) was 1.00, and the number of segregating sites (S) was 14. The phylogenetic analysis grouped the various populations into two clades, and the result showed German populations placed into two clades, which showed high variability in haplotype supported by the haplotype network. Tajima (D) and Fu's Fs were found to be negative (P > 0.05), whereas the overall FST value was 0.31040 (P = 0.118). In conclusion, genetic analysis revealed 31.04% variation among groups/populations and 68.95 within populations, indicating a low genetic variation between the same populations of A. obtusicaudatus belonging to the same country. [ABSTRACT FROM AUTHOR]