Pheretimoid earthworms of India: new insight from molecular systematics and phylogenetic relationship with new records

Around the world, the spread of pheretimoid earthworm species from Southeast Asia has raised ecological, environmental, and conservation concerns in urban-suburban settings and forest habitats. There is currently a global discourse surrounding the taxonomic status of pheretimoid earthworms. Therefore, a comparative molecular systematics study was conducted on pheretimoid, utilizing an integrative taxonomy approach that relied on morpho-anatomical characterization and the COI gene. The study generated and compared the 51 COI barcodes of pheretimoid with existing 156 COI sequences of pheretimoid earthworms worldwide, with the primary goal of testing various analytical methods for species delimitation and examining phylogenetic reconstruction. Seven different methods of species delineation were applied, viz., Automatic Barcode Gap Discovery (ABGD), Assemble Species by Automatic Partitioning (ASAP), General Mixed Yule Coalescence (GMYC), Poisson Tree Processes (PTP), Bayesian Poisson Tree Processes (bPTP), Multiple Poisson Tree Processes (mPTP), and Refined Single Linkage (RESL). Additionally, trees using Bayesian Inference (BI) and Maximum Likelihood (ML) were created for phylogenetic studies. The results unveiled 10 species belonging to 3 genera, viz., Amynthas, Metaphire, and Polypheretima. Furthermore, the study reported one new record from India, Amynthas andersoni choprai, and range expansion of Amynthas alexandri, Metaphire posthuma, and Polypheretima elongata to Manipur, the north-eastern region of India. Further, the peregrine species Amynthas corticis was reported for the first time in Madhya Pradesh in the central part of India. The study concluded that the genera Amynthas, Metaphire, and Pheretima do not exhibit monophyletic lineages which corroborates with previous studies. The study aligns with earlier studies that recommended reassessing the numerical revision of the genus Pheretima auct. (Sims & Easton, 1972). In addition, a comprehensive analysis of the evolutionary relationships between multiple pheretimoid earthworms in India has been provided, laying the foundation for understanding their origins.