DNA barcoding reveals cryptic diversity in the peanut worm Sipunculus nudus

Area of Science:

• Marine Biology
• Genetics
• Biodiversity

Background:

• Peanut worm (Sipunculus nudus) is a cosmopolitan marine invertebrate.
• Previous analysis of mitochondrial COI gene sequences showed high genetic variation and paraphyletic relationships in S. nudus.
• This suggests potential misidentification or cryptic diversity within the genus Sipunculus.

Purpose of the Study:

• To investigate the genetic diversity of Sipunculus nudus in coastal waters of southern China and Taiwan.
• To understand the genetic structure and potential cryptic diversity of this species.
• To inform resource management strategies for S. nudus.

Main Methods:

• Collected Sipunculus nudus specimens from southern China and Taiwan.
• Analyzed mitochondrial cytochrome c oxidase subunit I (COI) gene sequences.
• Constructed phylogenetic trees to assess genetic relationships and population structure.

Main Results:

• Identified four distinct clades of S. nudus in the study region.
• Three clades (A, B, C) were unique to southern China and Taiwan.
• One clade (D) grouped with individuals from the Atlantic coast of Central America, and clades A and D co-occurred geographically, challenging isolation hypotheses.

Conclusions:

• The study reveals underestimated genetic diversity in Sipunculus nudus, with four distinct clades identified.
• Geographic distribution patterns do not solely explain the observed genetic divergence.
• The identified cryptic diversity is particularly vulnerable to anthropogenic pressures in coastal ecosystems.