Surprisingly high levels of biodiversity and endemism amongst Antarctic rotifers uncovered with mitochondrial DNA

Abstract

Antarctica is one of the harshest environments on the planet because of its extreme climatic conditions, with prolonged winters, freezing temperatures and lack of liquid water. While almost the entire continent (99.7%) is covered year round by snow and ice, some mountain peaks and coastal areas are ice-free and sustain life. Invertebrates dominate in this environment, but despite their obvious abundance, little is known of one major player, the rotifers. In this study, we examine the distribution and diversity of rotifers from across continental Antarctica using mitochondrial c oxidase subunit I DNA sequences, and compare to sequences extracted from specimens collected in limited locations in the Antarctic Peninsula (AP) and in Tierra del Fuego (TF) in South America. We identified rotifers of the Class Bdelloidea to be the most frequently sampled micro-organisms in soil and limno-terrestrial environments. From the Antarctic samples, 514 sequences were generated and 37 distinct lineages were identified (40 putative species based on the PTP model) within Philodina, Adineta and unidentified bdelloids (all currently considered endemic to Antarctica). Overall, we observed widespread ranges for some rotifers in continental Antarctica, many of them exceeding 2000 km. Only one bdelloid lineage (Adineta cf. gracilis) from continental Antarctica was also present in maritime Antarctica. No close similarities were found with worldwide locations, or amongst AP and TF. Our broad coverage across Antarctica shows unique lineages that may represent potential species surpassing what is presently known from morphology, even when conservative approaches are applied for species delimitation.

Keywords:

• bdelloid
• COI gene
• continental Antarctica
• DNA lineage
• endemicity
• biogeography
• limno-terrestrial environment
• microfauna

Acknowledgements

We would like to thank Vanessa Reid (managing editor of Biodiversity), Diego Fontaneto and an anonymous reviewer for their valuable feedback and contribution to improving the manuscript. This study was partially funded and supported by the Australian Antarctic Division Project (ASAC 2355). We want to thank the University of Adelaide for a PhD scholarship to AVC and the South Australian Museum Mawson Trust for providing funding for the Sir Douglas Mawson Doctoral Scholarship. We would also like to thank the Australian Antarctic Stations leaders and assistants who supported field work in Antarctica. We deeply thank Mark Shultz (The University of Melbourne) for sampling in Antarctica. We would also like to thank Chester Sands, Sandra McInnes, Peter Convey and Paul Geissler (British Antarctic Survey) for contributing with soil samples (from AP and DML) and laboratory facilities; and to Allan Green, Leopoldo Sancho and Ana Pintado (Complutense University of Madrid) for providing soil samples from TF and laboratory facilities. We are grateful to Mohammad Javidkar, Andrew Austin and Steven Cooper (The University of Adelaide) for their intellectual support; and to Kirsty Kemp (Zoological Society of London) and the International Graduate Training Course in Antarctic Biology for help with specimen collection. We also appreciate the laboratory support provided by Maria Manjarrez, Rebecca Stonor, Tanya Matic, Pauline Glocke (The University of Adelaide) and Federica Colombo. We are grateful to the DNA sequencing agencies BOLD and the Canadian Centre for DNA Barcoding (CCDB).