Distribution of two notodendrodid foraminiferal congeners in McMurdo Sound, Antarctica: an example of extreme regional endemism?

We used morphological and molecular surveys to determine the presence or absence of Notodendrodes antarctikos and its congener, Notodendrodes hyalinosphaira, at diverse sites within McMurdo Sound, Antarctica. Morphological surveys were performed using shipboard box-core sampling, as well as handheld coring and visual inspection by divers in shallow (< 23 m) waters. Concurrent molecular analyses were performed using species- and genus-specific PCR primers on environmental DNA extracts. Both survey methods show that N. hyalinosphaira is widely distributed in the region but that N. antarctikos was not detected outside its originally reported range. The survey methods show complementary strengths and weaknesses, with morphological detection being more sensitive in areas where large and distinctive adult forms are present and with molecular detection being more effective for identification of presumed juvenile or propagule stages. Our results suggest that N. antarctikos is a highly endemic protist and may have one of the most restricted ranges ever reported for an Antarctic organism.