Distributional Patterns of Polychaetes Across the West Antarctic Based on DNA Barcoding and Particle Tracking Analyses

Abstract

Recent genetic investigations have uncovered a high proportion of cryptic species within Antarctic polychaetes. It is likely that these evolved in isolation during periods of glaciation, and it is possible that cryptic populations would have remained geographically restricted from one another occupying different regions of Antarctica. By analysing the distributions of nine morphospecies, (six of which contained potential cryptic species), we find evidence for widespread distributions within the West Antarctic. Around 60% of the cryptic species exhibited sympatric distributions, and at least one cryptic clade was found to be widespread. Additional DNA barcodes from GenBank and morphological records extended the observed range of three species studied here, and indicate potential circum-Antarctic traits. Particle tracking analyses were used to model theoretical dispersal ranges of pelagic larvae. Data from these models suggest that the observed species distributions inferred from genetic similarity could have been established and maintained through the regional oceanographic currents, including the Antarctic Circumpolar Current (ACC) and its coastal counter current. Improved understanding of the distribution of Antarctic fauna is essential for predicting the impacts of environmental change and determining management strategies for the region.

DNA barcoding uncovers cryptic diversity in 50% of deep-sea Antarctic polychaetes

“…The geographical and depth distribution of the different cryptic clades and potential species identified within this study are yet to be investigated (Brasier et al  [65]), although some biogeographic implications of these data are already evident. The presence of cryptic Antarctic clades within morphospecies described from the Northern Hemisphere including Glycera capitata, Scalibregma inflatum and Maldane sarsi indicates that we should be questioning the current ‘usual’ identifications of cosmopolitan polychaete species.…”

Taxonomy and phylogeny of mud owls (Annelida: Sternaspidae), including a new synonymy and new records from the Southern Ocean, North East Atlantic Ocean and Pacific Ocean: challenges in morphological delimitation

“…The Antarctic specimens were also collected from relatively deep waters (~200-1500 m) and showed high connectivity along the western Antarctic Peninsula, reflecting the widespread distributional patterns recently found for many cryptic polychaete species collected from a similar depth range from across the West Antarctic (Brasier et al 2017). However, Brasier et al (2017) also found species from this region with highly restricted ranges, concluding that differences in Southern Ocean species distributions are more likely to rely on a complex of factors, rather than just a single factor such as oceanographic currents.…”

Annelids of the eastern Australian abyss collected by the 2017 RV ‘Investigator’ voyage

“…While the geographic range from eastern Australia to the GAB is likely, the apparent broad bathymetric range from shelf to abyssal depths (60–3884 m) requires further investigation as this putative depth range would extend vertically across shelf, slope and abyssal faunal zones. Genetic evidence suggests some deep-water annelids have ‘broad’ (> 2500 m sensu Glazier and Etter 2014 ) depth ranges, e.g., the maldanid Nicomache lokii range 3668 m ( Eilertsen et al 2018 ), but bathymetric ranges of other deep-sea annelid species are more restricted e.g., 1300 m for the spionid Laonice weddellia (see Brasier et al 2017 ). According to the census of abyssal polychaetes (> 2000 m), ~ 62–78% of species within a family had bathymetric ranges smaller than 1000 m ( Paterson et al 2009 ).…”