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 Western Antarctic region. 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 was 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. West Antarctic continental shelf populations may be connected via the Antarctic Circumpolar Current or its coastal Counter Current, dependent on particle release location. Improved understanding of the distribution of Antarctic fauna is essential for predicting the impacts of environmental change and determining management strategies for the region.
Highlights
Enclosed by both the Antarctic Circumpolar Current (ACC) and frontal systems the Southern Ocean is often described as an isolated marine environment, Figure 1
Prior to DNA barcoding, a biogeographic distribution classification; cosmopolitan, circum-Antarctic or restricted, was allocated to each initial morphospecies analyzed (Table 1), where: “cosmopolitan” species are those that have been recorded throughout the majority of the world’s oceans and both hemispheres; “cicrum-Antarctic” species are those that have been collected within different regions of the Southern Ocean and are considered to be widespread around the Antarctic and “restricted” species are those only recorded in one Antarctic region or location with no records within the Register of Antarctic Marine Species (RAMS) recorded or Basic Local Alignment Search Tool (BLAST) matches from other localities
No specimens of H. fuligineum were identified from the Weddell Sea, but specimens were found within the Amundsen and Scotia Arc regions
Summary
Enclosed by both the Antarctic Circumpolar Current (ACC) and frontal systems the Southern Ocean is often described as an isolated marine environment, Figure 1. These oceanographic features act as a physical barrier, which are thought to have prevented species movement into and out of the Southern Ocean. A further biogeographic pattern that has long been associated with Antarctic marine fauna is the circum-polarity or circumAntarctic distributions (Arntz et al, 1997; Clarke and Johnston, 2003). Larval dispersal around the continent could be aided by oceanographic currents, including the ACC, its coastal counter current ( referred to as East Wind Drift), and the Weddell and Ross Sea gyres, Figure 1 (Orsi et al, 1993, 1995; Fahrbach et al, 1994; Linse et al, 2007)
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