Antarctic Bdelloid Rotifers: Diversity, Endemism and Evolution
1 Antarctic bdelloid rotifers: diversity, endemism and evolution 2 3 Introduction 4 5 Antarctica’s ecosystems are characterized by the challenges of extreme environmental 6 stresses, including low temperatures, desiccation and high levels of solar radiation, all of 7 which have led to the evolution and expression of well-developed stress tolerance features in 8 the native terrestrial biota (Convey, 1996; Peck et al., 2006). The availability of liquid water, 9 and its predictability, is considered to be the most important driver of biological and 10 biodiversity processes in the terrestrial environments of Antarctica (Block et al., 2009; 11 Convey et al., 2014). Antarctica’s extreme conditions and isolation combined with the over- 12 running of many, but importantly not all, terrestrial and freshwater habitats by ice during 13 glacial cycles, underlie the low overall levels of diversity that characterize the contemporary 14 faunal, floral and microbial communities of the continent (Convey, 2013). Nevertheless, in 15 recent years it has become increasingly clear that these communities contain many, if not a 16 majority, of species that have survived multiple glacial cycles over many millions of years 17 and undergone evolutionary radiation on the continent itself rather than recolonizing from 18 extra-continental refugia (Convey & Stevens, 2007; Convey et al., 2008; Fraser et al., 2014). 19 With this background, high levels of endemism characterize the majority of groups that 20 dominate the Antarctic terrestrial fauna, including in particular Acari, Collembola, Nematoda 21 and Tardigrada (Pugh & Convey, 2008; Convey et al., 2012). 22 The continent of Antarctica is ice-bound, and surrounded and isolated from the other 23 Southern Hemisphere landmasses by the vastness of the Southern Ocean.
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