ABSTRACT
Crustacea are an enormously diverse natural group. Although a few lineages have adapted to life on land, the vast majority of them (more than 52,000 described species) are aquatic, living in marine or freshwater environments, where they are as abundant as insects are on land. The aquatic realm also includes a proportion of settings where the modest ≈ 3.5% of earth’s oceans salt concentration can be vastly exceeded, at times approaching levels close to halite precipitation. Until recently, these aquatic ecosystems were largely considered devoid of life and trivial. The later discovery of rich microbial communities overturned such ideas and sparked interest. The list of eukaryotic saltysurvivors though is very limited. Among metazoans, admittedly the most accomplished survivors of hypersaline settings come from Crustacea and are the brine shrimps of the genus Artemia. This ancient anostracan lineage is a close relative to other freshwater branchiopod representatives, which collectively comprise the main component of continental zooplankton. Artemia has developed remarkable adaptations that enable it to cope with the extreme challenges of brine life. Freshwater and hypersaline ecosystems share many attributes, but they also differ in many ways. We know more about phylogeographic patterns in the former type, presumably due to higher relative occurrence and associated lineage diversity. Similar research on the latter type of ecosystems has only recently been accumulating and a reasonable query is whether genealogical patterns in hypersaline habitats are in any way particular. In this chapter, an overview of current phylogeographic knowledge in brine settings is given using Artemia as a model-system. Phylogeographic investigations in this crustacean, coupled with or aided by phylogenetic and systematic assessments, have revealed patterns, some of which bear an idiosyncratic signature. The chapter concludes by highlighting the potential of Artemia in modern evolutionary research as well as in surveys dealing with genomic responses to extreme environments.
