Abstract
The distributional patterns of Arctic species are commonly affected by the recurring Pleistocene glaciations, which contributed to transient or permanent genetic isolation. Here we explore the phylogeography of the climate-sensitive Arctic fairy shrimp Branchinecta paludosa, which has a circumpolar range of distribution, with certain southern alpine outreaches. We sequenced the mitochondrial cytochrome oxidase I subunit from samples collected at ten Nearctic and nine Palaearctic sites, including southern alpine populations. A handful of ambiguous bases in certain sequences strongly suggested heteroplasmy, possibly being reported for the first time in anostracans. Evolutionary analysis of the sequence variations showed a temporal divergence coinciding with the flooding of the Beringia land bridge. Sequence alignment with outgroup taxa for phylogenetic analysis showed three distinct major clades, reflecting geographical isolation. The most divergent clade, from isolated alpine ponds in the Rocky Mountains, probably represents a different and undescribed species. Two other major clades corresponded to the geographical areas of Nearctic and Palaearctic. Finally, the southern Palaearctic outstretch showed genetic separation, most likely representing a geographical and climatic isolated relict population.
Highlights
The Arctic offers an important field of research for understanding dispersal, vicariance and recent responses to climate change
The historical fusion of Palaearctic and Nearctic regions via the Beringia land bridge, which persisted through the Miocene and during the Pleistocene, allowed an intercontinental flux of species (Cook et al, 2005)
We amplified the COI region of Branchinecta paludosa, which has proved useful in resolving geographic structuring within a number of different species, including branchiopod crustaceans (Cox & Hebert, 2001; Reniers et al, 2013)
Summary
The Arctic offers an important field of research for understanding dispersal, vicariance and recent responses to climate change. The Beringia land bridge was dominated by cold steppe climate, favouring ephemeral ponds and temporal water bodies, suitable for short-lived freshwater crustaceans. These invertebrates disperse over land by drought- and frost-resistant resting eggs by means of wind or zoochory, and may persist in dormancy for decades (Hairston, 1996). Muller 1788) offers the most distinct biogeographic exception It is widespread in small cold water lakes and ponds around the Arctic Sea, with southern outreaches along the Rocky Mountains and in the alpine regions of South Norway and Sweden, and a last isolated outpost in the Tatra Mountains (Slovak republic; Fig. 1). It is widespread in small cold water lakes and ponds around the Arctic Sea, with southern outreaches along the Rocky Mountains and in the alpine regions of South Norway and Sweden, and a last isolated outpost in the Tatra Mountains (Slovak republic; Fig. 1). Fugate (1992) compared morphology and allozymes for 15 Nearctic and two Eurasian branchinectids and considered B. paludosa as the bridging species between the Nearctic and Palaearctic lineages, implying that Old world Branchinecta species should form a phylogenetic cluster of relatively closely related species
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