Abstract
The paradigm of large geographic ranges in the deep sea has been challenged by genetic studies, which often reveal putatively widespread species to be several taxa with more restricted ranges. Recently, a phylogeographic study revealed that the tubeworm Sclerolinum contortum (Siboglinidae) inhabits vents and seeps from the Arctic to the Antarctic. Here, we further test the conspecificity of the same populations of S. contortum with additional mitochondrial and nuclear markers. We also investigate the genetic connectivity of another species with putatively the same wide geographic range - Nicomache lokii (Maldanidae). Our results support the present range of S. contortum, and the range of N. lokii is extended from vents and seeps in the Nordic Seas to mud volcanoes in the Barbados Trench and Antarctic vents. Sclerolinum contortum shows more pronounced geographic structure than N. lokii, but whether this is due to different dispersal capacities or reflects the geographic isolation of the sampled localities is unclear. Two distinct mitochondrial lineages of N. lokii are present in the Antarctic, which may result from two independent colonization events. The environmental conditions inhabited by the two species and implications for their distinct habitat preference is discussed.
Highlights
The fragmented distribution of reducing environments implies that CBE-restricted species have to disperse across areas of unsuitable habitat to colonize new localities and to maintain connectivity between populations
This study aims to: 1) further test the conspecificity of the populations of S. contortum from the Arctic, Gulf of Mexico and Antarctic with additional mitochondrial and nuclear markers, 2) test the conspecificity of the populations of N. lokii from the Arctic, Barbados Trench and the Antarctic, 3) compare the genetic divergence and putative population connectivity from the Arctic to the Antarctic of S. contortum and N. lokii and 4) assess how the environmental conditions inhabited by these two species may relate to their habitat preference and distributions
The results presented here support that both Nicomache lokii and Sclerolinum contortum are distributed all the way from the Arctic to the Antarctic, giving them the widest recorded geographic range of any species obligate to chemosynthesis-based ecosystems, which is supported by genetic data
Summary
The fragmented distribution of reducing environments implies that CBE-restricted species have to disperse across areas of unsuitable habitat to colonize new localities and to maintain connectivity between populations. We present new findings of worms morphologically identified as N. lokii from the HMMV, the Barbados Trench mud volcanoes[33] and from hydrothermal vents in the Antarctic If these populations are conspecific, it would extend the range of N. lokii from the Arctic to the Barbados Trench and the Antarctic, giving it a similar range as S. contortum. This study aims to: 1) further test the conspecificity of the populations of S. contortum from the Arctic, Gulf of Mexico and Antarctic with additional mitochondrial and nuclear markers, 2) test the conspecificity of the populations of N. lokii from the Arctic, Barbados Trench and the Antarctic, 3) compare the genetic divergence and putative population connectivity from the Arctic to the Antarctic of S. contortum and N. lokii and 4) assess how the environmental conditions inhabited by these two species may relate to their habitat preference and distributions
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