Morphological and genetic variability in cosmopolitan tardigrade species - Schill, Förster, Dandekar & Wolf, 2010.

was described from Alaska (USA) based on integrative taxonomy and later reported from various geographical locations making it a true cosmopolitan species. The 'Everything is Everywhere' (EiE) hypothesis assumes that microscopic organisms have unique features that help them to inhabit many different environments, meaning they can be considered cosmopolitan. In the present work we report four new populations of from the Northern Hemisphere which suggests that the 'EiE' hypothesis is true, at least for some tardigrade species. We also compared all known populations of at the genetic and morphological levels. The p-distances between COI haplotypes of all sequenced populations from Albania, Antarctica, Canada, Italy, Madeira, Mongolia, Spain, USA and Poland ranged from 0.002% to 0.005%. In total, twelve haplotypes (H1-H12) of COI gene fragments were identified. We also report statistically significant morphometrical differences of species even though they were cultured and bred in the same laboratory conditions, and propose epigenetic factor as a main cause rather than temperature, predation risk and food availability. Furthermore, we also discuss differences in the potential distribution of two species.