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

Abstract

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