Integrative taxonomy allows the identification of synonymous species and the erection of a new genus of Echiniscidae (Tardigrada, Heterotardigrada)

Abstract

The taxonomy of tardigrades is challenging as these animals demonstrate a limited number of useful morphological characters, therefore several species descriptions are supported by only minor differences. For example, Echiniscus oihonnae and Echiniscus multispinosus are separated exclusively by the absence or presence of dorsal spines at position Bd. Doubts were raised on the validity of these two species, which were often sampled together. Using an integrative approach, based on genetic and morphological investigations, we studied two new Portuguese populations, and compared these with archived collections. We have determined that the two species must be considered synonymous with Echiniscus oihonnae the senior synonym. Our study showed generally low genetic distances of cox1 gene (with a maximum of 4.1%), with specimens displaying both morphologies sharing the same haplotype, and revealed character Bd to be variable. Addition-ally, a more detailed morphological and phylogenetic study based on the 18S gene uncovered a new evolutionary line within the Echiniscidae, which justified the erection of Diploechiniscus gen. nov. The new genus is in a sister group relationship with Echiniscus and is, for the moment, composed of a single species.

Data from new taxa inferIsoechiniscoidesgen. nov. and increase the phylogenetic and evolutionary understanding of echiniscoidid tardigrades (Echiniscoidea: Tardigrada)

“…include both molecular and morphological data whenever possible. This approach has successfully been applied with other tardigrades (Bertolani et al ., ; Vicente et al ., ). Despite high posterior probability and bootstrap support for several clades, the relationships among the various clades were largely unsupported or had incongruent support from the two methods of analysis, i.e.…”

“…The conserved nuclear 28S rRNA gene and the highly variable mitochondrial COI were chosen for amplification as they have previously been used to resolve echiniscoid phylogeny at the family level and to distinguish between various species (Jørgensen et al ., ; Vicente et al ., ). Two overlapping fragments of the 28S rRNA gene were amplified with two primer pairs, 28Sa (Whiting et al ., ) – 28Srd5b (Schwendinger & Giribet, ), and 28Srd4.8a–28Srd7b1 (both from Schwendinger & Giribet, ) using the settings from Guil et al .…”

“…For instance, Jørgensen, Møbjerg & Kristensen () reported up to 50% COI sequence variation within the terrestrial Echiniscidae and Vicente et al . () reported 20% COI variation between the echiniscids, Testechiniscus and Diploechiniscus . Echiniscoides was once considered a monospecific genus and E. sigismundi was thought to be an example of a cosmopolitan marine tardigrade (Crisp & Hobart, ; Grimaldi de Zio, Morone De Lucia & D'Addabbo, ).…”

The impact of fire on terrestrial tardigrade biodiversity: a first case-study from Portugal

“…This accounts for a Kimura 2-parameters distance of 4% (Vicente et al, 2013), still within the single-species limits. Only haplotypes A2, F1 and H1 are represented both pre-and post-main fire.…”

“…Specimens pertaining to Diploechiniscus oihonnae (Richters, 1903) (GenBank A.N. JX676191-4) were already analysed in Vicente et al (2013) and they were also included in the present analysis. Minimum spanning network analysis between haplotypes was performed by using Arlequin 3.1 (Excoffier et al, 2005) and visualized by using HapStar (Teacher and Griffiths, 2011).…”