Genetic and chaetal variation in Nais worms (Annelida, Clitellata, Naididae)

Abstract

The genus Nais is a group of oligochaetous clitellates, common in eutrophic freshwater habitats. About 30 species are described. Species identification is based primarily on chaetal characters, which are often subtle, inconsistent, and even overlapping between nominal species. We investigated the correlation between genetic variation and chaetal morphology in this genus. Eighty‐one individuals from Europe, North America, and China were included in the study. Seventy‐five of these were preserved as vouchers. They were scrutinized with regard to chaetal morphology, and ten different morphotypes were identified. Three molecular markers, two mitochondrial (the COI gene and 16S rDNA) and one nuclear (the ITS region), were used to establish the genetic lineages in the material. Genetic variation was found to be largely congruent with chaetal character patterns. However, at least nine separately evolving lineages (all supported by mitochondrial as well as nuclear data) correspond to at most six nominal species. Four morphotypes/lineages are recognized as Nais barbata, Nais christinae, Nais elinguis, and Nais stolci, respectively, whereas five, or possibly more, lineages represent a morphological continuum covering the variation of the Nais communis/variabilis complex. Thus, cryptic speciation is revealed. Our results indicate that a taxonomic revision of the genus will be needed in the future.

Investigating the Clitellata (Annelida) of Icelandic springs with alternative barcodes

“…argentea (Michaelsen, 1889), Mesenchytraeus cf. armatus, and Nais communis/variabilis (Piguet, 1906; i.e., we found here morphotype A3 sensu Envall et al 2012). Moreover, there is still some uncertainty whether the earthworm Bimastos rubidus (Savigny, 1826) should include B. subrubicundus (Eisen, 1874), and B. tenuis (Eisen, 1874), all three of which have been reported from Iceland.…”

“…Christerius litoralis (Erséus, 1976) Erséus 1976 Clitellio arenarius (Müller, 1776) Hrabě 1952;Brinkhurst 1963;Erséus 1976 Nais communis Piguet, 1906Hrabě 1952Lindegaard 1979 Nais communis/variabilis species complex, morphotype A3 (see Envall et al 2012) This study…”

Limnodrilus sulphurensis n. sp., from a sulfur cave in Colorado, USA, with notes on the morphologically similar L. profundicola (Clitellata, Naididae, Tubificinae)

“…Recent molecular studies of Clitellata have shown that species boundaries (in the sense of De Queiroz 2007) can be firmly established using a combination of mitochondrial and nuclear DNA data. This has led to the conclusion that cryptic speciation has previously been underestimated in the diversification of various families of this group (e.g., Gustafsson et al 2009;Kvist et al 2010;Envall et al 2012;Matamoros et al 2012;Martinsson et al 2013Martinsson et al , 2015Martinsson & Erséus 2014). Interestingly, in several of these cases, re-evaluation of morphological characters has ultimately supported new species delimitations accomplished on a genetic basis.…”

First report of Chaetogaster limnaei (Annelida: Naididae) in Chile based on samples retrieved from an invasive freshwater snail

“…The analysis was run for 3 million generations sampling every 1,000 generations; posterior probabilities were obtained using a burn-in period of 10%. The analyses were performed together with 16S rRNA sequences from other congeners and naidid taxa (Bely & Sikes, 2010;Envall et al, 2006Envall et al, , 2012Sjölin et al, 2005).…”