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The phylogenetic relationships within Naidinae (Annelida, Clitellata, Naididae) were investigated, using six molecular markers, both mitochondrial (12S rDNA, 16S rDNA, the COI gene) and nuclear (18S rDNA, 28S rDNA, the ITS region). Thirty-seven nominal species, representing 16 of the 22 genera recognized in the subfamily, were included, and the Nais communis/variabilis species complex was represented by six different morphotypes. Ten other species of Naididae were selected as outgroups. The data were analysed by Bayesian inference and Maximum Likelihood. The phylogeny corroborates monophyly of the Naidinae, and the separate status of the genus Pristina (Pristininae) and the Opistocystinae. Relationships within Naidinae are largely well supported, but in some parts unexpected: (1) A clade containing the largely tropical genera Dero and Branchiodrilus is sister to the rest of the subfamily, and together with a third tropical genus, Allonais, they form a basal paraphyly. All these genera show morphological adaptations to environmental hypoxia, leading to the conclusion that Naidinae originated in tropical freshwaters. (2) The genera Dero, Nais and Piguetiella are paraphyletic. (3) At least Branchiodrilus, Paranais, Chaetogaster, Nais, Stylaria appear to contain cryptic species. Morphological characters, especially those associated with chaetae, are to a great extent homoplastic within Naidinae, which certainly has contributed to the overall taxonomic confusion of this subfamily.

Limnodrilus species are annelid worms distributed worldwide in various freshwater sediments. The systematics of Limnodrilus has chiefly been based on morphology, but the genus has not been subject to any closer phylogenetic studies over the past two decades. To reconstruct the evolutionary history of Limnodrilus, and to assess the monophyly of this genus and its systematic position within the subfamily Tubificinae (Annelida: Clitellata: Naididae), 45 Limnodrilus specimens, representing 19 species, and 35 other naidid species (representing 24 genera) were sampled. The data consisted of sequences of three mitochondrial genes (COI, 12S and 16S rDNA) and four nuclear markers (18S and 28S rDNA, Histone 3, and ITS). The phylogeny was estimated, using Maximum Likelihood and Bayesian analyses of concatenated data of seven DNA loci, as well as a multi-locus coalescent-based approach. All analyses strongly suggest that Limnodrilus is monophyletic, but only if the morphospecies L. rubripenis is removed from it. Limnodrilus rubripenis and (at least) Baltidrilus, Lophochaeta and some species attributed to Varichaetadrilus comprise the sister group to the clade Limnodrilus sensu stricto, and the latter is further divided into three well-supported groups. One of them contains morphospecies characterized by short cuticular penis sheaths and enlarged chaetae in anterior segments (L. udekemianus, L. silvani and L. grandisetosus). The second is a small group of species with moderately long penis sheaths, i.e., L. sulphurensis and L. profundicola. The third, and largest group, includes not only the multitude of cryptic species in the L. hoffmeisteri complex, but also other, morphologically distinct, species nested within this complex. All studied species in this large group have long penis sheaths, which are exceptionally long in L. claparedianus, L. maumeensis, and a form morphologically intermediate between L. claparedianus and L. cervix. The identification and classification of these groups provide a framework for directed sampling in further phylogenetic studies, and for revisionary work on the L. hoffmeisteri complex and other unresolved Limnodrilus species.

Prior attempts to resolve the phylogenetic relationships of the cosmopolitan, marine clitellate genus Tubificoides, using only morphology, resulted in unresolved trees. In this study, three mitochondrial and three nuclear loci (5912 aligned sites) were analyzed, representing 14 morphologically separate species. Genetic distances within and between these forms on the basis of the mitochondrial genes (COI, 16S and 12S) revealed that 18 distinct mitochondrial lineages were represented in the data set. After analyzing also nuclear data (28S, 18S and ITS) we conclude that 17 separately evolving lineages (i.e., phylogenetic species) were represented, including three new, cryptic species closely related to T. pseudogaster, T. amplivasatus and T. insularis, respectively. Special emphasis was put on the DNA barcoding gene (COI), which was subject to haplotype diversity analysis and, for four species, diagnostic position (as determined by the Characteristic Attribute Organization System [CAOS]) screening. Typically, the intralineage variation was 1-2 orders of magnitude smaller than the interlineage divergence, making COI useful for identification of species within Tubificoides. The genetic data corroborate that many of the morphospecies are coherent but widely distributed metapopulations. Monophyly of the genus is supported and the evolutionary history of parts of the genus is revealed by phylogenetic analysis of the combined data set. A northern hemisphere origin of the genus is suggested, and most of the widely distributed species are members of one particular clade. Two morphological characters previously emphasized in Tubificoides taxonomy (hair chaetae and cuticular papillation) were optimized on the phylogenetic tree, revealing considerable homoplasy, belying the utility of these features as phylogenetic markers.

Naidinae (former Naididae) is a group of small aquatic clitellate annelids, common worldwide. In this study, we evaluated the phylogenetic status of Naidinae, and examined the phylogenetic relationships within the group. Sequence data from two mitochondrial genes (12S rDNA and 16S rDNA), and one nuclear gene (18S rDNA), were used. Sequences were obtained from 27 naidine species, 24 species from the other tubificid subfamilies, and five outgroup taxa. New sequences (in all 108) as well as GenBank data were used. The data were analysed by parsimony and Bayesian inference. The tree topologies emanating from the different analyses are congruent to a great extent. Naidinae is not found to be monophyletic. The naidine genus Pristina appears to be a derived group within a clade consisting of several genera (Ainudrilus, Epirodrilus, Monopylephorus, and Rhyacodrilus) from another tubificid subfamily, Rhyacodrilinae. These results demonstrate the need for a taxonomic revision: either Ainudrilus, Epirodrilus, Monopylephorus, and Rhyacodrilus should be included within Naidinae, or Pristina should be excluded from this subfamily. Monophyly of four out of six naidine genera represented by more than one species is supported: Chaetogaster, Dero, Paranais, and Pristina, respectively.

The tubificid clitellates are a common component in the freshwater bottom fauna and are also the most abundant oligochaete group in marine habitats. There are over 800 described species classified in six subfamilies; Tubificinae, Limnodriloidinae, Rhyacodrilinae, Telmatodrilinae, Phallodrilinae, and Naidinae. In this study we examine the phylogenetic relationships in Tubificidae using a combination of mitochondrial 16S rDNA and nuclear 18S rDNA sequence data. Sequences were obtained from five outgroup and 56 ingroup taxa, including five of the six subfamilies of Tubificidae. The data were analysed by maximum parsimony and Bayesian inference. The resulting tree topologies are virtually without conflict. Several associations traditionally recognized within the family Tubificidae are supported, in the Bayesian analysis including a sister group relationship between Tubificinae and Limnodriloidinae. The results also indicate that Rhyacodrilinae is polyphyletic-some of its members (Heterodrilus spp.) fall into a clade with Phallodrilinae, all other groups with Naidinae. Naidinae is also polyphyletic with two rhyacodriline genera, Monopylephorus and Ainudrilus, nested within. Most of the tubificid genera included in the study are supported as monophyletic; however, Tubifex and Limnodriloides are refuted. and Tubificoides is unresolved from other tubificine taxa. (c) 2005 Elsevier Inc. All rights reserved.

Naidids are tiny, primarily freshwater oligochaete annelids which reproduce asexually by fission. We investigated the phylogenetic relationships within this group by sequencing 1224 bp of the mitochondrial gene cytochrome oxidase I (COI) from 26 species of naidids (representing 13 of the 23 genera currently recognized), as well as from four tubificids, their closest allies. Although not completely concordant, maximum parsimony and Bayesian inference analyses agreed in several important respects, with no well-supported conflicts. Our study, the first detailed molecular investigation of naidid relationships, suggests that naidids fall into two groups, one comprised of the genus Pristina, and another comprised of all other genera sampled. The clear division of naidids into these two groups best matches an early, simple classification of the group by Lastockin (1924); the more recent classifications proposed by Sperber (1948) and Nemec and Brinkhurst (1987) are not as consistent with our results. We note that our study suggests the genus Stylaria is comprised of two distinct species, Stylaria lacustris and Stylaria fossularis, rather than merely two morphotypes of a single species. Based on our phylogenetic results, we suggest that pigmented eyes evolved only once among naidids but must have been lost multiple times, and that the elongation of the prostomium into a proboscis evolved at least twice independently. The simplest form of fission, architomy (fragmentation), occurs in two of the most basally branching naidid genera, and may represent the plesiomorphic condition for naidids.

Tubificids are aquatic clitellate worms, but recent analyses of morphological characters suggested that this family, as currently recognized, is paraphyletic. Sequences of the 18S rDNA gene of 40 protostome worm species (including 13 representatives of the Tubificidae) and 2 mollusc species were cladistically analyzed to test the monophyly of the Tubificidae and that of some of its constituent subfamilies. Under all alignments tested, the same general phylogenetic pattern emerged. The data support the idea that the Naididae, another clitellate taxon, is associated with some "rhyacodriline" groups within the Tubificidae. The data also corroborate the idea that the Tubificinae and the Limnodriloidinae are monophyletic but indicate that the Rhyacodrilinae and the Phallodrilinae are not. Bathydrilus does not appear to be closely related to other "phallodriline" genera.

OpistocystidaeCernosvitov, 1936 is a largely Neotropical oligochaete taxon containing seven species. Its familial status has never been formally challenged, although possible close relationships with Naididae and Phreodrilidae have been noted. Mitochondrial 12S and 16S rDNA, and nuclear 18S rDNA, of a range of aquatic oligochaete taxa, including Trieminentia corderoi (Opistocystidae), were analysed by Bayesian inference. This showed that T. corderoi is a derived lineage within Naididae, closely related to Pristina and its monotypic subfamily Pristininae. Opistocystidae as a whole (with its three genera, Opistocysta, Trieminentia, and Crustipellis) is thus likely to be a group within Naididae. Fil: Erseus, Christer. University of Gothenburg; Suecia Fil: Ervall, Ida. Stockholm University; Suecia Fil: Marchese Garello, Mercedes Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Gustavsson, Lena. Swedish Museum of Natural History; Suecia

The phylogeny of the Tubificidae, and of most of its subfamilies and some of its genera, is revisited, on the basis of sequences of 18S ribosomal DNA in a selection of species. Forty-six new 18S sequences of Naididae (6), Tubificidae (37), Phreodrilidae (1), Lumbriculidae (1), and Enchytraeidae (1) are reported and aligned together with corresponding sequences of 21 previously studied taxa. The 18S gene of Insulodrilus bifidus provides the first molecular evidence that phreodrilids are closely related to tubificids, corroborating previous conclusions based on morphology. The data further support the monophyletic status of Tubificidae, provided that the "Naididae" is regarded a part of this family; "naidids" may not even constitute a monophyletic group. It is thus suggested that the family name Naididae is formally suppressed as a junior synonym of the Tubificidae. The 18S gene also resolves a number of relationships within the tubificids. Among the subfamilies, Tubificinae is supported, Rhyacodrilinae and Phallodrilinae are revealed as nonmonophyletic, and Limnodriloidinae remains unresolved. Most tubificid genera tested for monophyly are corroborated by the data, only one (Tubifex) is refuted, and two (Tubificoides and Limnodriloides) are unresolved from other taxa. It is concluded that it will be valuable to expand the taxonomic sampling for 18S rDNA in clitellates, and in annelids in general, as this is likely to improve the resolution at many levels. However, it will be equally important to combine the annelid 18S data with other gene sequences and nonmolecular characters, to estimate the phylogeny of these common and diverse worms with greater precision.