The disjunct distribution of relict earthworm genera clarifies the early historical biogeography of the Lumbricidae (Crassiclitellata, Annelida)

Catch-All No More: Integrative Systematic Revision of the Genus Allolobophora Eisen, 1874 (Crassiclitellata, Lumbricidae) with the Description of Two New Relict Earthworm Genera

The taxonomy of earthworms has been riddled by instability, lack of systematically useful characters, and lax diagnoses of some genera. This has led to the use of some genera such as Allolobophora Eisen, 1874 as taxonomic wastebaskets, blurring their evolution and biogeographical history. The implementation of molecular techniques has revolutionized the systematics of the genus; however, some of its species have not been previously included in molecular phylogenetic analyses. Thus, the molecular markers COI, 16S, ND1, 12S, and 28S were sequenced for six endemic species including several taxa of Allolobophora and Aporrectodea Örely, 1885 (another related catch-all genus). Phylogenetic relationships determined by Bayesian inference and maximum likelihood analyses support the status of two of the six taxa examined (Allolobophora burgondiae Bouché, 1972 and Aporrectodea icterica Savigny, 1826) as part of Allolobophora sensu stricto and a presumed synonymy between Allolobophora and Heraclescolex Qiu and Bouché, 1998. Branch lengths and average pairwise genetic distances support the transfer of Allolobophora satchelli Bouché, 1972 to the genus Panoniona Mršić and Šapkarev, 1988 and the emergence of two new genera, Heraultia gen. nov. and Vosgesia gen. nov., endemic to France, hosting Allolobophora tiginosa Bouché, 1972 and Allolobophora zicsii Bouché, 1972, respectively. The aforementioned changes of status and the diagnosis for Heraultia and Vosgesia are presented. These results provided more evolutionarily and biogeographically coherent earthworm groups and highlighted that the Maghreb and the area around the Alps are potential key locations for the diversification of Allolobophora and several lineages of Lumbricidae.

First molecular evidence of hybridization in endosymbiotic ciliates (Protista, Ciliophora)

Hybridization is an important evolutionary process that can fuel diversification via formation of hybrid species or can lead to fusion of previously separated lineages by forming highly diverse species complexes. We provide here the first molecular evidence of hybridization in wild populations of ciliates, a highly diverse group of free-living and symbiotic eukaryotic microbes. The impact of hybridization was studied on the model of Plagiotoma, an obligate endosymbiont of the digestive tube of earthworms, using split decomposition analyses and species networks, 2D modeling of the nuclear rRNA molecules and compensatory base change analyses as well as multidimensional morphometrics. Gene flow slowed down and eventually hampered the diversification of Lumbricus-dwelling plagiotomids, which collapsed into a single highly variable biological entity, the P. lumbrici complex. Disruption of the species boundaries was suggested also by the continuum of morphological variability in the phenotypic space. On the other hand, hybridization conspicuously increased diversity in the nuclear rDNA cistron and somewhat weakened the host structural specificity of the P. lumbrici complex, whose members colonize a variety of phylogenetically closely related anecic and epigeic earthworms. By contrast, another recorded species, P. aporrectodeae sp. n., showed no signs of introgression, no variability in the rDNA cistron, and very high host specificity. These contrasting eco-evolutionary patterns indicate that hybridization might decrease the alpha-diversity by dissolving species boundaries, weaken the structural host specificity by broadening ecological amplitudes, and increase the nuclear rDNA variability by overcoming concerted evolution within the P. lumbrici species complex.

Molecular analysis of five controversial Balkanic species of Allolobophora (sensu lato) Eisen, 1873 (Lumbricidae, Clitellata) with emendation of the genus Cernosvitovia Omodeo, 1956

Allolobophora (sensu lato) is one of the most controversial genera in the taxonomy of Lumbricidae. Due to its poor definition, this genus is plagued by extensive taxonomic confusion, and its generic composition and internal relationships have remained uncertain, especially in species of the Balkan Peninsula. In this study, we have combined the study of morphological data and molecular phylogenetics based on five genetic markers, regions of the nuclear 28S rRNA and mitochondrial 16S rRNA, 12S rRNA, NADH dehydrogenase (ND1) and cytochrome oxidase C subunit 1 (COI), to delimit the taxonomic status of five controversial Balkanic endemic species, Allolobophora (s.l.) dofleini, Allolobophora (s.l.) serbica, Allolobophora (s.l.) strumicae, Allolobophora (s.l.) paratuleskovi and Allolobophora (s.l.) treskavicensis, sampled in the Kopaonik Mountain. Phylogenetic analyses based on our sampling of these five species recovered a well-supported clade containing the species Allolobophora (s.l.) robusta, Allolobophora (s.l.) mehadiensis mehadiensis, Allolobophora (s.l.) sturanyi dacica, Cernosvitovia rebeli and Cernosvitovia dudichi. Based on these results and previous evidence, the aforementioned Balkanic species are transferred to a redefined Cernosvitovia. We further present a revised list of all species currently included in Cernosvitovia., which includes now 21 species and subspecies taxa, 13 of them newly combined here. Serbiona Mršić & Šapkarev, 1988 is considered a junior synonym of Cernosvitovia Omodeo, 1956.  

Evaluating the Conservation Status of a North-Western Iberian Earthworm (Compostelandrilus cyaneus) with Insight into Its Genetic Diversity and Ecological Preferences

In spite of the high conservation value of soil fauna, the evaluation of their conservation status has usually been neglected. This is more evident for earthworms, one of the most important ecosystem service providers in temperate habitats but rarely the subject of conservation research. These studies have not been developed in Western Europe, which comprises high diversity and several early-branching, relic genera. One potentially menaced representative of this fauna is Compostelandrilus cyaneus; this risk can be assessed by implementing potential distribution modeling and genetic diversity monitoring to their known populations. Genetic barcoding was performed in representatives of four populations (three of them newly sampled) in order to estimate genetic diversity and population genetics parameters. Ensemble species distribution models were built by combining several algorithms and using the five more relevant bioclimatic and soil variables as predictors. A large amount of genetic diversity was found in a small area of less than 20 km², with populations located in less managed, better-preserved habitats showing higher genetic variability than populations isolated from natural habitats and surrounded by anthropic habitats. Potential distribution appears to be strongly restricted at a regional scale, and suitable habitats within the extent of occurrence appear fragmented and relatively limited. In addition, the main variables determining the ecological niche of C. cyaneus suggests a vulnerability to climate change and increasing soil compaction. Based on this knowledge, this species was assessed as Critically Endangered following the IUCN Red List of Threatened Species criteria, and some potential conservation actions are suggested.