Daniel F. Marchán

New light into the hormogastrid riddle: morphological and molecular description of Hormogaster joseantonioi sp. n. (Annelida, Clitellata, Hormogastridae)

Abstract The earthworm family Hormogastridae shows a remarkable disjunction in its distribution in the Iberian Peninsula, with the Hormogaster elisae species complex isolated from the rest of the species. Hormogaster joseantonioi sp. n., a new species found in the intermediate area between the main ranges (in Teruel, Aragón), was described following the integrative approach, as it is suitable for earthworms due to their highly homoplasic morphology. The phylogenetic analysis of the molecular markers placed the new species as a sister taxon to H. elisae, thus showing the colonizing lineage of Central Iberian Peninsula could have originated near the H. joseantonioi sp. n. current range. External morphological characters revealed some degree of overlap with previously described species, but internal characters presented configurations/states unknown from other members of the family. These traits make the new species a key piece to understand the evolution of Hormogastridae.

Compilation of morphological and molecular data, a necessity for taxonomy: The case of Hormogaster abbatissae sp. n. (Annelida, Clitellata, Hormogastridae)

Conflict among data sources can be frequent in evolutionary biology, especially in cases where one character set poses limitations to resolution. Earthworm taxonomy, for example, remains a challenge because of the limited number of morphological characters taxonomically valuable. An explanation to this may be morphological convergence due to adaptation to a homogeneous habitat, resulting in high degrees of homoplasy. This sometimes impedes clear morphological diagnosis of species. Combination of morphology with molecular techniques has recently aided taxonomy in many groups difficult to delimit morphologically. Here we apply an integrative approach by combining morphological and molecular data, including also some ecological features, to describe a new earthworm species in the family Hormogastridae, Hormogaster abbatissaesp. n., collected in Sant Joan de les Abadesses (Girona, Spain). Its anatomical and morphological characters are discussed in relation to the most similar Hormogastridae species, which are not the closest species in a phylogenetic analysis of molecular data. Species delimitation using the GMYC method and genetic divergences with the closest species are also considered. The information supplied by the morphological and molecular sources is contradictory, and thus we discuss issues with species delimitation in other similar situations. Decisions should be based on a profound knowledge of the morphology of the studied group but results from molecular analyses should also be considered.

Phylogenomic analyses of a Mediterranean earthworm family (Annelida: Hormogastridae)

Earthworm taxonomy and evolutionary biology remain a challenge because of their scarce distinct morphological characters of taxonomic value, the morphological convergence by adaptation to the uniformity of the soil where they inhabit, and their high plasticity when challenged with stressful or new environmental conditions. Here we present a phylogenomic study of the family Hormogastridae, representing also the first piece of work of this type within earthworms. We included seven transcriptomes of the group representing the main lineages as previously-described, analysed in a final matrix that includes twelve earthworms and eleven outgroups. While there is a high degree of gene conflict in the generated trees that obscure some of the internal relationships, the origin of the family is well resolved: the hormogastrid Hemigastrodrilus appears as the most ancestral group, followed by the ailoscolecid Ailoscolex, therefore rejecting the validity of the family Ailoscolecidae. Our results place the origin of hormogastrids in Southern France, as previously hypothesised.

Diversification patterns in cosmopolitan earthworms: similar mode but different tempo ☆

Comparative phylogeography of widespread species that span the same geographic areas can elucidate the influence of historical events on current patterns of biodiversity, identify patterns of co-vicariance, and therefore aid the understanding of general evolutionary processes. Soil-dwelling animals present characteristics that make them suitable for testing the effect of the palaeogeographical events on their distribution and diversification, such as their low vagility and population structure. In this study, we shed light on the spatial lineage diversification and cladogenesis of two widely-distributed cosmopolitan and invasive earthworms (Aporrectodea rosea and A. trapezoides) in their putative ancestral area of origin, the Western Palearctic, and a few populations in North America. Molecular analyses were conducted on mitochondrial and nuclear markers from 220 (A. rosea) and 198 (A. trapezoides) individuals collected in 56 and 57 localities, respectively. We compared the lineage diversification pattern, genetic variability and cladogenesis in both species. Our findings showed that both species underwent a similar diversification from the Western Mediterranean plates to (i) Northern Europe and (ii) the Iberian Peninsula, establishing their two main lineages. Their diversification was in concordance with the main palaeogeographical events in the Iberian Peninsula and Western Mediterranean, followed by a later colonization of North America from individuals derived exclusively from the Eurosiberian lineage. Their diversification occurred at different times, with the diversification of A. rosea being potentially more ancient. Cladogenesis in both species seems to have been modelled only by the Mediterranean plate shifts, ignoring historical climatic oscillations such as the Messinian salinity crisis. Their high genetic variability, strong population structure, lack of gene flow and stepping-stone-like cladogenesis suggest the existence of different cryptic lineages. Our results may indicate a recurrent event in invasive earthworms within their ancestral distribution areas in the Western Palearctic.

Pinpointing cryptic borders: Fine-scale phylogeography and genetic landscape analysis of the Hormogaster elisae complex (Oligochaeta,Hormogastridae)

Spatial and temporal aspects of the evolution of cryptic species complexes have received less attention than species delimitation within them. The phylogeography of the cryptic complex Hormogaster elisae (Oligochaeta, Hormogastridae) lacks knowledge on several aspects, including the small-scale distribution of its lineages or the palaeogeographic context of their diversification. To shed light on these topics, a dense specimen collection was performed in the center of the Iberian Peninsula - resulting in 28 new H. elisae collecting points, some of them as close as 760m from each other- for a higher resolution of the distribution of the cryptic lineages and the relationships between the populations. Seven molecular regions were amplified: mitochondrial subunit 1 of cytochrome c oxidase (COI), 16S rRNA and tRNA Leu, Ala, and Ser (16S t-RNAs), one nuclear ribosomal gene (a fragment of 28S rRNA) and one nuclear protein-encoding gene (histone H3) in order to infer their phylogenetic relationships. Different representation methods of the pairwise divergence in the cytochrome oxidase I sequence (heatmap and genetic landscape graphs) were used to visualize the genetic structure of H. elisae. A nested approach sensu Mairal et al. (2015) (connecting the evolutionary rates of two datasets of different taxonomic coverage) was used to obtain one approximation to a time-calibrated phylogenetic tree based on external Clitellata fossils and a wide molecular dataset. Our results indicate that limited active dispersal ability and ecological or biotic barriers could explain the isolation of the different cryptic lineages, which never co-occur. Rare events of long distance dispersal through hydrochory appear as one of the possible causes of range expansion.

A new earthworm species within a controversial genus: Eiseniona gerardoi sp. n. (Annelida, Lumbricidae) - description based on morphological and molecular data

Abstract The morphological and anatomical simplicity of soil dwelling animals, such as earthworms, has limited the establishment of a robust taxonomy making it sometimes subjective to authors’ criteria. Within this context, integrative approaches including molecular information are becoming more popular to solve the phylogenetic positioning of conflictive taxa. Here we present the description of a new lumbricid species from the region of Extremadura (Spain), Eiseniona gerardoi sp. n. The assignment to this genus is based on both a morphological and a phylogenetic study. The validity of the genus Eiseniona, one of the most controversial within Lumbricidae, is discussed. A synopsis of the differences between the type species and the west-European members of the genus is provided.

Insights into the diversity of Hormogastridae (Annelida, Oligochaeta) with descriptions of six new species

The earthworm family Hormogastridae is a relatively diverse group in the Western Mediterranean basin. Since 1887, around thirty species have been described and assigned to four genera. However, from 2010 on, molecular, ecological and morphological studies have questioned the validity of those genera. Meanwhile, new species were discovered and assigned to them, pending a formal systematic revision; such a revision has been performed recently by integrating all the existing sources of information. The resulting classification consists of nine genera, including four newly erected ones. This revised systematic background is used in the current work as a base for the description of six new hormogastrid species: Diazcosinia sacrarium Marchán, Fernández, Díaz Cosín Novo, sp. nov., Boucheona martae Marchán, Fernández Díaz Cosín, sp. nov., Boucheona rosae Marchán, Díaz Cosín Novo, sp. nov., Norana emiliae Marchán, Fernández, Díaz Cosín Novo, sp. nov., Norana xylocerasi Marchán, Fernández, Díaz Cosín Novo, sp. nov., and Norana beatrizae Marchán, Fernández, Díaz Cosín Novo, sp. nov. Norana is a new replacement name for the preoccupied Nora Marchán, Fernández, Díaz Cosín Novo, 2018. Likewise, Xanina is proposed to replace the preoccupied Xana Díaz Cosín, Briones Trigo, 1989. We provide an overview of the currently known diversity of the different genera, and we further propose common names in several languages for some of the species of Hormogastridae.

DNA barcoding of the Italian anecic Octodrilus species in rural (vineyard) and forested areas with description of Octodrilus zicsiniello sp. nov. (Clitellata, Megadrili)

DNA barcoding of 172 anecic Octodrilus specimens collected in NE Italy and bordering Croatia has been carried out. The Bayesian phylogenetic tree showed high support for almost all currently recognized species, however, some unexpected results also appeared. The clade representing Oc. pseudocomplanatus contains a highly advanced subclade, which morphologically resembles Oc. slovenicus. The highly supported Oc. tergestinus clade consists of four unresolved divergent lineages of which the first corresponds to Oc. istrianus and the second resembles Oc. mimus morphologically; the third and fourth clades show typical tergestinus characters. The widely distributed Oc. complanatus consists of three highly divergent subclades which are sister to a new species, Oc. zicsiniello sp. nov., hereunder described.

Integrative systematic revision of a Mediterranean earthworm family: Hormogastridae (Annelida, Oligochaeta)

Abstract. The problem of reconciling earthworm taxonomy and phylogeny has shown advances with the application of molecular techniques, yet they have proven insufficient. Integrative systematics could solve this by combining multiple sources of evolutionary information. Relatively low diversity, restricted range and low nomenclatural conflict make Hormogastridae Michaelsen, 1900 a desirable target for an integrative systematics approach. The main systematic conflicts within this family are the polyphyly of the species Hormogaster pretiosa Michaelsen, 1899, the widespread presence of cryptic lineages, the lack of resolution of supraspecific relationships and the paraphyly of the genus Hormogaster Rosa, 1877 (found to be composed of four well-supported genus-level clades by molecular phylogenetic inference). This work integrates all the existing information by performing phylogenetic inference based on morphological, molecular and total evidence datasets, comparing their performance with the topology obtained by phylogenomic analyses. It also includes a comparative study of representatives of the main clades based on microcomputed tomography (µCT) reconstructions. The addition of morphological characters improved the resolution of the Hormogastridae tree; ancestral state reconstruction displayed the evolution of character states and provided morphological diagnoses for the genera within a new system, which incorporates information about ecological niches and biogeography.