Five new pseudocryptic land planarian species of Cratera (Platyhelminthes: Tricladida) unveiled through integrative taxonomy

Species delimitation with limited sampling: An example from rare trapdoor spider genus Cyclocosmia (Mygalomorphae, Halonoproctidae)

The outcome of species delimitation depends on many factors, including conceptual framework, study design, data availability, methodology employed and subjective decision making. Obtaining sufficient taxon sampling in endangered or rare taxa might be difficult, particularly when non-lethal tissue collection cannot be utilized. The need to avoid overexploitation of the natural populations may thus limit methodological framework available for downstream data analyses and bias the results. We test species boundaries in rare North American trapdoor spider genus Cyclocosmia Ausserer (1871) inhabiting the Southern Coastal Plain biodiversity hotspot with the use of genomic data and two multispecies coalescent model methods. We evaluate the performance of each methodology within a limited sampling framework. To mitigate the risk of species over splitting, common in taxa with highly structured populations, we subsequently implement a species validation step via genealogical diversification index (gdi), which accounts for both genetic isolation and gene flow. We delimited eight geographically restricted lineages within sampled North American Cyclocosmia, suggesting that major river drainages in the region are likely barriers to dispersal. Our results suggest that utilizing BPP in the species discovery step might be a good option for datasets comprising hundreds of loci, but fewer individuals, which may be a common scenario for rare taxa. However, we also show that such results should be validated via gdi, in order to avoid over splitting.

Phylogenetic relationships of the Geoplaninae land planarians (Platyhelminthes, Tricladida) assessed with a total evidence approach, with the description of a new species of Gigantea

Several studies have focused on the phylogenetic relationships within the Geoplaninae land planarians (Tricladida). In those studies, ancient phylogenetic relationships remained obscure. In this work, the phylogeny of Geoplaninae is assessed through three different datasets, namely morphological, molecular, and both datasets combined, i.e, a total evidence approach (TE). The data matrix consisted of six DNA regions, including a newly developed marker (DOM5), and a morphological matrix with 37 characters. The study produced the best-resolved hypothesis so far for the phylogeny of Geoplaninae, although ancient clades still remain elusive. The effect of the morphological data on the TE tree topology and clade support is seemingly negligible. The phylogenetic tree also suggests that most of the diagnostic morphological characters of the genera are homoplastic, while unambiguous unique synapomorphies can characterize some supra-generic informal groupings.

The discovery of new Chilean taxa revolutionizes the systematics of Geoplaninae Neotropical land planarians (Platyhelminthes: Tricladida)

Two subfamilies of land planarians (Geoplanidae) are endemic to the Neotropical region, namely Geoplaninae (with 29 genera and 346 nominal species, most of which are from Brazil) and its sister-group Timyminae, with only two Chilean species. The systematics of these groups through morphology and molecular data (COI and 28S rDNA genes), including nine new Chilean species, is re-assessed in this study. The great morphological diversity of the Chilean species is congruent with the molecular trees and, accordingly, five new genera (Adinoplana, Harana, Myoplana, Sarcoplana and Transandiplana) are proposed, each characterized by putative synapomorphies. Seven new tribes are also erected (Adinoplanini, Gusanini, Haranini, Inakayaliini, Myoplanini, Polycladini and Sarcoplanini), each one monogeneric, except Geoplanini (which includes all genera under the current concept of Geoplaninae plus the Chilean Transandiplana) and Sarcoplanini (with Sarcoplana and the already known Mapuplana, Pichidamas and Wallamapuplana). Re-diagnoses of Geoplaninae, Timymini, Gusana, Inakayalia, Polycladus and Pichidamas are proposed and biogeographic remarks on Transandiplana are provided

Current state of knowledge on freshwater planarians (Platyhelminthes, Tricladida, Dugesiidae) from Chile

The unique geography of Chile encompasses a wide diversity of ecosystems and a rich biodiversity. However, the platyhelminth fauna has been poorly studied. The aim of this work is to compile the historical record of freshwater planarians described for this country. We accessed worldwide databases and published articles to provide a comprehensive review of their discovery history, morphological characteristics and their localities. Freshwater planarians have been collected mainly in central and southern Chile, while in the northern region a single species has been described. The discovery of new species of freshwater triclads has the potential to reveal novel animal models to study regeneration and/or biological adaptations, as some species are suitable for culture in the laboratory. We discuss the many reasons why further research is needed for this animal group, which should include genomic and molecular genetic studies.

Planarians, a Neglected Component of Biodiversity in Groundwaters

Underground waters are still one of the most important sources of drinking water for the planet. Moreover, the fauna that inhabits these waters is still little known, even if it could be used as an effective bioindicator. Among cave invertebrates, planarians are strongly suited to be used as a study model to understand adaptations and trophic web features. Here, we show a systematic literature review that aims to investigate the studies done so far on groundwater-dwelling planarians. The research was done using Google Scholar and Web of Science databases. Using the key words “Planarian cave” and “Flatworm Cave” we found 2273 papers that our selection reduced to only 48, providing 113 usable observations on 107 different species of planarians from both groundwaters and springs. Among the most interesting results, it emerged that planarians are at the top of the food chain in two thirds of the reported caves, and in both groundwaters and springs they show a high variability of morphological adaptations to subterranean environments. This is a first attempt to review the phylogeny of the groundwater-dwelling planarias, focusing on the online literature. The paucity of information underlines that scarce attention has been dedicated to these animals. Further revisions, including old papers and books, not available online will be necessary.