Unexpected species diversity within Japanese Mundochthonius pseudoscorpions (Pseudoscorpiones : Chthoniidae) and the necessity for improved species diagnosis revealed by molecular and morphological examination

Abstract

Using the complementary approaches of morphological and molecular taxonomy is essential to further our understanding of invertebrate diversity, including the identification of cryptic species. Although the species classification of a widespread group of arachnids, the pseudoscorpions, has been based on traditional diagnostic characters for a long time, recent taxonomic studies have suggested that some of these are unreliable for distinguishing species. Thus, the application of molecular taxonomy may be particularly useful in this group. Here, we performed molecular phylogenetic analyses and species delimitation analyses based on partial sequences of mitochondrial DNA cytochrome c oxidase I and nuclear DNA 18S rRNA genes to assess the taxonomy of species and the reliability of morphological characteristics for distinguishing species in the Japanese soil-dwelling genus Mundochthonius (Chthoniidae). Our results revealed the existence of seven major genetic clades, likely corresponding to three described species and four cryptic species. Although two described species, M. kiyoshii and M. itohi, were represented by single clades in the phylogenetic analysis, a third, M. japonicus, was composed of multiple clades, highlighting inconsistencies between phylogenetic relationships and current species classifications using traditional morphological diagnostics. This study exemplifies the need for further exploration of pseudoscorpion taxonomy and species diversity. In particular, detailed morphological examinations are expected to help determine differences among cryptic species.

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

“…Similar results are also documented from other mygalomorph lineages (Hamilton et al, 2014), scorpions (Klesser et al, 2021) and pseudoscorpions (Ohira et al, 2018) and generally regarded as inflated in terms of the number of species it delimits. However, it is also possible that these results are a consequence of limited Cyclocosmia sampling.…”

Integrative Taxonomy Approach Reveals Cryptic Diversity within the Phoretic Pseudoscorpion Genus Lamprochernes (Pseudoscorpiones: Chernetidae)

“…nov. and L. chyzeri , indistinguishable morphologically, differed by 11.1–12.2% (p-distance and Tamura-Nei, respectively). Such distances are more congruent with interspecific divergences among valid pseudoscorpion species than with reported values of intraspecific diversity [ 29 , 118 , 119 ]. The intraspecific distances reported from other Chernetidae taxa inhabiting the same geographic region are generally much lower (~1–5.5%), with the exception of Dinocheirus panzeri (C.L.…”

“…Barcoding has helped to uncover cryptic diversity among various arachnid groups, including pseudoscorpions [ 29 , 118 , 119 , 120 , 121 ]. The results of this study highlight the usefulness of barcoding data for cryptic-diversity detection, even in regions considered as well known.…”

The dark side of pseudoscorpion diversity: The German Barcode of Life campaign reveals high levels of undocumented diversity in European false scorpions

“…The retention of ancestral morphology—despite rapid genetic differentiation—often makes it difficult to distinguish closely related species on the basis of morphological features alone (Šťáhlavský et al., 2009 ). In addition, certain morphological characters once in use to diagnose pseudoscorpion species have been proven to be unreliable in species delineation (Ohira et al., 2018 ). Even specialists of the group may face difficulties in identification of certain specimens and thus make use of the identification tool on BOLD.…”