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Invertebrate Systematics Invertebrate Systematics Society
Systematics, phylogeny and biogeography
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Invertebrate Systematics

Invertebrate Systematics

Volume 39 Number 7 2025

IS24084Does morphological diversity in amphidromous Macrobrachium (Decapoda: Caridea: Palaemonidae) reflect species homology or habitat partitioning?

Valentin de Mazancourt 0000-0003-3739-603X, Pierre Feutry, Coline Bernard 0009-0002-2902-2871, Gérard Marquet, Philippe Keith 0000-0002-1600-4909 and Magalie Castelin 0000-0002-9984-2122

A gradient map showing how clades of Macrobrachium have developed morphological adaptations depending on the current at various elevations.

We apply rigorous taxonomic and phylogenetic frameworks to shed light on both the taxonomy and evolution of amphidromous freshwater shrimps. Automatic species delineation methods based on molecular data revealed the existence of several species complexes within Macrobrachium. Results suggest habitat-driven speciation modes, where species differentiate in similar habitats distributed across the Indo-Pacific. The morphology of amphidromous Macrobrachium reflects numerous conserved adaptations to flow velocity. (Image credit: Valentin de Mazancourt.)

IS24103Paedomorphic adaptations in a new Heterostigma species: a novel strategy for ascidians to live in soft-bottom habitats

Riccardo Virgili 0000-0003-0536-7939, Valentina Tanduo, Salvatore D’Aniello, Angelo Fontana, Xavier Turon and Fabio Crocetta

Three images that show sessile to motile phenotype shift of Heterostigma monniotae, its complete mitochondrial genome, and the phylogenetic placement within Pyuridae ascidians.

Heterostigma is a poorly known genus of pyurid ascidian, deemed to inhabit the interstitial space between coarse sand grains. A new species, Heterostigma monniotae, is described, updating the taxonomy of the genus and clarifying its phylogenetic position through analyses of single loci and complete mitochondrial genome. In addition, observations on live specimens revealed an ontogenetic shift in mature specimens from a sessile to a motile phenotype. These new findings shed light on the evolutionary implications of this adaptive strategy. (Image credit: R. Virgili.)

IS24101The phylogeny and systematics of the Costellariidae (Caenogastropoda: Turbinelloidea) revisited

Alexander Fedosov 0000-0002-8035-1403, Philippe Bouchet 0000-0001-5864-8676, Aart Dekkers, Sandro Gori, Shih-I Huang, Yuri Kantor 0000-0002-3209-4940, Thomas Lemarcis, Maxwell Marrow, Claudia Ratti, Gary Rosenberg, Richard Salisbury, Sofia Zvonareva and Nicolas Puillandre

Phylogenomic tree of Costellaridae showing the relationships of the nine new genera and their shell forms.

The family Costellariidae is a charismatic, species-rich, yet poorly studied group of marine gastropod molluscs. Recent analyses of DNA sequences and shell features have failed to embrace the complexity of the group. Here, we analyse the morphology, DNA barcodes and genomic data from over 200 species, with emphasis on the South Pacific and Caribbean faunae, describing 9 new genera and 23 new species. Our results update the phylogeny and systematics of Costellariidae, corroborating patterns of species diversity in tropical seas. (Image credit: Alexander Fedosov.)

IS25025Cryptic species, mitochondrial phylogenomics and historical biogeography in the endemic genus Schistodesmus (Bivalvia, Unionidae) from China

Kaiyu Hou, Xianan Wang, Junli Jia, Xiongjun Liu, Xiaoping Wu, Dandong Jin, Jianmei An and Ruiwen Wu 0000-0002-8936-6054

Picture of shells of five Schistodesmus species.

An integrative taxonomic approach, including morphological and molecular data, revealed three new cryptic species: Schistodesmus luqiaoensis, Schistodesmus tongpenensis, and Schistodesmus xinyuensis. Maternal mitochondrial genomes of the first two species and Schistodesmus lampreyanus were sequenced, and interspecific relationships elucidated based on mitochondrial phylogenomics. Molecular clock analysis and biogeographical reconstruction based on fossil-calibrated dating indicated that the ancestor of Schistodesmus originated in the paleo-Yangtze River Basin during the Eocene (c. 50.74 Ma) and began diversifying c. 18.68 Ma in the Neogene. (Photography by Kaiyu Hou.)

IS25009Taxonomy and systematics of the Australasian gum nut orb-weaving spider genus Carepalxis (Araneae, Araneidae)

Pedro de S. Castanheira 0000-0002-0623-1622, Dimitar Dimitrov 0000-0001-5830-5702, Renner L. C. Baptista, Nikolaj Scharff and Volker W. Framenau

Frontal view of a female Carepalxis montifera showing the paired cephalic humps, which are characteristic of the genus.

The molecular phylogeny of the gum nut orb-weaving spider genus Carepalxis was investigated, revealing a polyphyletic Carepalxis: its Australasian representatives were part of the informal clade ‘backobourkiines’, and the Neotropical species were related to the genus Ocrepeira. A revised Carepalxis, recognised by the presence of two cephalic humps in females and two enlarged tibial spines in males, is composed of seven endemic Australian species, including four new species described here, and C. beelzebub, which also occurs in New Guinea. (Photography by Pedro Castanheira.)

IS25029Phylogeny and evolution of male genitalia in Withiidae (Arachnida: Pseudoscorpiones)

Catalina Romero-Ortiz 0000-0001-8939-7814, Mark S. Harvey 0000-0003-1482-0109, Ligia R. Benavides 0000-0003-4387-1220, Sebastian Cuadrado-Rios 0000-0002-1060-820X and Carlos E. Sarmiento 0000-0003-4012-8108

Examples of long and short type ejaculatory canals of male Withiidae and their evolutionary rate of change from long to short.

Pseudoscorpions show great promise for studying the evolution of genitalia because of their many unique sexually related features. We estimated a dated phylogeny based on morphology and genes for Withiidae to understand how quickly certain body parts changed. Sensory organs were found to change faster than genitalia, suggesting that environmental adaptation might exert stronger selective pressures than sexual selection in shaping their morphology. Our study also highlights the importance of considering both morphological features and genes when examining evolution. (Image credit: Catalina Romero-Ortiz.)

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