Dmitry Kulagin

Aim: To reconstruct the phylogeny of the genus Pasiphaea across the benthopelagic interface, a unique evolutionary frontier involving migrations between the seafloor and the water column, and to analyse the environmental variables associated with clade separation. Location: Global deep‐sea ecosystems, encompassing both horizontal geographic distributions (latitudinal gradients) and vertical marine dimensions (pelagic water column and seafloor topography). Time Period: Contemporary global distribution data. Major Taxa Studied: Global fauna of the Glass shrimps Pasiphaea (Decapoda: Pasiphaeidae). Methods: Reconstruction of a robust molecular phylogenetic dataset comprising 121 sequences from three genes, integrating available reliable data on the geographical and bathymetric distribution and phylogeny of Pasiphaea , followed by the evaluation of environmental variables associated with clade separation using various statistical models. Results: Primary deep‐scale phylogenetic divergence was linked to pelagic environmental filtering, specifically latitude (as a proxy for temperature and productivity) and pelagic depth (nighttime habitat), which separated a high‐latitude, deep‐mesopelagic lineage (Clade A) from a lower‐latitude, shallower‐dwelling radiation (Clade B). In contrast, secondary diversification into terminal clades was associated with benthic factors, including seafloor geography (vicariance) and bottom depth (daytime habitat). Main Conclusions: We propose a “dual‐link” hierarchical framework for benthopelagic evolution, showing that while pelagic factors explain the broad evolutionary trajectory and deep‐scale divergence of benthopelagic taxa, the seafloor provides the geographic anchors necessary for further terminal speciation. This underscores the critical importance of integrating both vertical and horizontal environmental dimensions to understand the complex mosaic of deep‐sea benthopelagic diversification.

The present correction concerns the catalogue numbers of the examined material in the paper

The genus Pasiphaea Savigny, 1816, comprises a diverse assemblage of meso- to bathypelagic shrimps, currently including 69 valid species. Taxonomic investigations have long been hampered by numerous synonymies and by species known only from their original, overly brief descriptions. Here, we address these deficiencies by examining Pasiphaea specimens collected in the Western and Central Pacific during multiple research cruises using mid-water trawls. Integrating traditional morphological characters (carapace carination, pleonal relief, telson end morphology, and pereopodal dentition) with a novel morphometric framework, we standardized terminology and defined a suite of quantitative measurements across the carapace, pleon, telson, and chelae. In order to corroborate species boundaries, we sequenced three mitochondrial gene markers (COI, 16S rDNA, and 12S rDNA) and calculated genetic distances under the Kimura two-parameter model. This combined approach extended or confirmed the geographic ranges of five described taxa, facilitated the formal description of eight new species, and demonstrated the synonymy of P. gracilis Hayashi, 1999, and P. fragilis Hayashi, 1999. Phylogenetic reconstructions further highlighted cases of pseudocryptic speciation in neighboring bathyal habitats. Our results expose substantial lacunae in the Southwest Pacific Pasiphaea fauna and substantiate the necessity for a comprehensive, genus-level revision. This study thereby contributes to both refining species diagnoses and advancing our understanding of deep-sea crustacean biodiversity.

Leptochela Stimpson (1860) is a shallow-water, benthopelagic genus within the predominantly pelagic superfamily Pasiphaeoidea. We inventoried a global fauna of 17 currently valid species of Leptochela and identified a newly discovered eighteenth species. Our analysis combined both morphological and molecular data, using 13 characters (including two multistate characters) and 5 gene markers, respectively. The results revealed incongruence between the molecular and morphological datasets. However, our phylogenetic conclusions were based on a consensus approach, integrating morphological, molecular, and total evidence trees, which revealed three robust clades. We discuss the evolutionary development of quantitative and qualitative morphological traits in Leptochela and explore the potential causes of the incongruence between morphological and molecular signals, particularly in the context of pelagic eucarids transitioning from pelagic to benthopelagic habitats. Additionally, we describe the new species from Madagascar and provide a key to all known species of Leptochela.

Hansarsia megalops and Thysanoessa gregaria are two abundant krill species in the warm-temperate belts in the North and South Atlantic. This pattern of disjunct distribution, often referred to as anti-tropical (or bipolar), is a regular phenomenon among marine organisms that can appear at different taxonomic levels. Analysis of spatial genetic diversity based on variation of the mitochondrial cytochrome oxidase I (COI) gene was carried out to understand whether these broadly sympatric krill species have similar patterns in population structure and demographic history. The results suggested that the anti-tropical distribution of both species was driven by trans-equatorial migrations during different historical periods. We observed contrasting differences in genetic diversity between species coupled with similar patterns of genetic diversity and structure in disjunct populations on both sides of the equator. We also found additional genetically distinctive populations of T. gregaria in the South Atlantic in Subantarctic waters and showed that the Southern Subtropical Frontal Zone acts as a strong boundary between two genetically distinctive populations of T. gregaria. The results suggest that both species-specific habitat preferences and interactions between closely related species (congeners) may shape differences in population genetic diversity and structure among species.

A recent molecular phylogenetic and biogeographic study on the krill genus Hansarsia revealed undescribed cryptic diversity in the Atlantic. Each of four species analysed encompassed robust molecular clades that were linked to dimorphic males in H. microps, H. atlantica and H. tenella. We tested the robustness and divergence of the observed clades using an integrative approach including (1) three independent species delimitation methods for the mitochondrial COI gene (ASAP, GMYC, bPTP), (2) variability of two nuclear genes (H3 and ITS1) and (3) morphological analysis (MDS and PCA) with a dataset of 22 characters scored for 131 specimens. Both molecular and morphological analyses resulted in at least six distinct clades within the Atlantic Hansarsia. The strongest divergence was revealed between the two clades of H. tenella, one of which we diagnosed as a new species. Two clades of H. megalops also showed significant divergence but in the absence of males, we were reluctant to designate new species. Different clades linked to male forms in H. microps and H. atlantica are suggested as an incipient species. We also hypothesise an unusual trend in the evolution of euphausiids, in which visual recognition enhances tactile interaction during mating. Our results show that analyses of ostensibly well studied groups may yet yield taxonomic surprises. ZooBank: urn:lsid:zoobank.org:pub:AE045636-50EF-450A-B9B3-9231E8B91522

Экология гидросферы, Гидробиология