# Deep‐sea caridean shrimps collected from the South China Sea with emphasizing their phylogenetic relationships

## TL;DR

This study reports 31 deep-sea caridean shrimp species from the South China Sea, revealing that similar physical traits do not always mean close evolutionary relationships.

## Contribution

The study provides the highest species coverage to date for deep-sea caridean shrimps in the South China Sea and challenges assumptions about morphological similarity and phylogeny.

## Key findings

- Two species, Janicella spinicauda and Systellaspis curvispina, were newly documented in the South China Sea.
- Phylogenetic analysis showed that morphological similarity does not always reflect close evolutionary relationships.
- Some defining traits may result from convergent evolution rather than shared ancestry.

## Abstract

Despite the high biological and ecological diversity of the South China Sea, limited research has been conducted on the deep‐sea species diversity of caridean shrimps. Based on the collections from three scientific expeditions conducted in the South China Sea, 31 caridean species, belonging to nine families, were reported, including the identification of two species not previously documented in this region, namely Janicella spinicauda (A. Milne‐Edwards, 1883) and Systellaspis curvispina Crosnier, 1988. In addition to morphological features, the COI and 16S gene sequences of these species were analyzed to assess their evolutionary relationships within each family. Phylogenetic analyses, with highest species coverage to date, indicated that similarity in morphological characteristics does not always lead to closer phylogenetic relationships and some defining characteristics for specific taxa are not always synapomorphies but may be the result of convergent evolution. Our results establish reliable evolutionary relationships within specific taxa and highlight the necessity for further taxonomic revisions within these taxa.

The South China Sea is known for its rich biological and ecological diversity. We present the findings from three scientific expeditions conducted in the South China Sea, reporting a total of 31 caridean shrimp species belonging to nine families. The results challenge the conventional notion that morphological similarity indicates close phylogenetic relationships.