Hidden in Plain Sight: Integrative Taxonomy Discovers Two New Species of Digitate Soft Corals in the Urban Waters of China's Greater Bay Area

Digitate or lobate scleralcyonacean soft corals are common in tropical reef ecosystems, yet their morphological plasticity and insufficient genetic information hinder our understanding of their diversity. In the China Seas, only four such species, all in the genus Paraminabea (Coralliidae), have been documented. Here, we describe Parasphaerasclera dimorpha sp. nov. (Parasphaerascleridae) and Paraminabea inflata sp. nov. from the urban waters of Hong Kong and Zhuhai. These species are distinct in morphology (colony shape and sclerite structure) and genetics from previously reported species. Genome skimming data of two new species and Param. rubeusa from two families were analyzed. Phylogenetic analyses were conducted using MutS, 28S rRNA, and 14 mitochondrial protein-coding genes, which recovered Paras. dimorpha sp. nov. as sister to Paras. grayi and Param. inflata sp. nov. as sister to Param. aldersladei. Seven mitochondrial gene orders and six rearrangement events were detected across families, and Parasphaerascleridae represents an early diverging clade within scleralcyonacean soft corals with a conserved gene order. In contrast, within Coralliidae, there are seven gene rearrangement patterns. Overall, we discovered two new species of digitate soft corals, underscoring the high diversity of soft corals in China's Hong Kong–Zhuhai–Macau Greater Bay Area and the urgency of documenting cryptic marine diversity in this highly urbanized area. Our genome skimming data for these two species, as well as a species without any molecular data before this study (i.e., Param. rubeusa), will be useful for further phylogenetic studies of soft corals.