Abstract
BackgroundMangroves are tropical and subtropical intertidal forests colonising sheltered coasts across the world. They host a unique faunal community, dominated by brachyuran crabs and gastropods. These invertebrates strongly contribute to the functionality of the entire forest. The reliable assessment of mangrove faunal diversity is, thus, a crucial step for efficient management and conservation plans, but it is hindered by difficulties in species identification. Here we provide a verified DNA barcode library for brachyuran crabs and gastropods inhabiting the mangroves of the Greater Bay Area, Southern China. In particular, we collected and morphologically identified 1100 specimens of mangrove associated brachyuran crabs and gastropods. The partial sequences of the mtDNA cytochrome oxidase subunit I gene were obtained from 275 specimens. Barcode sequences were then used to delineate Molecular Operational Taxonomic Units (MOTUs), employing three different delimitation methods: the automatic barcode gap discovery (ABGD) method, the general mixed Yule coalescent (GMYC) model and a Bayesian implementation of the Poisson tree processes (bPTP) model.ResultsBy integrating DNA barcodes with morphology, we identified 44 gastropod species and 58 brachyuran species associated with Hong Kong mangroves, with five and seven new records, for gastropods and crabs, respectively, for the Greater Bay Area. The delineation of MOTUs based on barcode sequences revealed a strong congruence between morphological and molecular identification for both taxa, showing the high reliability of the barcode library.ConclusionsThis study provides the first reference barcode library for mangrove-associated macrobenthic fauna in the Greater Bay Area and represents a reliable tool to management and conservation plans. Our molecular analyses resolved long lasting taxonomic misidentifications and inconsistencies and updated the knowledge on the geographical distribution of Asian mangrove associated fauna, ultimately highlighting a level of biodiversity higher than previously thought for Southern China.
Highlights
Mangroves are tropical and subtropical intertidal forests colonising sheltered coasts across the world
The objectives were to (1) create a complete Deoxyribonucleic acid (DNA) barcode library for all known brachyuran crabs and gastropods inhabiting mangrove forests in the Pearl River Delta, and (2) to resolve long lasting species misidentifications and discrepancies between morphological and genetic identifications to achieve a reliable and updated list of mangrove-associated fauna. We argue that this library, and the associated species list, represent a useful inventory of the biodiversity of mangrove-associated crabs and molluscs in Hong Kong and the whole Greater Bay Area, and are a key tool for mangrove biodiversity monitoring programs in China and the whole of East Asia
Sermyla riqueti, belonging the family Thiaridae was not included in the c oxidase subunit 1 (COxI) dataset because this species is rare in Hong Kong mangroves and we only had a single small specimen available for genetic analysis, from which we did not recover a reliable barcode sequence
Summary
Mangroves are tropical and subtropical intertidal forests colonising sheltered coasts across the world. Despite accounting for only 0.7% of the total tropical forests of the world [1], mangroves play a critical role in the protection of coastal areas, act as nurseries for many species, sequestrate carbon, recycle nutrients, and provide benefits to people through the direct exploitation of their resources [2,3,4,5] Such ecosystem services are provided by a unique biome represented by a floral community of terrestrial origin and the specialised marine and intertidal macroinvertebrate assemblages thriving in these forests [2, 6,7,8]. Conservation efforts and good restoration practices are paramount to preserve functional and viable mangrove patches, and they need to be put in place rapidly [11]
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