Tuesday, June 8, 2021

[Crustacea • 2021] Evidence of Cryptic Diversity in Freshwater Macrobrachium Prawns from Indochinese Riverine Systems revealed by DNA Barcode, Species Delimitation and Phylogenetic Approaches

Live habitus coloration of five common Macrobrachium species;
A. M. equidens B. M. niphanae C. M. sintangense 
D. M. dienbienphuense and E. M. lanchesteri.  

in Siriwut, Jeratthitikul, ... et Sutcharit, 2021.

The diversity of Indochinese prawns in genus Macrobrachium is enormous due to the habitat diversification and broad tributary networks of two river basins: the Chao Phraya and the Mekong. Despite long-standing interest in SE-Asian decapod diversity, the subregional Macrobrachium fauna is still not yet comprehensively clarified in terms of taxonomic identification or genetic diversification. In this study, integrative taxonomic approaches including morphological examination, DNA barcoding, and molecular species delimitation were used to emphasize the broad scale systematics of Macrobrachium prawns in Indochina. Twenty-seven nominal species were successfully re-verified by traditional and molecular taxonomy. Barcode gap analysis supported broad overlapping of species boundaries. Taxonomic ambiguity of several deposited samples in the public database is related to inter- and intraspecific genetic divergence as indicated by BOLD discordance. Diagnostic nucleotide positions were found in six Macrobrachium species. Eighteen additional putative lineages are herein assigned using the consensus of species delimitation methods. Genetic divergence indicates the possible existence of cryptic species in four morphologically complex and wide-ranging species: M. lanchesteri, M. niphanae, M. sintangense, and some members of the M. pilimanus group. The geographical distribution of some species supports the connections and barriers attributed to paleo-historical events of SE-Asian rivers and land masses. Results of this study show explicitly the importance of freshwater ecosystems in Indochinese subregions, especially for the Mekong River Basin due to its high genetic diversity and species composition found throughout its tributaries.

Representative morphology and live habitus coloration of five common Macrobrachium species;
A. M. equidens B. M. niphanae C. M. sintangense D. M. dienbienphuense and E. M. lanchesteri.
Approximate size shown in scale bar (5 mm).

This study provides the first DNA barcode library and cryptic evidence of genus Macrobrachium in Indochina. Diagnostic characters of some species have been detected from nucleotide positions and can be included as additional characters for taxonomic identification and species validation (S1 Table). Despite wide geographical dispersion, several species show low genetic affinity between different geographical populations. In contrast, the morphologically complex Macrobrachium species group possesses high genetic diversity and the geographical distribution shows allopatry between Chao Phraya and Mekong river basins. The broad scale phylogenetic relationships of Indochinese species from the COI dataset are still unresolved. However, examples of stable clade composition and monophyletic lineages are found, especially in estuarine species. The DNA species delimitation suggests several candidate OTUs which might be cryptic species hidden within common species, such as the M. lanchesteri, M. sintangense and M. pilimanus species groups. The barcode gap analysis provides a delimitation threshold for Indochinese taxa despite the high intraspecific variation detected in some species. The inappropriate taxonomic identification of some available sequences from the public database raises caution and suggests that dataset reconstruction and re-verification for further taxonomic comparison is required. Finally, the results of this study indicate that the regional fauna share interconnection with other neighboring regions such as India-Burma and East Asia, as indicated by the records of some widely dispersed species.

Warut Siriwut, Ekgachai Jeratthitikul, Somsak Panha, Ratmanee Chanabun, Peng Bun Ngor and Chirasak Sutcharit. 2021. Evidence of Cryptic Diversity in Freshwater Macrobrachium Prawns from Indochinese Riverine Systems revealed by DNA Barcode, Species Delimitation and Phylogenetic Approaches.   PLoS ONE. 16(6): e0252546. DOI: 10.1371/journal.pone.0252546

A. กุ้งฝอยสิงคโปร์ 𝑀𝑎𝑐𝑟𝑜𝑏𝑟𝑎𝑐ℎ𝑖𝑢𝑚 𝑒𝑞𝑢𝑖𝑑𝑒𝑛𝑠 B. กุ้งฝอยคุณนิพันธ์ 𝑀𝑎𝑐𝑟𝑜𝑏𝑟𝑎𝑐ℎ𝑖𝑢𝑚 𝑛𝑖𝑝ℎ𝑎𝑛𝑎𝑒 C. กุ้งฝอยซินตัง 𝑀𝑎𝑐𝑟𝑜𝑏𝑟𝑎𝑐ℎ𝑖𝑢𝑚 𝑠𝑖𝑛𝑡𝑎𝑛𝑔𝑒𝑛𝑠𝑒 D. กุ้งก้ามขนเดียนเบียนฟู 𝑀𝑎𝑐𝑟𝑜𝑏𝑟𝑎𝑐ℎ𝑖𝑢𝑚 𝑑𝑖𝑒𝑛𝑏𝑖𝑒𝑛𝑝ℎ𝑢𝑒𝑛𝑠𝑒 E. กุ้งฝอยแลนเชสเตอร์ 𝑀𝑎𝑐𝑟𝑜𝑏𝑟𝑎𝑐ℎ𝑖𝑢𝑚 𝑙𝑎𝑛𝑐ℎ𝑒𝑠𝑡𝑒𝑟𝑖