Diversity, phylogeny, and DNA barcoding of brachyuran crabs in artificially created mangrove environments

Globally, at the rate of 1-2 percent per annum, mangrove coverings are disappearing and 35 percent have been lost in the last 20 years due to changes in climate and human activities. No mangrove-associated crabs were found when the mangroves were artificially transplanted 25 years ago in the Vellar estuary. This mangrove ecosystem was sampled for brachyuran biodiversity estimation, species abundance, composition and evaluation of the effectiveness of DNA barcoding in brachyuran crabs species identification. A total of 2844 crabs were collected, representing 35 species within 8 families belonging to 20 genera. Four brachyuran crab species, that is, Uca lactae, U. Triangularis, Selatium brockii, and Neosarmatium asiaticum account for >70% of the total abundance. An approximate 87.5% of crab species estimated to occur by various species estimator were recovered in the present study. Between Uca lactea and U. triangularis, the maximum association index value was observed (97.7%). Cluster analysis grouped the sampled stations according to the types of mangrove species, clearly influencing the structure and composition of the brachyuran crabs. In general, vegetative cover composed of multiple species of mangroves is preferred for the abundance of all collected crabs species, and particularly Neosarmatium asiaticum. Analysis of DNA barcoding indicates that 40% of the brachyuran species gathered in this sample were first barcoded. The advent of new high-throughput sequencing technologies will change biomonitoring applications and surveys drastically in the near future, making reference datasets like ours relevant.