DNA barcoding and diversity of groundwater oligochaetes in Benin (West Africa)

Abstract

Background: Groundwater is a major ecosystem in terms of biodiversity, endemism and relict species. However, its stygofauna, the obligate groundwater fauna, remains too often ignored, although present on all continents. Its knowledge is of particular interest for public health as groundwater is also the main drinking water reservoir on earth. This study aims to build a genetic database of groundwater oligochaetes at the Beninese country, which can be used as a reference for future studies based on DNA barcoding. It comes in a larger framework using the stygofauna as an indicator for water quality. Results: 96 wells were sampled in 2015 and 2016, and COI barcodes were obtained from 126 specimens of the genera Aulophorus (Naididae) and Haplotaxis (Haplotaxidae), the main two oligochaete components in Beninese wells. Molecular data enabled an interesting comparison between both genera, in terms of species diversity, distribution, and dispersal capacities. The numerous specimens of the stygophile Aulophorus proved to consist of 4 species, widely distributed, with low intraspecific genetic variability, suggesting an important dispersal capacity. In contrast, 7 potential species were identified in the rare stygobiotic Haplotaxis, each of them being restricted to one station, with one exception, so that each hydrogeographic basin can be characterized by its unique assemblage of Haplotaxis species. Significance: These first data suggests an interesting potential use of groundwater oligochaetes for water management in Benin: (1) the presence of Haplotaxis is an indicator of the phreatic origin of water in wells and, as such, suggests good water quality; (2) in contrast, the presence of Aulophorus species in a well gives evidence of poor protection of the later against exogenous elements, which can have a negative impact on water quality.