Assessing genetic diversity of springtails (Collembola) across the Namib Desert and the potential role of environmental parameters in driving this diversity

Abstract

Desert environments are characterised by harsh conditions and possess low biodiversity largely caused by abiotic factors such as; low precipitation, soil organic matter, high temperatures, high levels of evapo-transpiration, pH and salinity. These factors significantly reduce primary production, which influences the availability of food resources for deserts organisms. The diversity and the drivers of diversity for below ground invertebrates including Collembola (springtails) are relatively unknown in the Namib Desert. Previous morphological studies have found only five species on the basis of traditional taxonomy. This study assesses the diversity of Namib Desert Collembola and determines the effect of environmental parameters on this diversity, The diversity of Namib Desert Collembola was assessed using DNA Barcoding. The sequence information of the 178 Collembola specimens, taken from mitochondrial barcoding using the Cytochrome-c oxidase subunit I (COI) gene, was analyzed and Molecular Operational Taxonomic Units (MOTUs) were defined. Collembola community responses to soil physicochemical properties were investigated by using Redundancy Analysis (RDA). MOTUs were successfully indentified to family level (Isotomidae, Neanuridae and Sminthuridae). The researcher found a total of 30 MOTUs, most of which showed limited geographical localisation. The mtDNA COI (barcode) locus revealed high levels of previously unreported genetic diversity of Collembola in the Namib Desert. The RDA indicated that none of the soil physicochemical properties significantly drove variation in Collembola community composition. However, total soil nitrogen was shown to be a strong but not significant driver of variation in community composition (p<0,054). The taxonomic identification of the Collembola specimens was also attempted using traditional morphological analysis. A total of 23 individuals, collected from pitfall traps or extracted from soil samples, were selected for identification. Available European keys were used for identification to genus level where possible. A total eight of specimens were identified to genus level (Folsomides sp), 14 to family level (Entomobryidae) and one to order level (Symphypleona). Both Symphypleona and Entomobryidae were previously unreported from the Namib Desert. The Folsomides genus and the family Entomobryidae were the most abundant groups. This research suggests that soil dwelling Collembola in the Namib Desert have a much higher level of diversity than previously known. However, the study also highlighted the need for a more comprehensive database for Namib Collembola that includes COI sequence data as well as the morphological identification of species.