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.
