Ancient landscapes of the Namib Desert harbor high levels of genetic variability and deeply divergent lineages for Collembola

Abstract

Aim To assess spatial patterns of genetic and species‐level diversity for Namib Desert Collembola using mitochondrial DNA cytochrome c oxidase subunit I (COI) gene sequences. Location Namib Desert gravel plains. Taxon Collembola (springtails). Methods A total of 77 soil samples were collected along NE‐SW (60 km) and E‐W (160 km) transects from within a 4,000 km 2 area of the Namib Desert gravel plains. We extracted 434 springtails from the 37 samples which contained Collembola and sequenced them at the COI gene locus. In the absence of specific taxonomic keys and previous genetic data for these taxa, we used Generalized Mixed Yule Coalescent (GMYC) analyses to provide putative species‐level designations. Results We obtained 341 successful COI sequences, 175 of which were unique haplotypes. GMYC analyses identified 30 putative species, with up to 28% sequence divergence (uncorrected p‐distance). The distribution of genetic variants was disjunct, with 97% of haplotypes and 70% of “GMYC species” found only at single sites. Main conclusions Dispersal events, although rare, may be facilitated by environmental events such as prevailing onshore winds or occasional flow of rainwater to the coast. We conclude that the high genetic diversity we observed is the result of ancient springtail lineages, patchy distribution of suitable habitats, and limited dispersal (gene flow) among habitable locations.

The limited spatial scale of dispersal in soil arthropods revealed with whole‐community haplotype‐level metabarcoding

“…However, they do not inform about colonization and establishment success (effective dispersal) and possibly only pertain to a few highly dispersive species. Additionally, the dispersal potential may have been overestimated due to the low resolution of morphological species identification (Cicconardi et al., 2013) leading to perceived low turnover among sites, as evident from recent large‐scale barcoding studies (Collins, Hogg, Baxter, Maggs‐Kölling, & Cowan, 2019; Young et al., 2019). Our results at the community level thus raise doubts about a generalized dispersal advantage for small‐bodied arthropods and instead indicate very small dispersal distances, even over evolutionary timescales, for the majority of species that make up the complex mesofauna communities of the soil.…”

High diversity and local endemism in Aotearoa New Zealand's groundwater crustacean fauna

“…Climatic events appear to be the main factor in changing hydrological connectivity and genetic isolation for tectonically stable continents like Europe, North America, Australia, and Africa (Collins et al, 2019 ; King & Leys, 2014 ; Lefébure et al, 2006 ; Witt et al, 2006 ). Both glaciations and aridity are strongly implicated in creating hydrological barriers that isolated populations of stygofauna, leading to genetic divergence and speciation.…”

Nematode communities indicate diverse soil functioning across a fog gradient in the Namib Desert gravel plains

“…Namib Desert gravel plains soils contain many of the invertebrate taxa found in soils globally, including microarthropods such as collembola (Collins et al, 2019 ) and mites (André et al, 1997 ), but little is known about soil nematodes. Nematode diversity and abundance have been studied in soils under Acanthosicyos horridus (!nara melon shrubs) in the Namib Desert sand dunes (Marais et al, 2020 ), and some nematode species have been described that were isolated from soil associated with Welwitschia mirabilis plants in the gravel plains (Rashid et al, 1990a , 1990b ; Rashid & Heyns, 1990a , 1990b ).…”