Abstract
Seven species of springtail (Collembola) are present in Victoria Land, Antarctica and all have now been sequenced at the DNA barcoding region of the mitochondrial cytochrome c oxidase subunit I gene (COI). Here, we review these sequence data (n = 930) from the GenBank and Barcode of Life Datasystems (BOLD) online databases and provide additional, previously unpublished sequences (n = 392) to assess the geographic distribution of COI variants across all species. Four species (Kaylathalia klovstadi, Cryptopygus cisantarcticus, Friesea grisea and C. terranovus) are restricted to northern Victoria Land and three (Antarcticinella monoculata, Cryptopygus nivicolus and Gomphiocephalus hodgsoni) are found only in southern Victoria Land, the two biogeographic zones which are separated by the vicinity of the Drygalski Ice Tongue. We found highly divergent lineages within all seven species (range 1.7 – 14.7%) corresponding to different geographic locations. Levels of genetic divergence for the southern Victoria Land species Gomphiocephalus hodgsoni, the most widespread species (~ 27,000 km2), ranged from 5.9% to 7.3% at sites located within 30 km, but separated by glaciers. We also found that the spatial patterns of genetic divergence differed between species. For example, levels of divergence were much higher for Cryptopygus terranovus (> 10%) than for Friesea grisea ( 5%) populations and over 87% of the total genetic variation (based on AMOVA) on either side of a single, 16 km width glacier. Collectively, these data provide evidence for limited dispersal opportunities among populations of springtails due to geological and glaciological barriers (e.g. glaciers and ice tongues). Some locations harboured highly genetically divergent populations and these areas are highlighted from a conservation perspective as well as avoiding human-mediated transport between sites. We conclude that species-specific spatial and temporal scales need to be considered when addressing ecological and physiological questions as well as conservation strategies for Antarctic Collembola.
Highlights
Due to the extreme environmental conditions that characterize Antarctica (Convey, 2013), as well as the geographical, and island-like, isolation of suitable terrestrial habitats (Bergstrom and Chown, 1999), long-range dispersal events for Antarctic Collembola are rare and they usually rely on liquid water for transport via flotation (Hawes et al, 2008; McGaughran et al, 2011a; Carapelli et al, 2017)
The final alignments for each species varied in length (422–586 bp), largely due to variation in sequence quality, and we treated each species separately for biogeographic analyses to maximize variability within the datasets, a final alignment trimmed to 422 bp was used to construct the phylogenetic tree (Figure 3)
In this study we examined the available c oxidase subunit I gene (COI) sequence data for all seven of the Collembola species that occur within Victoria Land (71◦ to 78.5◦S)
Summary
Due to the extreme environmental conditions that characterize Antarctica (Convey, 2013), as well as the geographical, and island-like, isolation of suitable terrestrial habitats (Bergstrom and Chown, 1999), long-range dispersal events for Antarctic Collembola (springtails) are rare and they usually rely on liquid water for transport via flotation (Hawes et al, 2008; McGaughran et al, 2011a; Carapelli et al, 2017). It is likely that springtails are currently unable to disperse among the three Antarctic Conservation Biogeographic Regions (ACBRs; Terauds and Lee, 2016) in the Ross Sea Sector of Antarctica: northern Victoria Land (NVL), southern Victoria Land (SVL), and the Transantarctic Mountains (TAM), owing to various physical obstacles in the marine and terrestrial realms (e.g., the Drygalski Ice Tongue; Figure 1). Within each of these three ACBRs, available habitat is patchy and local microhabitats are likely to be important for long-term persistence of populations (Sinclair and Sjursen, 2001). This is unfortunate as such an analysis could help to assess the relative role of geographic barriers in structuring populations of Antarctic springtails
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