How the small host the small: Cryptogam trait-mediated structuring of Antarctic microarthropod communities

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Primary producers shape terrestrial biodiversity, yet, most research has focused on vascular plants and the role of cryptogams (mosses, lichens and algae) remains under-explored. Cryptogams dominate Antarctic vegetation and support diverse microarthropod communities. However, how cryptogam traits influence these communities remains poorly understood. We therefore investigates the role of 28 cryptogam species and one vascular plant, via their functional traits, in shaping microarthropod communities across three contrasting sites in the maritime Antarctic. We hypothesized that vegetation traits, major microarthropod taxa, and abiotic drivers interact to influence community patterns The green alga Prasiola crispa hosted the highest microarthropod abundance (737 ind. g -1 ), while mosses supported greater microarthropod diversity and springtail abundance (68.9 ind. g -1 ) than lichens (1.6 ind. g -1 ). In contrast, lichens hosted more mites (38.6 ind. g -1 ) than mosses (13.7 ind. g -1 ). The grass Deschampsia antarctica showed intermediate abundances but the highest species richness and Shannon diversity. As hypothesized, mosses supported twice the richness and 1.4× greater diversity than lichens. Springtails were consistently more abundant in mosses and mites in lichens at the two northern sites, but this pattern disappeared at the climatically harshest southernmost site, suggesting environmental conditions modulate host preferences. Cryptogam nitrogen and moisture contents strongly predicted microarthropod community patterns, although their influence varied with vegetation type and location. Among mosses, moisture increased springtail abundance but reduced diversity due to the dominance of Cryptopygus antarcticus . In lichens, nitrogen had a stronger influence than in mosses, particularly on mite abundance and Shannon diversity. As hypothesized, moisture was more important at the harshest southern site, while nitrogen had stronger effects at more productive northern locations. These findings emphasize the role of cryptogam traits in structuring Antarctic terrestrial biodiversity. With future shifts predicted in vegetation composition, the functional traits of emerging dominant species may restructure microarthropod communities and their ecological functions.

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