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

Primary producers shape terrestrial biodiversity, but most research has focused on vascular plants, while 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 investigated the role of 28 cryptogam species and one vascular plant, via their functional traits, in shaping microarthropod communities across three contrasting sites (Signy Island, Byers Peninsula and Rothera) in the maritime Antarctic. We hypothesized that vegetation nitrogen and moisture content, major microarthropod taxa, and abiotic drivers interact to influence community patterns. Vegetation type effects on total microarthropod abundance were context-dependent. Mosses hosted more microarthropods than lichens at Signy Island, but these differences diminished further south. Microarthropod richness and springtail abundance were consistently higher in mosses than lichens across all sites, whereas mite abundance did not differ between vegetation types. Cryptogam nitrogen and moisture content 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 that the influence of cryptogam traits in structuring Antarctic terrestrial biodiversity is modulated by the environmental context. With future shifts predicted in vegetation composition, the functional traits of emerging dominant species may restructure microarthropod communities and their ecological functions.