Desiccation tolerance of terrestrial fern gametophytes is linked to light levels in the sporophyte habitat in a cloud forest

Premise Ecological niche differentiation of spore germination and sporophyte habitat promote the coexistence of fern species in the cloud forest, but the role of the gametophyte is unknown. Because fern sporophytes only establish where the inconspicuous gametophytes grow and reproduce, the environmental tolerance of the gametophyte has been hypothesized to be associated with the light preference of the sporophyte. Methods We measured environmental variables of the sporophyte and gametophyte of nine coexisting fern cloud forest species and manipulated water availability in the air and soil to quantify the desiccation tolerance of gametophytes. Results Gametophytes of all species dried quickly but maintained at least half of their photosynthetic efficiency (ΦPSII) after losing 80% of their relative water content (RWC). However, pretreatment F v / F m values were not recovered after rehydration of gametophytes with 80%, 50%, or 20% of RWC. Passive water loss through the gametophyte cuticle was slower in species from exposed areas than in shaded areas. Gametophytes of sun species dried slowly and had high ΦPSII at low RWC (20%), whereas those of species from shaded, humid sites were less desiccation‐tolerant. The gametophytes of all species, especially those from shaded habitats, were more sensitive to low air humidity than to low soil moisture. Conclusions The physiology of the gametophyte was positively linked to the preferred light habitat of the sporophyte. Low physiological resilience to low to moderate desiccation events may compromise gametophyte survival and fern diversity in the face of habitat transformation and climate change.