Dispersal of lichens along a successional gradient after deglaciation of volcanic mesas on northern James Ross Island, Antarctic Peninsula

摘要

Aerial dispersal in the colonization of bare ground by lichens in the polar regions remains poorly understood. Potential colonists may arrive continually, although extreme abiotic conditions limit their viability. We investigated the vegetative dispersal of Antarctic macrolichens along a successional gradient (from 8.6-7.0 ka BP up to present) after glacial retreat on James Ross Island, in the Antarctic Peninsula region. We collected lichen fragments by means of sticky traps glued on the ground and exposed for 1 year. Foliose or fruticose growth types were the most frequently recorded species (namely Usnea spp. and Leptogium puberulum) together with widely distributed fungi mycelia, while crustose lichens were not found. Although these two lichen species are also locally the most common, their frequency of occurrence in the traps was largely unrelated to local dominance, indicating long-distance dispersal. On the other hand, the dispersed community assembly was related to overall lichen cover and ground physical structure (clast size). There was a gradient of species occurrence frequency increasing with maximal clast size and distance from the glacier front. These results imply that there is no dispersal limitation (at least for certain lichen species) in the colonization of newly deglaciated substrates at the regional scale on James Ross Island. However, lichen establishment is rather rare, and growth of a lichen community is therefore a long-term process.