Species-specific detection of Lobaria pulmonaria (lichenized ascomycete) diaspores in litter samples trapped in snow cover

The foliose lichen Lobaria pulmonaria has suffered a substantial decline in central and northern Europe during the twentieth century and is now consid ered to be critically endangered in many European lowland regions. Based on demographic studies, it has been proposed that under the present environme ntal conditions and forest management regimes, dispersal of diaspores and s ubsequent establishment of new thalli are insufficient to maintain the remn ant small lowland populations. Chances of long-term survival may therefore be reduced. The data and analytical power of these demographic studies are limited. Since lichen diaspores show very few species-specific morphologica l characteristics, and are therefore almost indistinguishable, the accurate assessment of diaspore flux would be a fundamental first step in better un derstanding the life cycle of L. pulmonaria. Here we present a new molecula r approach to investigate the dispersal of L. pulmonaria diaspores in its n atural environment by specifically identifying small amounts of DNA in snow litter samples at varying distances from known sources. We used a species- specific polymerase chain reaction (PCR) primer pair to amplify the ribosom al internal transcribed spacer region (ITS rDNA) and a sensitive automated PCR product detection system using fluorescent labelled primers. We detecte d considerable amounts of naturally dispersed diaspores, deposited as far a s 50 m away from the closest potential source. Diaspores were only found in the direction of the prevailing wind. Diaspore deposition varied from 1.2 diaspores per m(2) per day at 50 m distance from the source to 15 diaspores per m(2) per day at 1 in distance. The method described in this paper open s up perspectives for studies of population dynamics and dispersal ecology mainly in lichenized ascomycetes but also in other organisms with small, wi nd-dispersed diaspores.