Juvenile development and diaspore survival in the threatened epiphytic lichen species Sticta fuliginosa, Leptogium saturninum and Menegazzia terebrata: Conclusions for in situ conservation

Development and growth of the three threatened epiphytic lichen species Sti cta fuliginosa (Hoffm.) Ach,, Leptogium saturninum (Dicks.) Nyl. and Menega zzia terebrata (Hoffm.) Massal. was investigated by low temperature scannin g electron microscopy and macro-photography. Small cotton gauze discs actin g as artificial substrata were fixed with aluminium staples on the bark of selected trees and vegetative diaspores (isidia or soredia) were transferre d onto these discs. The subsequent development into small thalli of up to 3 mm length was observed within the 32-month study period. All three species produced anchoring hyphae within the first month after transplantation. Tw o months later 52% of the S. fuliginosa diaspores were still on the gauze d iscs and after 16 months 29% remained attached. For L. saturninum, the corr esponding percentages were 46% and 19%, respectively. First lobes resemblin g adult thalli were observed after 8 to 12 months in S. fuliginosa and L. s aturninum but only after 16 months in M. terebrata. All three species devel oped usually more than one thallus primordium (pseudomeristematic growth zo ne) per isidium or soredial cluster. Transplanted thallus fragments were ab le to fix themselves on the new substratum but in all three species large p arts degenerated and fell off during the first year, particularly in S. ful iginosa. The results show that the juvenile development of the investigated species is not restricted by microclimatic factors at the study site. We t herefore conclude that the juvenile development is not the restricting fact or in regard to growth and population survival. Other factors, such as the competition with bryophytes, insufficient diaspore dispersal or forest mana gement practice must account for the small population sizes. The described transplantation technique of vegetative diaspores has proved to be very use ful for the augmentation of small populations without damaging the existing thalli and we suggest use of this method for in situ conservation of endan gered lichen species.