Juvenile Development and Diaspore Survival in the Threatened Epiphytic Lichen Species Sticta fuliginosa, Leptogium saturninum and Menegazzia terebrata: Conclusions for in situ Conservation

Abstract

Development and growth of the three threatened epiphytic lichen species Sticta fuliginosa (Hoffm.) Ach., Leptogium saturninum (Dicks.) Nyl. and Menegazzia terebrata (Hoffm.) Massal. was investigated by low temperature scanning electron microscopy and macro-photography. Small cotton gauze discs acting as artificial substrata were fixed with aluminium staples on the bark of selected trees and vegetative diaspores (isidia or soredia) were transferred 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. Two months later 52 % of the S. fuliginosa diaspores were still on the gauze discs and after 16 months 29 % remained attached. For L. saturninum, the corresponding percentages were 46 % and 19 %, respectively. First lobes resembling adult thalli were observed after 8 to 12 months in S. fuliginosa and L. saturninum but only after 16 months in M. terebrata. All three species developed usually more than one thallus primordium (pseudomeristematic growth zone) per isidium or soredial cluster. Transplanted thallus fragments were able to fix themselves on the new substratum but in all three species large parts degenerated and fell off during the first year, particularly in S. fuliginosa. The results show that the juvenile development of the investigated species is not restricted by microclimatic factors at the study site. We therefore conclude that the juvenile development is not the restricting factor in regard to growth and population survival. Other factors, such as the competition with bryophytes, insufficient diaspore dispersal or forest management practice must account for the small population sizes. The described transplantation technique of vegetative diaspores has proved to be very useful for the augmentation of small populations without damaging the existing thalli and we suggest use of this method for in situ conservation of endangered lichen species.

Key words

Lichenized fungi - juvenile development - vegetative diaspores - conservation

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Section Editor: H. M. Jahns