Journal
AMERICAN JOURNAL OF BOTANY
Volume 101, Issue 11, Pages 1836-1848Publisher
BOTANICAL SOC AMER INC
DOI: 10.3732/ajb.1400272
Keywords
Calopadia puiggari; campylidia; conidia; foliicolous lichens; lichen development; lichen life cycle; lichenization; photobiont; prothallus; pycnidia; symbiont codispersal
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Premise of the study: The life histories of lichen fungi are not well known and cannot be readily studied in laboratory culture. This work documents in situ the complete life cycle of the widespread crustose lichen Calopadia puiggarii, which reproduces sexually and asexually on the surfaces of leaves. Methods: Plastic cover slips held in a mesh frame were placed over leaves in the fi eld and successively removed for microphotography of colonizing lichens. Key results: Macroconidia produced within campylidia encircled photobiont cells and codispersed with them, a feature not reported previously for C. puiggarii. Dispersed macroconidia readily germinated and lichenized the photobionts. Algal cells were often dislodged from the encircling macroconidia, providing a likely source for the free-living populations observed. Aposymbiotically dispersed ascospores germinated and lichenized nearby algal cells soon after dispersal. Thallus areolae merged readily in early development, although adjacent mature thalli were often separated by growth inhibition zones. Pycnidia are reported for the fi rst time in Calopadia; their pyriform microconidia probably function as male gametes (spermatia). Pycnidia, apothecia, and campylidia began development similarly as darkly pigmented primordia on the fungal prothallus. Conclusions: Abundant dispersal of ascospores, conidia, and photobionts allows C. puiggarii to quickly colonize leaves with the dual advantages of sexual and asexual reproduction, and with the added convenience of having its algal partner on hand. Fusions and prothallic capture of additional algae provide many opportunities for multiple mycobiont and photobiont genotypes to be combined in a single thallus, but the outcomes of such events remain to be explored.
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