Search

PREMISE OF THE STUDY: Some common leaf-dwelling lichen fungi produce asexual spores (conidia) within curved, dorsiventral structures called campylidia. Their shape and tendency to face in the same direction have generated speculation about how dispersal is accomplished. Here we tested the hypothesis that campylidia orient their spore-producing surface against runoff currents and examined the effects of hydration to better understand the spore dispersal mechanism. METHODS : Palm leaves bearing lichens (Calopadia) were surveyed with a dissecting microscope for campylidia with fibrous debris entangled around the base. Where possible, the direction of runoff flow was inferred from the position of the entangled debris; the angle between this direction and that toward which the spore-producing side faced was calculated for 67 campylidia. Other fresh-collected campylidia were photographed in the air-dry state and again after hydration. KEY RESULTS: Orientation of campylidia was strongly correlated with direction of runoff flow, such that the spore-producing side faced against oncoming runoff. Hydration of campylidia quickly resulted in swelling of the conidial mass beneath a thin flap of tissue covering the conidiogenous surface. The flap then bulged outward, exposing the conidial mass from above within its pocket-like compartment. CONCLUSIONS: Our results support previous contentions that water impact against campylidia is important in spore dispersal. However, the morphology of hydrated campylidia and their strong tendency to face upstream suggest that water currents impact laterally upon the thin tissue covering the hydrated conidial mass, thereby extruding spores apically. We contrast these findings with previous suggestions that campylidia act as splash cups. [ABSTRACT FROM AUTHOR]

* 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 field 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 first 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. [ABSTRACT FROM AUTHOR]