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Abstract Detail



Symbioses: Plant, Animal, and Microbe Interactions

Sanders, William [1].

Light microscope observation of lichen establishment and development in a subtropical foliicolous (leaf-dwelling) community.

The difficulty of observing microscopic events in nature has limited our knowledge of lichen symbiont dispersal, encounter, and subsequent coordination of growth to form a thallus under field conditions. The foliicolous lichens represent a community of diverse taxa highly specialized to complete their life cycle in the limited lifetime of their leaf substratum. Adapted to colonize a smooth surface, they will also readily colonize strategically placed transparent materials, enabling early stages of colonization and development to be studied with light microscopy. In the present work, transparent vinyl microscope cover slips were fitted onto plastic netting and displayed on Sabal palmetto leaves in an oak hammock in southwest Florida. Cover slips were removed at intervals (destructive sampling), wet mounted and observed with light microscopy. Germinating lichen propagules began to appear on cover slips within a week after placement, with those of Calopadia spp. (most likely C. puiggarii and perhaps C. fusca) most abundant by far. The asexual propagules of Calopadia consisted of elongate conidia wrapped around unicellular trebouxioid green algae, with which they were clearly co-dispersed. Such propagules were often observed in large masses. Co-dispersed algal cells could also become free from the surrounding conidia, and small populations of similar-appearing algae were observed in cell division unassociated with any fungal symbiont. Hyphae arising from germinating conidia enveloped algal cells and radiated with abundant branching along the substratum, where they often contacted and ultimately merged in growth with many nearby lichenized units. Multicellular (muriform) ascospores, presumably resulting from sexual processes, were also produced by Calopadia, and were commonly observed germinating from many of their component cells. Germ hyphae from such spores were frequently seen contacting and surrounding trebouxioid algal cells in their vicinity and upon the surface of the spores themselves. Distinct patches of dark bluish-green coloration on the fungal prothallus often presaged the development of fungal reproductive structures such as the conidia-producing campylidia, urn-shaped spermagonia, and apothecia. Apparent trichogynes were also observed. Thalli of Gyalectidium spp., Tricharia sp. and 2-3 other unidentified members of the Gomphillaceae also developed on the cover slips. The former include G. paolae and G. appendiculatum as evidenced by their distinctive hyphophores. Diahyphal propagules were initiated by one such thallus after only ≤ 36 days. The trebouxioid algal symbionts of all these lichens were morphologically indistinguishable, suggesting the possibility that the lichen fungi of this community associated with the same or similar algal species.

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1 - College of Arts And Sciences, Florida Gulf Coast University, 10501 FGCU Blvd. South, Ft Myers, FL, 33965-6565, USA

Keywords:
foliicolous
lichens
development
lichenization
photobionts.

Presentation Type: Oral Paper:Papers for Topics
Session: 8
Location: Prince of Wales/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 8:30 AM
Number: 8003
Abstract ID:139
Candidate for Awards:None


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