Message - 7th IAL Symposium

Lichen: from genome to ecosystem in a changing world
3A-P
(3A-P7) Submission ID: IAL0091-00001
GENUS AND SPECIES CONCEPTS IN DICTYONEMA S. L.
Dalforno M. 1 , Lücking R. 2 , Bungartz F. 3 , Yanez A. 3 , Lawrey J. 1
1 Environmental Science and Policy, George Mason University, Fairfax, Virginia, United States
2 Botany, The Field Museum, Chicago, United States
3 Biodiversity Assessment, Charles Darwin Foundation, Santa Cruz, Galapagos, Ecuador
Dictyonema sensu lato is a large, pantropical genus of basidiolichens that produces crustose to foliose
thalli lichenized with cyanobacteria and corticioid to stereoid basidiocarps. There are thought to be more than 20
species in the genus, but species concepts are currently not well established. The most widely used concepts
are those of Parmasto (1978), who adopted a relatively wide species concept, emphasizing thallus anatomy and
treating morphological differences largely as phenotypic variation. Consequently, his monograph synonymized
several different taxa under key names such as Dictyonema pavonia (Cora glabrata) and Dictyonema sericeum.
Recent investigations in our labs have begun to use DNA sequences obtained from hundreds of Neotropical
specimens, including extensive collections from the Galápagos Islands, to elucidate relationships of Dictyonema
species and their close relatives. Molecular phylogenies based on nuLSU and nuITS rDNA sequences have
resolved five distinct generic lineages within Parmasto’s concept of Dictyonema sensu lato: Cora, Corella, Dictyonema
s.str., Cyphellostereum and the monospecific Acantholichen pannarioides. The entire group includes
very different morphotypes and photobiont interactions, although all species form lichenized associations with a
scytonematoid Rhizonema photobiont. In Dictyonema s.str. and Cyphellostereum, the cyanobacteria maintain
their filamentous structure, while in Cora, Corella, and Acantholichen, the cyanobacterial cells assume a “chroococcoid”
shape. Based on our phylogenetic reconstructions, we are now able to recognize important characters
for delimiting genera and species, including color of the thallus, presence of a hypothallus and/or prothallus,
growth form, texture of upper and lower surfaces, presence and shape of basidiocarps, and anatomical features
of the cyanobacteria and fungal sheath cells. Based on these results, we conclude that the collective species
Dictyonema glabratum, D. sericeum, and D. phyllogenum represent about 25 to 30 different species.
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