SYMBIOSIS - Cyanobacteria - page 397

strains from epiphytic lichens as well as cyanobionts collected from terrestrial and lithophytic
habitats (Stenroos et al ., 2006).
Papaefthimiou et al . (2008) conducted a preliminary clustering of Nostoc strains (cyanobionts
from bryophytes, cycads and Gunnera spp.) with the help of amplifi ed rDNA restriction analysis
(ARDRA) and the phylogeny has been reconstructed on the basis of 16S rRNA gene sequences
coupled with morphological characterization. They also confi rmed the existence of all cyanobionts
from the above hosts in two clades. Together with these several free-living Nostoc strains of the
species of N . muscorum , N . calcicola , N . edaphium , N . ellipsosporum and strains related to N . commune
are clustered together. A phylogenetic study conducted by Otálora et al . (2010), based on rbcLXS
sequences sampled from 79 lichen thalli of Collemataceae with 163 Nostoc sequences from GenBank,
recognized two major clades. Clade I included both free-living and symbiotic Nostoc strains. Clade II
comprised of both free-living and symbiotic strains. However, clade II could be further resolved into
three sub-clades. In sub-clade I besides free-living Nosto c strains, cyanobionts from North American
( Peltigera dactyla ), South American ( Leptogium azureum , L. cyanescens ) and a European ( Fuscopannaria
leucophaea ) lichen species are clustered together. Cyanobionts from other lichen thalli ( Leptogium
lichenoides , Sticta hypochroa , S . gaudichaldia , Peltigera malacea and Protopannaria pezizoides ) are present
in the sub-clade II. Large majority of the symbiotic Nostoc strains (from G . pyriforme , vast majority
of lichens including members of Collemataceae and C . circinalis , G . manicata and Stangeria paradoxa )
and some free-living ones are clustered together. In this respect, the phylogenetic relationships
drawn by others (Wirtz et al ., 2003; O'Brien et al ., 2005; Stenroos et al ., 2006; Myllys et al ., 2007) have
been confi rmed by them.
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