New aerophytic morphospecies of Nostoc ( Cyanobacteria ) from São Paulo State , Brazil

(New aerophytic morphospecies of Nostoc (Cyanobacteria) from São Paulo State, Brazil). Brazilian aerophytic biotopes are almost completely unknown regarding to cyanobacterial flora. During the study of this special flora, three morphospecies of the genus Nostoc from different habitats in the State of São Paulo, Brazil, were found. Based on their morphology, especially by formation and shape of the akinetes, life cycles and ecology, these populations were considered distinct from all known taxa of Nostoc and are proposed as new species: N. interbryum, N. viride, and N. alatosporum.


Introduction
The modern cyanobacterial taxonomic studies are based mostly on the combined phenotypical, ultrastructural, ecological and molecular data.However, particularly in extreme tropical biotopes, morphological studies and detailed investigation of its biodiversity remain very little known.On that account, descriptions of evidently new morpho and ecospecies are very important for recognition of cyanobacterial diversity under natural conditions.
Studies of aerophytic cyanobacteria from tropical and subtropical habitats in the State of São Paulo, Brazil, started only recently.In numerous special habitats, such as wet rocks, bark of trees in rainy forest, and wet lateritic soils, several special morphotypes occur, which do not correspond to any described species.Their cultivation is difficult and, consequently, the description of such natural populations is very important for future research.Thus, during the development of these studies, three new morphospecies corresponding with the genus Nostoc, were found in different habitats.
The genus Nostoc comprises around 200 species mostly growing in benthonic communities of lakes or in aerophytic habitats (Komárek et al. 2003).In spite of this great number of species, the Brazilian literature mentions only eight species of Nostoc, most part living in aerophytic habitats.These species do not correspond morphologically and ecologically to the studied populations which display a group of characteristics that makes them perfectly distinct from all species of Nostoc described up to now.
Habitat: macroscopic irregular mats forming slimy layers on wooden substrates in a greenhouse.
The morphology of heterocytes and particularly of ripe akinetes is not yet known within the genus Nostoc.Similar widened epispores were described only in the genera Cylindrospermum and benthic species of Anabaena.
Habitat: macroscopic mass on side banks of stream.

Discussion
The intrageneric taxonomy of the genus Nostoc is very complicated.Particularly the molecular evaluations indicate the heterogeneity of this genus, which will be probably divided in several generic entities (Turner 1997, Rudi et al. 1998, Ventura et al. 2002, Rajaniemi et al. 2005).This revision is closely connected also with revision of ecological and morphological markers, which should coincide with genetic background (Hrouzek et al. 2005).Division of the genus Nostoc in several genera according to morphology of colonies was discussed by several previous authors (Drouet 1977, Elenkin 1936-1949).However, this classification must be revised according to modern data compatible with molecular research.In spite of this prospective trend in cyanobacterial taxonomy, several specific morphotypes have been discovered in various extreme and poorly known habitats in the biosphere (mainly in tropical and subtropical regions).Valid descriptions and presentation of such special morphotypes, which are evidently morphologically and ecologically different from all up to known and described species, are very important for the understanding the cyanobacterial diversity in different ecosystems and regions.