Should ecomorphs be conserved? The case of Nostoc flagelliforme, an endangered extremophile cyanobacteria

Abstract

Nostoc flagelliforme has been reported from deserts of all continents and more recently from semiarid environments in south-east Spain and Australia. Its cylindrical thalli are very conspicuous on soils after rains and can be easily differentiated from other taxa and it is considered endangered in countries as China. It was firstly described as variety flagelliforme of Nostoc commune but later was considered a separate species. The morphology, fine structure and ecology of populations of both taxa from Australia and different regions of Spain were studied and 16S rRNA and trnLLeu (UAA) genes were sequenced to know their intraspecific genetic variation. The morphological study even when revealed the presence of several intermediate morphs, from spheres and sheets to ribbons followed by the cylindrical thalli and the overlapping of cell dimensions, permit the differentiation of cylindrical morphs from the others. The molecular data did not allow for a distinction between Nostoc commune and Nostoc flagelliforme which is clearly polyphyletic and both show a high genetic diversity. The presence of cylindrical thalli seems to be related to extreme conditions of aridity, usually on soils but occasionally on rock walls. The ecotype that Noctoc flagelliforme represents deserves to be protected for itself and for the evolutionary process it represents opening the possibility of implementation of recovering measures and even to explore its biotechnological production from a different point of view.