Pectenia plumbea vs Nephroma laevigatum

    It seems that in the areas (hyperoceanic woods and forest) where both Degelia plumbea et Nephroma laevigatum occur, a kind of attraction of Degelia plumbea towards Nephroma laevigatum can be observed. Indeed, thallus of Degelia plumbea growing on those of Nephroma laevigatum are often observed (and never the contrary, according to our observations). Both species share the same photobiont, a Nostoc, and maybe they are competing for a particularly performing lineage of Nostoc...because it is possible to see, in the case of two neighbouring thallus of Degelia plumbea, a difference in colour (see picture), but it is also possible to consider a competition simply for light, because there is no visible damage on host, which would point out a kind of paratism, but only a progressive alteration of Nephroma laevigatum thallus, disappearing at the end, leaving alone the thallus of Degelia plumbea, except on fringes where lobules of Nephroma laevigatum, with light, can survive. These observations are still in progress, in order to elucidate the kind of "relationships" between these two species.*