Vellozioid roots allow for habitat specialisation among rock- and soil-dwelling Velloziaceae in campos rupestres

1. Plant growth on harsh substrates (habitat specialisation) requires specific traits to cope with stressful conditions. 2. We tested whether traits related to nutrient acquisition (root colonisation by fungal symbionts, and plant morphological and physiological specialisations), and nutrient use (leaf nitrogen (N) and phosphorus (P) concentrations and N- and P-remobilisation efficiency), were related to habitat specialisation for 27 species of Velloziaceae growing either in soil or on rocks in extremely P-impoverished campos rupestres habitats. If habitat specialisation were to drive trait sorting, then we expect traits to differ between those substrates. 3. Both soil and rock-dwelling species presented a very low proportion of root length colonised by arbuscular mycorrhizal and dark septate fungi. However, rhizosheaths were only observed in soil-dwelling species, and vellozioid roots, a specialisation that allows for mining P and dissolving quartzite rock, were mostly found in rock-dwelling species. We did not observe differences in nutrient-use traits between rock- and soil-dwelling species. 4. Roots specialisations are strongly correlated with microhabitats, and the presence of vellozioid roots seems to mediate bare rock specialisation. There is an overall P limitation of plant productivity both on rock and in soil of campos rupestres, which does not drive the sorting of traits related to aboveground nutrient use and symbiotic P acquisition. Therefore, nutrient impoverishment is indeed a very strong environmental filter in campos rupestres as a whole, but habitat specialisation plays an important role in the spatial distribution of Velloziaceae between contrasting substrates.