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.