Quercus lusitanica Lam. is an Iberian endemic dwarf oak that forms distinctive shrubland communities across Atlantic and Mediterranean landscapes. Although often regarded as a marginal or secondary oak, it plays an important ecological role in open woodlands, heathlands, forest gaps and drought-adapted shrublands. Its communities occur along marked climatic, edaphic and successional gradients, making them particularly relevant for conservation, climate-change assessment and restoration planning. However, their floristic composition, ecological drivers and potential responses to environmental change remain insufficiently understood at the community level.

We used Joint Species Distribution Models to analyse plant assemblages associated with Q. lusitanica across its distribution range. Unlike single-species models, this approach considers co-occurrence patterns among species and identifies groups of taxa structured by shared environmental responses. An extensive vegetation dataset was combined with climatic and soil predictors to assess the main gradients controlling species turnover and community differentiation.

The models revealed a strong environmental structuring of Q. lusitanica communities. Climate and soil properties emerged as the main drivers of assemblage composition, with temperature-related variables, soil acidity and soil texture showing particularly important effects. These results confirm the broad ecological amplitude of Q. lusitanica, which occurs both in drought-prone Mediterranean shrublands and in more Atlantic, temperate and early-successional vegetation mosaics. The species therefore appears not only as a characteristic element of rare Iberian oak shrublands, but also as a pioneer or transitional component in heathlands, degraded forest margins and recovering woodland systems.

By modelling entire assemblages rather than isolated taxa, this work provides a more realistic framework for assessing the conservation value and vulnerability of Q. lusitanica vegetation under environmental change. The results can support the identification of priority areas for habitat protection, the definition of floristically coherent restoration targets and the anticipation of community-level responses to climate change. This approach reinforces the importance of integrating community ecology, biogeography and predictive modelling in the conservation and recovery of rare Mediterranean oak habitats.