Environmental variation is related to morphotype differentiation in a Brunfelsia (Solanaceae) complex

This study combines morphological and environmental data to better understand a Brunfelsia (Solanaceae) species complex, aiming to clarify patterns of variation and identify ecological factors that shape morphotype boundaries. Such an approach provides a broader perspective on how organisms respond to environmental gradients and contributes to a more comprehensive understanding of biodiversity.

We analyzed 254 herbarium specimens for 13 morphological traits using univariate and ordination analyses. Climatic and edaphic variables were extracted for all specimens with georeferenced records. To assess habitat suitability and the ecological niche of each predefined morphotype, niche models under present conditions and niche overlap tests were conducted. Ordination analyses were applied to evaluate how environmental predictors explain variation in vegetative and floral traits, whereas supervised multivariate classification was applied to estimate membership probabilities based on morphological and environmental data.

Integrating morphological, climatic, and edaphic data proved to be a significant approach for refining the species limits within the complex. Although three morphotypes were evaluated, our analyses consistently recovered two well-differentiated groups: the "capitata-hydrangeiformis" morphotype, allegedly composing a cline, and the ecologically and morphologically distinct "bahia" morphotype. Environmental factors explained more variation in floral than in vegetative traits, with floral traits able to delineate morphotypes more robustly when considered in isolation. The "capitata-hydrangeiformis" and "bahia" groups also exhibited markedly differences in predicted habitat suitability, with clear separation of the "bahia" morphotype from the others in both geographical and environmental space. Key morphological characters for the taxonomy of Brunfelsia partially covaried with environmental variables, particularly floral traits.

Our findings support the recognition of "bahia" morphotype as a distinct species to be formally described. This integrative approach contributes to understanding diversification processes in a biodiversity hotspot and reveals previously unrecognized taxonomic diversity within Brunfelsia, a genus that harbors many rare and narrow-endemic taxa.