Intraspecific Morphological Variation and Environmental Drivers in Macleania rupestris: A Model-Based Population Classification

Denisse F Peña^1*Paulina Villena¹Diana Curillo¹Carlos A Jiménez²Eduardo Ordoñez²Oswaldo Jadán^3*

• ¹Grupo de Biotecnología Agropecuaria, Facultad de Ciencias Agropecuarias, Universidad de Cuenca, University of Cuenca, Cuenca, Ecuador
• ²Instituto Nacional Autónomo de Investigaciones Agropecuarias, Gualaceo, Azuay, Ecuador
• ³Grupo de Ecología Forestal, Agroecosistemas y Silvopasturas en Sistemas Ganaderos, Facultad de Ciencias Agropecuarias, Universidad de Cuenca, Cuenca, Ecuador

Macleania rupestris, an ecologically and culturally important species of the Ericaceae family, inhabits the montane forests of southern Ecuador and exhibits significant but understudied intraspecific morphological variation. We analyzed 15 quantitative traits in 200 individuals from four populations at the Azuay and Cañar provinces to identify morphological groups and assess their environmental drivers. Using hierarchical clustering and Random Forest classification, we identified two distinct morphological groups, primarily differentiated by seed number per fruit, fruit humidity, fruit length and width, and petiole length, together explaining over 75% of the observed variation. Generalized linear models revealed that climatic seasonality and spatial autocorrelation significantly influenced these key traits. Notably, seed number and fruit length responded strongly to variations in temperature and precipitation. Additionally, other traits such as fruit humidity and petiole length showed moderate sensitivity to environmental gradients, indicating complex adaptive responses. A Random Forest classification model, based on the most relevant traits, achieved 99.5% accuracy, allowing robust assignment of new individuals into morphological groups. Our results highlighted the influence of environmental heterogeneity on intraspecific differentiation in M. rupestris and provide evidence for local adaptation along climatic gradients. This study offers a novel framework for trait-based classification and highlights the importance of integrating morphological variation and environmental factors in conservation planning. By identifying environmentally driven morphological groups, these findings can guide seed sourcing strategies and restoration efforts aimed at enhancing resilience in montane forest ecosystems of southern Ecuador under changing climatic conditions.