Morphological characteristics of Bombax costatum as indicators of the species ethnotypes in Burkina Faso

Agroforestry species are often exploited by local people based on their morphological characteristics. Knowledge of morphological characteristics and local preferences is useful for species selection and domestication. This study aims to assess the morphological diversity of Bombax costatum in two climatic zones in Burkina Faso. Semi-structured interviews were conducted with 376 informants from four ethnic groups in the Sudano-Sahelian and the Sudanian zones. Variations in the morphotypes' characteristics and their environmental drivers were assessed on 172 trees based on trunk, crown, leaves, and flowers. Five ethnotypes, namely, dark red petals, light red petals, red petals, white petals, and yellow petals, were identified. Preference for ethnotypes was oriented toward petal color and bark aspect, with the red petals with rough bark ethnotype being the most preferred (p-value< 0.001), and the white petals the least preferred (p-value< 0.0001). Based on measured morphological characteristics, three morphotypes were identified: morphotype 1 with yellow-orange petals, red calyx, dark-grey and spiny bark, morphotype 2 with yellow-orange petals, red calyx, dark-grey and rough bark, and morphotype 3 with yellow-orange petals, red calyx, light-grey, and rough bark. Morphotype 1 had the lowest (p-value< 0.0001) diameter at breast height, diameter at 50 cm height, collar diameter, and the highest petal number (p-value< 0.05). Morphotype 1 was more homogeneous for trunk characteristics with lower standard deviations than the others. Morphotypes 2 and 3 had the highest trunk characteristics. Morphotype 3 had the highest calyx weight (p-value< 0.05), and was more homogeneous with lower standard deviation. The findings highlight significant morphological variability, useful for selection and conservation purposes.