Impacts of land use and abiotic factors on fruit, seed, and leaf morphology of the desert date Balanites aegyptiaca in Benin: Implications for management

Preserving intraspecific phenotypic variation within socio-economically important but declining species is fundamental in the current context of rapid change in land use and environmental conditions. Balanites aegyptiaca (L.) Delile is a valuable seed oil tree species native to the arid and semi-arid regions of Africa. Notable morphological variations within the species are recognized by local communities, who often select trees with preferred traits for preservation in croplands. This study compared phenotypic variation in B. aegyptiaca based on sixteen phenotypic traits of fruits, seeds, and leaflets between trees in a strictly protected area and those in croplands. Furthermore, the relative role of land use, soil characteristics, bioclimatic variables, elevation, and slope in the observed variation was analysed. Student t-test, principal component analysis, redundancy analysis, and variance partitioning were used for data analysis in R software. Results showed that, after accounting for tree variation, significant differences were observed in only two traits: seed ratio, and leaflet dry weight, with mean values in cropland being 1.470 (higher), and 0.943 (lower) times that of wild trees, respectively. Furthermore, principal component analysis showed great overlap between ellipses of cropland and wild trees. The variance partitioning analysis showed that bioclimatic variables explained 18 % of the total variation followed by soil characteristics (11 %), and land use (9 %). These findings collectively suggest weak impacts of croplands and a lack of domestication syndrome in B. aegyptiaca in Benin, potentially due to persisting gene flow between wild and cropland trees, inadvertent species management, or low intensity of selection pressures. Future studies should explore organoleptic properties, physico-chemical characteristics of the pulp and seed oil and discern the extent to which observed differences are attributable to genetic factors and biotic factors (pest attacks, plant-plant interactions, etc.).