Wood anatomical diversity and distribution modelling of Pterocarpus Jacq. (Fabaceae: Dalbergieae): Ecological and systematical implications

The wood structure of five species of Pterocarpus from Nigeria, distributed in tropical Africa, was studied using light and scanning electron microscopy. This was done to explore the usefulness of wood anatomical characters in distinguishing the species and investigate the influence of climatic factors in wet and dry tropical Africa on anatomical traits and distribution of Pterocarpus species. To investigate the ecological patterns of the wood anatomical features of the species, quantitative data from the wood traits and climatic variables from the species distribution were compiled and analyzed for Principal Component Analysis (PCA) using R. The Pterocarpus species studied can be distinguished by ray cell number and height. The ray cells are exclusively uniseriate in P. erinaceous, uniseriate with a few biseriate in P. osun and P. santalinoides and mostly multiseriate in P. lucens. Large ray height (>1 mm) is only found in P. lucens. The Pterocarpus species found in the dry tropical biome (P. erinaceous and P. lucens) have shorter vessel elements, higher vessel frequency, higher vessel grouping, and narrower vessels. These wood traits play a significant role in the vulnerability of wood xylem to cavitation and water conductance efficiency. The positive correlation observed between the percentage of solitary vessels and climatic factors means that as the environment gives way to higher rainfall and a more stable climate, there will be an increase in the number of solitary vessels in the species.