Young stem and leaf anatomy of 15 Malagasy-endemic Diospyros species (Ebenaceae): taxonomic implications

Eighty-eight of the 255 Diospyros species from Madagascar are potential sources of ebony wood. Unfortunately, several species are currently threatened with extinction due in part to illegal and unsustainable logging. Reliable identification of living Diospyros species is necessary prior to any sustainable exploitation, so as not to compromise those species threatened with extinction. This study aims to identify features that might contribute to supporting taxonomic studies and to provide a complementary tool for the identification of standing trees. Fifteen species of Diospyros endemic to Madagascar were studied using standard anatomical methods. Each species showed a different shape of the leaf midrib and some have distinctive leaf anatomical characteristics, such as the presence of extrafloral nectaries in the distal part of the petiole in Diospyros baronii and filiform sclerenchyma in the mesophyll in Diospyros lewisiae. Statistical analysis showed that petiole and midrib vascular patterns, spongy parenchyma structure, the presence of papillae, thickness of epidermis, presence of extrafloral nectaries, stratification of epidermis, and presence of a cuticle are useful to distinguish species groups and even some species. The anatomy of young stems and leaves of Diospyros species from Madagascar is examined for the first time; the study will be extended to other potentially exploitable species.