Taxonomic studies of the genus Tephrosia Pers. (Papilionaceae) in Nigeria

Abstract

The relationship between eleven Tephrosia species occurring in Nigeria was examined using a number of taxonomic tools. Fresh and herbarium specimens were used for this purpose and methods followed conventional taxonomic practice. Although the species occur in savanna ecosystems, herbarium collections revealed an abundant distribution in the southern part of Nigeria. Morphometric studies revealed that four quantitative characters viz: leaflet length, lamina length, fruit length and pedicel length can be used to delimit members of this genus. Based on the cluster analysis using average linkage within group, the closest species are T. leptostachya and T. purpurea with the shortest distance measure (0.713). T. linearis has the smallest leaflet, in length and width. Further morphological studies also showed that T. vogelii has the largest pod while T. barbigera has the highest number of seeds per pod. Generally, the species have very short petiolule ranging between 0.2cm and 0.3cm in length, on the average. Foliar micro-morphological studies also showed that the species generally possess polygonal cells with straight to curved anticlinal walls and anisocytic stomata types while pollen studies revealed tricolporate pollen grains to be predominant within the taxa. Although, the present study has added to the existing information regarding Tephrosia species, it also suggests further research to ascertain its taxonomic position within the Papilionaceae.