Taxonomic revision of the Genus Crotalaria L. (Fabaceae) in Nepal

Abstract

Crotalaria L. is a large genus of the family Fabaceae with 702 species worldwide. Due to this large number of species in this genus, none of the studies till yet have been able to include all the species in their study. Different taxonomic research has found to comprise one or few Nepalese species but comprehensive taxonomic study including all the Nepalese species was lacking. This study was carried out to make a comparative and comprehensive study of detailed morphological structures, distribution patterns, and reproductive phenology. Field observations, sample collection and detail herbarium study of national and international herbaria from a taxonomic point of view was done. Some anatomical observations were also done preparing temporary slide. Many morphological characters related to shape, size, surface, orientation and position of different vegetative (stem, stipule, leaf, bract, bracteoles and peduncle) and reproductive (inflorescence, flower, calyx, standard petals, ovary, style, fruit and seed) structures of Crotalaria species are found to be important as diagnostic characters and for taxonomic delimitation. Total 18 species are found to be present in Nepal. Among them, 15 are native, one is naturalized (C. pallida) and two are exotic (C. micans and C. juncea). C. juncea is cultivated exotic, while the state of C. micans in nature needs further exploration, as the labels of herbarium specimens of this species deposited at TUCH show they have also been collected from the wild. Excluding two exotic species, 16 species are distributed in three different sections (Calycinae, Crotalaria and Hedriocarpae) but section of C. acicularis is still unclear. Due to some distinctive differences in some morphological aspects of the plant like (habit, leaf texture, color, size and surface of fruit) there are two probable new varieties of C. prostrata. Crotalaria quinquefolia has been recollected after 60 years from the same district. Crotalaria species are found to be widely distributed within Nepal from east to west. The most suitable bioclimatic zones for Crotalaria in Nepal are found to be tropical and subtropical zones but two species (C. calycina and C. sessiliflora) are found up to sub-alpine zone as well. With the exception of the endemic species C. kanaii all the other species are common to SE Asia. Among the micromorphological characters, Leaf epidermal cell shape and cell wall pattern both did not show much significance, but stomatal index can be used in combination with macromorphological characters in species delimitation. Regarding phenological patterns, flowering has been found to viii begin in three different seasons. The majority of species start flowering in summer, C. medicaginea in spring while other flowers in early autumn (C. spectabilis and C. calycina) to mid-autumn (C. acicularis and C. quinquefolia). Moreover, based on overall similarity, cluster analysis showed C. acicularis and C. prostrata as being very close, while the two species, C. sessiliflora and C. calycina, although having similar appearance, stomatal index value, and distributional elevational range, were not found to be closely associated in cluster analysis.