Indigofera Linnaeus (1753:751)

Krishnaraj, Moothedathu Venugopalan Nair & Mohanan, Narayanan Nair, 2012, Notes on the identity and status of two Legumes (Fabaceae: Papilionoideae) from India, Phytotaxa 66 (1), pp. 13-20 : 13

Indigofera Linnaeus (1753:751)

Gillett (1960), Sanjappa (1995), and Murthy & Sanjappa (2002) discussed the status of Indigofera hirsuta Linnaeus (1753: 751) and Indigofera astragalina Candolle (1825: 228) based on morphology and SEM analysis of seed coat, and they retained them at specific level. According to Sanjappa (1985, 1995), I. astragalina shows continuous variation in size of the plant, nature of leaflets, length of peduncle, color of flowers, indumentum of pods, and number of seeds/pods, and he followed Gillett (1960) to separate it from the closely allied I. hirsuta at specific level. However, the diversity in seed types and its importance in evolution as argued by Corner (1951) in Leguminosae prompted Murthy & Sanjappa (2002) to evaluate the seed morphology of 51 species of Indigofera in India. Their analysis again emphasized the differences between I. hirsuta and I. astragalina . The seed coat is granulate in I. astragalina and striate–rugose in I. hirsuta at high magnification. Even after much taxonomic studies in these two taxa, there continue to be problems (as revealed by innumerable misidentified specimens in various herbaria in India) with the identity at morphological level due to close affinity. Recently Rajakumar et al. (2011) proposed a new species, Indigofera karaiyarensis Rajakumar et al. (2011: 485) from South India. While going through the protologue of I. karaiyarensis , we did not observe any progressive character states that could clearly distinguish I. karaiyarensis from allied I. astragalina . It is also evident that the authors did not consult relevant publications ( Gillett 1960, Murthy & Sanjappa 2002), and type specimens [e.g., type of I. hirsuta :— SRI LANKA. Herbarium Hermann Vol. 1, fol. 60, no. 172 (lectotype BM!), designated by De Kort & Thijsse 1984; see figure 1 ], before describing their new species. According to Rajakumar et al., (2011) I. karaiyarensis is allied to I. astragalina but differs from the later in having smaller size, short rachis, black dotted leaflets, shorter raceme and fruit shape (“ amplitudine parva, rachidi curta, foliolis atro -punctatis, racemo curto et forma fructus differt’’). These character states occur within the circumscriptional range of I. astragalina rather than that of I. hirsuta ( Sanjappa 1985, 1995, De Kort & Thijsse 1984). Therefore we synonymize I. karaiyarensis under I. astragalina to avoid further confusion.

Figures

FIGURE 1. Lectotype of Indigofera hirsuta L., Hermann Herb. Vol. 1, fol. 60. no. 172 (BM, Barcode no. 000621434) © Natural History Museum, London.