A TAXONOMIC REVISION OF AXONOPUS P. BEAUV. (POACEAE: PANICOIDEAE) IN INDIA

The status of the genus Axonopus P.Beauv. in India has been varyingly depicted by different workers so far. After comprehensive study, two species, namely A. compressus (Sw.) P. Beauv. and A. fissifolius (Raddi) Kuhlm., are justified for the country. The distributional incongruity of both species in India is unravelled here. The present record of A. fissifolius in Sikkim confirms its extended distribution to the Indian Eastern Himalaya. Additionally, this species is also reported for the first time from Meghalaya. Detailed descriptions of both species are appended here. Illustrations and photoplates, along with notes on habitat, phenology, and distribution, are also presented. A key to the Indian species of Axonopus is incorporated for correct identification and easy recognition.

The monophyly of Axonopus is strongly recommended by López and Morrone (2012) and Delfini et al. (2020).They advocated inclusion of Centrochloa Swallen and Ophiochloa Filg., Davidse & Zuloaga within the generic circumscription of Axonopus, supported by both morphological and molecular evidences.Gledhill (1964) discussed the origin and taxonomy of the West African representatives of Axonopus.The genus in Europe was first revised by Diego Giraldo-Cañas (2008) and five new synonyms were proposed for Axonopus compressus (Sw.)P. Beauv.and A. scoparius (Flüggé) Kuhlm.Cytogenetic and evolutionary relationships in the genus Axonopus were illustrated by Hickenbick (1975).The suitability of Axonopus compressus for the removal of petroleum hydrocarbons from contaminated soil was assessed by Bordoloi et al. (2012).Ibeh and Ezeaja (2011) studied the antidiabetic activity of methanolic leaf extract of Axonopus compressus in alloxan-induced diabetic rats.
The genus is variously interpreted by different researchers in terms of number of species in India resulting in confusion.Besides, regional distribution in the country (state wise) differs substantially in different literature.
While surveying the grass flora of North Sikkim, few notable specimens of Axonopus were collected from Chungthang and Lachen.After critical examination of the collected materials and perusal of relevant literature (Noltie, 2000;Chen and Phillips, 2006), these were identified as A. fissifolius (Raddi) Kuhlm.This discovery constitutes the first instance of this species in the Indian Eastern Himalaya.
In addition, during the present investigation two specimens of the genus collected from Shillong, Meghalaya were located at CAL (Deka 18394; identified as A. compressus) and ASSAM (Rup Chand 8195; identified as A. fissifolius).Both the specimens were reexamined and meticulous observation revealed that Rup Chand 8195 was rightly identified as A. fissifolius, while Deka 18394 also appears to be A. fissifolius.This finding validates the species' wider distributional range, extending to Meghalaya, the second state in Northeast India after Assam.
Besides, though several workers (Naithani and Raizada, 1977;Naithani, 1990;Shukla, 1996;Kellogg et al., 2020) claimed this species for Uttar Pradesh, however, it is now excluded from the flora of the state with evidence.On the contrary, report of this species from Uttarakhand is accepted with justification.
In this communication, a revision of Axonopus in India is presented based on field observation as well as study of the herbarium specimens.In addition, we illustrate the current distribution of both species in the country.The new distributional records of A. fissifolius are elucidated with evidence.The elaborate morphological descriptions of both members, along with detailed citations and type information, are incorporated herewith for better taxonomic understanding.Hand drawings and photo plates are also included for easy recognition and correct identification.Habitat information, phenological data, exsiccate and key to the Indian species of the genus are also provided.

Materials and Methods
Rigorous field surveys have been conducted during 2021-2024 in different parts of India and a considerable number of specimens of Axonopus were collected.During collection, all relevant field data have been recorded to understand the morphological attributes of the members of the genus and also to observe the variation and variability of morphological features between the populations and even within the population, if any.The characters which are widely used in segregating species as discussed earlier have been critically encountered in the field itself.Digital photographs have been captured.Specimens were collected at least in triplicates from each population.To ascertain the taxonomy and distribution of both the members of the genus in India, collections of Axonopus housed at ARUN, ASSAM, BSA, BSD, BSID, BSHC, CUH, CAL, DD, MH, PBL and TBGT were rigorously studied.Relevant literature were also consulted.The identity of both the species was confirmed after having an eye to the protologues and matching with the type specimens or digital images of the types as well as with other authentic specimens available at JSTOR and other online herbarium databases.Voucher specimens are deposited at CUH for future reference.

Key to the Indian species of
In the case of A. fissifolius, the same contradiction prevails.According to Naithani and Raizada (1977), A. fissifolius was first recorded by R.B. Majumdar, as evident from his note on the herbarium sheet Naithani 1868 (CAL), where he stated that "I have also reported it from Assam, where it is also naturalized.But my report has not yet been published".However, Naithani and Raizada (1977) published the first evidence on its occurrence in India from Dehra Dun.Later on, Naithani (1990) stated its distribution in Uttar Pradesh.Subsequently, referring to Naithani and Raizada (1977), its distribution in Uttar Pradesh was also reported by Shukla (1996), though no specimen was scrutinized by him.Notably, Uniyal et al. (2007) did not include the genus Axonopus in the checklist of flowering plants in Uttarakhand.On the other hand, while updating the grass flora of Uttarakhand, Kandwal and Gupta (2009) reported only A. compressus for the state.Furthermore, under the present investigation, one specimen collected from Gori Valley region of Uttarakhand and identified as A. affinis (≡A.fissifolius) has been traced at BSD.Though it apparently looks like A. fissifolius, in-depth character assessment confirms its identity as A. compressus.
Recently, Kellogg et al. (2020) documented this species in Uttar Pradesh based on Naithani (1990).But we failed to trace any representative specimen in any herbaria collected from present day Uttar Pradesh.Notably, Naithani and Raizada (1977) recorded this species in Dehra Dun, the capital of Uttarakhand, and thus the distributional data by Kellogg et al. (2020) is corrected here for this state.Therefore, Uttar Pradesh is excluded from the distributional range of this species, which also corroborates Agnihotri et al. (2023), where the genus Axonopus is not considered under the recent floristic checklist of the state.Prasanna et al. (2020) claimed the distribution of A. fissifolius in Andaman & Nicobar Islands and Assam.But specimens from neither of the states have been traced during this study, hence, the existence of the species in these two states is doubtful.