ON The Phytogeography of the Tribe () VED PRAKASH & S.K JAIN Central Drug Research Institute, Lucknow National Botanical Research Institute, Lucknow

(Accepted December 1985)

The tribe Isachneae is apparently a natnral assemblage of 5 genera namely, , , Limnopoa, and Heleranthoecia. The latter 3 genera arc monotypic; Limnopoa is endemic to South , Sphaerocaryumis distributed in Southeast andHeteranthoecia is confined to tropical . The Coelachne comprising ca 10 species, extends from tropical East Africa eastward to and northern parts of . Isachne is the largest genus of the tribe comprising 110 species and extending to tropical and subtropical regions of both hemispheres. The geographical range of the above genera and distribution pat­ terns of species are discussed in deuil. The study rewals that (i) the tribe is csonccntrated in the tropical and subtropical regions of the world (ii) concentration is lower in the western hemisphere than in the eastern hemi­ sphere (iii) centre of diversification is Southeast Asia and (iv) region of maximum abundance is Indo^ which is a positive indication that the tribe might have originated in this region.

Originally the tribe Isachneae was estab­ Morphologically the tribe Isachneae differs lished by Bentham (1881) with 7 genera; from all other tribes of Poaceae and particularly Priomchne Nees, Isachne R. Br„ Zenkeria from its nearest tribe Paniceae in structure and Trin., F. V Muell., Coelachne R. Br., articulation of the spikelet. In Paniceae the Airopsis Desv. and Eriachne R. Br. Hubbard glumes are unequal ( lower glume is small to (1943) modified the circumscription of the tribe very small compared with the upper glume or Isachneae and included 5 genera; Isachne R. sometimes it is even absent) and the spikelets Br., Coelachne R. Br., Limnopoa Hubb., have an articulation below the glumes so that Sphaerocaryum Nees ex Hook. f. and Heteran- the spikelet falls entire alongwith glumes at thoecia Stapf. Subsequent studies on morphol­ maturity. But, in the tribe Isachneae the glumes ogy, , cytology, anatomy (Potztal, are almost subequal and the spikelets are articu­ 1952; Tateoka, 1957; Bor, 1960; Metcalfe, lated above the glumes so that the spi kelets break 1960; Ved Prakash & Jain, 1984) have revealed up at maturity above them and between the that the tribe Isachneae (sensu C.E.Hubbard) florets. Although glumes are not persistent in was apparently a natural assemblage of 5 genera most of the species of Isachneae, they often fall namely, Isachne, Coelachne, Limnopoa, separately at maturity leaving scars on the lowest Sphaerocaryum and Heleranthoecia which intemode of the rachilla. show affinity in most characters and constitute a well-defined natural and distinct group. The Distribution Pattern - An outline of the members of the tribe are mostly hygrophilous or geographical distribution of the gentra Isachne, occur in forests and their margins in the u-(^ics Coelachne, Limnopoa, Sphaerocaryum and and subtropics, fipom sea level to ca 3000 m al­ Heleranthoecia is shown in Fig.l and in titude. Table. 1. The last three genera'are monotypic. E d

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I I Table 1 Distribution of Genera of tribe Isachneae

Genera Distribution Species in world Species in India

Isachnc Tropics & Sub-tropics of both 100-110 29 hemispheres Coelachne In Old World tropics & Sub-tropics 10 (+1) 3 Limnopoa Indi* ( 1 1 and ) Sphaerocaryum Tropical Asia 1 1 Heleranlhoecia Tropical Africa 1

Table 2 World Distribution of Species of Coelachne Distribution (In old world)

Spcciei Africa Asia Australia

Coclachne africana

I’lJger +, Rhodesia (-) (-)

C. friesiorum Hubb. +, (-) (■)

C. infirm i Busc (-) +, , Sumalra (-)

C. hacJcleii Merr. (-) +. (-)

C. japonica Hack (-) +, Japan (endemicX-)

C. minuta Bor (-) +. India (endonic) (-)

C. paludosa Pelcr +, Tropical (•)

East Africa

C. perpusUtaThvi. (-) +, India (S.India), (-)

Sri Lanka

C.pulchellaKMi. (-) - +,

C. simpliciuscula Benlh. (-) + , Widely distributed in South east Asia (-)

C. soerensenii Bor (-) +, (endemic) (-) + = present; - = tbw nt The type species of Limnopoa, L.meeboldii species of Isachne can be divided into 3 main (Fischer) Hubb. is endemic to India. groups: It is a very rare grass and was known to 1. Species of New World - There are ca 12 occur only in Emakulam district of Kerala. species of Isachne in the New World Recently, it is reported from Trichur and Can- (Hitchcock, 1920; Hitchcock & Chase, I9I7; nanore districts of Kerala (Nair etal., 1985) and Chase & Niles, 1962). The majority of species south Kanaradistrictof Karnataka (Bhatt, 1986). are distributed from South Mexico to Brazil It grows in tanks forming thick mass of tangled through Central Amcrica. There is no species stems on the surfacc of water. of Isachne in the temperate regions of the New Sphaerocaryum malaccense (Trin.) Pilgcr World. It is remarkable that all the species of is distributed in southeast Asia. In India it oc­ the New World are confincd to that region. curs only in , Meghalaya and Nagaland. The following species of Isachne are native The genus Heteranthoecia is confined to to the New World: (l)l.anguscifoliaNash (2) /. tropical Africa. arundinacea (Swartz) Griscb. (3) I. brasii Hhchc. (4)1. disperm (Lam.) Docll. (5)I.leer- The genus Coelachne comprising ca 10 sioides Griseb.(6)/. ligulata Swallen (7) I. species, extends from tropical East Africa polygonoides Lam. (8) I. pubescens Swallen (9) eastward to Japan and to the northern parts of I. pygmaea Gri.seb. (10)/. rigens (Swartz) Trin. Australia. No specics of Coelachne occurs (1 ])/. rigidifolia (Pair) Urban and {\2)I.villosa throughout the geographical range of the genus. (Hitchc.) Reeder. However C.simpUciuscula (Wt. & Am. ex Steud.) Benth.is distributed widely in Southeast 2. Species of Africa - There are ca a dozen Asia. There are 3 species of Coelachne in India. species of Isachne in Africa (Suipf & Hubbard, Of these Cminuta Bor is cndemic to India 1930-1934; Clayton, 1972). Of these, the (Western Ghats). The distribution of Coelachne majority of species occur in the mountains of species in the world is shown in Table 2. tropical West Africa especially in the Congo Isachne is the largest genus of the tribe region. I.hiflora (Lam.) O.Kzte and I.vaughanii Isachneae, comprising ca 110 species, and ex­ Boiv. ex A. Camus and I.longifoUa C. Cardcm. tending to tropical and subtropical regions of arc found in the Reunion Islands. About 5 both hemispheres. It is well- repre.sented in species are reported from Malagasy. Africa and Asia. However, the centre of main It is remarkable that all the African species distribution and diversification is Southeast are confined to that region. The following Asia, particularly Indo-Malaysian region. Only species are native to the mainland of Africa: I. a few specics of Isachne arc wide. None ex­ angolensis Rendle., Iangusta Slapf I.bomoen- tends throughout the geographical range of the sis Vand.J.brixhii Vand. I. buettneri Hack., / genus. SOMwetVerj Stapf & Hubb. I.guineensisSvat^t&. The genus has not yet received a critical Hubb., IMdumaensis Vand. /. kingundaensis monographic treatment for its entire range. We Vand., I kiyalaensis (Vand.) Robyns, have recently studied the taxonomy and /.mauritiana Kunth., I.mayocoensis Vand., phytogcography of the Indian taxa, and have Lmortehani Vand. /.rterva/aFranch. m dU can- made an attempt to provide the geographical dis­ dens Hubb. tribution of the whole genus, based mainly on 3. Species of Eurasia, Australia and literature. Pacific Islands - There ai« ca 60-70 species of Based on the distributional patterns, the Isachne in these regions (Chase & Niles, 1962; Gilliland, 1971; Honda. 1930,- Jansen, 1953. Species endemic to India:-I. angladei Fis­ Keng, 1965; Froideville, 1968; Merrill, 1926; cher, /. bicolor Naik,I. horii Hemadri, /. hour- Ohwi, 1947; and Vansleenis, 1979). However neorum Fischer, I. clarkei Hook.f. /. there is no species of the genus in Europe and deccartensis Bor, /. dimyloides Bor, /. elegans the Mediterranean region. An analysis of the Fischcr, l.fischeri Bor, I. gracilis Hubb, /, lis- species of these regions reveals that distribution hoae Hook.f., /. meeholdii (Fischcr) Hubb, /. pattems-wise, there are again 3 categories. mysorensis Raghavan, /. oreades (Domin) Bor. a) Indo-Australian wide speciesSpccics l.scabrosa Hook.f., /. setosa Fischcr. /. sik.- belonging to this category occur widely in kimensis Bor, [. swaminathaii Ved Prakash & Southeast Asia and Australia. l.globosa Jain. (Thunb.) O.Ktze and l.confusa Ohwi arc the Species endemic to Malaysian regions: only species of this category. J.myosotis Nees is /. albomarginata Jansen, I. arfakensis Ohwi, /, widely distributed in Malaysian region and dementis Mcrr., /. diaholica Ohwi, I. Australia but not reported from the mainland of longkawiensis Jansen, I. obtecta Reeder, /. Asia. pangerangensis Zoll. & Mor., /. pauciflora b) Indo-Malaysian wide speciesSpccics Hack.,/.saxicola Ridl.,/.Jansen,/.,sv/- of this category dif fer from the first only in that ve.v/mRidl.,/. trachycaula Ohwi. the species concerned do not occur in Australia. Species endemic to : - 1, ciliasifiora There are c.a 10-12 spccics belonging to this Keng, /. hainancnsis Keng, /. fun Keng, I. category which are widely distfibuted in South­ repens Keng, /. Schmidiii Hack., I. lenuis Keng, east Asia. These are l.alhens Trin., I.heneckei /. truncaia A. Camus. W-dcV..,!.dispar Trin., I. hirsuta (Hcx)k.f.) Keng, Species endemic to other countries: - 1. /. kinabalunsis Mcrr., Lkunthiana Wt. & Am. arisanensis Hayata (Japan); /. camhodiensis ex Thw., /. miliacea Roth ex Roem. & Schult., Ohwi ();/./fluriei Ohwi (Formosa); I.pulchella Roth ex Roem. & Schult. Some /. multiflora (Thw,) Ferg. (); /, pallcns species are not wide spread, l.walkeri (Am. ex Hillebr (Hawaiian Islands);/./j<-re/«f/i A. Camus Steud.) Thw. is known from India and Sri Lanka; ( Indochina); /. puberula Bor and I. l.himalaica Hook.f. is known from India and smiiinandiana A. Camu.s (Thailand); I. suh- Pakistan; J.nippoensis Ohwi is known from glohosa Hatusima &'Koyama (Japan); /. vitien- China and Japan and l.debilis Rendle is known sis Rendle ( Islands). from China and the Phillippines. c) Endemic species A large number of DISCUSSION The above account of the tribe Isachneac reveals the following con­ species belong to this category and are confined spicuous features in geographical distribution. to one particular country or region. Many species are restricted and occur only within a (i) Concentration of the tribe in the tropi­ single floristic region. It is remarkable that 18 cal and sub-tropical regions of the world; All species are endemic to India. Of these, 14 arc the species of Isachneae occur only in the tropi­ confined to Peninsular India. India, thus takes cal and subtropical part.s of the world. Hartley the first place in number of endcmic species of (1958) pointed out that the gras.ses of the Isachne. About 12 species are confined to panicoid group (Andropogoncae & Paniceae) Malaysian region and 7 to China. Some species are mainly distributed in tropical-subtropical are endemic to Sri Lanka, Japan, Thailand, For­ habitat and reach their highest dcvclc^ment in mosa and the Fiji Islands. A list of species en­ hot moist climate. The geographical survey of demic to various countries is given below: the tribelsachneae also supports the conclusion + + + +

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CO I drawn from morphological, anatomical and species and 1 variety of Coelachne and 1 species cyiological evidences that the tribe is panicoid of Limnopoa and Sphaerocaryum from India. in nature. The tribe shows high degree of endemism in (ii)Concentration lower in the western India. It is seen that 18 species of Isachne and hemisphere than in the eastern hemisphere : I species and 1 variety of Coelachne and the The tribe Isachneae is represented in the gtnus Limnopoa are endemic to India. Most of Western hemisphere by only one genus out of 5 the species are confined to the Western Ghats. genera and 10-12 species out of ca 125 species Only two species of Isachne are endemic to Sik­ of the genus. This suggests that the tribe Isach­ kim and 2 to Khasi Hills (Meghalaya). Several neae has not reached its full development in this species of Isachne are so restricted that they are region and that it has spread to the American hitherto known only from their type locality and continent comparatively recently from a centre thus they are very rare and threatened (Ved or ccntres of origin in the Old World. Prakash & Jain, 198.3). The occurrence of tribe Isachneae in India is shown in Table 3. Oiii) Centre of distribution in Asia and Africa: The tribe Isachneae is well represented Acknowledgement VP is grateful to in Asia and Africa. There are ca 25 species of Government oflndia for financial assistance. Isachne and 3 .species of Coelachne in Africa. The monotypic genus, Heieranthoecia is en­ REFERENCES demic to Africa. The number of species of BENTHAM G 1881 Notes on Gramineae./ Isachne and Coelachne is greater in Asia than Linn Sac. 19 14-134, in Africa. Moreover, the two genera, Sphaerocaryum and Limnopoa are endemic to BHATT K G K 1986 Limnopoa meeboldii (Fis­ Southeast Asia. At present there is no strong cher) C E HUBB (Poaceae) A new record for evidence that the tribe has spread to Africa from Karnataka//id/9 275. a centre of origin in Asia. It is probably that somewhat parallel evolution occurred in Africa BOR N L 1960 The Grasses of Burma Ceylon and in Asia but spread to other regions retain­ India and Pakistan (excluding Bambuseae) ing its tendency to attain maximum diversifica­ Pergamon, Oxford. tion in the regions of Southeast Asia. It is, therefore, of interest to consider CHASE A & CD NILES 1962 IndextoGrass whether the two regions of distribution are suf­ Species Vol 1-3 G K HALL & Co Boston. ficiently distinctive to indicate that they may be independent centres of distribution for the tribe. CLAYTON W D 1972 Gramineae In Flora of Tropical Africa Vol 3 Ed F N Hopper Lon­ (iv) The region of maximum abundance don PP 349-512. in Indo-Malaysia: The highest number of species of Isachneae occur in the Indo- FROIDEVILLE Ch 1968 Poaceae In Flora of Malaysian region. These include ca 60-70 Java Vol 3 Eds C A Backer & R C Bakhuizen species of Isachne, ca 8 species of Coelachne & Vanden Brink Jr. Groningen. and the monotypic genera Limnopoa and Spkaerocaryum. The greater relative abun­ HARTLEY W 1958 Studies on the origin dance of Isachneae in this region is a positive in­ evolution and distribution of the Gramineae I dication that the tribe may have originated here.- TheTribeAndropogneac/4u.vjy Bot6 116-128; We recognize 29 species of Isachne, 3 II ThetribePaniceae/laj/y Bot6 347-357. HITCHCOCK A S 1920 Revision of North 1985 On the colleciion of Limnopoa meebol­ American species of Isachne Contr U S Natl dii (Fischer) C E Hubb (Gramineae); An ex­ Herb 22. 115-121. tremely rare endemic and endangere-d species of Kerala7 EconTaxBotl 210. HITCHCOCK AS & A CHASE 1917 Gras­ ses of West Indies ContrUSNatlHerblS 261­ OHWIJ 1947 New or noteworthy grasses from 471. Asia Bull Tokyo Sci Mus 18 1-15. HONDA M 1930 Monographia Poaccarum POTZTAL E 1952 Uber die Blattanatomit dcr Japonicarum, Bambusoidcs cxclusis J Fac Sci LsachneaeiJo; Jahrb.lS 551-559. UnivTokyo SectUl Bot 3 1-484. STAPF O & C E HUBBARD 1930-1934, HUBBARD C E 1943 Limnopoa meeboldii (C Gramineae In Prain FI Trop Africa 9 769­ E C Fischer) C E Hubb Hook Ic PI V tab 3439 1132. Descripiion of tribe Isachneae. TATEOKA T 1957 Notes on .some gra.sses VI JANSEN P 1953 Notes on Malaysian grasses (9 Coelachne and Sphaerocaryum 10 Reinwardlia 2 225-350. Chromosome and leaf struciiire of .several spccies) Bot Mag Tokyo 1{) 119-125. KF>1G P C 1965 Revision of the genus hachne R.Br. (Gramineae) of China Act Phytotax Sinaca 10 6-24. VAN STEENIS C G G J 1979 geography of East Malcsia BoiJLinn Soc. 79 97-179. MAHESWARI el al 1965 Flora The Gazet­ teer of India 1: 163-229. VED PRAKASH & S K JAIN 1983 Tribc- MERRIL F D 1926 An enumeration of Phillip- Isachncac (Pam Poaceae) - it.s endemism anti pine flowering 4 Manila. rarity in India. In An assessment of threatened plants of India Eds S K JAIN & R R RAO METCALFE C R 1960 Anatomy of the Botanical Survey of India Howrah pp 256­ moiitycotyledons I. Gramineae Oxford Univer­ 264. sity, London. VED PRAKASH & S K JAIN 1984 Poaceae; NAIR V J, R ANSAR! & P V SREEKUMAR Tribe-Isachneae Fasc FI India 14 1 '42.