104 AROIDEANA, Vol. 28 Flowering Phenology and Beede Pollination in Theriophonum infaustum N.E.Br. (Araceae) M. Sivadasan and Raghavan Kavalan* DepanrnnentofBotany University of CaJicut CaJicut University P.O. Kerala----673 635 India (e-mail: [email protected]) .. Present address: Jawahar Navodaya Vidyalaya, Almati Dam Site, Bijapur Dist., Karnataka-5S6 201, India ABSTRACT deals with temperate genera (Gibernau, 2003). The only tropical aroid genus that Tberiophonum injaustum N.E.Br. (Ara­ is fairly well-known in this regard is Amor­ ceae), an endemic species of SW India, phophallus, mainly from the work of Pijl consists of small tuberous plants. The spe­ (937). The works of Hubbard (895), cies was found to have protogynous inflo­ Cleghorn (913), Knoll (926), Pijl (1937), rescences and to be visited by several Meeuse & Hatch (960), Dormer (960), kinds of beetles. Beetles belonging to the species Anotylus rubidus Cameron (Cole­ Monteith (973), Williams & Dressler optera, Staphylinidae) are found to be the (976), Golubev & Volokitin (983), Shaw main potential pollinators. Other species & Cantrell (983), Valerio (984), Gotts­ observed were only casual visitors. A de­ berger & Amaral (984), Pellmyr (985), tailed account on the process of canthar­ Young (986), Whitehill (993), Patt et al. ophily in this species is given with explan­ (995), Gibernau et al. (999), & Gibernau atory illustrations. et al. (2003) are some of the significant works on members of Araceae. In India KEYWORDS not much work has been done on this as­ pect especially in Araceae, and only scat­ Araceae, cantharophily, India, Tberio­ tered and fragmentary information is avail­ phonum. able. The work of Barnes (934) who de­ scribed the mode of pollination and pol­ INTRODUCTION linators in Arisaema occurring in the The family Araceae is mainly tropical in Nilgiri Hills, and that of Banerji (947) on distribution, with a few temperate genera, Typhonium trilobatum are worth mention­ constituted of herbs and vines comprising ing. A detailed account of cantharophily in about 105 genera and about 3,300 species Amorphophallus hohenacheri (Schott) (Mayo et al., 1997). It is characterised by Eng1. & Gehrm., with a brief review on the a spadix which is subtended by a spathe. general pollination biology with special Tberiophonum B1. of the subfamily Ar­ reference to Araceae was provided by Si­ oideae is a small genus of five species en­ vadasan & Sabu (989). Beath (996) pro­ demic to South and Central India with one vided the details of pollination in Amor­ species extending to Sri Lanka (Sivadasan phophallus johnsonii. Gibernau (2003) & Nicolson, 1982). Tberiophonum injaus­ provided an up-dated list of aroid polli­ tum N.E.Br. is restricted to SW India. nators which is the latest covering all the Information on pollination biology of available data on this aspect. the members of Araceae is meagre as most According to the most far-reaching gen­ of the information available on this aspect eralizations, as far as is known the Araceae M. SIVADASAN, R. KAVALAN, 2005 105 are considered to be exclusively ento­ cinity by the commencement of SW mon­ mophilous, and in most cases the polli­ soon (June-September). nators are beetles (Coleoptera) and flies It is a small, tuberous herb reaching a (Diptera) (termed cantharophily and my­ height of about 12 to rarely 30 cm (Fig. 1). ophily respectively). Bees (Hymenoptera) The corm is somewhat subglobose to cy­ are rarely reported as pollinators as in the lindric in shape, ca. 0.5-4.00 cm thick and case of Spathiphyllum (Williams & Dress­ 0.7-1.8 cm diam. The leaves have distinct ler, 1976) and Anthurium (A Beath, T. petioles which arise from the top of the Croat, pers. comm.), especially those with tuber. The lamina is glabrous, reticulate­ sweet-scented flowers such as the mem­ veined, and is highly variable in size and bers of Anthurium sect. Calomystrium. shape, narrowly to broadly hastate-sagit­ Beetles have the oldest fossil record of any tate, rarely broadly ovate-cordate, 4.6-12 of the four anthophilous orders of insects cm long, lateral lobes rounded to ovate or viz., Coleoptera, Lepidoptera, Diptera and with acute tip. The inflorescence is borne Hymenoptera. Thus, it is widely presumed on an erect peduncle, which arises in leaf that beetles were the pollinators of the ear­ axils, and during its early developmental liest entomophilous angiosperms (Gray­ stage is completely encased by the vagi­ urn, 1984). nate leaf-base. This species, like many oth­ Floral morphology is the most important ers in the genus, also reproduces by veg­ element in determining the system of pol­ etative means. lination of a particular type of blossom. Structural features have long been recog­ STUDY SITE AND METHODS nised as a diagnostic specialization for par­ The study was carried out at the Calicut ticular broad categories of insect-pollina­ University Campus and its surroundings tion. Faegri & Pijl (1979) gave an account (latitude: 11°35'-45'N, longitude: 75°45'- of the syndrome of cantharophily. It in­ 50'E, at an altitude of 40-60 m; average cluded the features such as a pollination annual rainfall of ca. 300 cm; and temper­ unit with few visual attractions, no nectar ature ranging from 17-35°C). Flowering guide, generally large, flat, cylindric or period is from June-September and begins shallow, bowl-shaped-sometimes closed, one month after the first rains. easy of access, dull colour, frequently Flowering individuals in the study area greenish or white, and strong odour­ were located and tagged. A total of 50 in­ fruity or aminoid. The beetle-pollinated florescences were observed and data col­ flowers are protogynous. In addition to the lected during the study period. Observa­ protogyny, cantharophily is generally as­ tions were made on the morphology and sociated with phenomena like thermogen­ phenology of the inflorescences along esis, musty odour, crowded pistillate and with the details of the pollinators and their staminate flowers enclosed by bracts dur­ activities. Insect visitors to the inflores­ ing a brief nocturnal anthesis. cences were collected, and preserved in Many beetles of different families are re­ 70% alcohol for identification. Insects ported to be involved in the pollination of were also collected from other popula­ Araceae, with most of the beetles from the tions along with inflorescences to verify family Scarabeidae (Grayum, 1984). But whether the pollinators are common to all Staphylinidae are also common in Araceae populations. Voucher specimens of all outside the New World (Gibernau, 2003). beetles are deposited at Commonwealth Institute of Entomology, London. THERIOPHONUM INFAUSTUM OBSERVATIONS Theriophonum infaustum, an endemic Floral Morphology species of SW India grows abundantly on The inflorescence is solitary, completely the Calicut University Campus and its vi- enclosed by the petiolar sheath in the ear- 106 AROIDEANA, Vol. 28 .~. :'" -", ~::~.-...... <:: .. /.~,,,. .... .:::'_._ .. -..... .... ,. ...... 2:::..-..... E u C") E u D Fig. 1. Tberiopbonum inJaustum N.E.Br.: A. Habit; B. Inflorescence; C. Inflorescence with spathe cut open to show spadix; D. Spadix. (f: female flowers; i: interstice; m: male flowers. n: neuter flowers; sat: stalk of spadix-appendix; sa: spadix-appendix). ly stage. Peduncle ca. 5.5 cm long and 4 with a zone of neuter flowers ca. 3 rom rom diam., greenish to purplish. Spathe long, followed by naked slender interstice erect, to about 6 cm long, differentiated, ca. 6 rom long, followed by male portion into a basal completely convolute tubular ca. 5 rom long and terminating in a creamy portion, and an upper initially convolute, purplish sterile appendix ca. 2.5 cm long but later with a spreading yellowish-green with a distinct stipe ca. 3.5 rom long. Pis­ limb portion separated by a slight constric­ tillate flowers 4-8, in a single whorl; ovary tion between the two; the basal convolute ovoid, yellowish green, unilocular with 4- tubular portion is 1.0-1.6 cm long, 0.6-1.2 5 basal and apical sub-orthotropous cm diam., upper limb portion oblong, 3-5 ovules; stigma sessile, discoid. Neuter cm long and 1-1.5 cm broad. The overlap­ flowers subulate to subclavate, verrucu­ ping of the margins of the spathe is either lose, creamy purplish, ca. 3.5 mm long. to the right or to the left as observed ear~ Staminate flowers 23-48, closely arranged, lier by Barnes (1938). The spadix is sessile, purplish, sessile and truncate, each with 2 almost equalling or slightly shorter' than distinct anther lobes, dehiscing by apical the spathe, to ca. 4.5 cm long, with basal pores. Fruit a berry, 6-8 per infructes­ female portion ca. 2 mm long, contiguous cence, each to ca. 1 cm long and 5 rom M. SIVADASAN, R. KAVALAN, 2005 107 diam., ovoid, green, 2-3-seeded. Seeds to escape from the tube, crawling up, but broadly ovoid with basal white tissue. on every attempt they fell down because of the smoothness of the inner surface of Phenology and Pollination the basal tube of the spathe. The beetles Mechanism carrying pollen moved across and overthe pistillate flowers, Simultaneously effecting The spadices were observed to be pro­ pollination. The release of odoudasted for togynous. The exact time of receptivity of a period of 3.5 to 6 hours, but with a rel­ pistillate flowers is difficult to determine atively short period of maximum intensity. because there is no clear indication to this When the odour started fading, the spathe­ effect. Initially the spathe is completely limb began to roll and close forming a tu­ rolled tightly around the spadix (Fig.2A). bular structure, leaving only a small open­ At maturity, the spathe unrolled and ing. at the top. At this stage, the spathe at opened during the afternoon of the first the constriction between the limb and the day.