Pleione 11(1): 1 - 9. 2017. ISSN: 0973-9467 © East Himalayan Society for Spermatophyte Taxonomy

Phenology and floral visitors of Acer caesium Wall. ex Brandis () – A threatened Himalayan tree

Sudip K. Roy, Arun K. Pandey1 and Ashok K. Bhatnagar Department of Botany, University of Delhi, Delhi-110007, 1 Corresponding author, e-mail: [email protected] [Received 17.01.2017; Revised & accepted 03.02.2017; Published 30.06.2017]

Abstract Recurring and periodic life cycle events are the most important aspects of fitness and survival strategy of a species, and play significant role by variable interaction with other species in the ecosystem. Evidence show that climate change affects phenology and interaction among species both at local and global levels. Climate change driven shifts in the phenology across the flora and fauna lead to asynchrony and mismatch among the mutualistic and co-existing species, leading to loss of biodiversity. Thus, under the current scenario of global climate change, studies on phenology of a species become imperative as these help in monitoring and predicting the timing of recurrent life cycle events. The present records shows the phenological events and different floral visitors of Acer caesium Wall. ex Brandis, a threatened tree species endemic to Central and Western Himalaya. The data would help in formulation of species-specific conservation strategies and can serve as a database for future climate-change monitoring. Key words: Acer caesium, Phenolgy, Pollination biology, Dioecious, Himalaya, Climate change

INTRODUCTION The study of reproduction is crucial for the conservation of threatened species. A thorough investigation of the reproductive biology is needed to understand the cause of depletion of a population in a landscape or ecosystem. The management and conservation of natural systems can be critically enhanced with a greater understanding of the phenology of species (Morellato et al. 2016; Yadav et al. 2016). Phenological information is necessary to find the timing of critical stages in the life cycle of a species which may be impediment in its effective propagation and regeneration. Unfortunately, details of plant reproduction remain poorly understood across the tropics, especially in highly a seasonal ecosystems (Morellato et al. 2013). More so, tropical countries lack adequate data acquisition networks or citizen science initiatives that are analogous to important phenological programs in North America; Canada and Europe (Gonsamo et al. 2013). This study presents precise data on the phenology and floral visitors of Acer caesium Wall. ex Brandis, a threatened endemic tree species of Western and Central Himalaya. The data can prove useful in conservation of the species, and can be used as a reference to identify if the species is resilient or sensitive to future climate-change scenarios. Genus Acer L. is presently classified under the family Sapindaceae, subfamily Hippocastanoideae (APG IV 2016). The genus Acer was traditionally placed under Aceraceae but several recent studies using pollen morphology (Müller & Leenhouts 1976: Lama et al. 2015b), phytochemistry (Umadevi & Daniel 1991) and molecular sequence data 2 Phenology and floral visitors of Acer caesium (Gadek et al. 1996; Savolainen et al. 2000; Harrington et al. 2005; Buerki et al. 2009; APG III 2009) have suggested the placement of Aceraceae and Hippocastanaceae in a single family, Sapindaceae. Representatives of genus Acer are present in a wide range of ecologically and climatically diverse habitats. Approximately 124 species are distributed in both temperate and tropical regions of Africa, Asia, Europe, Central and North America, and (Renner et al. 2007). Hooker (1875) recorded thirteen species of Acer from British-India and recently Lama (2004) and Lama et al. (2015a) also reported 13 species from Darjiling-Sikkim parts of Eastern Himalaya. Acer caesium Wall. ex Brandis, commonly known as Himalayan , is endemic to Central and Western Himalaya with sparse distribution from Kashmir to at altitudes 2,000 – 3,000 m above mean sea level. Within India, natural distribution of A. caesium is reported from Himachal Pradesh, Uttarakhand and Jammu & Kashmir. Himalayan maple is the largest maple in the Western Himalaya, growing up to 30 m in height, and is a characteristic tree of the moist temperate deciduous forests. Once a very common tree in its range, it became a threatened species due to overexploitation for both industrial and domestic uses. The species was placed in the Red Data Book of Indian (Nayar & Sastry 1987) and has been categorized as a Vulnerable and Data Deficient species by IUCN Red Data Book (2015).

MATERIAL AND METHODS Study site The present study was conducted in Kedarnath Wildlife Sanctuary (KWS) which is one of the largest protected areas of Western Himalaya located in Chamoli and Rudraprayag districts of Uttarakhand (PLATE-IA). The climate of the study area is typical moist temperate type. The site encounters three main seasons; the cool and relatively dry winter (December to March); the warm and dry summer (mid-April to June); and a warm and wet period (July to mid-September) of monsoon. Apart from these main seasons, there are short transitional periods interconnecting monsoon and winter, and winter and summer referred to as autumn (October to November) and spring (February to March). The study was executed at three distant populations in KWS. Which were designated as KWLS-I, KWLS-II and KWLS-III. Phenological observations The periodicity of various vegetative and reproductive phenoevents that occurred during the years of study (2011 – 2014) was closely observed and was carefully documented. These events included: time and duration of leaf fall; date of emergence of first vegetative and reproductive buds; duration and termination of flowering; initiation of fruits and their maturation; period of seed dispersal and seedling establishment. Environmental parameters such as temperature, relative humidity and rainfall were taken into consideration to assess their influence on plant’s vegetative and reproductive behaviour. Following steps were taken for the study of the inflorescence: Twenty inflorescences from 10 individual trees, 5 males and 5 females, at the bud stage on different branches were tagged. Each bud was tagged with a distinctive marking for further identification and observation. The progress in development of inflorescence (under natural conditions) was observed each day until flower opening, followed by observations taken every hour. On the day of flower opening, observations were taken throughout the day, and also during the night at short intervals (2 hrs). For every observation, a complete set of data for each flower was recorded. Foraging behaviour and temporal details of insect visitation The number of different types of insects visiting both male and female flowers was recorded starting from 06-00 to 18-00 hrs each day for a period for one week. Possibility of nocturnal Sudip K. Roy et al. 3

A

B C

D E PLATE-I. Acer caesium: Phenoevents at Kedarnath Wildlife Sanctuary, A. View of a study site; B. Male and female trees during complete leafless stage; C. Male and female 4 Phenology and floral visitors of Acer caesium pollination was determined by taking observations during night time for two consecutive nights starting from 18-00 to 04-00 hrs with the help of a torch. Red light was used for night observation to minimize effects on the behaviour of insects on the inflorescence. The number of visits made by an insect and the average time spent by an insect on the flower were recorded with the help of a stop-watch. A visit is defined as landing on or touching a flower. The time interval between the successive movements of an insect within an inflorescence was taken as the time spent on a flower. Observations were taken in the intervals of 10 minutes in which the number of visits to a known number of inflorescences was carefully recorded. The number of inflorescences watched was adjusted so that an accurate count can be obtained, with more inflorescences being watched when visitation rates were low. To minimise the confusion between flower visitors and pollinators, only visitors those touched either the anther or the stigma were regarded as pollinators. Documentation of the type of visitor, average time spent on each inflorescence, and foraging behaviour was carefully accomplished. For studying behaviour of the foragers, the methods described by Dafni (1992) and Kearns and Inouye (1993) were followed. Insects were collected and were killed in a glass jar having ethyl acetate soaked cotton swab. Each forager caught was kept separately in a pollen-clean vial with a numbered label (to correspond with the observation records). The wings and the body parts of captured insects were stretched and pinned on a thermocol sheet and dried for five days. The collected insects were coded and then stored in air-tight plastic boxes. Insects were identified by the entomologists at the Indian Agricultural Research Institute (IARI), New Delhi (India).

OBSERVATIONS AND DISCUSSION Flowering phenology of the Acer caesium comprised of four phenopahses (Figure 1B- E; Figure 2): leaf sprouting and development; flowering; fruit maturation; leaf shading; seed dispersal. Leaf sprouting began during the third week of February, followed by flowering which was initiated from first week of March (Table 1). After this, trees had a three week long bud-stage period. A prominent peak in the flowering occurred in late March and continued till late April. During this phase, pale yellowish green flowers, borne in inflorescences, were conspicuous and covered the entire tree. Fruit initiation was recorded in the last week of April and it reached its peak by August. At this time all the trees were loaded with winged samaras. Fruit maturation is a long process extending over almost five months, from June to October. Diaspore dispersal was recorded during November and December. Trees remain leafless during November to February. Flowering intensity, at individual tree level and population level, flowering in both male and female trees, shows peak during second fortnight of March. Peak of fruiting intensity was observed during 1st – 15th May. The species shows wind pollination syndrome. The flowers are yellowish green, small and the male flowers have exserted stamens and the female flowers have sticky papillate stigmas which is well exposed to wind but the flowers are visited by many insect species during flowering time (Table 2). During day time different insect species visited the male and female inflorescences and collect pollens. Apis dorsata and Apis cerena were the two main bees which actively take part in pollination; the other insect species were mere visitors and did not affect pollination (Figure 3). Largely the phenological pattern of all the marked trees was seasonal and synchronized. However, there were a few instances of advanced male flowering in populations KWLS-I and KWLS-II (Table 1). This may have happened to increase the Sudip K. Roy et al. 5

PLATE II. Acer caesium: Phenogram showing vegetative and reproductive phases of the species 6 Phenology and floral visitors of Acer caesium

B

A

E

C

F

D

H

G I PLATE III. Acer caesium: Insect pollinators and visitors: A. Apis dorsata foraging on male flowers; B. Apis cerena indica on male flower; C-D. Syrphus sp. foraging on male flowers; E. Bombylius major visitation on male flower; F. Syrphus sp. foraging on female flower; G. Apis dorsata foraging on female flower; H. Chrysomya sp. visitation on female flower; I. Coccinella sp. visitation on female flower Sudip K. Roy et al. 7 Table 1. Acer caesium: First flowering dates at three different populations in Kedarnath Wildlife Sanctuary (2012 – 2014).

First flowering dates Tree Population Male trees Female trees No. 2012 2013 2014 2012 2013 2014 1. February 25 March 02 March 07 February 27 March 04 March 09 2. March 01 March 04 March 06 March 01 March 06 March 08 KWLS- 1 3. February 26 March 05 March 07 March 04 March 08 March 08 4. February 28 March 08 March 06 March 01 March 07 March 09 5. February 26 March 03 March 08 February 28 March 04 March 11 6. March 03 March 02 March 04 February 28 March 07 March 10 7. March 01 March 05 March 08 March 06 March 09 March 11 KWLS- 2 8. February 26 March 04 March 06 March 04 March 11 March 09 9. February 27 March 08 March 05 February 27 March 10 March 10 10. March 03 March 09 March 08 March 01 March 06 March 10 11. February 28 March 06 March 09 March 03 March 07 March 11 12. March 02 March 05 March 09 March 01 March 08 March 11 KWLS- 3 13. February 28 March 08 March 08 March 03 March 11 March 09 14. February 26 March 08 March 09 March 02 March 09 March 10 15. February 26 March 07 March 08 March 04 March 08 March 10

Table 2. Acer caesium: List of pollinators and visitors on inflorescences Kedarnath Wildlife Sanctuary

Insect name Family/ Order Common Reward Visitation name pattern Giant Asian Apis dorsata Apidae, Hymenoptera Pollen Regular honeybee Asian honey Apis cerena indica Apidae, Hymenoptera Pollen Regular bee Peleteria sp. Tachinidae, Diptera Tachinid fly Pollen Regular Tabanus sp. Tabanidae, Diptera Horse fly Pollen Regular Old world blow Chrysomya sp. Calliphoridae, Diptera Pollen Occasional fly Eristalis tenax Syrphidae, Diptera Hover fly Pollen Occasional Syrphus sp. Syrphidae, Diptera Hoverfly Pollen Regular Bombylius major Bombyliidae, Diptera Large bee fly Pollen Occasional Ichneumonidae, Gen. et sp. Indet. - Pollen Occasional Hymenoptera attraction to potential pollinators and insects as pollen is the sole reward in the absence of nectar in the flower. The starting date of flowering was almost similar for both male and female trees during the study years 2012 and 2013. However, in 2014 flowering 8 Phenology and floral visitors of Acer caesium was delayed by almost one week probably due to prolonged winter. These results exemplify how abiotic and biotic interactions can shape its flowering phenology of a species. Rapid evolution of flowering phenology of a species for adaptation to its local environment is supported by evidence of phenological divergence between plant populations within the same species (Quinn & Wetherington 2002; Antonovics 2006). These microevolutionary shifts imply that plant populations often harbour sufficient genetic variance in phenology for a selection response (Elzinga et al. 2007). However, phenological variation in populations in response to variation in environmental factors (e.g. light intensity, rainfall, competition) is usually phenotypic plastic response and may not be genetically modulated to some extent (Mazer & Schick 1991). Role of biotic agents of selection is of special relevance as large-scale disturbances of biotic interactions are prone to phenological changes of a species. This is because changes in climatic conditions might act differentially on interacting species and could lead to phenological mismatches that would affect whole communities (Visser & Holleman 2001). This becomes more important for plants those rely completely or partly on animal pollinators for successful reproduction. Maintenance of phenology is not only significant for the pollinators but also the visitors. Therefore, conservation of mutualists and their interactions are important for the maintenance of essential ecosystem services (Cruz-Neto et al. 2011; Garibaldi et al. 2013; CaraDonna et al. 2014).

Acknowledgements The authors are grateful to the Ministry of Environment, Forests and Climate Change, New Delhi, (India) for providing necessary research funding as part of “All India Co-ordinated Research Project on Reproductive Biology of RET Tree Species” (2010 – 2014).

LITERATURE CITED Angiosperm Phylogeny Group (APG) IV. 2016. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants. Bot. J. Linn. Soc. 181: 1 – 20. Antonovics, J. 2006. Evolution in closely adjacent plant populations: long-term persistence of prereproductive isolation at a mine boundary. Heredity 97 (1): 33 – 37. Buerki, S.; Forest, F.; Acevedo-Rodríguez, P.; Callmander, M.W.; Nylander, J.A.; Harrington, M.; Sanmartín, I.; Küpfer, P.; Alvarez, N. 2009. Plastid and nuclear DNA markers reveal intricate relationships at subfamilial and tribal levels in the soapberry family (Sapindaceae). Mol. Phylogenet. Evol. 51 (2): 238 – 258. CaraDonna, P.J.; Iler, A.M. & Inouye, D.W. 2014. Shifts in flowering phenology reshape a subalpine plant community. Proc. Natl. Acad. Sci. 111 (13): 4916 – 4921. Cruz-Neto, O.; Machado, I.C.; Duarte Jr., J.A.; & Lopes, A.V. 2011. Synchronous phenology of hawkmoths (Sphingidae) and Inga species (Fabaceae–Mimosoideae): implications for the restoration of the Atlantic forest of northeastern Brazil. Biodiv. Conserv. 20 (4): 751 – 765. Dafni, A. 1992. Pollination Ecology: A Practical Approach. Oxford University Press. New York. Elzinga, J.A.; Atlan, A.; Biere, A.; Gigord, L.; Weis, A.E. & Bernasconi, G. 2007. Time after time: flowering phenology and biotic interactions. Trends Ecol. & Evol. 22(8): 432 – 439. Gadek, Paul A. et al. 1996. : Molecular Delimitation and Infraordinal Groups. Am. J. Bot.. 83 (6): 802 – 811. Sudip K. Roy et al. 9 Garibaldi, L.A. et al. 2013. Wild pollinators enhance fruit set of crops regardless of honey bee abundance. Science. 339 (6127): 1608 – 1611. Gonsamo, A.; Chen, J.M. & Wu, C. 2013. Citizen Science: linking the recent rapid advances of plant flowering in Canada with climate variability. Sci. Rep. 31(1): 1 – 19. Harrington, M.G. et al. 2005. Phylogenetic inference in Sapindaceae sensu lato using plastid matK and rbcL DNA sequences. Syst. Bot. 42 (1): 366 – 382. Hooker, J.D. 1875. The Flora of British India. Vol. 1, L. Reeve & Co., Kent, London. Pp. 692 – 695. IUCN 2015. The IUCN Red List of Threatened Species. Version 2015. IUCN, Gland. Kearns, C.A. & Inouye, D.W. 1993. Techniques for Pollination Biologists. University press of Colorado, Colorado. Lama, D. 2004. Taxonomical, distributional and ecological studies of Acer L. (Aceraceae) in the Darjeeling- Sikkim Himalayas. Ph.D. Thesis, University of North Bengal, Siliguri. Lama, D.; Moktan, S. & Das, A.P. 2015a. Diversity and distribution of Acer Linnaeus (Sapindaceae) in Darjiling and Sikkim Himalayas. Pleione 9(1): 61 – 73. Lama, D.; Moktan, S. & Das, A.P. 2015b: Diversity of pollen morphological characters in Acer Linnaeus (Sapindaceae) from Darjiling and Sikkim Himalayas. In: Tripathi, S.K. (ed.), Biodiversity in Tropical Ecosystems. Today & Tomorrow’s Printers and Publishers, New Delhi. Pp. 153-165 Mazer, S. & Schick, T.C. 1991. Constancy of population parameters for life-history and floral traits in Raphanus sativus L. II. Effects of plant density on phenotype and heritability estimates. Heredity 45 (8): 1888 – 1907. Morellato, L.P.C.; Camargo, M.G.G. & Gressler, E. 2013. A review of plant phenology in South and Central America. In: Schwartz, M.D. (Ed.), Phenology: An Integrative Environmental Science. Springer. Pp. 91 – 113. Morellato, L.P.C. et al., 2016. Linking plant phenology to conservation biology. Biol. Cons. 195: 60 – 72. Müller, J. & Leenhouts, P.W. 1976. A general survey of pollen types in Sapindaceae in relation to taxonomy. In: Ferguson, I.K. & Müller, J. (Eds.), The Evolutionary Significance of the Exine: Academic Press, London. Pp. 407 – 445. Nayar, M.P. & Sastry, A.R.K. 1987. Red Data Book of Indian Plants. Botanical Survey of India. India, Calcutta. Quinn, J.A. & Wetherington, J.D. 2002. Genetic variability and phenotypic plasticity in flowering phenology in populations of two grasses. J. Torrey Bot. Soc. 129 (2): 96 – 106. Renner, S.S. et al. 2007. The evolution of dioecy, heterodichogamy and labile sex expression in Acer. Evolution. 61: 2701 – 2719. Savolainen, V. et al. 2000. Phylogeny of the : a newly complete familial analysis based on rbcL gene sequences. Kew Bull. 55 (2): 257 – 309. Umadevi, I. & Daniel, M. 1991. Chemosystematics of the Sapindaceae. Fedd. Rep. 102(7- 8): 607 – 612. Visser, M.E. & Holleman, L. 2001. Warmer springs disrupt the synchrony of oak and winter moth phenology. Proc. R. Soc. Lond. B: Biol. Sci. 268 (1464): 289 – 294. Yadav, N, Pandey, A.K. & Bhatnagar, A.K. 2016. Cryptic monoecy and floral morph types in Acer oblongum(Sapindaceae): An endangered taxon. Flora. 224: 183 – 190.