Reproductive ecology of Syzygium alternifolium (Myrtaceae), an endemic and endangered tropical tree species in the southern Eastern Ghats of India
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Journal of Threatened Taxa | www.threatenedtaxa.org | 26 August 2014 | 6(9): 6153–6171 Reproductive ecology of Syzygium alternifolium Raju et al. 6157 Floral biology The flowers open during 16:00–18:00 hr with maximum flower production at 17:00hr (Image 1 e–k). Anther dehiscence occurs following anthesis by longitudinal slits. Each anther produces 4136±192 pollen grains and the total pollen output per flower is 5,25,272±12,408. The pollen-ovule ratio varies from 13,833 to 25,013. The pollen grains are creamy-white, triangular, tricolporate, triangular, 16.6µm in size, powdery and fertile (Image 1o). The apertures appear as short furrows in a thickened portion of the wall. The distinctive pattern seen in polar view is formed by thinning of the exine. Most of the pollen is dislodged as single grains and it enters the ambient environment by wind. Two peak pollen concentrations were recorded, one with 17,832 pollen grains per m 3 of air sampled in the evening hours between 17:00 and 20:00 hr and another with 5,721 pollen grains per m 3 of air sampled in the morning hours between 07:00 and 10:00 hr. In the circadian cycle, the pollen grain concentrations varied between 17,832 and 843 for cubic meter of air sampled. The pollen concentration at peak pollen release hour (19:00hr) at a distance of 0m was 17,832, at 5m 15,821, at 10m 12,981, at 15m 7,432, at 20m 1500, and at 25m Image 1. Syzygium alternifolium: a - Habitat; b - Leaf flushing; c -Flowering phase; d -A cluster of inflorescences with buds and flowers; e - Mature buds; f-k - Different stages of anthesis; l. & m - Calyx cup with centrally located ovary terminated with simple stigma; n - Ovules; o - Pollen grains. © Prof. A.J. Solomon Raju. a c e k g m b d f l h n i o j Journal of Threatened Taxa | www.threatenedtaxa.org | 26 August 2014 | 6(9): 6153–6171 Reproductive ecology of Syzygium alternifolium Raju et al. 6158 659. The pollen concentration at second peak hour (09:00hr) was 5,721 at 0m, 4057 at 5m, 3947 at 10m, 3254 at 15m, 2874 at 20m and 1647 at 25m. The stigma receptivity begins at 20:00hr and remains until the end of 2
nd day. The stamens fall at the 2 nd day of flower life while the remaining parts of the flower remain intact for five days if not pollinated. In pollinated flowers, the calyx cup is persistent and the fruit emerges out when fully grown. The nectar is secreted in the orange coloured part of the cup continuously for a period of four days from the time of anthesis. A total of 12.7±4.32 µl of nectar is produced in the total life span of the flower. The nectar sugar concentration is 16.44±3.1 %; the sugars include sucrose (2.55µg), fructose (2.37µg) and glucose (0.13µg). The nectar includes six essential and nine non-essential amino acids. The essential amino acids are arginine, histidine, lysine, threonine, tryptophan and valine. The non-essential amino acids are alanine, aspartic acid, cysteine, cystine, glutamic acid, glysine, hydroxyproline, serine and tyrosine. The total protein content in the nectar is 2.55µg. Flower visitors and pollination The flowers completely expose the anthers as well as the stigma. The flower visitors accessed the floral rewards with great ease. A total of 33 species consisting of bees, wasps, flies, beetles, butterflies (diurnal foragers), the hawk moth (crepuscular forager), and the reptilian (nocturnal forager) was recorded (Table 2). The bees included Apis dorsata (Image 2c), A. cerana (Image 2d), A. florea, Trigona iridipennis (Image 2e),
these, Trigona bees foraged for nectar and also pollen, while all others for nectar only. The wasps were nectar
1. -- -- -- -- -- -- 2. -- -- -- -- -- -- 3. 19 April
7 May 20 19 April 10 May 22 4. -- -- -- -- -- -- 5. -- -- -- -- -- -- 6. 18 April 6 May 19 -- -- -- 7. -- -- -- 18 April 8 May
21 8. 26 April 14 May 19 -- -- -- 9. -- -- -- -- -- -- 10. -- -- -- -- -- -- 11.
-- -- -- 14 April 6 May
22 12.
-- -- -- -- -- -- 13. -- -- -- -- -- -- 14.
26 April 14 May
19 19 April
14 May 26 15. -- -- -- 13 April 7 May
25 16.
-- -- -- -- -- -- 17. 26 April
11 May 16 -- -- -- 18. -- -- -- 14 April 7 May
23 19.
19 April 11 May
23 -- -- -- 20.
21 April 6 May
16 -- -- -- 21.
-- -- -- -- -- -- 22. -- -- -- -- -- -- 23.
19 April 11 May
23 20 April
10 May 21 24. 17 April 7 May
21 18 April
6 May 19 25. -- -- -- 17 April 5 May
19 Table 1. Flowering phenology of Syzygium alternifolium 17 April - 14 May 13 April - 14 May. Flowering days: 16–23 (Mean 19 days) 19–26 (22 days) Journal of Threatened Taxa | www.threatenedtaxa.org | 26 August 2014 | 6(9): 6153–6171 Reproductive ecology of Syzygium alternifolium Raju et al. 6159 foragers and they were Eumenes sp. (Image 2h), Vespa cincta (Image 2i) and V. orientalis (Image 2j). Both the bees and wasps were regular foragers. Flies were occasional nectar foragers and they were Chrysomya
Beetles were Popillia impressipyga (Image 2m) and one unidentified species (Image 2n); the former was a resident forager feeding on flower parts and contributed to 26% of flower damage in 2011, 20% in 2012 and 6% depending on flowering intensity while the latter was an occasional nectar forager. The butterflies were regular foragers and they were Papilio polytes (Image 3a), Graphium nomius, Catopsilia pyranthe (Image 3b), C. pomona (Image c,d), Euploea core (Image 3e), Tirumala limniace (Image 3f), Precis iphita (Image 3g), Junonia lemonias (Image 3h), Melanitis leda (Image 3i), Danaus genutia (Image 3j), Neptis hylas (Image 3k), Mycalesis perseus (Image 3l), Moduza procris, Arhopala amantes (Image 3m), Pseudocoladenia indrani (Image 4a), Borbo cinnara (Image 4b), Hasora chromus (Image 4c) and Celaenorrhinus ambareesa (Image 4d). The sphingid, Cephonodes hylas (Image 4e) was the only diurnal moth visiting the flowers regularly. The African fat-tailed gecko, Hemitheconyx caudicinctus was a resident nectar
a d h l b e i m f j n c g k o Journal of Threatened Taxa | www.threatenedtaxa.org | 26 August 2014 | 6(9): 6153–6171 Reproductive ecology of Syzygium alternifolium Raju et al. 6160 forager during night time from 0600–1000 hr (Image 2o). The first visitor to just open flowers in the evening was the diurnal hawk moth, Cephonodes hylas; it continued its foraging from 16:00–19:00 hr. The same moth was the first visitor to the flowers in the morning and it foraged from 06:00–09:00 hr (Fig. 7). All other insects visited the flowers from 07:00–12:00/13:00 hr (Fig. 1–6); the flies made a few visits during 15:00–16:00 hr (Fig. 3). The intense foraging activity was recorded during 09:00–11:00 for most of the insects. Of the total foraging visits made by insects except beetles during the 3-year period, bees constituted 25%, wasps 15%, flies 3%, butterflies 50% and hawk moth 7% (Fig. 8). The honey bee, A. dorsata, wasps, butterflies and the hawk moth foraged for nectar very frequently between closely and distantly spaced conspecific trees while other bees, the unidentified beetle and the gecko tended to stay mostly on the same tree for forage collection.
Time (hr) Journal of Threatened Taxa | www.threatenedtaxa.org | 26 August 2014 | 6(9): 6153–6171 Reproductive ecology of Syzygium alternifolium Raju et al. 6161 Flower bud as oviposition site for an unidentified moth A moth species (unidentified) used the flower buds as oviposition site. It deposited its eggs in young flower buds and the emerged larvae consumed the entire bud over a period of approximately 3–4 days (Image 2a,b). The percentage of infested flower buds is 21% in 2011, 17% in 2012 and 4% in 2013. Consolidated mounds formed by buds and flowers were also found and such flowers subsequently fell off (Image 4f). These infested flowers were found on all flowering branches in 2011, randomly in 2012 and rarely in 2013. These bud and flower infestations were found be to be related to the intensity of flowering in each study year.
Pollination mode No. of flowers bagged/tagged/ pollinated No. of fruits produced Fruit set (%) Autogamy (bagged) 366 0 0 Autogamy (manual pollination, bagged) 75 0
Geitonogamy (manual pollination, bagged) 80 0
Xenogamy (manual pollination, bagged) 60 34
Open-pollination (Flowers tagged prior to anthesis) 1030
116 11
a d
j b e h k l c f i m Journal of Threatened Taxa | www.threatenedtaxa.org | 26 August 2014 | 6(9): 6153–6171 Reproductive ecology of Syzygium alternifolium Raju et al. 6162 Breeding and fruiting behavior Hand-pollination experiments indicated that autogamy and geitonogamy are non-functional while xenogamy is the only mode of pollination for fruit set. In this mode, fruit set stands at 56% while in open- pollination mode, it is 11% only (Table 3). The fertilized flowers grow, mature and ripen within two months (Image 4g-k). Fruit exhibits different colours - green, light purple, dark purple and violet during growing and maturing phase (Image 4l). It is a globose berry, luscious, fleshy, 25–30 mm in diameter and edible. It has a combination of sweet, mildly sour and astringent flavor and colours the tongue purple when eaten. The green and light purple fruits are very tasty and sweet while the dark purple and violet ones are sweet and bitter. Each fruit produces a single large seed only. The fruits fall off during late July–August. The locals were found to collect ripe fruits from trees and fallen fruits from the ground since they are edible and have commercial value.
The habitat of the plant is rocky with steep slope covered with little litter and moisture. The seedlings recorded in the area were 58 in 2011, 32 in 2012 and 17 in 2013. These were subjected to drought stress due to erratic rainfall. Further, extensive and robust grass cover during that period was found to be having impact on the surviving seedlings of the plant. Finally, Image 4. Syzygium alternifolium: a - Pseudocoladenia indrani; b - Borbo cinnara; c - Hasora chromus; d - Celaenorrhinus ambareesa; e - Cephonodes hylas; f - Infestation of buds and flowers; g - Fruiting phase; h-k - Stages of fruit maturation; l - Ripen fruits; m-p - Stages of seed germination and seedling formation. © Prof. A.J. Solomon Raju. a e b f c d g h m i n j o l k p
Journal of Threatened Taxa | www.threatenedtaxa.org | 26 August 2014 | 6(9): 6153–6171 Reproductive ecology of Syzygium alternifolium Raju et al. 6163 27 seedlings in 2011, 16 in 2012 and seven in 2013 have established and are growing continually at slow pace. The soil analysis for available nitrogen (N), phosphorous (P) and potassium (K) indicated that N is 270 kg/ha, P 13.57 kg/ha and K 282 kg/ha. These values show that these nutrients are not present in optimal levels and hence there is a deficiency in essential nutrients in the soil. The seeds sown in experimental bags showed that seeds germinate within two weeks and form seedlings subsequently (Image 4m-p). The seed germination rate is 74%.
DISCUSSION S. alternifolium is a semi-evergreen mass-flowering tree species in the study area. It is not only endemic but also endangered due to its declining population. The plant is not found in some sites where it was reported by previous workers as cited above. It is exploited for various local uses and hence it has now attained “Endangered” status. It qualifies for inclusion in the IUCN Red List. In Syzygium genus, the flowering pattern is of two types, mass flowering and short-period steady state flowering but most species exhibit mass flowering such
Figure 4. Hourly foraging activity of Papilionid and Pierid butterflies on Syzygium alternifolium
Time (hr) Journal of Threatened Taxa | www.threatenedtaxa.org | 26 August 2014 | 6(9): 6153–6171 Reproductive ecology of Syzygium alternifolium Raju et al. 6164 as S. tierneyanum (Lack & Kevan 1984), S. cuminii (Reddi & Rangaiah 1999–2000), S. luehmannii (Sanewski 2010),
& Kundu 2008). S. alternifolium is also a mass bloomer and it flowers during dry season. The flowering occurs after partial leaf shedding and leaf flushing occurs after the completion of flowering. This finding does not agree with the observation made by Mohan & Lakshmi Order/Family Scientific Name Common Name Forage collected Visiting status Hymenoptera Apidae
Apis dorsata F. Rock bee
N Regular
A. cerana F. Indian honey bee N Regular
A. florea F. Dwarf honey bee N Regular
Trigona iridipennis Smith Stingless bee N + P Regular
Amegilla sp. Digger bee N Regular
Crabronidae Stizus sp. Sand wasp N Regular
Vespidae Eumenes sp. Potter wasp N Regular
Vespa cincta F. Yellow-banded wasp N Regular
V. orientalis L. Oriental Hornet N Regular
Diptera Calliphoridae Chrysomya megacephala F. Oriental latrine fly N Occasional Syrphidae Helophilus sp. Hoverfly
N Occasional Coleoptera Scarabaeidae Popillia impressipyga Ohaus -- Flower parts Resident Unidentified sp. -- N
Lepidoptera Papilionidae Papilio polytes L. Common Mormon N Regular
Graphium nomius Esper Spot Swordtail N Regular
Pieridae Catopsilia pyranthe L. Mottled Emigrant N Regular
Catopsilia pomona F. Common Emigrant N Regular
Nymphalidae Euploea core Cramer Common Indian Crow N Regular
Tirumala limniace Cramer Blue Tiger N Regular
Precis iphita Cramer Chocolate Pansy N Regular
Junonia lemonias L. Lemon Pansy N Regular
Melanitis leda L. Common Evening Brown N Regular
Danaus genutia Cramer Common Tiger N Regular
Neptis hylas L. Common Sailer N Regular
Mycalesis perseus F. Common Bushbrown N Regular
Moduza procris Cramer The Commander N Regular
Lycaenidae Arhopala amantes Hewitson Large Oakblue N Regular
Hesperiidae Pseudocoladenia indrani F. Tricolour Pied Flat N Regular
Borbo cinnara Wallace Rice Swift N Regular
Hasora chromus Cramer Common Banded Awl N Regular
Celaenorrhinus ambareesa Moore Common Spotted Flat N Regular
Sphingidae Cephonodes hylas L. Pellucid Hawk Moth N Regular
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