Floral Biology of Myristica insipida (Myristicaceae), a Distinctive Beetle Pollination Syndrome Author(s): Joseph E. Armstrong and Anthony K. Irvine Source: American Journal of Botany, Vol. 76, No. 1 (Jan., 1989), pp. 86-94 Published by: Botanical Society of America, Inc. Stable URL: http://www.jstor.org/stable/2444777 Accessed: 06-09-2016 16:15 UTC REFERENCES Linked references are available on JSTOR for this article: http://www.jstor.org/stable/2444777?seq=1&cid=pdf-reference#references_tab_contents You may need to log in to JSTOR to access the linked references. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://about.jstor.org/terms Botanical Society of America, Inc. is collaborating with JSTOR to digitize, preserve and extend access to American Journal of Botany This content downloaded from 132.198.8.49 on Tue, 06 Sep 2016 16:15:01 UTC All use subject to http://about.jstor.org/terms Amer. J. Bot. 76(1): 86-94. 1989. FLORAL BIOLOGY OF MYRISTICA INSIPIDA (MYRISTICACEAE), A DISTINCTIVE BEETLE POLLINATION SYNDROME' JOSEPH E. ARMSTRONG AND ANTHONY K. IRVINE Department of Biological Sciences, Illinois State University, Normal, Illinois 61761; and CSIRO Tropical Forest Research Centre, PO Box 780, Atherton, Queensland 4883, Australia ABSTRACT The floral biology and pollination of Myristica insipida were studied in two different rain forest communities in Queensland. Floral morphology of M. insipida resembles that of M. fragrans in virtually all respects. The majority of female flowers were receptive 48-72 hr. Male flowers were shorter-lived, functional for 12-48 hr. Both male and female flowers opened daily between 1800 and 2200 hr, but the activity of floral visitors did not begin until the next morning. The inconspicuous, creamy-white to light-green flowers had a strong, pleasant "floral" fragrance. The male flowers only offered pollen as a reward, and female flowers, offering no reward, were judged to function by automimicry. A taxonomically diverse array of small, pollen-foraging beetles were the effective pollinators, although thrips and ants were common floral visitors. In almost all respects, the beetle pollination syndrome of Myristica differs from the cantharophily of most other primitive angiosperms. WITHIN THE MAGNOLIALES there exists a di- represent a highly specialized pollination syn- versity of floral forms and pollination syn- drome involving pollinator constancy and re- dromes, although beetle pollination, canthar- wards of food, predator protection, breeding ophily, is common in many of these families site, and brood substrates (Gottsberger, 1974, (Gottsberger, 1974, 1977; Thien, 1974, 1980; 1977; Thien, 1974, 1980; Beach, 1982; Pell- Endress, 1986; Bernhardt and Thien, 1987). myr, 1984, 1985; Pellmyr and Thien, 1986; The small, inconspicuous, unisexual flowers of Tang, 1987). the Myristicaceae are not like the large, many- A study of cultivated nutmeg indicated that parted, spirally-arranged flowers usually as- the male flowers only offered pollen as a re- sociated with beetle pollination, and thought ward, that the female flowers offered little or of as "primitive" and "typical" in the Mag- no reward, functioning by automimicry (Arm- noliales. Myristica fragrans, the nutmeg of strong and Drummond, 1986). The small, bee- commerce, has been reported to be pollinated tle pollinator did not engage in breeding activ- by small insects, moths, or possibly wind ities or destructive feeding on floral parts. This (Deinum, 1949; Mcllroy, 1967; Purseglove, is similar in many respects to the beetle pol- 1968; Cobley, 1976), but was found to be pol- lination reported for Drimys brasiliensis and linated by a small beetle (Armstrong and Diospyros pentamera (Gottsberger, 1977; Drummond, 1986). Gottsberger, Silberbauer-Gottsberger, and Eh- Cantharophily is a diverse pollination syn- rendorfer, 1980; House, 1985). There is some drome and even among primitive angiosperms chance that the flowers or flowering of culti- different aspects of beetle-plant interactions vated nutmeg may have been altered through have been identified (Gottsberger, 1977; Thien, conscious or unconcious selection during their 1980). Several studies have demonstrated that domestication. Further, in a plantation setting, the "primitive," magnoliacious flowers polli- pollinators and pollinator activity may differ nated by the haphazard, "mess-and-soil" ac- from those in a natural, rain forest community. tivities of beetles (sensu Faegri and Pijl, 1971), In order to corroborate and further document this unusual type of beetle pollination, we stud- ied a species of Myristica in its natural rain forest communities. Submitted for publication 29 June 1987; revision ac- Myristica insipida is a subcanopy tree that cepted 13 May 1988. occurs in several different rain forest com- The first author wishes to thank the staff of the CSIRO Tropical Forest Research Centre for their assistance and munities in Queensland. We studied the floral support. We are grateful for the discussions with P. Bern- biology and pollination of this nutmeg species hardt and 0. Pellmyr, and the comments of anonymous in two different rain forest communities, a low- reviewers, that contributed to this manuscript. J. Bouse- land study site at Little Pine Creek (LPC) and man, Illinois Natural History Survey, kindly provided family identifications of the beetles. This research was an upland study site at Curtain Fig State Forest supported by NSF Grant INT-85 13473. (CF), described in the preceding paper (Arm- 86 This content downloaded from 132.198.8.49 on Tue, 06 Sep 2016 16:15:01 UTC All use subject to http://about.jstor.org/terms January 1989] ARMSTRONG AND IRVINE-MYRISTICA FLORAL BIOLOGY 87 strong and Irvine, 1989). Specifically, our stud- trees, over 85% of each day's flowers open be- ies were designed to answer the following ques- tween 1800 and 2200 hr. The remaining flow- tions about floral function and pollinators: 1) ers reach anthesis during the remainder of the What are the flowering patterns and longevities night. No new flowers open from 400 to 1800 of the male and female flowers? 2) What are hr. the floral attractants and rewards? 3) What are Male flowers are relatively short-lived and the floral visitors and pollen vectors? The sea- show visible signs of senescence after 12 hr sonal flowering, sex ratios, spacing, and repro- with 40% abscising after 12-24 hr and the re- duction were studied also and the results re- maining 60% abscising between 24-48 hr (Ta- ported in the preceding paper. ble 1). Newly-opened male flowers have creamy-white to light-green perianths, and METHODS- Floral longevity was determined creamy-white, turgid androecia. After 12 hours by making daily observations of marked in- the androecia start to shrivel and turn a pink dividual flowers on conveniently located and to light-brown color. The pollen was viable accessible trees. Observations of the frequency, and could successfully pollinate female flowers duration, and diversity of floral visitors were throughout the life ofthe male flowers. In many made hourly over a 24-hr period on several cases flowers still borne on a tree largely were occasions. Changes in floral appearance, odor, depleted of pollen. Fresh male flowers produce presence or quantity of secretions and pollen a strong fragrance, which wanes as the flowers were noted. Visual changes in the female flow- senesce. However, even senescent and abscised ers were experimentally coordinated with stig- flowers produce some fragrance. We judged ma receptivity by pollinating flowers of known male flowers to be functional as long as they age and visual condition with a 200+ pollen contained pollen and/or remained on the tree. load from distant intrapopulation donor trees. The female flowers are functional longer than Floral visitors were captured and examined male flowers with 69.5% lasting longer than 48 microscopically for pollen loads. Voucher hr and a few lasting over 72 hr (Table 1). The specimens were sent to the CSIRO Division of perianths, pistils, and stigmas are colored a Entomology in Canberra. Visited flowers were light-green to greenish-white to creamy-white examined for evidence of damage or visitors' while fresh. Fresh stigmas always appear moist reproductive activities. Fresh, functional flow- but show no accumulation of liquid. The fe- ers were stained with 0.1 % neutral red for twen- male flowers are very fragrant when fresh and ty minutes and then rinsed with distilled water they remain very fragrant until senescence be- to identify any secretory tissues (Vogel, 1962). gins. The stigma and tips of the tepal lobes of postpollinated and senescent flowers turn a RESULTS-Floral morphology-The flowers dark, red-brown color (Fig. 4). The color change of Myristica insipida are identical to those of of the stigma was highly correlated with loss M. fragrans in essentially all respects (see Wil- of receptivity. Light-colored stigmas are re- son and Maculans, 1967; Armstrong and ceptive continuously until the beginning of col- Drummond, 1986; Armstrong and Tucker, or changes that mark the onset of senescence. 1986, for details of floral morphology). Both The stigmas of hand-pollinated flowers turned male and female flowers are borne on axillary dark within 12-24 hr post-pollination. inflorescences (Fig. 2) and have a 3-merous, syntepalous perianth subtended by a minute Floral attractants and rewards-Both male bracteole (Fig. 3-6). Both male and female and female flowers produce a similar fragrance flowers are small, although differing slightly in that is a slightly heavy, sweet, pleasant, "floral" size and shape. Female flowers were 4-5 mm odor. Individual female flowers seemed to be tall and 3-4 mm in diameter with a vase shape more strongly scented than individual stami- that was widest at the bottom (Fig.