MAJOR ARTICLE TAPROBANICA , ISSN 1800–427X. December, 2013. Vol. 05, No. 02: pp. 131–137. © Taprobanica Private Limited, 146, Kendalanda, Homagama, Sri Lanka. http ://www.sljol.info/index.php/tapro MIXED BREEDING SYSTEM AND ENTOMOPHILY IN Malachra capitata L. (MALVACEAE) Sectional Editor: James L. Reveal Submitted: 19 August 2013, Accepted: 18 November 2013 P. Suvarna Raju1,2 and A. J. Solomon Raju1 1 Department of Environmental Sciences, Andhra University, Visakhapatnam 530 003, India E-mail: [email protected] Abstract Malachra capitata is a small seasonal herb. Flowering occurs during September–October. It is hermaphroditic and self-compatible with a mixed breeding system. The conspicuous floral displays, non-tubular nature of the flower, and the small volume of nectar with high sugar concentration attract bees and butterflies with bees serving as the principal pollinator. The fruit set is 21% in open- pollination mode despite the hectic foraging activity of bees and butterflies. The observed fruit set rate is attributed to the high percentage of flower predation by beetles, and by the nature of soil nutrient/environment requirements. The fruit is a schizocarp with five 1-seeded indehiscent mericarps. New plants arise from seed during the rainy season mostly at parental sites and usually form pure stands; the plants complete their life cycle within six or seven months. Key words: mangrove associate, herb, insects, pollinator, soil binder, landward plant, India Introduction In India, there are a few studies made on the Carpenter bees are the main pollinators for pollination biology of mangroves. Solomon Caesalpina nuga, sunbirds for Acanthus Raju (1990) and Subba Reddi & Solomon Raju ilicifolius, and flies for Avicennia officinalis. (1997) provided some information on the floral Solomon Raju et al. (1994) suggested that there biology of some mangroves in the state of is an urgent need for extensive studies on the Andhra Pradesh. These authors reported that reproductive biology of mangrove plants for pollen vectors are essential for fruit set in their conservation and management. Based on Caesalpinia nuga (L.) Ait. and Acanthus the results of pollinator exclusion experiments, ilicifolius L. In A. corniculatum (L.) Blanco and Pandit & Choudhury (2001) reported that Lumnitzera racemosa Willd., fruit set occurs pollinators are important for the success of principally through autogamy. In Avicennia sexual reproduction in Aegiceras corniculatum officinalis L., the flowers are self-compatible and Sonneratia caseolaris (L.) Engl. An but the sexual system promotes outcrossing. explosive pollination mechanism has been 131 TAPROBANICA VOL. 05: NO. 02 MIXED BREEDING SYSTEM & ENTOMOPHILY IN Malachra capitata reported for Ceriops tagal (Perr.) C. B. Rob. the protocol given by Cruden (1977). An H2O2 and an non-explosive pollination mechanism in test reported by Dafni et al. (2005) was its sister species, C. decandra (Griff.) W. followed to record the period of stigma Theob.; both are adapted for insect pollination receptivity. Nectar volume and sugar (Jonathan & Solomon Raju, 2009; Solomon concentration was recorded as per the protocol Raju & Jonathan, 2008; Solomon Raju et al., given in Dafni et al. (2005). 2006). Except for these studies, there is no information available on the pollination biology Breeding system: Fifty flowers each from ten of other mangrove species, especially so for the randomly selected plants were used for each so-called mangrove associates. Malachra mode of breeding system. The methods capitata L. (Malvaceae) is a widely distributed described by Dafni et al. (2005) were followed herb found towards and along the landward to test for apomixis, autogamy (manipulated side of the mangrove forests in general and and spontaneous), geitonogamy, and especially in the Coringa mangrove forest of xenogamy. All these modes of pollination were Andhra Pradesh, India. It has not been studied followed for one month to calculate the for any aspect of reproduction or regeneration percentage of fruit set in each mode. Two and even its taxonomic description is hundred flowers in different flowering patches incomplete. The intent of the present study is to were tagged in the field prior to anthesis and provide details of floral biology, pollination followed for fruit and seed set rate in open- and seed dispersal in M. capitata with reference pollinations. Fruit maturation period, fruit to its importance as a source of forage for local dehiscence, seed dispersal, and establishment insects. were also observed. Materials and Methods Observations and collection of floral foragers: Study site: The Coringa mangrove wetland lies The foragers included bees, butterflies and between 16º30′–17º00′N and 82º10′–80º23′E. beetles. The species were identified based on Freshwater flows into the mangrove wetlands comparisons with already identified specimens for a period of six months with peak flow available in the department. They were normally during July–September, coinciding observed for ten hours a day for fifteen days with the southwest monsoon season. During during the flowering season. The hourly this period the entire delta, including the foraging visits of each species of bee and mangrove wetland, is submerged under butterfly species were recorded on ten different freshwater since penetration of sea water is days in 1 x 1 m flowering patch. The data completely blocked by the large amount of obtained were used to calculate the percentage incoming freshwater. Brackish water condition of foraging visits made by each species per day prevails from October to February and sea and the percentage of foraging visits of bees water dominates the entire mangrove wetland and butterflies per day. Simultaneously, the from March to May due to absence of bees and butterflies were observed for their freshwater discharge. foraging behaviour such as mode of approach, landing, probing behaviour, the type of forage Floral presentation and reproductive traits: they collected, and contact with essential Field investigations and experiments were organs critical for pollination. These insects conducted on Malachra capitata from February were captured during 1000–1200h on five 2010 to October 2012. The details of flower different days for pollen analysis in the morphology such as flower sex, shape, size, laboratory. For each bee and butterfly species, colour, odour, sepals, petals, stamens and ovary ten specimens were used and each specimen were described. Anthesis and anther was washed first in ethyl alcohol and the dehiscence schedule was recorded as per the contents stained with aniline-blue on a glass protocol given in Dafni et al. (2005). The slide and observed under microscope to count flower life was recorded by marking twenty the number of pollen grains present. For pollen just open flowers and following them until collecting bees, pollen loads on their corbiculae abscisions. Twenty mature but un-dehisced were separated prior to washing. From pollen anthers were collected from five randomly counts, the average number of pollen grains selected plants to determine pollen output per carried by these species was calculated to know anther/flower and then pollen-ovule ratio as per their pollen carryover efficiency. In the case of 132 TAPROBANICA VOL. 05: NO. 02 SUVARNA RAJU & SOLOMON RAJU, 2013 beetles, they were observed for their flower Floral Biology: The mature flower buds open feeding activity resulting in flower damage and daily quickly during 0600–0800 h. Anther subsequent fall off. A sample of five hundred dehiscence takes place during mature bud stage flowers collected from different flowering by transverse slits at the top of the anthers; this patches was used for calculating the flower divides the anther into two halves liberating the predation rate by beetles. pollen grains. The pollen output per monothecous anther is 89 ± 7.6 (Range 80–98). Photography: Plant, flower and fruit details, The pollen grains are bright yellow, ellipsoidal, together the foraging activity of foragers, were spinous, sticky, large and 134.8 µm in size. A documented with Nikon D40X Digital SLR flower produces 1.8 ± 0.13 µl of nectar with a (10.1 pixel) and TZ240 Stereo Zoom sugar concentration of 37 ± 1.9%. The stigma Microscope with SP-350 Olympus Digital attains receptivity one hour after anthesis and Camera (8.1 pixel). Magnus Compound stays so until 1700 h. The corolla, staminal Microscope, 5x, 10x, 40x and 100x column and stigma fall off by the evening of magnification was used for studying the pollen the second day. The calyx is persistent and characteristics. harbours the growing fruit. Results Breeding Systems: The results of breeding Phenology: Malachra capitata is a small, system studies indicate that the flowers are self- coarse, erect, simple or branched annual herb compatible and capable of both self- and cross- which is covered with hairs. It is common pollination. Fruit set is 4% in autogamy along the margins of the landward low salinity (unmanipulated), 24% in autogamy areas of Coringa mangroves. It forms pure (manipulated), 38% in geitonogamy but 82% in stands in areas lining the outermost land areas xenogamy, and 21.2% in open-pollinations of mangroves and, as a mangrove associate, is (Table 1). Seeds are produced by all modes of an important soil-binding species. Leaf flushing pollination. Bud and flower abortion was and new growth occurs during the rainy season absent. from June to August while flowering is from September to October. Flowers are borne