Philippine Journal of Science 142: 69-82, Special Issue ISSN 0031 - 7683 Date Received: ?? ???????? 2013 Role of Light in the Life Stages of Mt. Makiling Populations of Alocasia zebrina, An Endangered Philippine Plant Species1 Niko Niño G. Briones and Virginia C. Cuevas Institute of Biological Sciences (IBS), College of Arts and Sciences, University of the Philippines Los Baños (UPLB), College, Laguna, the Philippines Populations of Alocasia zebrina growing in a secondary forest on Mt. Makiling were studied to determine the influences of sunlight on its life stage development. The study site was dominated by Swietenia macrophylla in association with some members of Palm family. Large canopy gaps were present that allowed ground penetration of high light intensity. The life stages of Alocasia zebrina were identified to be, namely seed, juvenile, adult vegetative and adult sexually mature, based mainly on the number of mature leaves and reproductive capability. Statistical analyses showed a positive correlation between the number of mature leaves and the increase of total monthly minutes of sunshine. Furthermore, the field data analysis suggested that light plays a major role in determining not only where A. zebrina population will be established, but also the rate at which an individual can complete an entire life cycle. Key Words: Alocasia zebrina, life stages, light intensity, Araceae, vegetation, endangered Philippine plant species INTRODUCTION petiole attached to the end of the midrib and extends up to 1.1 m has varying shades of distinct green and brown Except for A. macrorrhizos (L.) G. Don, all indigenous oblique streaks. The colours and design of the petiole with species in the genus Alocasia are endemic in the stripe has earned its local name as ‘gabing tigre’. The Philippines (Medecillo et al. 2007). Alocasia zebrina inflorescence that may occur in pairs is a spadix and has Schott ex van Houtte of the Family Araceae is a herb with a peduncle nearly 25 cm long. The white spathe more or leaves that grow together in a sympodial manner and found less 16 cm long, covers the young inflorescence and opens in rainforests at low to medium elevations of Quezon, up when the flowers mature. The flowers are subsessile Bicol, Leyte, Samar, and Mindanao. Hay (1999) has the and occur in clusters or zones. The male zone occurs on following description of Alocasia zebrina - top of the inflorescence, about 3-4.5 cm long and cylindric The glossy green leaf blade of about 80 cm long has its in orientation. The female zone is at the bottom of the base bisected into narrow triangular lobes with the anterior spadix, globose in appearance and 4 -5.5 cm long. During end also triangular to ovate in shape. Four to 10 primary the fruiting stage this female zone appears globose up to lateral veins that arise in almost perpendicular manner 4.5 cm in diameter. There is a sterile zone in between and from the midrib run roughly straight to the margin. The male and female clusters which can be up to 1 cm long. Corresponding Author: [email protected] 1Portion of the undergraduate thesis of the senior author under the degree program of UPLB BS Biology (Ecology), 2010 69 Philippine Journal of Science Briones & Cuevas: Role of light in the life stages Vol. 142: Special Issue of Alocasia zebrina Apparently, the striped petiole that is characteristic of of dispersion for both populations at these two elevations the species, together with its white spathed-inflorescence exhibited a clumped distribution pattern. It was noted and beautifully shaped, dark green glossy leaves, that elevation together with the reported difference in make it a favourite among ornamental growers and relative humidity and soil pH does not have any significant landscape architects. The species is included in influence on its local distribution. Madulid’s (1995) publication of Philippine Ornamental Plants with notes on its high rate of disappearance The present study was conducted to characterize the different because of massive collection for its ornamental life stages of A. zebrina and to monitor the influence of and economic importance as a foliage plant. This light on the transition from vegetative stage to reproductive phenomenon together with its habitat destruction leads to stage of the life cycle of the plant. The identified life stages, its classification of a conservation status as a vulnerable together with the factor(s) that show influence on the to endangered species (Tan et al. 1986; Amoroso et al. transition in the life cycle can give an overview of the life- 2009). Fernando et al. (2008) classified the species history strategies of the plant population of this species. This as vulnerable as defined by the following criteria: (1) information can further serve as an initial reference for other population reduction in the form of a decline in area of detailed studies on its population dynamics. The results from occupancy, extent of occurrence and/or quality of habitat; this study can also help in planning for effective conservation (2) extent of occurrence estimated to be less than 20,000 measures for the species. km2 or area of occupancy is estimated to be less than 2,000 km2 with a continuing decline. Ramirez (1997) in his study of the plant’s distribution MATERIALS AND METHODS pattern at two altitudinal sites in the north eastern slope of Makiling Forest Reserve (MFR) concluded that the Study Site populations of the species occurred only between 250 m The study was conducted in a secondary forest at the and 700 m above sea level (asl) with most populations northeast slope of Mt. Makiling with the summit located occurring at 700 m and 300 m asl. The computed index at 121°11’ E by 14°08’ N (Figure 1). The study site is one Figure 1. a). Map of the Philippines showing location of Makiling Forest Reserve (MFR); b). Northeastern trail with the study site highlighted in green at 300 m. asl. 70 Philippine Journal of Science Briones & Cuevas: Role of light in the life stages Vol. 142: Special Issue of Alocasia zebrina of the six Permanent Field Laboratory Areas (PFLA 3) of modules of one individual, based on the definitions given the College of Forestry and Natural Resources (CFNR), by Begon et al. (2006) of modular populations. A total University of the Philippines Los Baños (UPLB) and an of 21 subpopulations were monitored. Morphometric established Mahogany plantation since 1940 within the parameters which include number of leaves, plant height, Makiling Forest Reserve (MFR) located east of Barangay and leaf area (measured using LI-3100C Area Meter) were Galugod Baboy. It is one of the two sites identified by recorded for vegetative individuals and individuals with Ramirez (1997) in his study on population distribution flowers. Fruit and inflorescence counts, and spadix length pattern of the species on the north eastern slope of MFR. were also gathered in sexually reproducing individuals. The subpopulations were monitored and the changes in morphometric measurements were noted in situ for Vegetation associated with A. zebrina 9 months, from July 2009 to April 2010. Pictures of Two methods of analysis were used to characterize the the different subpopulations were taken to illustrate the vegetation associated with A. zebrina. Point Center Quarter different life stages. Method (PCQM) was used to characterize palms and trees, while Line Intercept Method (LIM) was used for the herbaceous species (Mueller-Dombois & Ellenberg 1974). Meteorological data PCQM involved measurements of basal area, distances Monthly measurements of minutes of sunshine for the between plants and diameter at breast height (dbh) of same months of the study (July 2009 to April 2010) were plants with dbh > 1cm within a 30 meter transect line. The obtained from the Philippine Atmospheric Geophysical understory vegetation was surveyed and described using Astronomical Services Administration (PAGASA) two replicates of 5 meter transect lines. Importance value National Agro-Meteorological Station at UPLB located (I.V.) of species for PCQM is computed using the formula: at coordinates 14°11’ N, 121°15’ E. The station is within the 25 km radius of the study site thus their data obtained relative frequency + relative dominance + relative density held true also for the site. Light intensity was measured I.V. = 3 intermittently from January to April 2010 study using light meter (Center 337 mini Light Meter, range 0~40,000 lx) Frequency referred to presence/absence of the species at in subpopulation to describe the light environment of the each sample point. Dominance indicated the total basal study site. area of all individuals of the species in the sample points of the 30-m transect line. Density denoted the total number Data analysis of the individuals of the species in all the sample points. Shapiro-Wilk Statistical Test for normality was first used Relative frequency was computed as the frequencies of the to determine whether the data on leaf area measured for species in all sample points divided by the total frequencies both vegetative and reproductive individuals followed of all species in the 30-m transect line. Likewise, relative a normal distribution. When the test showed that the dominance referred to total basal area of a species in all the measured values did not follow the normal distribution, sample points divided by the total basal areas of all species a non-parametric test (Mann-Whitney U test) was used encountered. Similarly, relative density was computed as to compare mean leaf area of vegetative and reproductive the total number of individuals of the species divided by the individuals. Additionally, a parametric test (t-test for 2 total number of trees encountered in all the sample points independent samples) was utilized to compare the means (Mueller-Dumbois & Ellenberg 1974).