Fruit-frugivore interactions in a Malagasy littoral forest - Universiteit ...

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Phenology of the littoral forest of Sainte Luce, south-east Madagascar AN BOLLEN, GIUSEPPE DONATI BIOTROPICA (SUBMITTED) Phenology ABSTRACT From January 2000 through December 2002 phenological transects were carried out to assess monthly leaf, flower and (ripe) fruit presence for 423 individual plants (95 plant species, 43 families) within the littoral forest of Sainte Luce. Fruit-on-trail-counts were conducted additionally in the year 2000 to allow comparison between both methods. Despite low climatic seasonality and absence of a dry season in the littoral forest, interannual phenological patterns were seasonal at our site. Within-year variability was present with clear periods of abundance and scarcity. All phenophases were highly intercorrelated and peak from November through February. This was found in other humid Malagasy forests as well, while in dry Malagasy forests phenophases seemed to be more spaced in time due to the more seasonal climate. Day length seems to have the strongest impact on all phenophases, while rainfall is associated with flushing only and temperature with fruiting and ‘ripe fruiting’. Differences in presence of ripe fruits when comparing between both sampling methods can be explained by the differential contribution of several life forms in both methods, which influence overall fruiting patterns. INTRODUCTION Phenological studies address the timing of reproductive events in plants such as bud formation, flowering and fruiting along with vegetative processes like leaf flushing and shedding. Tropical trees display an enormous variety in temporal patterns of flowering and fruiting. Both flowers and fruits are patchily distributed in time and space and are relatively scarce food items compared to leaves and insects (Howe 1984). Therefore it is critical to study food availability and distribution in order to understand the behavioural ecology of tropical wildlife. In the tropics, many animal species are frugivorous to a lesser or greater degree and in terms of biomass, frugivores are the dominant trophic group in most tropical forest mammalian communities (Terborgh 1983). This is further reflected by the dominance (60-90%) of zoochorous plant species producing fleshy fruits (Howe and Smallwood 1982). Quantifying fruit availability has been a primary objective in many studies, which focus on the ecology of tropical fruiting trees and their consumers (Chapman et al. 1992a; Janson and Chapman 1999). During the alternation of seasons and years in rain forests, the availability of vegetative and reproductive plant parts is irregular and induces periods of abundance and scarcity of food for consumers (Brugiere et al. 2002). These temporal 15
Chapter 1 changes in resource availability are both affected by abiotic or climatic variables as well as by biotic factors through herbivory, pollination and seed dispersal. Up to present, several short-term phenological studies have been published for Madagascar, where 96% of the tree species are endemic (Schatz 2001). Phenological studies have been carried out in dry deciduous and semi-deciduous forests in the West (Meyers and Wright 1993; Sorg and Rohner 1996; Curtis and Zaramody 1998; Rasmussen 1999; Yamashita 2002) as well as in lowland and mid-altitude rainforest in the East (Andrianisa 1989; Overdorff 1993a, 1993b; Rigamonti 1993; Freed 1996; Hemingway 1996, 1998; Andrews and Birkinshaw 1998). Most of these studies represent data from one year and often include only a limited number of species. At present, no data are available for the littoral forest. This paper presents the first findings from a detailed phenology of plant guilds in the littoral forest of Sainte Luce (south-east Madagascar) in the interest of revealing broad community-wide patterns of leafing, flowering, fruiting in the course of three years. This study generates indices to the food supply available to animal consumers, but also addresses the impact of abiotic factors. Furthermore, we compare phenological patterns of different Malagasy forest types. In this study several aspects will be looked at closely. First, we describe the temporal fluctuations of flushing, flowering and fruiting inter- and intra-annually based on data from phenological transects and fruit-on-trail-counts, which are considered to be the most common phenological methodologies (Chapman et al. 1992a; Chapman and Wrangham 1994). Secondly, we look for correlations between these phenological patterns and different abiotic factors such as rainfall, temperature and day length, that may trigger phenological events. Finally, we compare our data with the results of other Malagasy study sites. METHODS Study site The littoral forest of Sainte Luce (24º45'S 47º11'E) is located in south-eastern Madagascar, 50km up north of Fort-Dauphin. Research was carried out in a 377-ha large forest fragment, called S9 (Fig. 1). Littoral forest is characterised by a relatively open or non-continuous canopy, which is 6 to 12m in height with emergents up to 20m. The diameter at breast height (DBH) of trees rarely exceeds 30-40cm. Littoral forest grows on sandy soils and occurs within 2-3km of the coast at an altitude of 0-20m (Lewis Environmental Consultants 1992a). Abiotic factors Daily rainfall was measured with a plastic rain gauge (TruCheck) during the research period. Rainfall data from February till September 2001 were not available for Sainte Luce. A thermo-hygrograph (Box Pro) was placed in primary forest at one meter height to record the daily march of temperature and relative humidity. Variation in day length was calculated using Stephen Moshier’s Ephemeris Program v5.1 (Moshier 1991) for the Sainte Luce latitude. Mean monthly values were calculated for all abiotic factors. 16
Page 1 and 2: Fruit-frugivore interactions in a M
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Page 5 and 6: Table of contents III. General conc
Page 7 and 8: Acknowledgements A special word of
Page 10: PREFACE Preface This work brings to
Page 13 and 14: General introduction Finally, seed
Page 15 and 16: General introduction high as 98% fo
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Page 41 and 42: Malagasy proverb Drawing © Giusepp
Page 43 and 44: Chapter 2 the successful establishm
Page 45 and 46: Chapter 2 40 Table 1. The frugivore
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Page 49 and 50: Chapter 2 Overall fruit trap data d
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Page 53 and 54: Chapter 2 depressed seeds (Fig. 3a)
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Chapter 3 dominant plant families s
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Chapter 3 Table 4. Morphological an
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Chapter 3 Table 4 Continued Paramet
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Chapter 3 Besides testing feeding s
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Chapter 3 and do not consume the fi
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Chapter 3 (1997) already pointed ou
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Chapter 3 1989; Galetti 1993; Saini
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Chapter 3 Appendix I. All plant spe
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Chapter 3 Other SD Hss Rats Rr Ew 8
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Pteropus rufus Feeding ecology of P
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Pteropus rufus number per species a
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Pteropus rufus Table 1 Continued Fr
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Pteropus rufus larger number of spe
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Table 2 Continued Number of seeds/d
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Pteropus rufus Food selection: expl
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Pteropus rufus presence. On the oth
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Pteropus rufus Marshall (1983). Occ
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Coracopsis nigra The feeding ecolog
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Coracopsis nigra fruit pulp (70%) b
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Coracopsis nigra Table 1 Continued
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Coracopsis nigra Table 2. Morpholog
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Malagasy proverb Drawing of fruits
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Chapter 4 Most seed dispersal studi
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Chapter 4 Mean temperature is aroun
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Chapter 4 Number of seeds: 1-2, 3-1
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Chapter 4 Fig. 2. Monthly fruit ava
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Chapter 4 120 Table 3. Soil charact
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Chapter 4 Table 4. Morphological ch
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Chapter 4 Table 5. Biochemical char
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Chapter 4 Chemistry At both sites,
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Chapter 4 considering species numbe
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’Ny valala tsy indroa mandry eo a
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Chapter 5 environmental degradation
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Chapter 5 at a very low density in
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Chapter 5 Table 1. A list of plant
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Chapter 5 (Ganzhorn et al. 1999a).
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Chapter 5 Animals The degree of vul
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Chapter 5 comm.). Mixed species pla
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Chapter 5 data are needed we believ
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General conclusion as in other site
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General conclusion selection pressu
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General conclusion are consumed by
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Samenvatting omstandigheden zijn bo
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Samenvatting vruchtkenmerken. Beide
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Samenvatting zaadverspreiding moete
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Résumé température et précipita
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Résumé (Sud-est de Madagascar) et
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Résumé des frugivores sur l’év
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References Bollen A, Van Elsacker L
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References Dowsett JR (2000) Le sta
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References Godfrey LR, Junger WL, R
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References Janson CH, Chapman CA (1
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References Marshall AG (1983) Bats,
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References Rabevohitra R, Lowry PP,
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References Tattersall I (1982) The
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family Loganiaceae scientific name
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