The Reproductive Biology of Euglossine-Pollinated Plants in the Natural Reserve Nouragues, French Guiana
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THE REPRODUCTIVE BIOLOGY OF EUGLOSSINE-POLLINATED PLANTS IN THE NATURAL RESERVE NOURAGUES, FRENCH GUIANA DISSERTATION zur Erlangung des Doktorgrades Dr. rer. nat. der Fakultät für Naturwissenschaften der Universität Ulm vorgelegt von Heiko Hentrich aus Schwäbisch Hall Ulm 2008 Amtierender Dekan: Prof. Dr. Klaus-Dieter Spindler Erstgutachter: Prof. Dr. Gerhard Gottsberger Zweitgutachter: Prof. Dr. Manfred Ayasse Tag der Promotion: Legend to pictures of the title page: A B A: Euglossa cf. chalybeata approaching flower of Voyria clavata (Gentianaceae) C D B: Euglossa cf. chalybeata approaching flower of Rapatea paludosa (Rapateaceae) C: Exaerete frontalis sucking nectar at a flower of Bonafousia disticha (Apocynaceae) D: Eulaema bombiformis collecting floral perfume at an inflorescence of Spathiphyllum humboldtii (Araceae) Table of contents TABLE OF CONTENTS Summary................................................................................................................. 1 Zusammenfassung ..................................................................................................................19 CHAPTER 1 REPRODUCTIVE ISOLATION BY FLORAL SCENT IN THREE SYMPATRIC EUGLOSSINE-POLLINATED ANTHURIUM AND SPATHIPHYLLUM (ARACEAE) SPECIES IN FRENCH GUIANA .............................................................................. 49 Abstract................................................................................................................................49 Introduction..........................................................................................................................50 Material & Methods.............................................................................................................52 Results..................................................................................................................................54 Discussion............................................................................................................................63 Acknowledgements..............................................................................................................67 References............................................................................................................................68 CHAPTER 2 FLORAL SCENT COLLECTION AT THE PERFUME FLOWERS OF ANTHURIUM RUBRINERVIUM (ARACEAE) BY THE KLEPTOPARASITIC ORCHID BEE AGLAE CAERULEA (EUGLOSSINI) .................................................................................... 73 Introduction..........................................................................................................................73 Material & Methods.............................................................................................................74 Results..................................................................................................................................75 Discussion............................................................................................................................78 Acknowledgments ...............................................................................................................80 References............................................................................................................................81 I Table of contents CHAPTER 3 DOES SELECTION FAVOR SELFING IN MYCO-HETEROTROPHIC PLANTS? - THE REPRODUCTIVE BIOLOGY OF VOYRIA (GENTIANACEAE) SPECIES IN FRENCH GUIANA................................................................................................................85 Abstract ............................................................................................................................... 85 Introduction ......................................................................................................................... 86 Material & Methods ............................................................................................................ 88 Results ................................................................................................................................. 91 Discussion ......................................................................................................................... 106 Acknowledgements ........................................................................................................... 111 References ......................................................................................................................... 112 CHAPTER 4 THE REPRODUCTIVE BIOLOGY OF EUGLOSSINE-POLLINATED UNDERSTORY PLANTS IN A LOWLAND RAINFOREST IN FRENCH GUIANA – A COMPARATIVE STUDY.................................................................................................................117 Abstract ............................................................................................................................. 117 Introduction ....................................................................................................................... 118 Material & Methods .......................................................................................................... 120 Results ............................................................................................................................... 124 Discussion ......................................................................................................................... 145 Acknowledgments............................................................................................................. 154 References ......................................................................................................................... 155 Publications from this thesis and contributions of co-authors ........................................ 163 Acknowledgments .................................................................................................164 Curriculum vitae.................................................................................................................. 167 II Summary SUMMARY The reproductive biology of euglossine-pollinated plants in the natural reserve Nouragues, French Guiana GENERAL INTRODUCTION Tropical lowland rainforests are characterized by a high plant diversity and low population densities (Kress & Beach 1994, Myers et al. 2000). The wide spacing between conspecifics (Hubbel & Foster 1983, Ashton 1984, Bawa et al. 1985a) leads to more intense selection for long-distance pollen flow than in other communities (Janzen 1970, Bawa 1990). Hereby, plant species of different forest strata have evolved different ways to attain pollen flow, which is generally attributed to environmental factors (particularly light intensity) and the stratification of pollen vectors (Bawa 1983, Bawa 1990, Kress & Beach 1994, Kato 2005). In the forest canopy mass-flowering species dominate, which attract a broad species spectrum of foraging insects, and are either visited by large numbers of small diverse insects or medium- to large-sized bees (Frankie et al. 1983, Bawa et al. 1985b, Bawa 1990, Kress & Beach 1994, Momose et al. 1998). Interplant movement of pollinators is attained by the exact timing of flowering and nectar production of the conspecifics (Frankie et al. 1976, Frankie et al. 1983, Bawa et al. 1985b). Usually, blooming of an individual plant takes only a few days and different plant species are supposed to minimize competition for shared pollinators and interspecific gene-flow by short, non-overlapping flowering periods (Bawa 1983, Frankie et al. 1983). Since the risk of inbreeding depression caused by geitonogamy is high, most species have evolved self-incompatibility or dioecy (Heinrich & Raven 1972, Bawa 1990, Kress & Beach 1994). In the forest understory flower visitors are not attracted by large floral displays. Instead, plants are highly specialized in their reproductive biology to specific pollinators that primarily belong to the guilds of long-billed nectarivorous birds, long-tongued bees, and beetles (Bawa 1990, Kress & Beach 1994). Beetle-pollinated plants provide their visitors with food tissue, and achieve cross-pollination by the exact timing of the female and male blooming periods of different protogynous flowers or protogynous and monoecious inflorescences (Gottsberger 1970, Gottsberger & Amaral Jr. 1984, Bawa et al. 1985a, Young 1988, Gottsberger 1989, Gottsberger & Silberbauer-Gottsberger 1991, Kress & Beach 1994, Gottsberger & Silberbauer-Gottsberger 2006). Bird- and bee-pollinated plants produce few hermaphroditic flowers daily, which supply their visitors with large amounts of nectar. In order to prevent exploitation of the flowers by indiscriminate foragers, floral resources are 1 Table of contents hidden in long corolla tubes that are only accessible to the valid pollinators (Heinrich & Raven 1972, Stiles 1975, Feinsinger 1983, Momose et al. 1998). However, nectar amounts secreted by each plant are too low to saturate the daily energy requirements of the pollinators (Heinrich & Raven 1972, Stiles 1975, Bawa et al. 1985a). These have to visit various populations consecutively and cover several kilometers during foraging, which contributes to cross-pollination and large-distance gene flow (Stiles 1975, 1978). Thereby, the pollinators follow established flight routes that connect their host plants (‘trap-lining’; Janzen 1971, Stiles 1978, Sakai et al. 1999). The hosts represent reliable food resources as they produce