Aspectos da biologia floral, sucesso reprodutivo e polinização de cinco espécies de marantaceae na Amazônia Central

Abstract

Marantacae flowers have a unique and distinctive structure which needs effective pollinators To ensure their reproductive success. There are few studieson floral biology, reproductive success and pollination Marantaceae species in Central Amazonia. The present study aimed to investigate these aspects in five species of Marantaceae: Monotagma vaginum Hagber; Monotagma densiflorum (Körn.) K. Schum.; Calathea hopkinsii Forzza; Ischnosiphon arouma (Aubl.) Körn. and Ischnosiphon polyphyllus (Poep. & Endl.) Körn. The investigation lasted from november 2010 to april 2014 in six areas of Manaus, Amazonas, Brazil. The thesis is divided in three chapters. The first chapter discusses the phenology, floral biology, reproductive system and pollination for all the five species. Furthermore, the study analyzed space-time variation in the composition of pollinators; evaluated the relation between floral size and pollinator’s size and compared frequency of Pollinators visits for Monotagma vaginatum in continuous forest and fragmented forest. Blooming of species reached its peak in the months corresponding to the rainy season in the region. All the five species are self-compatible, however only Monotagma vaginatum and Monotagma densiflorum are autogamous. Formation of fruit was low for all species. Bees of the Euglossini tribe were efficient pollinators for four species in the study. Only Monotagma densiflorum had Thalurania furcata hummingbird as efficient pollinator which may be due to the absence of petaloid staminode, a floral structure that serves as lading platform for bees. In all four species pollinated by bees there was no space-time variation in the composition of pollinators. There was compatibility between the floral size and the tube length with the pollinator’s body size and tongues length, suggesting a functional and morphological specialization between the studied species and groups of pollinators compatible in size. Frequency of pollinators for Monotagma vaginatum increased in fragmented forest when compared to continuous forest. The availability of floral resources in the surrounding area and proximity of other species to Marantaceae may be factors to influence the attractiveness of pollinators to the flowers. The second chapter is about how many and which plant the Euglossini bees visited aside from Marantaceae species. In order to collect such data, analyses of pollen load attached to the body of bees collected after visiting M. vaginatum, C. densiflorum, I. arouma e I. polyphyllus were conducted. A total of 46 pollen types were found attached to the body of Euglossini bees that belonged to, in average, 20 botanical families. No Marantaceae pollen grain was found attached to the bodies of 50 Euglossini bees collected; therefore it is unlikely that they are efficient in pollen transportation for the studied species. Pollen analyses show that bees are generalist in collecting floral resources. However Marantaceae species are specialized in Euglossini species and their ability of tripping the style is important to the plants reproductive success. Pollen deposited on the stigma may come from other species if bees carry many heterospecific grains. Pollen limitation then may be one of the reasons for the low formation of fruits in the studied species. Third chapter enquires which factors influenced reproductive success and attraction of pollinators in Monotagma vaginatum and Ischnosiphon arouma. The number of pollinator visits, density of co-specific plants, number of flowers in bloom on the observed individual and luminosity were registered in the field. Frequency of visits from pollinators and luminosity were not variables that influenced fruit formation. Nutrients are, possibly, factors to influence reproductive success. Regarding attraction of pollinators, the number of individuals of Monotagma vaginatum and Ischnosiphon arouma and the number of flowers in bloom on these individuals were not factors that influenced frequency of visitors. Luminosity was a variable to influence the attraction of pollinators. Frequency of visits is not a fundamental factor for reproductive success for the species studied, but the pollinator’s effectiveness in transferring pollen in the first visit to the flowers. Pollen limitation and soil nutrients are, possibly, important resources for fruit formation in the studied species.