RESUMO
The aim of this work was to identify the pollination and dispersal systems among the species in a disjunct marginal cerrado area and to compare the frequency of these systems to those found in other Neotropical vegetation. The floral and diaspore traits and the pollination and dispersal systems of 176 species were analysed in a cerrado remnant in Southeastern Brazil. The most frequent pollination system was melittophily (63 percent of the studied species) with the remaining 37 percent distributed among diverse pollination systems. Zoochory was the predominant system of dispersal (44.9 percent). The frequencies of melittophily and zoochory observed in diverse tropical areas were the main feature that allowed the formation of distinct groups in the dendrograms generated by cluster analysis.
RESUMO
BACKGROUND AND AIMS: Bignoniaceae is a Neotropical family with >100 genera, only two of which, Jacaranda and Digomphia, have a developed staminode. Jacaranda oxyphylla, whose flowers possess a conspicuous glandular staminode, is a zoophilous cerrado species. Here, the composition of the secretion of the glandular trichome and the influence of the staminode on the pollination biology and reproductive success of J. oxyphylla were studied. METHODS: The floral morphology, pollen viability, stigma receptivity, nectar volume and nectar concentration were studied. Compatibility system experiments were performed and floral visitors were observed and identified. Experiments comparing the effect of staminode presence and absence on pollen removal and pollen deposition efficiency were conducted in open-pollinated flowers. Histochemistry, thin-layer chromatography (TLC) and gas chromatography coupled to flame ionization detection (GC-FID) analyses were performed to determine the main chemical components of the staminode's glandular trichome secretion. KEY RESULTS: Flower anthesis lasted 2 d and, despite the low frequency of flower visitation, pollination seemed to be effected mainly by medium-sized Eulaema nigrita and Bombus morio bees, by the small bee Exomalopsis fulvofasciata and occasionally by hummingbirds. Small bees belonging to the genera Ceratina, Augochlora and Trigona were frequent visitors, collecting pollen. Jacaranda oxyphylla is predominantly allogamous. Staminode removal resulted in fewer pollen grains deposited on stigmas but did not affect total pollen removal. The secretion of capitate glandular trichome occurs continually; the main chemical compounds detected histochemically were phenolic and terpenoid (essential oils and resins). Monoterpene cineole, pentacyclic triterpenes and steroids were identified by TLC and GC-FID. CONCLUSIONS: The staminode of J. oxyphyllla is multifunctional and its importance for female reproductive success was attributed mainly to the secretion produced by capitate glandular trichomes. This secretion is involved in complex chemical interactions with pollinating bees, including the solitary bees Euglossini. These bees are common pollinators of various species of Jacaranda.
Assuntos
Bignoniaceae/fisiologia , Pólen/fisiologia , Polinização/fisiologia , Animais , Bignoniaceae/anatomia & histologia , Bignoniaceae/citologia , Bignoniaceae/ultraestrutura , Brasil , Ecologia , Frutas/fisiologia , Insetos/fisiologia , Extratos Vegetais/metabolismo , Pólen/anatomia & histologia , Pólen/citologia , Pólen/ultraestrutura , Reprodução , Simbiose/fisiologia , Terpenos/metabolismoRESUMO
In order to evaluate the pollination strategies of Bignoniaceae, the floral biology and the floral visitors in five species, three cerrado shrubs (Arrabidaea brachypoda (DC.) Bor., Jacaranda decurrens Cham., and Jacaranda oxyphylla Cham.), and two lianas from the border of a semideciduous seasonal forest (Arrabidaea samydoides (Cham.) Sandw., and Arrabidaea triplinervia H. Baill.) were studied in Botucatu, São Paulo State, Southeastern Brazil. The flowering periods were partially overlapping, especially between species in the same habitat. All the five species were functionally allogamous, melittophilous, nototribic and mainly pollinated by long tongued large bees. Some medium-sized and small pollen-foraging bees were occasional legitimate visitors, whereas others visitors were robbers/thieves. Each species showed a particular set of pollinators. Only two pollinator species were observed in more than one bignon. There was no partition of pollinators even among the species of bignons blooming at the same time at the same habitat.
Com objetivo de avaliar as estratégias de polinização de espécies de Bignoniaceae, foram estudados a biologia floral e os visitantes florais de cinco espécies, três arbustivas do cerrado (Arrabidaea brachypoda (DC.) Bor., Jacaranda decurrens Cham. e Jacaranda oxyphylla Cham.) e duas lianas da orla da floresta estacional semidecidual (Arrabidaea samydoides (Cham.) Sandw. e Arrabidaea triplinervia H. Baill.), na região de Botucatu (22º52'20" S e 48(0)26'37" W), estado de São Paulo, sudeste do Brasil. Os períodos de florescimento, principalmente entre espécies do mesmo habitat, apresentaram sobreposição parcial. Observou-se que as cinco espécies são alogâmicas funcionais, melitófilas, nototríbicas, polinizadas principalmente por abelhas grandes de língua comprida. Algumas abelhas coletoras de pólen de tamanho médio e pequeno atuaram como polinizadoras ocasionais, enquanto outros visitantes foram pilhadores. Cada uma das Bignoniaceae apresentou um conjunto particular de polinizadores havendo apenas duas espécies comuns a mais de uma delas. Não houve partilha de polinizadores mesmo entre bignoniáceas que, no mesmo habitat, apresentaram períodos de florescimento simultâneo.