Pollination ecology of the tropical weed Triumfetta semitriloba Jacq. (Tiliaceae), in the South-eastern Brazil

Abstract

This work aimed to study the pollination ecology of the tropical weed Triumfetta semitriloba Jacq. (Tiliaceae), in Viçosa, South-eastern Brazil, during the flowering season of 1993 and 1994. Two patches located in pasture (P1 and P2) and one patch in a forest trail (P3) were chosen and ten plants on each patch were sorted. The number of opened flowers were counted during one day, in each flowering month and patch. All observed flower visitors were identified and their behavior while visiting flowers was recorded. Frequency of visits to flowered branches was obtained and some pollinator individuals were captured for analysis of pollen load. Flowers are conspicuously yellow and actinomorphic, with five nectaries around the ovary base, and opened sequentially in the afternoon. Flower phenology followed a modified steady-state Gentry's pattern. The number of opened flowers was higher in P2, but differences between months were not homogeneous between patches. Considering behaviour when collecting pollen or nectar, which permitted impregnation of stigma with pollen, visiting frequency and percent of T. semitriloba pollen on pollen load (100% for all of them, except for Augochlorella michaelis which was 81%) the following species were the mainly pollinators: Augochloropsis cupreola, Augochlorella michaelis, Cressomiella aff. sussurans, Cressomiella sussurans, Cressomiella sp., Pseudocentron paulistana, Ceratinula sp1, Ceratinula sp2 and Ceratinula sp3, Melissodes sexcincta, Apis mellifera, Plebeia cf. nigriceps, Plebeia droryana. Frequency of pollinators visitation was not different between patches and not uniform during anthesis. There was a higher pollinator activity between 15:00 and 17:00 hr.Key words: pollination, Triumfetta semitriloba, Tiliaceae, tropical bees, weed. RESUMOEcologia da Polinização da Planta Invasora, Triumfetta semitriloba Jacq. (Tiliaceae), no sudeste do Brasil Este trabalho tem por objetivo estudar a ecologia da polinização da planta invasora Triumfetta semitriloba Jacq. (Tiliaceae), em Viçosa, MG, Brasil, durante a estação de floração de 1993 e 1994. Foram escolhidas duas manchas de plantas localizadas em pastos abandonados (P1 e P2) e uma mancha em clareira de mata (P3). Dez plantas, em cada mancha, foram sorteadas. Durante um dia de cada mês de floração foi contado o número de flores abertas por planta. Todos os visitantes florais foram identificados e registrado o comportamento. Foi obtida a freqüência de visitas aos ramos floridos e alguns polinizadores foram coletados para análise da carga de pólen. As flores de T. semitriloba são actinomórficas com cinco nectários em torno da base do ovário, e abrem, seqüencialmente, no período da tarde. A fenologia floral seguiu o padrão "steady-state" modificado de Gentry. O número de flores abertas foi maior em P2, mas as diferenças entre meses não foram homogêneas entre as manchas.

Foraging behavior of bee pollinators on the tropical weed Triumfetta semitriloba: flight distance and directionality

“…Flowers open sequentially and the number of flowers per individual plant increases until 16 h. As flowers opened pollen-collecting bees depleted pollen resource with a low number of visits, as flower availability is low (Collevatti, 1998). As described by Collevatti (1998), flower opening pattern (sequential) and depletion of pollen by bee pollinators visiting may cause a patchy distribution of resource, with hot spots of justopened or non-visited flowers, with high level of pollen, and cold spots of already-visited flowers, with little or no pollen. This pattern of resource Thus, the maintenance of directionality, with high frequency of turning associated with an encounter of a hot spot, may be the best strategy for all patches.…”

“…In Viçosa, southeastern Brazil, flowering season occurs in autumn (March to May), and flowers open in the afternoon. Flowering phenology approaches a modified steady-state pattern, with many flowers per plant opening every day during all flowering season (Collevatti, 1998). Despite the existence of five floral nectaries around the ovary base, nectar secretion rate is negligible and pollinators visited the flowers mainly for pollen collection.…”

“…However, many small bees and other insects visit the flowers eventually for nectar collection. Flower visitors are mainly solitary bee species, although social bees, beetles, flies, bugs and butterflies have also been recorded (Collevatti, 1998).…”

Ontogenia dos nectários extraflorais de Triumfetta semitriloba (tiliaceae)

“…O gênero ocorre em toda a América tropical, e a família tem como centro de dispersão o Brasil e a África (Barroso, 1978). Collevatti et al (1997Collevatti et al ( , 1998, estudando o comportamento de forrageamento de visitantes florais em T. semitriloba, verificaram que os principais agentes polinizadores são abelhas e que o pólen é o principal recurso procurado, embora algumas espécies visitem as flores, principalmente à procura de néctar.…”

Reproductive Ecology of Birdville Indigo, Indigofera Linnaei Ali. (Fabaceae)

“…But, lack of knowledge on the biology and ecology of herbaceous weeds and their adaptation to environmental stress is a drawback to use them in the reforestation programs in order to counteract the effects of degraded sites where soil water is a major limiting factor in the growth, species composition and distribution of species. Collevatti et al (1998) stated that the knowledge of invertebrates and their interactions with native plants should be included in designing restoration programs and in ecological resilience. In this context, the herbaceous species of Indigofera assume importance since they normally grow as minor or major invasive weeds.…”