Biologia reprodutiva de Tilesia baccata (L.) Pruski (Heliantheae, Asteraceae): fenologia, polinização e dispersão

• Autor(a) principal: Fonseca, Rúbia Santos
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2507
• topic: Floresta Atlântica; Tilesia baccata; Reprodução; Atlantic forest; Tilesia baccata; Reproductive biology; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA

Tilesia baccata (L.) Pruski is the only species of the Asteraceae family with fruit consumed and seeds dispersed by birds in the neotropics. However, no studies are available concerning the reproductive aspects of this species. Thus, this work aimed to study the phenology, reproductive system, pollination and dispersion of T. baccata in a natural population located in a semidecidual seasonal forest fragment, known as Mata do Paraíso (20°45 S and 42°54 W), in Viçosa-MG. From August 2007 to August 2008, 15 individuals were marked for their phenological monitoring and observed for their flower and capitulum biology, reproductive system, pollination and dispersion. The phenological events were recorded monthly, for the vegetative phenophases (leaf flushing, young leaves, adult leaves, leaf fall), and weekly, for the reproductive phenophases (floral buds, flowering, immature fruit and mature fruit). To characterize the dynamics of the flower and capitulum biology, 20 inflorescences were monitored and their events recorded for anthesis of the first florets until dispersion of the diaspores. The following reproductive tests were conducted: manual self- pollination, agamospermy, cross-pollination, and open pollination (control) at the beginning and peak of flowering. The floral visitors and visitation frequency were assessed during flowering peak. Visitors that contacted the reproductive organs of the florets were considered pollinators. To assess seed dispersing birds, individuals of T. baccata were monitored to record all the animal species that fed on their fruit. Tilesia baccata presents phenological cycles adjusted to climate seasonality, influenced mainly by rainfall and temperature. Leaf fall occurs during the dry season while leaf flushing, and young and adult leaves are observed throughout the year, but at concentrated peaks; the reproductive phenophases, except fructification, are restricted to the rainy season; fructification, in turn, occurs between the rainy and dry season. Phenophases, except for the mature fruit, presented a high synchrony of expression, extremely important for species reproduction. Anthesis and senescence of the disc florets occur in centripetal sequences. During fructification, the capitulum undergoes several changes that allow fruit dispersion, such as: alterations from plane to convex receptacles, from yellow to orange-ish paleas, and fruit growth, with fruit becoming mature and apt to disperse at 55 days. The tubulous florets Tilesia baccata are matutinal and protandric. The secondary presentation of the pollen grains occurs in the first day of anthesis, between 10:00 am and 12:00 am, finalizing the staminate phase; the pistillate phase initiates at 2:00 pm on the same day, with the partial exposure of the stigmatic bands, and finalizes at the moment of flower senescence. This species is self- incompatible, non- agamospermic, and thus, dependent on pollinators for fruit production and maintenance of natural population. The floral visitors of T. baccata were 29 insect species, distributed among the orders Hymenoptera (13), Lepidoptera (12), Diptera (2), Coleoptera (1) and Orthoptera (1). Tilesia baccata is melittophilous and was pollinated mainly by Apis mellifera, Melipona quadrifasciata and Trigona spinipes, which, together, accounted for 76.52% of the visits. The fruit of T. baccata are consumed by six bird species belonging to four families, which were observed removing and swallowing (passeriformes; dispersers) or pecking at (trochilid; pulp eater) the fruit. The facultative frugivory species Basileuterus culicivorus, Tangara cayana and Tachyphonus coronatus are the most frequent birds, responsible for 77.4% of the visits, indicating that in fragmented environments, where alterations in the plant and animal communities occur, opportunistic birds can play an important role in the survival of ornithocoric plant species, regarding food acquisition. The results obtained in this work show that Tilesia baccata is a source of pollen and nectar for the floral visitors during the rainy season and a source of fruit for facultative frugivory species between the rainy and dry seasons.