Pollination Biology of Distylous Rubiaceae in the Atlantic Rain Forest, SE Brazil

Abstract

Data on pollination biology constitute important clues for the comprehension of pollen flow and genetic differentiation in plant populations. Pollinator type, availability and behaviour may modify morphological and mating patterns in populations of typically distylous species. This study investigates the pollination biology of four distylous species of Rubiaceae in the Atlantic rain forest, SE Brazil. Data on flowering phenology, floral lifespan, stigmatic receptivity, pollen availability, nectar volume and concentration, and pollinator activity were collected. The species studied flower sequentially throughout the wet season, and produce terminal inflorescences which bear small, tubular, diurnal, nectariferous flowers. Despite these similarities, some of the species studied are pollinated by different groups of pollinators, probably due to their distribution, availability of flowers and corolla length. On the other hand, pollinator specificity does not seem to be so important for distylous species. Long mouthparts, like those of most of the recorded pollinators, may reach lower sexual organs and, together with the self-and intramorph-incompatibilities observed, be sufficient to perform legitimate pollination and maintain levels of intermorph mating.

Distyly and variation in floral traits in natural populations of Psychotria ipecacuanha (Brot.) Stokes (Rubiaceae)

“…Some of these variant systems are reported in Rubiaceae. Selfand within-morph compatibility was reported in Palicourea padifolia (Ree 1997) and in Psychotria jasminoides (Castro & Oliveira 2002). Low fruit set following self-and illegitimate pollination was also observed by several authors (Bawa & Beach 1983, Sobrevila et al 1983, Barrett & Shore 1987, Castro & Araújo 2004, which suggest that the heteromorphic incompatibility system of some heterostylous Rubiaceae is not strict.…”

“…Moreover, corolla length may not differ between floral morphs, as reported in several Psychotria species: P. jasminoides, P. birotula L.B.Sm. & Downs, and P. pubigera (Castro & Oliveira 2002) and P. barbiflora DC. (Monteiro et al 1991).…”

“…Fruit production after agamospermy suggests the possibility that this strategy is used by P. ipecacuanha. Although infrequent in Rubiaceae, agamospermy has been recorded in other congeneric species, such as Psychotria birotula and P. nuda (Castro & Araújo 2004, Castro & Oliveira 2002. However, the floral arrangement exhibited by P. ipecacuanha makes the isolation of a flower bud difficult and there is a possibility that pollen grains may have fallen into stigmas during flower manipulation.…”

Variação floral e biologia reprodutiva de Manettia cordifolia Mart. (Rubiaceae)

“…& Downs e P. pubigera Schlecht. foram mais freqüentes do que flores brevistilas, indicando uma assimetria no fluxo do pólen em direção ao morfo longistílico (Castro & Oliveira 2002). Alterações na proporção de transferência de grãos de pólen e prevalência no estabelecimento de um morfo podem estar associados também a distúrbios ecológicos na área em que se encontra a espécie, tais como perturbação ambiental, isolamento geográfico, interação com polinizadores e variações nas características florais (Sobrevila et al 1983, Endels et al 2002.…”

“…Suas flores tubulares favorecem visitantes com aparelho bucal longo, sendo mais comumente polinizadas por borboletas e abelhas com probóscide longa (Taylor 1996, Stone 1996, Ortiz et al 2000, Castro & Oliveira 2002 ou freqüentemente por mariposas (Imbert & Richards 1993, Wolff et al 2003 e moscas (Riveros et al 1995, Ortiz et al 2000. Trabalhos mostrando visitas de beija-flores em espécies de Rubiaceae são comuns, como registrado para Psychotria, Manettia, Palicourea, Cephaelis, Hamelia e Ferdinandusa (Bawa & Beach 1983, Snow & Snow 1986, Feinsinger & Busby 1987, Passos & Sazima 1995, Castro & Oliveira 2001.…”