Breeding biology and distyly in Palicourea rigida H. B. & K. (Rubiaceae) in the Cerrados of Central Brazil

Abstract

Distyly is a floral polymorphism more common among the Rubiaceae than in any other angiosperm group. Palicourea rigida is a typically distylous species of the Rubiaceae widely distributed in the Brazilian Cerrados. This work aimed to study the floral biology and breeding system of P. rigida in order to verify if there wasasymmetry between floral morphs. The work was carried out at Fazenda Água Limpa, Brasília-DF, from 1993 to 1995; and at Serra Caldas Novas State Park-Goias and in Clube Caça e Pesca Itororó de Uberlândia-Minas Gerais in 2005 and 2006. Density, height and pin/thrum ratio were assessed for flowering individuals in all areas. Plants were investigated for differences in floral morphology, nectar production, reproductive success and site of self incompatibility reactions. Blooming period was long and concentrated during the rains. Flowers were clearly distylous and with reciprocal herkogamy. They produced nectar and lasted for a single day. In spite of differences in density and height, populations were mostly isoplethic. Nectar production varied in volume and concentration but the differences could not be associated with floral morphs. The species is self-incompatible but reproductive success was always high and independent of floral morphs. There were differences in the site of incompatibility barriers between floral morphs, which were similar to those observed for other Rubiaceae. The main floral visitors and pollinators were the hummingbirds Colibri serrirostris and Eupetomena macroura. High fruit-set indicates that the pollinators transported enough compatible pollen grains between floral morphs, despite their territorial behavior.

Floral resource availability and hummingbird territorial behaviour on a Neotropical savanna shrub

“…Different letters indicate statistically significant differences (P \ 0.05) advantageous for the plant. Palicourea rigida is a selfincompatible species, which requires cross-pollination between thrum and pin plants (Machado et al 2010). Territorial behaviour may limit pollen flow to one or a few plants, but the intruders in richer patches may increase pollen flow and favour cross-pollination, bringing pollen from other patches (Feinsinger 1978;Franceschinelli and Bawa 2000).…”

“…In the Cerrado, Palicourea rigida produces flowers between October and February during the rainy season. It is an evergreen shrub, usually smaller than 3 m, and has characteristic large coriaceous leaves and yellow-red flowers in cimose terminal inflorescences (Machado et al 2010). The typically ornithophilous flowers are tubular (length 17-19 mm and width 3.3-4.5 mm), with a nectary disc on the top of the ovary, producing relatively small amounts of nectar (7-17 ll and 19-22% sugar content), which accumulates at the base of the slightly gibbous corollar tube (see Machado et al 2010 for complete morphological and reproductive assessment).…”

“…pin vs. thrum ratio around 1:1) and there are no marked differences in flower size, number and nectar production between floral morphs. Hummingbirds are the main pollinators of P. rigida, although bees and butterflies are often observed visiting its flowers (Machado et al 2010).…”

Atypical distyly in Psychotria goyazensis Mull. Arg. (Rubiaceae), an intramorph self-compatible species

“…Such ratios can also be observed among populations of the same species (Koch et al 2010;Consolaro et al 2011;Farias et al 2012), as well as in congeneric species (Consolaro et al 2009), although other species are relatively stable (e.g. Machado et al 2010). In P. goyazensis, we were unable to determine how widespread pin monomorphism is among its populations.…”

“…In recent decades, the number of studies on heterostyly and phenology of heterostylous species in the cerrado has been increasing (Monteiro et al 1991;Coelho & Barbosa 2003;Coelho & Barbosa 2004;Consolaro et al 2005;Toledo et al 2007;Lenza et al 2008;Oliveira 2008;Consolaro et al 2009;Machado et al 2010;Consolaro et al 2011) and could be compared to those conducted in the Atlantic Forest (Passos & Sazima 1995;Lopes & Buzato 2005;Castro & Oliveira 2002;Castro et al 2004;Teixeira & Machado 2004a, 2004bRossi et al 2005;Pereira et al 2006;Mendonça & Anjos 2006;Virillo et al 2007, Fonseca et al 2008. To increase understanding of the heterostyly system in the cerrado, this study aimed to investigate the phenology, distylous features, reproductive biology and fl oral visitors of Psychotria goyazensis Mull.…”