Biologia reprodutiva de Melocactus glaucescens Buining & Brederoo e M. paucispinus G. Heimen & R. Paul (Cactaceae), na Chapada Diamantina, Nordeste do Brasil

Abstract

-(Reproductive biology of Melocactus glaucescens Buining & Brederoo and M. paucispinus G. Heimen & R. Paul (Cactaceae), in the Chapada Diamantina, northeastern Brazil). The reproductive biology of Melocactus glaucescens and M. paucispinus (Cactaceae) was studied in the municipality of Morro do Chapéu, Chapada Diamantina, Bahia State, comprising the phenology, floral biology, pollination and mating system of the species. It was recorded flowering and fruiting periods, flower visitors, frequency and kind of visits, and the strategy and behavior of the visitors on the flowers. Experimental pollinations were carried out to determine the mating systems of the species. The flowering period of both Melocactus species overlapped during the study period. The floral characteristics of the species are typical of ornithophily: showy colors, tubular structure, and nectar with low concentration of solutes, between 20% and 30%. The hummingbird Chlorostilbon aureoventris Boucier & Mulsant (1948) was the most frequent flower visitor, performing 82% and 89% of the visits in M. paucispinus and M. glaucescens, respectively. Other hummingbird and butterfly species also visited the flowers of both species. The overlap in the flowering period and the similarity in the guild of pollinators of those and other sympatric species of Melocactus favour the occurrence of hybridization, as it has been observed in that area. Melocactus glaucescens presented self-incompatibility and allogamy. Conversely, M. paucispinus is self-compatible and autogamous, however presenting lower fruit set in selfing than in outcrossing, possibly due to the occurrence of inbreeding depression.

Reproductive phenology of Melocactus (Cactaceae) species from Chapada Diamantina, Bahia, Brazil

“…Both males and females of Chlorostilbon aureoventris Boucier & Mulsant (1948) (a hummingbird) are the main pollinators of M. glaucescens in the study area, and were also observed visiting individuals of M. ernestii and M. ×albicephalus in the study area (Colaço et al 2006). The degree of flowering overlap observed between M. glaucescens and M. ernestii and between these two species and M. ×albicephalus suggests that competition for pollinators may not have been sufficiently strong through the evolutionary history of these populations to establish a separation of their flowering periods.…”

“…Long-term flowering (essentially continuous throughout the year in M. glaucescens and M. ×albicephalus, and for numerous months in M. ernestii) with just a few flowers opening each day can minimize intra-and interspecific competition. This reproductive strategy requires the movement of pollinators between individuals, thus increasing the probability of co-specific cross pollination (Locatelli & Machado 1999) and consequently increased reproductive success, principally in self-incompatible and allogamic species, as is the case with M. glaucescens (Colaço et al 2006). This same behavior, however, will also tend to favor hybridization between compatible sympatric species flowering at similar times.…”

“…Flowering displacement that avoids overlapping among sympatric species is an important pre-zygotic isolation mechanism, preventing interspecific hybridization and maintaining species integrity (Stace 1992, Levin 2000. This is particularly important among species demonstrating very similar flower morphology and that share pollinators, as observed in the genus Melocactus (Locatelli & Machado 1999, Nassar & Ramírez 2004, Colaço et al 2006. Phenological research at the population level in tropical regions has been expanding, although few references are found for the genus Melocactus.…”

Fenologia reprodutiva de Prepusa montana Mart. (Gentianaceae) em uma área de campo rupestre da Chapada Diamantina, BA, Brasil

“…Ramos (2005), Colaço et al (2006) e Costa et al (2007) também registraram, nas espécies de plantas de campo rupestre que estudaram na Chapada Diamantina, uma maior produção de flores na estação seca; Machado et al (2007) observaram, na mesma área do presente estudo, que cerca de 50% da comunidade de plantas visitadas por beija-flores, floresce neste período.…”

Beija-flores (Aves: Trochilidae) e seus recursos florais em uma área de caatinga da Chapada Diamantina, Bahia, Brasil

“…MACHADO & SAZIMA 1995, MACHADO & LOPES 2002, 2004, LEAL et al 2006, COLAÇO et al 2006, MACHADO et al 2007. Na Chapada Diamantina, porção norte da Cadeia do Espinhaço, no Estado da Bahia, apesar da riqueza de tipos vegetacionais, da grande diversidade e do elevado endemismo de espécies vegetais (GIULIETTI et al 1997, JUNCÁ et al 2005, as investigações sobre este tipo de interação somente foram conduzidas em áreas de campo rupestre (COLAÇO et al 2006, MACHADO et al 2007.…”