Reproductive Biology of Tropical Lowland Rain Forest Trees. I. Sexual Systems and Incompatibility Mechanisms

Abstract

Sexual systems of tropical lowland rain forest trees were investigated to estimate the relative proportions of hermaphroditic, monoecious, and dioecious species. Controlled hand pollinations were performed on hermaphroditic species to determine the proportions of self‐compatible and self‐incompatible species. A total of 333 species was examined; 65.5% species were found to be hermaphroditic, 11.4% monoecious, and 23.1% dioecious. There were no differences between canopy and subcanopy habitats in the distribution of various sexual systems. Out of the 28 species subjected to controlled pollinations, 24 showed the presence of self‐incompatibility. The site of the incompatibility barrier in distylous species was either in the stigma or in the style. In most of the monomorphic species, the incompatibility barrier was in the ovary. Although a majority of tree species in the rain forest appear to be obligate outcrossers (xenogamons), the potential for inbreeding due to small effective population size still remains to be explored.

Plant sexual systems, dichogamy, and herkogamy in the Venezuelan Central Plain

“…Vegetation changes from an open to a close bush savanna-forest were observed during 20 years in the VCP (San Jose´and Farin˜as, 1983). Dioecy has been considered as characteristic of later stages of succession and primary forests (Bawa et al, 1985;Oliveira, 1996;Opler et al, 1980); this agrees with the results of this study. On the other hand, monoecy represents the sexual condition promoting cross-pollination in early successional stages.…”

“…This period includes all life forms in the studied area (Ramı´rez, 2002). In contrast, flowering of tree species peaks during the dry season in the Venezuelean Central Plain (VCP, Ramı´rez, 2002), and dioecious species are often woody (Bawa and Opler, 1975;Bawa et al, 1985;Bullock, 1985;Fox, 1985; and many others). Therefore, dioecy could be expected to be an important sexual system during the dry season.…”

Diet and Feeding Ecology of Ateles chamek in a Bolivian Semihumid Forest: The Importance of Ficus as a Staple Food Resource

“…We calculated species-specific basal area values as a mean for the entire home range, averaging across the 3 vegetation types according to their relative contribution. For dioecious tree species, such as Pseudolmedia laevis and 25 other species in the study area (Bawa and Krugman 1991;Bawa et al 1985;Justiniano et al 2003;Kubitzki and Kurz 1984;Mostacedo et al 2003;Ressell et al 2004), we assumed that half of the trees were female and produced fruit, per Fredericksen et al (1999). For trees, we calculated a monthly index T:…”

Fruiting phenology in a tropical dry evergreen forest on the Coromandel coast of India in relation to plant life-forms, physiognomic groups, dispersal modes, and climatic constraints

“…They include abiotic factors such as precipitation, temperature, number of dry months and photoperiod (Frankie et al, 1974;Leigh and Windsor, 1982;Opler et al, 1976;Prasad and Hegde, 1986;Reich and Borchert, 1984;Van Schaik et al, 1993;Wright and Van Schaik, 1994); seed dispersers and predators (Ashton et al, 1988;Foster, 1982; Gautier-Hion, 1991;Janzen, 1967;Snow, 1965;Wheelwright, 1985); favourable seed germination conditions (Garwood, 1983;Primack, 1987) and phylogenetic relationship hypothesis (Gorchov, 1990;Kochmer and Handel, 1986;Martin-Gajardo and Morellato, 2003;Poulin et al, 1999;Smith-Ramı´rez et al, 1998). At the same instant plant life-history characters or ecological traits have been proposed to affect the fruiting phenology including life form (Marques et al, 2004;Ramı´rez, 2002;Sarmiento and Monasterio, 1983), plant physiognomic groups (Bhat, 1992;Funch et al, 2002;Williams et al, 1999), forest structure (Newstrom et al, 1994;Shukla and Ramakrishnan, 1982), dispersal modes (Griz and Machado, 2001;Smythe, 1970;Snow, 1965) and plant sexual systems (Bawa et al, 1985;Kang and Bawa, 2003;Ramı´rez, 2005). These studies have warranted that the variation in fruiting patterns may be associated with the categories of different ecological traits.…”