Bark and latex harvesting short-term impact on native tree species reproduction.

The bark and the latex of plants constitute non-timber forest products (NTFPs) of medicinal and economic value that are widely harvested throughout the world. Bark and latex harvesting impacts on plant reproduction are controversial in the literature. Some species are negatively impacted, some do not show any response, and others may exhibit higher flower and fruit production after harvesting. In areas of rainforests and cerrado (tropical savanna) in northeastern Brazil, local people intensely remove the bark of Himatanthus drasticus (for latex collection) and Stryphnodendron rotundifolium for medicinal purposes. We aimed to investigate the short-term impact of harvesting upon reproductive effort of tree species, using those species as models. We assumed that bark harvesting negatively interferes in the reproductive capacity of plant species. Individuals of both species were harvested 2 months before blooming (treated) and the production of reproductive structures, physical characteristics of fruits and seeds, and the pre-emergent reproductive success were compared between treated and control (intact) individuals. All parameters of H. drasticus declined after bark removal, except pollen and ovule production. The only reproductive parameters of S. rotundifolium that were negatively affected were pollen and ovule production, and the pre-emergent reproductive success was higher in treatment individuals. We discuss the differences found between the species regarding responses to harvesting. Our results show that harvesting have short-term effects upon reproduction and may impair gene flow by affecting pollination and seed dispersal of tree species.

Floral polymorphism in Chamaecrista flexuosa (Fabaceae-Caesalpinioideae): a possible case of atypical enantiostyly?

BACKGROUND AND AIMS: Reciprocal herkogamy, including enantiostyly and heterostyly, involves reciprocity in the relative positions of the sexual elements within the flower. Such systems result in morphologically and, since pollen is deposited on and captured from different parts of the pollinator, functionally distinct floral forms. Deviations from the basic pattern may modify the functionality of these mechanisms. For heterostylous species, such deviations are generally related to environmental disturbances, pollination services and/or reduced numbers of one floral morph. Deviations for enantiostylous species have not yet been reported. This study aims to investigate enantiostyly in Chamaecrista flexuosa, in particular the presence of deviations from the standard form, in an area of coastal vegetation in north-east Brazil. METHODS: Observations and investigations of floral biology, the reproductive system, pollinator behaviour, floral morphology and morphometry were performed. KEY RESULTS: In C. flexuosa flowers, anthers of different size but similar function are grouped. The flowers were self-compatible and set fruits after every treatment, except in the spontaneous self-pollination experiment, thereby indicating their dependence on pollen vectors. The flowers were pollinated by bees, especially Xylocopa cearensis and X. grisencens. Pollen is deposited and captured from the ventral portion of the pollinator's body. Variations in the spatial arrangement of floral elements allowed for the identification of floral morphs based on both morphological and functional criteria. Using morphological criteria, morphologically right (MR) and morphologically left (ML) floral morphs were identified. Three floral morphs were identified using functional criteria: functionally right (FR), functionally central (FC) and functionally left (FL). Combinations of morphologically and functionally defined morphs did not occur in equal proportions. There was a reduced frequency of the MR-FR combination. CONCLUSIONS: The results indicate the occurrence of an atypical enantiostyly in C. flexuosa. This seems to improve reproductive success by increasing the efficiency of pollen deposition and capture.