The role of nectar production, flower pigments and odour in the pollination of four species of Passiflora (Passifloraceae) in south-eastern Brazil

The pollination biology of four species of passionflower was studied in south-eastern Brazil, specifically the importance of chemical features of floral nectar, pigments and odours. All species required pollinators to produce fruits: P. alata was pollinated by bees, P. speciosa by hummingbirds, and P. galbana and P. mucronata by bats. Pollinators consumed nectar as a food source. The activity of vertebrate pollinators reflected resource availability: they foraged when large amounts of nectar were available and when quantitative resource predictability was greater. The nectar of the vertebrate-pollinated species was richer in cholesterol and phospholipids, and had a potassium-sodium ratio higher than 1.0. For all species, the light absorption of flowers was paralleled by the pollinators' visual spectral sensitivity. This first report on Passiflora floral volatile compounds showed that there was a greater chemical class diversity among the species pollinated by animals with an acute olfactory sense, such as bees and bats. Benzenoid alcohols were the most represented compounds. The fragrances contained compounds that occur in other plant species and in the exocrine secretions of bees. This study shows a strong association between pollinators and the attracting and rewarding features of flowers.     

Seasonal variation of tadpole spatial niches in permanent streams: The roles of predation risk and microhabitat availability

Phenotypic plasticity can improve fitness in unstable environments and can be expressed in many traits, such as life history attributes, growth and behavioural features. Microhabitat choice can have important consequences for development and survival of aquatic organisms and is expected to vary in response to stimuli, such as predation risk, food availability and temperature. At seasonal sites, microhabitat availability and associated benefits may change from season to season, which might lead to altered patterns of microhabitat use by tadpoles. We investigated this hypothesis in 17 streams from two localities in south‐eastern Brazil. We tested whether water level drops significantly during the dry season, whether lower water level results in altered microhabitat availability and whether predation risk changes between seasons, based on predator density. We then tested whether tadpoles change their pattern of microhabitat use, their spatial niche breadth (given by diversity of used microhabitats) and spatial niche overlap (in the case of co‐occurring species). We were able to include in our analyses tadpoles of four species of Hylidae, that occurred throughout both seasons. Stream depth decreased in the dry season, but microhabitat availability remained relatively stable in many streams, and predator density did not change significantly. Tadpoles of three out of the four species studied were more abundant during the dry season, which may be an adaptation to adjust time of metamorphosis to the rainy season. Tadpoles changed their patterns of microhabitat use between seasons, although the potential causing factors investigated did not seem to be responsible. Tadpole plasticity in microhabitat use may indicate the existence of selective pressures that vary through time and space and are still not well understood.     

Breeding system and thrips (Thysanoptera) pollination in the endangered tree Ocotea porosa (Lauraceae): implications for conservation

Ocotea porosa has been extensively exploited over the past few decades because of the quality of its wood. Today, populations are reduced and the species is now included in the Red List of threatened species by the International Union for Nature Conservation. For conservation and management purposes, it is extremely important that we understand its reproductive ecology. Floral morphology was described based on field and scanning electron microscopic examination. The reproductive system was determined through experimentally controlled pollination along with observations of pollen tube growth. Pollinators were identified through field observations. Flowers of O. porosa are small, shallow, inconspicuous, asynchronous and grouped in inflorescences. This species presented self‐compatibility, but did not reproduce through apomixy and spontaneous self‐pollination was very rare (5%). Despite being monoclinal, flowers were protogynic, and the gynoecium was receptive after the first day of anthesis when the anthers were closed. Spontaneous self‐pollination was avoided by the extrorse position of the anthers of the internal stamens. Frankliniella gardeniae (Thysanoptera) was the only pollinating species observed and, after visiting several asynchronous flowers in the same inflorescence, favors geitonogamy. Together the small distance supposedly achieved by thrips in flight and the small population density of O. porosa can reduce the chances of cross‐pollination in this species. If so, conservation measures must include preservation of the current population and possibly planting to increase population density. This would reduce the distance between individuals and increase genetic variability. Thrips as pollinators must be included in conservation planning for O. porosa.