To be or not to be fragrant: floral scent of some bat-pollinated cacti.

Floral scent is a key olfactory cue in both diurnal and nocturnal pollination systems. In the case of nocturnal systems, such as bat-pollinated flowers, odour seems to play a more important role than visual cues. Cactaceae include many bat-pollinated species; however, few studies have investigated the olfactory cues in this family. We analysed and compared the chemical composition of the floral bouquet of three chiropterophilous cactus species, among which are a pair of congeners that differ considerably in scent intensity. Our research presents novel findings regarding the floral scent chemistry of chiropterophilous cactus species. We documented the first case of a bat-pollinated cactus whose flowers lack perceptible floral scent and in which no volatile compounds were detected in our chemical analyses. Additionally, we provide a comprehensive analysis of the chemical composition of the floral bouquet of the other two bat-pollinated species, revealing a resemblance among closely related species within the same genus. We highlight the need for further studies using biotests to investigate the mechanisms through which bats find flowers lacking scent.

Pollination of the strongly scented Sarcoglottis acaulis (Orchidaceae) by male orchid bees: nectar as resource instead of perfume.

The Neotropical orchid genus Sarcoglottis comprises ~40 species, which emit strong floral scents, presumably involved in pollinator attraction. Information on basic aspects of its natural history is scant, with the few studies available so far pointing to nectar-seeking orchid bees as pollinators. Here, we investigated the reproductive biology of Sarcoglottis acaulis, addressing the ecological meaning of its floral scent. In Atlantic Forest fragments of NE Brazil, we described the floral biology, determined the breeding system and recorded the pollinators of S. acaulis. Additionally, we chemically characterized its floral scent and assessed its role on pollinator attraction. Although self-compatible, S. acaulis depends on pollinators to boost fruit set. Male orchid bees of Eulaema atleticana and E. niveofasciata were the only recorded pollinators. They foraged for nectar only, in spite of the strong scent emitted by S. acaulis flowers. The floral scent is composed of six compounds, of which geraniol and nerol elicited electroantennographic responses in Eulaema bees. A synthetic mixture of these compounds attracted Eulaema bees in field assays but did not trigger the stereotyped scent-gathering behaviour. The floral scent of S. acaulis acts in signalling and nectar is the sole reward for pollinators. Despite the low pollinator frequency, S. acaulis shows a high fruit set (77%), particularly when compared to other orchids. Attributes such as pollinia that release small pollen loads, allowing a single pollinia-carrying bee to pollinate several flowers, low amount of nectar, steady-state flowering and traplining behaviour of pollinators, might act together to assure this outstanding fruit set.

Reproductive biology of Syagrus coronata (Arecaceae): sex-biased insect visitation and the unusual case of scent emission by peduncular bracts.

Several monoecious species of palms have developed complex strategies to promote cross-pollination, including the production of large quantities of floral resources and the emission of scents that are attractive to pollinators. Syagrus coronata constitutes an interesting model with which to understand the evolution of plant reproductive strategies in a monoecious species adapted to seasonally dry forests. We monitored blooming phenology over 1 year, during which we also collected and identified floral visitors and putative pollinators. We identified potential floral visitor attractants by characterizing the scent composition of inflorescences as well as of peduncular bracts, during both male and female phases, and the potential for floral thermogenesis. Syagrus coronata produces floral resources throughout the year. Its inflorescences are predominantly visited by a diverse assortment of small-sized beetles, whose richness and abundance vary throughout the different phases of anthesis. We did not find evidence of floral thermogenesis. A total of 23 volatile compounds were identified in the scent emitted by the inflorescences, which did not differ between male and female phases; whereas the scent of the peduncular bracts was composed of only 4-methyl guaiacol, which was absent in inflorescences. The composition of floral scent chemistry indicates that this palm has evolved strategies to be predominantly pollinated by small-sized weevils. Our study provides rare evidence of a non-floral scent emitting structure involved in pollinator attraction, only the second such case specifically in palms. The peculiarities of the reproductive strategy of S. coronata might play an important role in the maintenance of pollination services and pollen dispersion.

Functional decoupling between flowers and leaves in the Ameroglossum pernambucense complex can facilitate local adaptation across a pollinator and climatic heterogeneous landscape.

Decoupling between floral and leaf traits is expected in plants with specialized pollination systems to assure a precise flower-pollinator fit, irrespective of leaf variation associated with environmental heterogeneity (functional modularity). Nonetheless, developmental interactions among floral traits also decouple flowers from leaves regardless of selection pressures (developmental modularity). We tested functional modularity in the hummingbird-pollinated flowers of the Ameroglossum pernambucense complex while controlling for developmental modularity. Using two functional traits responsible for flower-pollinator fit [floral tube length (TL) and anther-nectary distance (AN)], one floral trait not linked to pollination [sepal length (SL), control for developmental modularity] and one leaf trait [leaf length (LL)], we found evidence of flower functional modularity. Covariation between TL and AN was ca. two-fold higher than the covariation of either of these traits with sepal and leaf lengths, and variations in TL and AN, important for a precise flower-pollinator fit, were smaller than SL and LL variations. Furthermore, we show that previously reported among-population variation of flowers associated with local pollinator phenotypes was independent from SL and LL variations. These results suggest that TL and AN are functionally linked to fit pollinators and sufficiently decoupled from developmentally related floral traits (SL) and vegetative traits (LL). These results support previous evidences of population differentiation due to local adaptation in the A. pernambucense complex and shed light on the role of flower-leaf decoupling for local adaptation in species distributed across biotic and abiotic heterogeneous landscapes.

Multidimensional assessment of sustainability extractivism of mangrove oyster Crassostrea spp. in the estuary of Cananéia, São Paulo, Brazil.

This study was carried out with groups of extractivists of mangrove oysters in the estuary of Cananéia, São Paulo State, Brazil, between the years 1999 and 2007 with the objective to evaluate and compare trends in the sustainability of this activity, in a multidimensional and integrated way, in social, economic, ecological, technological and ethical dimensions, using the method RAPFISH. The different groups had distinct trends related to sustainability and the social, technological and ethical dimensions had more influence on trends in sustainability than the ecological and economic dimensions. The group with the best performance in the sustainability assessment was Mandira, due to advances promoted by local social organization. On the other hand, the Porto Cubatão group showed the worst performance, once this is very recent group in the extractivism of oysters. The RAPFISH proved to be a useful tool for data assessment.

Pollination syndromes in a Caatinga plant community in northeastern Brazil: seasonal availability of floral resources in different plant growth habits.

To describe plant phenological patterns and correlate functioning for the quantity and quality of resources available for the pollinator, it is crucial to understand the temporal dynamics of biological communities. In this way, the pollination syndromes of 46 species with different growth habits (trees, shrubs, herbs, and vines) were examined in an area of Caatinga vegetation, northeastern Brazil (7° 28' 45″ S and 36° 54' 18″ W), during two years. Flowering was monitored monthly in all the species, over two years (from January 2003 to December 2004). Pollination syndromes were characterised based on floral traits such as size, colour, morphology, symmetry, floral resources, as well as on direct visual observation of floral visitors on focal plants and published information. We observed differences among the plant growth habits with respect to floral traits, types of resources offered, and floral syndromes. The flowering periods of the species varied among floral syndrome groups. The majority of the melittophilous species flowered during the rainy season in the two study years, while the species of the other pollination syndroms flowered at the end of the dry season. An asynchrony of flowering was noted among the chiropterophilous species, while the phalenophilous group concentrated during the rainy season. The overall availability of floral resources was different during the rainy and the dry seasons, and also it varied among plants with different growth habits. The availability of oil-flowers coincided with the period of low nectar availability. We observed a relationship between the temporal distribution of the pollination syndromes and the availability of floral resources among each growth habits in this tropical ecosystem. Resource allocation in seasonal environments, such as the Caatinga, can function as a strategy for maintaining pollinators, facilitating therefore the reproductive success of plant species. The availability of floral resources during all the year, specially in seasonal environments such as the Caatinga, may function as a strategy to maintain pollinator populations ensuring the reproductive success of the plants.

High specialisation in the pollination system of Mandevilla tenuifolia (J.C. Mikan) Woodson (Apocynaceae) drives the effectiveness of butterflies as pollinators.

Butterfly pollination in the tropics is considered somewhat effective or solely effective in a few plant species. In the present study, we tested the hypothesis that Mandevilla tenuifolia (Apocynaceae), which has floral attributes associated with psychophily, has strategies adapted to pollination by butterflies, restricting other floral visitors and making these insects act as efficient pollinators. We analysed the floral and reproductive biology of M. tenuifolia, as well as the frequency and efficiency of its flower visitors. M. tenuifolia is an herb whose flowers have strong herkogamy and secondary pollen presentation on the style head, which corresponds to 60.4% of pollen on the anthers. Flower longevity and the long period of receptivity of the stigmatic region associated with the large amount of pollen removed in the first visits suggest that flowers remain functionally female during part of anthesis. Butterflies, mainly of the families Nymphalidae and Pieridae, are the only pollinators of M. tenuifolia. Despite being self-compatible, M. tenuifolia depends on biotic vectors for fruit production. A non-significant difference in fruit set between controlled treatments and natural conditions suggests that the pollinators are efficient. The inclination resulting from the landing of butterflies on flowers, together with flower morphology, guiding the insect proboscis inside the floral tube, as well as the frequency and efficiency of butterfly visits, are evidence of the close relationship between butterflies and M. tenuifolia, and also of the efficiency of these insects as pollinators.

Pollination and seed dispersal of Melocactus ernestii Vaupel subsp. ernestii (Cactaceae) by lizards: an example of double mutualism.

Recent studies show that the mutualistic role of lizards as pollinators and seed dispersers has been underestimated, with several ecological factors promoting such plant-animal interactions, especially on oceanic islands. Our aim is to provide a quantitative assessment of pollination and seed dispersal mutualisms with lizards in continental xeric habitats. We carried out focal observations of natural populations of Melocactus ernestii (Cactaceae) in the Caatinga, a Brazilian semiarid ecosystem, in order to record the frequency of visits, kind of resource searched and behaviour of visiting animals towards flowers and/or fruits. We made a new record of the lizard Tropidurus semitaeniatus foraging on flowers and fruits of M. ernestii. During the search for nectar, T. semitaeniatus contacted the reproductive structures of the flowers and transported pollen attached to its snout. Nectar production started at 14:00 h, with an average volume of 24.4 µl and an average concentration of solutes of 33%. Approximately 80% of the seeds of M. ernestii found in the faeces of T. semitaeniatus germinated under natural conditions. The roles of T. semitaeniatus as pollinator and seed disperser for M. ernestii show a clear relationship of double mutualism between two endemic species, which may result from the environmental conditions to which both species are subject. Seasonality, low water availability and arthropod supply in the environment, high local lizard densities, continuous nectar production by the flower and fruits with juicy pulp may be influencing the visits and, consequently, pollination and seed dispersal by lizards in this cactus.

Enantiostyly in Chamaecrista ramosa (Fabaceae-Caesalpinioideae): floral morphology, pollen transfer dynamics and breeding system.

Enantiostyly is a form of reciprocal herkogamy, in which floral morphs present reciprocal differences in the position of sexual elements, and occurs in monomorphic and dimorphic forms. This polymorphism maximises cross-pollination and reduces self-pollination, being very common within the subtribe Cassiinae (Fabaceae). Nevertheless, few studies have investigated the functionality of enantiostyly, particularly in this plant group. The present study aimed to investigate enantiostyly and its functionality in Chamaecrista ramosa, a monomorphic enantiostylous shrub, in an area of coastal vegetation in northeast Brazil. Pollen deposition and capture on the body of floral visitors, the relationship of these data with floral biology and breeding system, and morph ratio were evaluated. Pollen deposition and capture occurred in specific sites of the floral visitor body, showing the functionality of enantiostyly. The floral architecture, associated with the floral visitor behaviour, resulted in indirect pollen deposition on the floral visitor body. This occurred through a loop made by the pollen upon the inner petal surface, similar that generally reported for other Cassiinae. Chamaecrista ramosa is self-compatible, although no fruit set was observed through spontaneous self-pollination. The occurrence and number of floral morphs was similar within clumps. Enantiostyly seems to be advantageous for this species, as it results in efficient pollen capture and deposition, reduces the chances of autogamy and maximises intermorph pollen flow.

Nectar regulation in Euphorbia tithymaloides L., a hummingbird-pollinated Euphorbiaceae.

Floral sexual phases can differ in nectar production and might be under selective pressure by pollinators. We studied Euphorbia tithymaloides, which has inflorescences that are initially female and then hermaphroditic. Volume and concentration of nectar were measured in both stages. Nectar production and the effect of extractions were determined using sets of bagged inflorescences; inflorescences in the hermaphroditic phase had higher values of nectar concentration, volume and sugar mass than inflorescences in the female phase. Nectar resorption was detected in senescent inflorescences. To test for homeostatic nectar regulation, artificial nectar was added and the response assessed after 24 h. The experiments showed that concentration and sugar mass are regulated within a narrow range, and the homeostatic points differ between the two sexual phases. These differences in nectar can be detected by hummingbirds, which prefer the female stage. Resorption and secretion seem to be part of a homeostatic mechanism by which nectar attributes are maintained to optimise sugar recovery.

Flowering dynamics and pollination system of the sedge Rhynchospora ciliata (Vahl) Kükenth (Cyperaceae): does ambophily enhance its reproductive success?

Cyperaceae are characteristically anemophilous, but there are some reports of species re-adapted to entomophily, such as Rhynchospora ciliata. Our objective was to investigate: (1) the distribution pattern of flowers in inflorescences of Rhynchospora ciliata; (2) the dynamics of its anthesis; and (3) whether R. ciliata is pollinated by bees, by wind or by both. Additionally, we tested the hypotheses: (i) the hypsophylls and/or anthers attract pollinators, and (ii) biotic vectors enhance the reproductive success of R. ciliata. We analysed floral biology, dynamics of anthesis, frequency and behaviour of insects visiting flowers; we also carried out experiments on flower attractiveness, pollination by wind and reproductive success. Rhynchospora ciliata has flowers with anemophilous attributes, including anthers exposed during anthesis; however, the anthers (here considered a mixed trait) together with the white hypsophylls can be considered as attributes that favour entomophily. Both wind and four species of bee were considered as pollen vectors of R. ciliata. Through flower attractiveness tests, we observed that the hypsophylls do not affect the frequency of pollinating bees and that the absence of exposed anthers affects the average number of visits, probably because pollen is the only floral resource. Reproductive tests indicate that R. ciliata is self-incompatible and that ambophily enhances its reproductive success.

Mangrove oyster (Crassostrea spp.) (Sacco, 1897) extractivism in Cananéia estuary (São Paulo, Brazil) from 1999 to 2006: capture and management evaluation.

The oyster Crassostrea spp. is one of the main fisheries resources in the southern portion of São Paulo State. This paper aims to evaluate the extractivism of that resource, supplying subsidies to the implementation of management regulations. This study was developed in Cananéia, from February 1999 to December 2006. The oyster production data in dozens was obtained through weekly or monthly interviews. The annual and average CPUE in dozens per day was analysis to verify significant differences along years. There are no regulations that limit the fishing effort or organize the admission in the fishermen. The admission is controlled by the condition of the market and there is a risk of increasing the fishing effort above the sustainable yield, which demands measures that control the number of fishermen engaged in the activity. Those measures, to be effective, must be created in discussion with the fisheries sector, based on technical information.