Bat-pollinated Plants Research Articles

A generalized pollination system in the tropics: bats, birds and Aphelandra acanthus

A number of different types of flower-visiting animals coexist in any given habitat. What evolutionary and ecological factors influence the subset of these that a given plant relies on for its pollination? Addressing this question requires a mechanistic understanding of the importance of different potential pollinators in terms of visitation rate (pollinator 'quantity') and effectiveness at transferring pollen (pollinator 'quality') is required. While bat-pollinated plants typically are highly specialized to bats, there are some instances of bat-pollinated plants that use other pollinators as well. These generalized exceptions tend to occur in habitats where bat 'quantity' is poor due to low or fluctuating bat densities. Aphelandra acanthus occurs in tropical cloud forests with relatively high densities of bat visitors, yet displays a mix of floral syndrome characteristics, suggesting adaptation to multiple types of pollinators. To understand its pollination system better, aspects of its floral phenology and the 'quantity' and 'quality' components of pollination by its floral visitors are studied here. Flowers were found to open and senesce throughout the day and night, although anther dehiscence was restricted to the late afternoon and night. Videotaping reveals that flowers are visited nocturnally by bats and moths, and diurnally by hummingbirds. Analysis of pollen deposition shows that bats regularly transfer large amounts of conspecific pollen, while hummingbirds occasionally transfer some pollen, and moths rarely do so. Hummingbirds and bats were comparable in terms of pollination 'quantity', while bats were the most effective in terms of 'quality'. Considering these components together, bats are responsible for approx. 70 % of A. acanthus pollination. However, bats also transferred remarkably large amounts of foreign pollen along with the conspecific grains (three of four grains were foreign). It is suggested that the negative effects of interspecific pollen transfer may decrease bat 'quality' for A. acanthus, and thus select for generalization on multiple pollinators instead of specialization on bats.

Effects of Sugar Composition and Concentration on Food Selection by Saussure's Long-nosed Bat (Leptonycteris curasoae) and the Long-tongued Bat (Glossophaga soricina)

In the Neotropics, bat-pollinated plants secrete relatively dilute nectars dominated by hexoses (glucose and fructose) with only small amounts of sucrose. We investigated the concentration and sugar composition preferences of Saussure's long-nosed bat (Leptonycteris curasoae) and the long-tongued bat (Glossophaga soricina) to test the hypothesis that bats prefer the predominant characteristics (sugar composition and concentration) found in their natural diets. We offered bats pairs of test diets in large outdoor enclosures that allowed free flying. We used artificial nectars that simulated compositions and concentrations found in flowers visited by these 2 species at the study site. Contrary to our predictions, bats showed no preference between sugar types when test solutions had the same concentration. However, L. curasoae preferred concentrated over dilute solutions independent of sugar type. Only 1 preference for concentrated over dilute solutions was recorded for G. soricina. Both species of bat appeared to perceive sugar types as energetically equivalent in most trials. Our study rejects the hypothesis that nectar-feeding neotropical bats act as a selective pressure on nectar composition in chiropterophilous plants. Other possible explanations for the predominance of hexose in chiropterophilous flowers need to be evaluated.

The power requirements (Glossophaginae: Phyllostomidae) in nectar-feeding bats for clinging to flowers

Nectar-feeding bats are the heaviest pollinators exploiting flowers in a hovering foraging mode. As hovering flight is considered to be energetically costly, clinging to flowers would be beneficial from an energetic perspective. I examined the rate of oxygen consumption and carbon dioxide release during clinging flower visitation in two 10-g Glossophaga soricina (Glossophinae: Phyllostomidae) to evaluate the potential energetic benefit of clinging versus hovering. In addition, I measured the duration of flower visits of free-ranging glossophagine bats to Markea neurantha (Solanaceae), a bat-pollinated plant that allows both hovering and clinging flower visitation. After 20 s of clinging to an artificial respiratory mask, the bats' respiratory exchange ratio did not significantly deviate from 1, indicating the combustion of sugar. The average oxygen uptake rate equaled 1.39 ml min(-1) (+/-0.38 SD, STPD) and the carbon dioxide release rate equaled 1.33 ml min(-1) (+/-0.20 SD, STPD) for feeder visits longer than 20 s (n = 79). Converting the oxygen uptake rate into power input yielded 0.49 W, less than a third of the power requirements for hovering for a 10-g bat. Free-ranging 10-g glossophagine bats exploited flowers of M. neurantha for, on average, 0.32 s (+/-0.14 SD, n = 273) during hovering and for 0.39 s (+/-0.18 SD, n = 152) during clinging visitations. A comparison between the power requirements of flower exploitation in differently sized bats indicates that clinging would benefit larger nectar-feeding bats to a greater extent than smaller species.

Floral scent of bat-pollinated species: West Africa vs. the New World

Floral scent of seven West African bat-pollinated tree species, belonging to six families, was collected in situ from flowering individuals using headspace adsorption. The seven species shared neither any specific compounds nor any other discernible pattern in their floral scent composition. Most of the identified compounds are common in the floral scent of species pollinated by a variety of animals. Adansonia digitata (Bombacaceae) was the only African species found to have a substantial proportion of sulphur compounds in its floral scent. This feature contrasts with the sampled New World bat-pollinated plants, which frequently contain these compounds. The floral scent of Ceiba pentandra (Bombacaceae), native to both South America and Africa, contained no sulphur substances, contradicting a previous study in the New World that identified the major floral compounds as dimethyl disulphide and dimethyl trisulphide. We suggest that the differences in the floral scent of C. pentandra, including the absence of sulphur compounds in the African variety, result from the different selective regimes exerted by the Pteropotidae bats, in Africa, and Phyllostomidae bats, in the New World, that visit their flowers. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82, 161–168.

Bat-pollinated Flower Assemblages and Bat Visitors at Two Atlantic Forest Sites in Brazil

A comparison between bat-pollinated plant assemblages at two sites in different altitudinal ranges covered by the Atlantic rainforest in southeastern Brazil is presented. The lowlands (5–90 m) harbour ten plant species in seven families, pollinated mostly by three glossophagine bat species. The highlands (1540–1600 m) harbour seven plant species in five families, pollinated by a single species of glossophagine. Bromeliads account for about 30% of the bat-pollinated species at each assemblage. Tube and brush shapes prevail in the flowers at both sites. Corolla lengths averaged 26.8 and 37.2 mm, sugar concentrations in nectar averaged 15.0 and 18.1%, and nectar volumes averaged 150.8 and 167.0 μl in the lowland and highland assemblages, respectively. The flowers are pollinated mostly by glossophagine bats during hovering visits, and the plants are visited in the trap-line foraging pattern. The plants bloom annually and both assemblages show a staggered continual flowering pattern. Flowering seasonality was found at both sites, with flowering clustering in the drier season at the lowland site and in the wetter season at the highland site. The ratio between bat-pollinated and hummingbird-pollinated species is 0.24 at the lowland site and 0.23 at the highland one. These similar values indicate that additional studies on bat- and bird-pollinated assemblages are merited at other Atlantic rainforest sites.

Floral Scent and Pollination in Browneopsis disepala (Leguminosae: Caesalpinioideae) in Western Ecuador

Aspects of the pollination ecology of Browneopsis disepala, including floral scent composition, were studied. Floral scent was collected with head space techniques and analyzed by coupled gas chromatography-mass spectrometry. Inflorescence and flower development were followed, and amount and concentration of nectar measured. Flower-visiting animals were observed nocturally and diurnally. Inflorescences of B. disepala emit a floral scent that is typical of neither moth- nor bat-pollinated plants, but contains some compounds related to both pollination types. Nectar is produced in quantities and with sugar concentrations falling within a range typical of both moth- and bat-pollinated plants. The inflorescences are visited by both moths and bats, but the behavior of the bats suggests that they are the more efficient pollinators. Browneopsis disepala has a mixed pollination system and is dependent on animals for pollination.

Headspace analysis of volatile flower scent constituents of bat-pollinated plants

The flower scents of 11 bat-pollinated plant species were investigated. GC and GC/MS analyses resulted in the identification of, among others, 11 sulphur containing compounds. The flower scents of 11 bat-pollinated plant species have been investigated using the ‘closed-loop-stripping’-adsorption technique. GC and GC/MS analyses of the headspace samples resulted in the identification of 49 compounds, comprising amongst others sulphur compounds, terpenoids and aliphatic compounds.

Headspace analysis of volatile flower scent constituents of bat-pollinated plants

The flower scents of 11 bat-pollinated plant species have been investigated using the ‘closed-loop-stripping’-adsorption technique. GC and GC/MS analyses of the headspace samples resulted in the identification of 49 compounds, comprising amongst others sulphur compounds, terpenoids and aliphatic compounds.

Floral scent in bat-pollinated plants: a case of convergent evolution

The chemical composition of floral scent in eight bat-pollinated species belonging to six different plant families was investigated. Floral scent was collected by headspace trapping using porous adsorbents and the chemical composition determined by coupled gas chromatography-mass spectrometry. In all species except one the floral scent was found to include sulphur-containing compounds, of which several are reported for the first time in floral scents. Three species contained mushroom-like smelling fatty acid derivatives with a C8-skeleton. Such flowers may be recognized by pollinators as humid environments in otherwise dry surroundings. The presence of similar or chemically closely related sulphur containing compounds in floral scent of bat-pollinated plant species from differing families may represent a case of convergent evolution in scent composition and an adaptation to attract this specific group of pollinators with similar sensory preferences.

Floral Nectary Structure and Nectar Composition in Eccremocarpus scaber (Bignoniaceae), a Hummingbird-Pollinated Plant of Central Chile

Surface features, anatomy, and ultrastructure of the floral nectary of Eccremocarpus scaber (Bignoniaceae), pollinated predominantly by the largest-known hummingbird (Patagona gigas gigas), were studied together with nectar sugar content and secretion rate. The annular disk nectary comprises epidermis, secretory and ground parenchyma with intercellular spaces, and branched vascular bundles terminating in the secretory parenchyma where only phloem is found. Amyloplasts and vacuoles increase in size throughout development, the latter becoming sites of organelle degradation. Transferlike cells in nectary phloem and P-proteinlike fibrillar material in phloem parenchyma were observed. Flowers produced around 32 μl of nectar (mostly after anthesis) with 11 mg of sugar composed of fructose, glucose, sucrose, and maltose in a ratio of 0.34:0.32:0.17:0.17. Morphological studies as well as the presence of maltose and glucose in nectar suggest storage of the originally phloem-derived sugars as starch with its subsequent hydrolysis. The low sucrose/hexose ratio (0.25) and high nectary secretion force (nectar per flower biomass) observed places E. scaber close to large-bodied bat-pollinated plants. A hypothesis based on nectar origin and nectar secretion is advanced to explain pollinator-correlated variation in sucrose/hexose ratio.

Floral Pigments and Nectar Constituents of Two Bat-Pollinated Plants: Coloration, Nutritional, and Energetic Considerations

Anthocyanin pigments and nectar constituents of Cheirostemon platanoides and Kigelia pinnata were analyzed in an effort to define provisionally a syndrome of floral phytochemical characters. Amounts and composition of sugar, protein, amino acid, and phenolic nectar constituents are presented. Genetic homology with related taxa appears to dominate over special adaptation to pollination by bats in determining floral pigments, but some evidence of adaptative change is present in nectar sugar composition. The contribution of nectar constituents to bat nutrition and energetics is discussed. THE EXISTENCE OF SYNDROMES of morphological characters associated with particular classes of pollinators is well documented. Recent evidence suggests that adaptively significant syndromes of phytochemical characters may also be associated with pollinator classes. Such studies have centered around floral pigments (Harborne and Smith 1978) and nectar constituents, especially sugars (Baker 1978). The existence of a morphological syndrome is well established (Faegri and Pijl 1966). This report provisionally defines a corresponding phytochemical bat syndrome. The taxa under investigation are Cheirostemon platanoides Humboldt and Bonpland (Chi ranthodendron pentadactylon Larreat.) (Sterculiaceae) and Kigelia pinnata DC. (Bignoniaceae). Cheirostemon is a monotypic genus native to montane cloud forests of southern Mexico and Guatemala. Kigelia consists of six species and is native to tropical Africa. Both of these taxa have been reported as classical bat-pollinated plants (Vogel 1958, Harris and Baker 1958). MATERIALS AND METHODS Nectar samples were taken from Cheirostemon platanoides plants cultivated at the Botanic Garden of the University of California at Los Angeles and from Kigelia pinnata cultivated at the Los Angeles State and County Arboretum. Samples were frozen and stored at -20 C until analysis. Corolla colors were determined by comparison with Royal Horticultural Society (London) Colour Chart standards. Corolla pigments were extracted into acidified methanol and purified by one-dimensional paper chromatography in BAW (BuOHHOAc-H20, 4:1:5). Pigments were identified by determining of Rf values with four solvents using standard methods (Harborne 1967). Total solids in nectar were determined in the field with a hand refractometer. Nectar sugar composition was determined by paper chromatography with appropriate standards using an ethyl acetatepyridine-water (12:4:5) solvent. Sugars were visualized using a benzidine spray, and subjective judgments of relative amounts were made on the basis of