Amino acid uptake and profile in bromeliads with different habits cultivated in vitro

Bromeliads can have terrestrial and epiphytic habits. Therefore, they have developed probably different mechanisms for the uptake of nutrients from distinct sources such as the pedosphere and the atmosphere. Many bromeliads, such as the epiphytes, absorb water and nutrients almost exclusively via their foliar trichomes. In contrast, terrestrial bromeliads essentially use their roots to withdraw the nutrients from the soil. The aim of this study was to compare nitrogen (N) nutrition between a terrestrial, Ananas comosus (L.) Merr., and an epiphytic, Vriesea gigantea Gaudich., bromeliad. The in vitro absorption of [³H]glycine and [³H]glutamine was investigated. Plants were also grown in vitro with NH₄⁺, glutamine (Gln) or glycine (Gly) as N sources, and the amino acid profile was analyzed. Ammonium treatment had little effect upon the A. comosus amino acid profile, while asparagine was the main amino acid accumulated in V. gigantea after 3 d in a medium with this nitrogen source. This suggests that V. gigantea accumulate N in compounds with high N/C ratio, allowing it to store higher N level when it is available in epiphytic environment. The two species were able to take up amino acids in vitro, although V. gigantea had a higher rate of amino acid uptake than the terrestrial bromeliad, A. comosus. For both species, Gly was taken up in a higher rate than Gln. The data support the idea that V. gigantea has a luxury consumption when inorganic and organic N are available in the environment, which does not happen in the case of the terrestrial bromeliad A. comosus. It has a more stable source of nutrients, the soil. We can also suggest that amino acids such as Gly, Gln and others present in the bromeliad tank water may be important N sources for V. gigantea and other epiphytic bromeliads in natural habitats.     

Ammonium and urea as nitrogen sources for bromeliads

Epiphytic bromeliads have no contact with the pedosphere, so they need to draw their nutrients from the atmosphere as well as from the host tree and animal debris. Terrestrial bromeliads, like Ananas comosus, generally depend on the soil as their main nutrient source. The aim of this study was to investigate and compare some aspects of the nitrogen metabolism of two bromeliads with different growth habits: Ananas comosus, a terrestrial bromeliad, and Vriesea gigantea, an epiphytic tank bromeliad. Nitrogen-starved plants were grown in vitro for 3, 7, 15, 30, and 60 days, either with 5 mmol L⁻¹ ammonium [(NH₄)₂SO₄] or urea as the sole nitrogen source. When NH₄⁺ was supplied to the plants, it stimulated a faster increase of chlorophyll content in A. comosus than in V. gigantea. In the presence of urea, after 15 days of the plants in culture, there was a significant increase in tissue free-NH₄⁺ and total amino acids for V. gigantea only. V. gigantea presented a higher level of total free amino acids than A. comosus when nitrogen was supplied to the plants. Asparagine was the main amino acid accumulated in both bromeliads when plants were transferred to the medium with nitrogen. When the ratio of the main individual free amino acids between the bromeliads grown in NH₄⁺ and urea was compared, values such as 7.2 for asparagine, 5.3 for glutamate, and 1.8 for aspartate in A. comosus, and values such as 2.3 for asparagine, 1.1 for glutamate and 0.7 for aspartate in V. gigantea were observed, demonstrating that the last is more efficient in assimilating urea. The results prompted us to support the idea that V. gigantea, an epiphytic tank bromeliad, is better adapted to absorb and assimilate organic nitrogen, such as urea, while A. comosus, a terrestrial plant, is better adapted to inorganic nitrogen forms, such as ammonium. The natural exposure of tank bromeliads to urea is discussed in the paper.     

Effects of NO3−, NH4+ and urea nutrition on endogenous levels of IAA and four cytokinins in two epiphytic bromeliads

The long-term effects of different nitrogen sources on the endogenous IAA and cytokinin levels in two bromeliad species were investigated. In nature, Vriesea philippocoburgii is a tank-forming epiphytic bromeliad which uses the tank water reservoir as a substitute for soil, whereas Tillandsia pohliana is a tankless atmospheric epiphytic species. A culture was established from seeds germinated in aseptic condictions, and the plantlets were grown for 6 months in a modified Knudson medium to which was added 8 mol m⁻³ of nitrogen in the form of NO₃⁻, NH₄⁺ or urea. The hormonal contents of the bromeliad shoots were determined by means of high-performance liquid chromatography (HPLC), coupled to an enzyme-linked immunosorbent assay (ELISA) for indole-3-acetic acid (IAA), isopentenyladenine (iP), isopentenyladenosine ([9R]iP), zeatin (Z) and zeatin riboside ([9R]Z). Nitrogen supplied in the form of urea gave the highest values of fresh and dry weights for both species, and this was positively correlated to IAA levels. The cytokinin patterns showed that isopentenyladenosine was the predominant form for both species in all samples. However, urea induced the highest level of this riboside form and also the highest level of total cytokinins for V. philippocoburgii, while NH₄⁺ had the same effect on the atmospheric species. These results are discussed in terms of the different growth habits of these two species in nature. It is suggested that urea may be an important source of nitrogen often found inside the tank of V. philippocoburgii. NO₃⁻ treatment increased the IAA/Cks balance, mainly for V. philippocoburgii, while urea and NH₄⁺ shifted this ratio in favour of cytokinins, thus apparently inhibiting root development in both species.     

<Emphasis Type="Italic">In vitro</Emphasis> nitrogen nutrition and hormonal pattern in bromeliads

Summary Four cytokinins (CKs), indole-3-acetic acid (IAA) and its ester and amino conjugates, and abscisic acid (ABA) levels of two bromeliads, Ananas comosus (L.) Merril and Vriesea gigantea Gaudich., grown in 5 mM (NH₄)₂SO₄ or urea as the sole nitrogen (N) form, were investigated. In both bromeliads, zeatin (Z) and zeatin riboside ([9R]Z) were the most abundant CKs. In A. comosus, CKs levels decreased drastically (≊ 12 times) after 7 and 30 d in media with ammonium and urea, respectively. After 3 d in media with N, V. gigantea CK levels decreased 30 and 20 times in the presence of ammonium and urea, respectively. N-starved A. comosus and V. gigantea exhibited similar ABA levels, but ABA decreased faster in V. gigantea when plants were transferred to media with N. Free IAA levels decreased until the 15th and 30th day when A. comosus was transferred to a medium with ammonium and urea, respectively. N-starved A. comosus amide, ester, and free IAA amounted to 81%, 14%, and 4%, respectively. There was a transient increase in the proportion of amide IAA and a corresponding decrease of the ester and the free IAA proportion when N-starved plants were transferred to media with N. The relationship between the internal hormonal patterns and the different ecological adaptations of the two bromeliads are discussed.     

Seed dispersal and population structure in Vriesea gigantea,a bromeliad from the Brazilian Atlantic Rainforest

Seed dispersal, population structure and the mating system of plant species can have great consequences on the genetic structure of populations. Vriesea gigantea is a bromeliad from southeastern Brazil which is self‐compatible and pollinator dependent for fruit set. Its populations are fertile in terms of the production of flowers, pollen, fruits and seeds. To assess the importance of seed supply for gene flow, colonization and distribution of adult individuals, the seed dispersal and population structure of V. gigantea were studied. Seeds are dispersed over short distances; most seeds land close to the mother plant. This pattern coincides with the reported aggregate distribution of bromeliad seedlings. Population structure results showed high seedling recruitment, because 51.3% developed into adults, although few juveniles reached this stage. This result is different from that for other bromeliad species from different habitat conditions. Seed dispersal and population structural patterns are consistent with previous molecular studies, revealing that V. gigantea populations are genetically structured, with low gene flow and a moderate outcrossing rate. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 317–325.     

Inbreeding depression in Vriesea gigantea,a perennial bromeliad from southern Brazil

Inbreeding depression is a reduction of fitness in the progeny of closely related individuals and its effects are assigned to selfing or biparental inbreeding. Vriesea gigantea is a self‐compatible bromeliad species distributed in the Brazilian Atlantic rainforest and habitat destruction and fragmentation and collection have decreased the natural populations. We aim to describe the occurrence of inbreeding depression (δ) in three natural populations of V. gigantea and to correlate this phenomenon with previous studies of fertility, genetic diversity, population genetic structure, gene flow, mating system and seed dispersal in this species. Fifty‐four adult plants were sampled and 108 flowers were used for pollination treatments (selfing, outcrossing and control). For adult plants, we analysed plant and inflorescence height, flower numbers and seed set. In the progenies, evaluated parameters included seed germination and seedling survival rate. The results indicated low to moderate levels of inbreeding depression in V. gigantea (δ = 0.02 to 0.39), in agreement with molecular data from a previous study. Vriesea gigantea populations tolerate some degree of inbreeding, which is consistent with previous results on fertility, mating system, genetic diversity and gene flow. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 312–319.     

Utilization of urea by leaves of bromeliad <Emphasis Type="Italic">Vriesea gigantea</Emphasis> under water deficit: much more than a nitrogen source

Vriesea gigantea Gaudichaud is an epiphytic bromeliad with a high capacity to take up urea. In plants, urea is hydrolyzed by urease into ammonium and CO₂, providing nitrogen to the plant. Most studies of urea nutrition have focused only on nitrogen metabolism, whereas scarce attention has been given to CO₂ assimilation. Therefore, this study attempted to investigate whether urea could play an important role as a carbon source, which could be of a significant importance under water deficit conditions because of the limitation in atmospheric CO₂ influx into the leaves due to stomatal closure. In this study, detached leaves of V. gigantea were exposed to water deficit and supplied with urea. The most photosynthetic parts of the leaf (mainly the apical leaf portion) showed higher urease activities and CO₂ buildup near chloroplasts, particularly during the nighttime under water deficit conditions when compared to urea application without the water deficit. Moreover, part of the CO₂ generated from urea hydrolysis was fixed into malate, probably via phosphoenolpyruvate carboxylase. Therefore, urea may contribute to the carbon balance of plants under water deficit conditions. Our data suggest that, besides being a source of nitrogen, urea might also be an important carbon source during CO₂-limited conditions in leaves of epiphytic bromeliads.     

Nitrogen fluxes from treefrogs to tank epiphytic bromeliads: an isotopic and physiological approach

Diverse invertebrate and vertebrate species live in association with plants of the large Neotropical family Bromeliaceae. Although previous studies have assumed that debris of associated organisms improves plant nutrition, so far little evidence supports this assumption. In this study we used isotopic (¹⁵N) and physiological methods to investigate if the treefrog Scinax hayii, which uses the tank epiphytic bromeliad Vriesea bituminosa as a diurnal shelter, contributes to host plant nutrition. In the field, bromeliads with frogs had higher stable N isotopic composition (δ¹⁵N) values than those without frogs. Similar results were obtained from a controlled greenhouse experiment. Linear mixing models showed that frog feces and dead termites used to simulate insects that eventually fall inside the bromeliad tank contributed, respectively, 27.7% (±0.07 SE) and 49.6% (±0.50 SE) of the total N of V. bituminosa. Net photosynthetic rate was higher in plants that received feces and termites than in controls; however, this effect was only detected in the rainy, but not in the dry season. These results demonstrate for the first time that vertebrates contribute to bromeliad nutrition, and that this benefit is seasonally restricted. Since amphibian–bromeliad associations occur in diverse habitats in South and Central America, this mechanism for deriving nutrients may be important in bromeliad systems throughout the Neotropics.     

Multiple Lines of Evidence Shed Light on the Occurrence of Paramecium (Ciliophora,Oligohymenophorea) in Bromeliad Tank Water

Phytotelmata are vegetal structures that hold water from the rain, and organic matter from the forest and the soil, resulting in small, compartmentalized bodies of water, which provide an essential environment for the establishment and development of many organisms. These microenvironments generally harbor endemic species, but many organisms that are found in lakes and rivers, are also present. Here, we report, for the first time, the occurrence of the ciliate genus Paramecium in the tank of the bromeliad species Aechmaea distichantha. The identification of the Paramecium species was performed based on live observations, protargol impregnation, scanning electronic microscopy, and sequencing of the 18s rRNA. The absence of Paramecium from bromeliad tank water was highlighted in several earlier investigations, and may be due to the fact that this species is unable to make cysts. The occurrence of Paramecium multimicronucleatum in our samples may be explained by the proximity between the bromeliads and the river, a potential source of the species. Further, we also believe that the counting methodology used in our study provides a more accurate analysis of the species diversity, since we investigated all samples within a maximum period of 6 h after sampling, allowing minimum loss of specimens.     

Aquatic Microbial Habitats Within a Neotropical Rainforest: Bromeliads and pH-Associated Trends in Bacterial Diversity and Composition

Tank-forming bromeliads, suspended in the rainforest canopy, possess foliage arranged in compact rosettes capable of long-term retention of rainwater. This large and unique aquatic habitat is inhabited by microorganisms involved in the important decomposition of impounded material. Moreover, these communities are likely influenced by environmental factors such as pH, oxygen, and light. Bacterial community composition and diversity was determined for the tanks of several bromeliad species (Aechmea and Werauhia) from northern Costa Rica, which span a range of parameters, including tank morphology and pH. These were compared with a nearby forest soil sample, an artificial tank (amber bottle), and a commercially available species (Aechmea). Bacterial community diversity, as measured by 16S rRNA analysis and tRFLP, showed a significant positive correlation with tank pH. A majority of 16S rRNA bacterial phylotypes found in association with acidic bromeliad tanks of pH < 5.1 were affiliated with the Alphaproteobacteria, Acidobacteria, Planctomycetes, and Bacteroidetes, and were similar to those found in acidic peat bogs, yet distinct from the underlying soil community. In contrast, bromeliads with tank pH > 5.3, including the commercial bromeliad with the highest pH (6.7), were dominated by Betaproteobacteria, Firmicutes, and Bacteroidetes. To empirically determine the effect of pH on bacterial community, the tank pH of a specimen of Aechmea was depressed, in the field, from 6.5 to 4.5, for 62 days. The resulting community changed predictably with decreased abundance of Betaproteobacteria and Firmicutes and a concomitant increase in Alphaproteobacteria and Acidobacteria. Collectively, these results suggest that bromeliad tanks provide important habitats for a diverse microbial community, distinct from the surrounding environment, which are influenced greatly by acid–base conditions. Additionally, total organic carbon (∼46%) and nitrogen (∼2%) of bromeliad-impounded sediment was elevated relative to soil and gene surveys confirmed the presence of both chitinases and nitrogenases, suggesting that bromeliad tanks may provide important habitats for microbes involved in the biological cycling of carbon and nitrogen in tropical forests.     

A set of polymorphic microsatellite loci for Vriesea gigantea and Alcantarea imperialis (Bromeliaceae) and cross‐amplification in other bromeliad species

Fifteen polymorphic microsatellite markers were isolated and characterized in two species of Bromeliaceae: Vriesea gigantea and Alcantarea imperialis. The number of alleles observed for each locus ranged from three to 16. The loci will be used for studies of the genetic structure of natural populations, reproductive biology, and evolutionary relationships among and within these genera. A cross‐amplification test in 22 taxa suggests that the markers will be useful for similar applications in numerous other bromeliad species.     

Location of glucose oxidase during production by Aspergillus niger

The production of the enzyme glucose oxidase by Aspergillus niger is well documented. However, its distribution within the fungal culture is less well defined. Since the enzyme location impacts significantly on enzyme recovery, this study quantifies the enzyme distribution between the extracellular fluid, cell wall, cytoplasm and slime mucilage fractions in an A. niger NRRL-3. The culture was separated into the individual fractions and the glucose oxidase activity was determined in each. The extracellular fluid contained 38% of the total activity. The remaining 62% was associated with the mycelia and was distributed between the cell wall, cytoplasm and slime mucilage in the proportions of 34, 12 and 16%, respectively. Intracellular cytoplasmic and cell wall sites were confirmed using immunocytochemical labelling of the mycelia. In the non-viable cell, the mycelial-associated enzyme was distributed between these sites, whereas in the viable cell, it was predominantly associated with the cell wall. The distribution of the enzyme activity indicates that recovery from the solids would result in a 38% loss, whereas recovery from the extracellular fluid would result in a 62% loss. The results also suggest, however, that this 62% loss could be reduced to around 34% by disintegrating the solids prior to separation due to the contribution of the enzyme in the cytoplasm and slime mucilage. This was confirmed by independently establishing the percentage activity in the liquid and solid portions of a disintegrated culture as 62 and 38%, respectively.     

Two coexisting tank bromeliads host distinct algal communities on a tropical inselberg

The tank bromeliads Aechmea aquilega (Salisb.) and Catopsis berteroniana (Schultes f.) coexist on a sun‐exposed Neotropical inselberg in French Guiana, where they permit conspicuous freshwater pools to form that differ in size, complexity and detritus content. We sampled the algal communities (both eukaryotic and cyanobacterial taxa, including colourless forms) inhabiting either A. aquilega (n = 31) or C. berteroniana (n = 30) and examined differences in community composition and biomass patterns in relation to several biotic and abiotic variables. Chlorella sp. and Bumilleriopsis sp. were the most common taxa and dominated the algal biomass in A. aquilega and C. berteroniana, respectively. Using a redundancy analysis, we found that water volume, habitat complexity and the density of phagotrophic protozoa and collector‐gatherer invertebrates were the main factors explaining the distribution of the algal taxa among the samples. Hierarchical clustering procedures based on abundance and presence/absence data clearly segregated the samples according to bromeliad species, revealing that the algal communities in the smaller bromeliad species were not a subset of the communities found in the larger bromeliad species. We conclude that, even though two coexisting tank bromeliad populations create adjacent aquatic habitats, each population hosts a distinct algal community. Hence, bromeliad diversity is thought to promote the local diversity of freshwater algae in the Neotropics.     

The isolation and characterization of copper-resistant mutants ofAspergillus nidulans

The presence of aminopeptidases in the cytoplasm, in the cell wall, and in the cytoplasmic membrane fractions ofStreptococcus sanguis 903 was demonstrated by isoelectric focusing in combination with enzyme-staining procedures. The cytoplasm and the cell wall both had two aminopeptidases (pI 4.25 and 4.3) with broad substrate specificities and one enzyme (pI 4.2) specific for arginine substrates. The former enzymes were both stimulated by Co²⁺ ions; the latter enzyme had no metal cofactor. The cytoplasmic membrane aminopeptidase (pI 4.65) was arginine specific and was not stimulated by metal ions.     

Inherently slow growth in two Caribbean epiphytic species: A demographic approach

Abstract. In relation to the drought‐prone and nutrient‐poor habitat, vascular epiphytes are routinely referred to as inherently slow‐growing plants, although actual evidence is rare. To test this notion we measured in situ growth of the understorey orchid Aspasia principissa and the tank bromeliad Vriesea sanguinolenta, and, for the latter species, also the growth under favourable conditions in the greenhouse. Using growth analysis we show: (1) that in an intraspecific comparison, small to intermediate individuals yield the highest relative growth rates (RGR) in situ: A. principissa: 1.6 10–³ d^‐1; V. sanguinolenta: 3.3 10–³ d^‐1; (2) that the bromeliad reaches maximum size after ca. 15 yr, while the orchid needs at least 20 yr; and (3) small V. sanguinolenta plants exhibit a highly plastic growth response to favourable conditions in the greenhouse, reaching an almost 10‐fold increase in RGR. In spite of a substantial increase in growth under more favourable conditions, our results are consistent with the notion that epiphytes are inherently slow growing organisms.     

Consequences of dispersal limitation and habitat fragmentation for the Brazilian heart‐tongued frogs (Phyllodytes spp.)

Poorly known species may be cryptically endangered, especially when they inhabit fragmented and threatened habitats. Heart‐tongued frogs (genus Phyllodytes, family Hylidae, Lophyohylinae) comprise 17 species of poorly known frogs that have obligatory associations with tank bromeliads. The distributions of all species are restricted to a small, extremely fragmented, region of Atlantic Forest in eastern Brazil. We model climate and tank bromeliad distributions to better understand frog distribution limits. Using records from several sources for frogs and bromeliads with climate data from WorldClim, we modelled the distribution of Phyllodytes using maximum entropy. We compared climate and altitude within the distribution and nearby to test how climate may limit distribution. Climate together with bromeliad distributions provided the best model and predicted the smallest suitable area for Phyllodytes that was larger than that occupied, from the state of Paraíba in the north to Rio Grande do Sul in the south. Phyllodytes occurs in lower elevations that are warmer, wetter and less variable than the surrounding regions where it does not occur, and dispersal is apparently limited by the surrounding, inhospitable, region. Dispersal limitation and habitat fragmentation have relegated Phyllodytes to many very small habitat fragments. With many species in this genus being known from a single or few samples, this unfortunate combination of limitation and fragmentation suggests that some or all species of Phyllodytes may be threatened with extinction, especially if habitat fragmentation continues at its present pace in eastern Brazil.     

Nitrogen metabolism in leaves of a tank epiphytic bromeliad: characterization of a spatial and functional division

The leaf is considered the most important vegetative organ of tank epiphytic bromeliads due to its ability to absorb and assimilate nutrients. However, little is known about the physiological characteristics of nutrient uptake and assimilation. In order to better understand the mechanisms utilized by some tank epiphytic bromeliads to optimize the nitrogen acquisition and assimilation, a study was proposed to verify the existence of a differential capacity to assimilate nitrogen in different leaf portions. The experiments were conducted using young plants of Vriesea gigantea. A nutrient solution containing NO₃⁻/NH₄⁺ or urea as the sole nitrogen source was supplied to the tank of these plants and the activities of urease, nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (NADH-GDH) were quantified in apical and basal leaf portions after 1, 3, 6, 9, 12, 24 and 48 h. The endogenous ammonium and urea contents were also analyzed. Independent of the nitrogen sources utilized, NR and urease activities were higher in the basal portions of leaves in all the period analyzed. On the contrary, GS and GDH activities were higher in apical part. It was also observed that the endogenous ammonium and urea had the highest contents detected in the basal region. These results suggest that the basal portion was preferentially involved in nitrate reduction and urea hydrolysis, while the apical region could be the main area responsible for ammonium assimilation through the action of GS and GDH activities. Moreover, it was possible to infer that ammonium may be transported from the base, to the apex of the leaves. In conclusion, it was suggested that a spatial and functional division in nitrogen absorption and NH₄⁺ assimilation between basal and apical leaf areas exists, ensuring that the majority of nitrogen available inside the tank is quickly used by bromeliad's leaves.     

阳春砂花粉的结构和生殖细胞的分离

阳春砂为自交植物,但花的雌蕊高于雄蕊,是研究单子叶植物纲生殖细胞分子生物学的典型材料。为了解决授粉难的问题,该研究采用植物组织化学方法,对阳春砂花粉的发育过程进行观察,以明确其花粉的结构特征;选择渗透压冲击法分离生殖细胞,以探讨阳春砂的授粉技术方法。结果表明:(1)阳春砂花粉发育的特殊性从四分体时期开始,在四分体时期缺少典型的胼胝质壁,而4个小孢子是由多糖性质的细胞壁分隔、包裹着;成熟的阳春砂花粉粒是二胞型花粉,且花粉细胞质中含有丰富的多糖淀粉和脂滴物质;成熟花粉外壁是由多糖物质构成,而非胡萝卜素和类胡萝卜素酯的孢粉素物质构成。(2)阳春砂花粉在2%甘露醇+5%丙酮的爆破液中,爆破率可达10.67%,并释放出花粉内含物,其中包含生殖细胞;在释放出的花粉细胞质中,生殖细胞可完整保留约30min;用显微操作仪将游离的生殖细胞收集成一定数量的群体,置离心管后即可保存在液氮罐中,每天可收集上百个阳春砂生殖细胞。     

Configurations of the rectus abdominis muscle of anuran tadpoles

Configurations of the rectus abdominis in tadpoles of 60 anuran species in 13 families were examined. This muscle is present by Gosner stage 25 and does not change until late in metamorphosis. The anterior terminus of the r. abdominis usually is a straight, transverse front or fan-shaped array only loosely associated with the rectus cervicis. In some suspension feeders (Rhinophrynus, Xenopus, but not microhylids), macrophagous suction feeders (Lepidobatrachus) and bromeliad inhabitants (Hyla bromeliacia) the r. abdominis is contigous with the r. cervicis which continues anterolaterally and dorsally from the wall of the spiracular cavity. Suctorial forms (Scutiger), those that live in confined spaces (burrowers, Centrolenella; bromeliad inhabitants, Hyla bromeliacia), and the taxa that have the r. cervicis and r. abdominis contiguous all have closed myosepta; the myosepta of other taxa; except for ones with large tadpoles (e.g., Rana catesbeiana), have large gaps between at least anterior myotomes. These initial data suggest that the configurations of the r. abdominis have responded to selection based on ecomorphological function and convergence among lineages are noted. © 1992 Wiley-Liss, Inc.     

Phoretic dispersal on bumblebees by bromeliad flower mites (Mesostigmata, Melicharidae)

Nectarivorous flower mites (Mesostigmata: Melicharidae) live mostly on hummingbird-pollinated plants in the New World. We observed Proctolaelaps sp. living on Neoregelia johannis (Bromeliaceae) in a coastal rain forest site in south-eastern Brazil. Flower anthesis of this bromeliad lasted a single day. We recorded mites moving into, feeding from, presumably mating and reproducing, and exiting bromeliad flowers within just a single day. We observed three ant species predating flower mites on bromeliads. The main visitor was the bumblebee Bombus morio, which always landed on the inflorescence to access nectar inside the bromeliad flowers. We found Proctolaelaps sp. mites on 47% of 38 bumblebees inspected, with each Bombus hosting 2 mites on average; only adults and mostly female mites (93%) usually found on the bumblebees’ gula region of the head. This is the first study to document nectarivorous flower mites living on a melittophilous host plant using bumblebees for phoretic dispersal.