Distribution and Flowering Ecology of Bromeliads along Two Climatically Contrasting Elevational Transects in the Bolivian Andes1

Origin and Function of Amino Acids in Nectar and Nectaries of Pitcairnia Species with Particular Emphasis on Alanine and Glutamine

Floral nectar contains sugars and numerous other compounds, including amino acids, but little is known about their function and origin in nectar. Therefore, the amino acid, sugar, and inorganic ion concentrations, as well as the activity of alanine aminotransferase (AlaAT) and glutamine synthetase (GS) in nectar, nectaries, and leaves were analyzed in 30 Pitcairnia species. These data were compared with various floral traits, the pollinator type, and the phylogenetic relationships of the species to find possible causes for the high amino acid concentrations in the nectar of some species. The highest concentrations of amino acids (especially alanine) in nectar were found in species with reddish flowers. Furthermore, the concentration of amino acids in nectar and nectaries is determined through analyzing flower color/pollination type rather than phylogenetic relations. This study provides new insights into the origin of amino acids in nectar. The presence of almost all amino acids in nectar is mainly due to their transport in the phloem to the nectaries, with the exception of alanine, which is partially produced in nectaries. In addition, active regulatory mechanisms are required in nectaries that retain most of the amino acids and allow the selective secretion of specific amino acids, such as alanine.

Opposing Patterns of Altitude-Driven Pollinator Turnover in the Tropical and Temperate Americas

AbstractAbiotic factors (e.g., temperature, precipitation) vary markedly along elevational gradients and differentially affect major groups of pollinators. Ectothermic bees, for example, are impeded in visiting flowers by cold and rainy conditions common at high elevations, while endothermic hummingbirds may continue foraging under such conditions. Despite the possibly far-reaching effects of the abiotic environment on plant-pollinator interactions, we know little about how these factors play out at broad ecogeographic scales. We address this knowledge gap by investigating how pollination systems vary across elevations in 26 plant clades from the Americas. Specifically, we explore Cruden's 1972 hypothesis that the harsh montane environment drives a turnover from insect to vertebrate pollination at higher elevations. We compared the elevational distribution and bioclimatic attributes for a total of 2,232 flowering plants and found that Cruden's hypothesis holds only in the tropics. Above 30°N and below 30°S, plants pollinated by vertebrates (mostly hummingbirds) tend to occur at lower elevations than those pollinated by insects. We hypothesize that this latitudinal transition is due to the distribution of moist, forested habitats favored by vertebrate pollinators, which are common at high elevations in the tropics but not in the temperate Americas.

Comparative analyses of the metabolite and ion concentrations in nectar, nectaries, and leaves of 36 bromeliads with different photosynthesis and pollinator types

Floral nectar contains mainly sugars as well as smaller amounts of amino acids and further compounds. The nectar composition varies between different plant species and it is related to the pollination type of the plant. In addition to this, other factors can influence the composition. Nectar is produced in and secreted from nectaries. A few models exist to explain the origin of nectar for dicotyl plant species, a complete elucidation of the processes, however, has not yet been achieved. This is particularly true for monocots or plant species with CAM photosynthesis. To get closer to such an elucidation, nectar, nectaries, and leaves of 36 bromeliad species were analyzed for sugars, starch, amino acids, and inorganic ions. The species studied include different photosynthesis types (CAM/C3), different pollination types (trochilophilous/chiropterophilous), or different live forms. The main sugars in nectar and nectaries were glucose, fructose, and sucrose, the total sugar concentration was about twofold higher in nectar than in nectaries, which suggests that sugars are actively transported from the nectaries into the nectar. The composition of amino acids in nectar is already determined in the nectaries, but the concentration is much lower in nectar than in nectaries, which suggests selective retention of amino acids during nectar secretion. The same applies to inorganic ions. Statistical analyses showed that the photosynthesis type and the pollination type can explain more data variation in nectar than in nectaries and leaves. Furthermore, the pollinator type has a stronger influence on the nectar or nectary composition than the photosynthesis type. Trochilophilous C3 plants showed significant correlations between the nitrate concentration in leaves and the amino acid concentration in nectaries and nectar. It can be assumed that the more nitrate is taken up, the more amino acids are synthesized in leaves and transported to the nectaries and nectar. However, chiropterophilous C3 plants show no such correlation, which means that the secretion of amino acids into the nectar is regulated by further factors. The results help understand the physiological properties that influence nectaries and nectar as well as the manner of metabolite and ion secretion from nectaries to nectar.

Multilocus Data Analysis Reveal the Diversity of Cryptic Species in the Tillandsia ionantha (Bromeliaceae: Tillansiodeae) Complex

Independent evolutionary lineages or species that lack phenotypic variation as an operative criterion for their delimitation are known as cryptic species. However, these have been delimited using other data sources and analysis. The aims of this study are: (1) to evaluate the divergence of the populations of the T. ionantha complex; and (2) to delimit the species using multilocus data, phylogenetic analysis and the coalescent model. Phylogenetic analyses, genetic diversity and population structure, and isolation by distance analysis were performed. A multispecies coalescent analysis to delimit the species was conducted. Phylogenetic analysis showed that T. ionantha is polyphyletic composed of eight evolutionary lineages. Haplotype distribution and genetic differentiation analysis detected strong population structure and high values of genetic differentiation among populations. The positive correlation between genetic differences with geographic distance indicate that the populations are evolving under the model of isolation by distance. The coalescent multispecies analysis performed with starBEAST supports the recognition of eight lineages as different species. Only three out of the eight species have morphological characters good enough to recognize them as different species, while five of them are cryptic species. Tillandsia scaposa and T. vanhyningii are corroborated as independent lineages, and T. ionantha var. stricta changed status to the species level.

Pollination by hummingbirds of Vriesea gigantea (Bromeliaceae) populations in Southern Brazil

Abstract The pollination syndrome hypothesis usually does not successfully apply to the diversity of floral phenotypes or help predict the pollinators of most plant species. In Bromeliaceae, there is a wide range of floral visitors, making its species ideal to test for a correlation between nectar and floral traits with pollination syndrome. In this study, we analyzed the floral features, nectar production patterns, pollinators and floral visitors of Vriesea gigantea, and discussed its potential adaptive and ecological significance. We study three natural populations from the Atlantic Forest, Southern Brazil. The species presented protogyny and herkogamy, and its anthesis occurred at different periods among different populations. Vriesea gigantea has a relatively constant rate of nectar production during the day that continues overnight but at a reduced rate. Newly opened flowers already have around 80.0 μl of nectar. Although classified as chiropterophilous, based on flower morphology and pollinator observations, our results show that hummingbirds are effective pollinators in the studied populations of V. gigantea.

Bromeliads going batty: pollinator partitioning among sympatric chiropterophilous Bromeliaceae

Pollinators can be a limited resource and natural selection should favour differences in phenotypic characteristics to reduce competition among plants. Bats are important pollinators of many Neotropical plants, including the Bromeliaceae; however, the pre-pollination mechanisms for isolation among sympatric bat-pollinated bromeliads are unknown. Here, we studied the mechanisms for reproductive segregation between Pitcairnia recurvata, Pseudalcantarea viridiflora, Werauhia noctiflorens and W. nutans. The study was conducted at Los Tuxtlas Biosphere Reserve, in Veracruz, Mexico We carried out ex situ and in situ manual pollination treatments to determine the breeding system by assessing fruiting and seedling success and sampled bat visitors using mist-nets and infrared cameras. We determined the nocturnal nectar production pattern, estimating the energetic content of this reward. All four bromeliads are self-compatible, but only P. recurvata appears to require pollinators, because the physical separation between anthers and stigma prevents self-pollination, it is xenogamous and presents a strictly nocturnal anthesis. The bats Anoura geoffroyi, Glossophaga soricina and Hylonycteris underwoodi are probable pollinators of three of the studied bromeliads. We did not record any animal visiting the fourth species. The flowering season of each species is staggered throughout the year, with minimal overlap, and the floral morphology segregates the locations on the body of the bat where the pollen is deposited. The most abundant nectar per flower is provided by P. viridiflora, but P. recurvata offers the best reward per hectare, considering the density of flowering plants. Staggered flowering, different pollen deposition sites on the body of the pollinator and differences in the reward offered may have evolved to reduce the competitive costs of sharing pollinators while providing a constant supply of food to maintain a stable nectarivorous bat community.

What Do Nectarivorous Bats Like? Nectar Composition in Bromeliaceae With Special Emphasis on Bat-Pollinated Species

Floral nectar is the most important reward for pollinators and an integral component of the pollination syndrome. Nectar research has mainly focused on sugars or amino acids, whereas more comprehensive studies on the nectar composition of closely related plant species with different pollination types are rather limited. Nectar composition as well as concentrations of sugars, amino acids, inorganic ions, and organic acids were analyzed for 147 species of Bromeliaceae. This plant family shows a high diversity in terms of floral morphology, flowering time, and predominant pollination types (trochilophilous, trochilophilous/entomophilous, psychophilous, sphingophilous, chiropterophilous). Based on the analyses, we examined the relationship between nectar traits and pollination type in this family. Nectar of all analyzed species contained high amounts of sugars with different proportions of glucose, fructose, and sucrose. The total concentrations of amino acids, inorganic cations, and anions, or organic acids were much lower. The analyses revealed that the sugar composition, the concentrations of inorganic cations and anions as well as the concentration of malate in nectar of bat-pollinated species differed significantly from nectar of species with other pollination types. Flowers of bat-pollinated species contained a higher volume of nectar, which results in a total of about 25-fold higher amounts of sugar in bat-pollinated species than in insect-pollinated species. This difference was even higher for amino acids, inorganic anions and cations, and organic acids (between 50 and 100-fold). In general, bat-pollinated plant species invest large amounts of organic and inorganic compounds for their pollinators. Furthermore, statistical analyses reveal that the characteristics of nectar in Bromeliaceae are more strongly determined by the pollinator type rather than by taxonomic groups or phylogenetic relations. However, a considerable part of the variance cannot be explained by either of the variables, which means that additional factors must be responsible for the differences in the nectar composition.

Reproductive traits and floral visitors of Aechmea distichantha plants growing in different habitats of a South American xerophytic forest

Abstract Aechmea distichantha, a widely-distributed facultative epiphytic bromeliad species, is present from rainforests to xerophytic forests. At its southernmost distribution (Humid Chaco) it grows in the understory and forest edges. This animal-pollinated bromeliad shows high phenotypic plasticity on its vegetative traits, but there is no information about plasticity on its reproductive traits. Infructescences from shade plants were heavier, had longer rachis, more spikelets, higher number of fruits/spikelet and higher number of seeds/fruit than those from sun plants, but they presented similar number of open flowers. The number of visitation events was similar in both habitats, but more flowers were visited in the sun than in the shade. Flowers were visited by seven species (six insects and one hummingbird). In the sun, the carpenter bee was the most frequent visitor and visited almost all flowers, whereas in the shade different species of visitors attained similar proportion of visits and number of visited flowers. Despite visitation events were similar in both habitats, plants growing in the shade set more seeds/fruit than plants growing in the sun. The higher proportion of visits accomplished by carpenter bees compared to hummingbirds is probably a consequence of the climatic conditions in the austral location of these populations.

Reproductive biology of Aechmea bracteata (Sw.) Griseb. (Bromelioideae: Bromeliaceae)

Individuals of Aechmea bracteata show inflorescences with red scape bracts and odourless, yellow, tubular diurnal flowers, with closely arranged sexual organs, producing a large amount of fruits. In order to investigate the reproductive system of this species, a suite of characters was assessed: phenology, floral morphology and biology, nectar production dynamics, and fruit and seed production and germination, as a result of controlled pollination crosses. The study was conducted during two flowering seasons in wild populations in Yucatán, Mexico. Results suggest an annual flowering pattern with one flowering peak; flowers were diurnal, showing partial dichogamy (protandry)-herkogamy, anthers and stigma become mature before floral aperture, which could lead to self-pollination, nectar is produced during anthesis, varying in volume and total sugar concentration during the day; fruits and seeds were produced in all experimental crosses (cross-pollination, obligated cross-pollination, assisted and unassisted selfing, geitonogamy and apomixis), as well as high percentage seed germination. Several species of Aechmea are reportedly self-compatible and autogamous, as suggested by results of selfing and non-assisted selfing crosses, but these results are negated by the presence of apomixis, indicating that the species is apomictic. This is the first report of this breeding system for subgenus Aechmea and the sixth for Bromeliaceae. Polyembryony is here suggested for the first time in this genus and family based on the fact that more seeds were recorded that expected based on ovule numbers. Finally, when performing experimental crosses, estimating reproductive success based on number of seeds is a better approach than number of fruits, due to the effect of pseudogamy.

From dusk till dawn: nocturnal and diurnal pollination in the epiphyte Tillandsia heterophylla (Bromeliaceae)

In order to compare the effectiveness of diurnal and nocturnal pollinators, we studied the reproductive biology and pollinators of Tillandsia heterophylla E. Morren, an epiphytic tank bromeliad endemic to southeastern Mexico. Since anthesis in T. heterophylla is predominantly nocturnal but lasts until the following day, we hypothesised that this bromeliad would receive visits from both diurnal and nocturnal visitors, but that nocturnal visitors would be the most effective pollinators, since they arrive first to the receptive flower, and that bats would be the most frequent nocturnal visitors, given the characteristics of the nectar. Flowering of T. heterophylla began in May and lasted until July. The species is fully self-compatible, with an anthesis that lasts for ca. 15-16 h. Mean volume of nectar produced per flower was 82.21 μl, with a mean sugar concentration of 6.33%. The highest volume and concentration of nectar were found at 20:00 h, with a subsequent decline in both to almost zero over the following 12-h period. T. heterophylla has a generalist pollination system, since at least four different morphospecies of visitors pollinate its flowers: bats, moths, hummingbirds and bees. Most of the pollinating visits corresponded to bats and took place in the early evening, when stigma receptivity had already begun; making bats the probable pollinator on most occasions. However, diurnal pollinators may be important as a 'fail-safe' system by which to guarantee the pollination of T. heterophylla.

Effect of biotic and abiotic factors on diversity patterns of anthophyllous insect communities in a tropical mountain forest

The determinants of diversity are a central issue in ecology, particularly in Andean forests that are known to be a major diversity hotspot for several taxa. We examined the effect of abiotic (elevation and precipitation) and biotic (flowering plant diversity) factors considered to be decisive causal factors of diversity patterns on anthophyllous insect communities on mountain forest. Sampling was carried out in 100-m transects at eight elevational levels and during a period of 8 months. All flowering plants in the understory and their flowering visitors were recorded. Species richness and diversity were estimated for each elevation and month. Diversity of flowering plants, elevation, and precipitation were used as independent variables in multiple regressions against insect diversity. The evaluated abiotic and biotic factors had contrasting effects on insect diversity: a significant decrease on insect diversity occurred at high elevation and dry months (i.e., threshold effect), while it showed a positive relationship with flowering plant diversity through time (i.e., linear effect), but not along elevation. Rapid turnover of species of both interacting guilds was observed every 100-m altitude and month. Local insect communities were also divided functionally depending on the plant family they visit. These results indicate that each insect community is distinctive among elevations and months and that diversity of flowering plants, precipitation, and elevation influence their structure and composition. Thus, conservation strategies should involve protection of forest cover at the whole elevation gradient, in order to preserve common and exclusive components of diversity and consequently, the mosaic of plant-pollinator interactions.

Diversidade beta de plantas que oferecem néctar como recurso floral aos beija-flores em cerrados do Brasil Central

Os ambientes abertos de Cerrado têm sido considerados ambientes marginais ou complementares para beija-flores, apesar do registro de considerável número de espécies deste grupo de visitantes florais. Estes utilizam uma variedade de plantas, incluindo aquelas sem características ornitófilas. O objetivo do trabalho foi investigar a flora utilizada por beija-flores como recurso alimentar em três áreas de Cerrado, distantes entre si de ca. 20 a 150 km. Em cada área foram demarcados, em cerrado s.s., dois transectos de 1 ha cada, que foram percorridos quinzenalmente para identificação das espécies utilizadas pelos beija-flores, os quais também foram identificados. A riqueza de espécies de plantas encontrada (26) foi maior que a registrada em outros estudos na mesma região, porém foi menor que na maioria dos ambientes florestais. Destas espécies, apenas nove (34%) apresentaram síndrome de ornitofilia. Foram registradas nove espécies de beija-flores (Trochilidae) nas três áreas. Apesar da grande diversidade beta descrita para plantas no Cerrado, a similaridade de espécies utilizadas pelos beija-flores foi alta entre os transectos das três áreas estudadas, independente de serem plantas tipicamente ornitófilas ou não. Havia plantas oferecendo recursos florais para os beija-flores durante praticamente todo o ano. O grande número de espécies não ornitófilas utilizadas por estas aves corrobora a ideia de que, em ambientes de Cerrado, as espécies vegetais que oferecem néctar parecem ser mais importantes para os beija-flores que vice-versa.

MC, Krömer T, García-Franco JG, Knauer A, Kessler M. First record of bat-pollination in the species-rich genus Tillandsia (Bromeliaceae)

BACKGROUND AND AIMS

Bromeliaceae is a species-rich neotropical plant family that uses a variety of pollinators, principally vertebrates. Tillandsia is the most diverse genus, and includes more than one-third of all bromeliad species. Within this genus, the majority of species rely on diurnal pollination by hummingbirds; however, the flowers of some Tillandsia species show some characteristics typical for pollination by nocturnal animals, particularly bats and moths. In this study an examination is made of the floral and reproductive biology of the epiphytic bromeliad Tillandsia macropetala in a fragment of humid montane forest in central Veracruz, Mexico.

METHODS

The reproductive system of the species, duration of anthesis, production of nectar and floral scent, as well as diurnal and nocturnal floral visitors and their effectiveness in pollination were determined.

KEY RESULTS

Tillandsia macropetala is a self-compatible species that achieves a higher fruit production through outcrossing. Nectar production is restricted to the night, and only nocturnal visits result in the development of fruits. The most frequent visitor (75 % of visits) and the only pollinator of this bromeliad (in 96 % of visits) was the nectarivorous bat Anoura geoffroyi (Phyllostomidae: Glossophaginae).

CONCLUSIONS

This is the first report of chiropterophily within the genus Tillandsia. The results on the pollination biology of this bromeliad suggest an ongoing evolutionary switch from pollination by birds or moths to bats.

Functional aspects of floral nectar secretion of Ananas ananassoides, an ornithophilous bromeliad from the Brazilian savanna

BACKGROUND AND AIMS

Several members of Bromeliaceae show adaptations for hummingbird pollination in the Neotropics; however, the relationships between floral structure, nectar production, pollination and pollinators are poorly understood. The main goal of this study was to analyse the functional aspects of nectar secretion related to interaction with pollinators by evaluating floral biology, cellular and sub-cellular anatomy of the septal nectary and nectar composition of Ananas ananassoides, including an experimental approach to nectar dynamics.

METHODS

Observations on floral anthesis and visitors were conducted in a population of A. ananassoides in the Brazilian savanna. Nectary samples were processed using standard methods for light and transmission electron microscopy. The main metabolites in nectary tissue were detected via histochemistry. Sugar composition was analysed by high-performance liquid chromatography (HPLC). The accumulated nectar was determined from bagged flowers ('unvisited'), and floral response to repeated nectar removal was evaluated in an experimental design simulating multiple visits by pollinators to the same flowers ('visited') over the course of anthesis.

KEY RESULTS

The hummingbirds Hylocharis chrysura and Thalurania glaucopis were the most frequent pollinators. The interlocular septal nectary, composed of three lenticular canals, extends from the ovary base to the style base. It consists of a secretory epithelium and nectary parenchyma rich in starch grains, which are hydrolysed during nectar secretion. The median volume of nectar in recently opened 'unvisited' flowers was 27·0 µL, with a mean (sucrose-dominated) sugar concentration of 30·5 %. Anthesis lasts approx. 11 h, and nectar secretion begins before sunrise. In 'visited' flowers (experimentally emptied every hour) the nectar total production per flower was significantly higher than in the 'unvisited' flowers (control) in terms of volume (t = 4·94, P = 0·0001) and mass of sugar (t = 2·95, P = 0·007), and the concentration was significantly lower (t = 8·04, P = 0·0001).

CONCLUSIONS

The data suggest that the total production of floral nectar in A. ananassoides is linked to the pollinators' activity and that the rapid renewal of nectar is related to the nectary morphological features.

Floral traits mediate the vulnerability of aloes to pollen theft and inefficient pollination by bees

BACKGROUND AND AIMS

Pollen-collecting bees are among the most important pollinators globally, but are also the most common pollen thieves and can significantly reduce plant reproduction. The pollination efficiency of pollen collectors depends on the frequency of their visits to female(-phase) flowers, contact with stigmas and deposition of pollen of sufficient quantity and quality to fertilize ovules. Here we investigate the relative importance of these components, and the hypothesis that floral and inflorescence characteristics mediate the pollination role of pollen collection by bees.

METHODS

For ten Aloe species that differ extensively in floral and inflorescence traits, we experimentally excluded potential bird pollinators to quantify the contributions of insect visitors to pollen removal, pollen deposition and seed production. We measured corolla width and depth to determine nectar accessibility, and the phenology of anther dehiscence and stigma receptivity to quantify herkogamy and dichogamy. Further, we compiled all published bird-exclusion studies of aloes, and compared insect pollination success with floral morphology.

KEY RESULTS

Species varied from exclusively insect pollinated, to exclusively bird pollinated but subject to extensive pollen theft by insects. Nectar inaccessibility and strong dichogamy inhibited pollination by pollen-collecting bees by discouraging visits to female-phase (i.e. pollenless) flowers. For species with large inflorescences of pollen-rich flowers, pollen collectors successfully deposited pollen, but of such low quality (probably self-pollen) that they made almost no contribution to seed set. Indeed, considering all published bird-exclusion studies (17 species in total), insect pollination efficiency varied significantly with floral shape.

CONCLUSIONS

Species-specific floral and inflorescence characteristics, especially nectar accessibility and dichogamy, control the efficiency of pollen-collecting bees as pollinators of aloes.

Phylogeny, adaptive radiation, and historical biogeography in Bromeliaceae: insights from an eight-locus plastid phylogeny

PREMISE

Bromeliaceae form a large, ecologically diverse family of angiosperms native to the New World. We use a bromeliad phylogeny based on eight plastid regions to analyze relationships within the family, test a new, eight-subfamily classification, infer the chronology of bromeliad evolution and invasion of different regions, and provide the basis for future analyses of trait evolution and rates of diversification.

METHODS

We employed maximum-parsimony, maximum-likelihood, and Bayesian approaches to analyze 9341 aligned bases for four outgroups and 90 bromeliad species representing 46 of 58 described genera. We calibrate the resulting phylogeny against time using penalized likelihood applied to a monocot-wide tree based on plastid ndhF sequences and use it to analyze patterns of geographic spread using parsimony, Bayesian inference, and the program S-DIVA.

RESULTS

Bromeliad subfamilies are related to each other as follows: (Brocchinioideae, (Lindmanioideae, (Tillandsioideae, (Hechtioideae, (Navioideae, (Pitcairnioideae, (Puyoideae, Bromelioideae))))))). Bromeliads arose in the Guayana Shield ca. 100 million years ago (Ma), spread centrifugally in the New World beginning ca. 16-13 Ma, and dispersed to West Africa ca. 9.3 Ma. Modern lineages began to diverge from each other roughly 19 Ma.

CONCLUSIONS

Nearly two-thirds of extant bromeliads belong to two large radiations: the core tillandsioids, originating in the Andes ca. 14.2 Ma, and the Brazilian Shield bromelioids, originating in the Serro do Mar and adjacent regions ca. 9.1 Ma.

Effects of climate on pollination networks in the West Indies

We studied the effect of climate on the plant-pollinator communities in the West Indies. We constructed plots of 200 m × 5 m in two distinct habitats on the islands of Dominica, Grenada and Puerto Rico (total of six plots) and recorded visitors to all plant species in flower. In total we recorded 447 interactions among 144 plants and 226 pollinator species. Specifically we describe how rainfall and temperature affect proportional richness and importance of the different pollinator functional groups. We used three measures of pollinator importance: number of interactions, number of plant species visited and betweenness centrality. Overall rainfall explained most of the variation in pollinator richness and relative importance. Bird pollination tended to increase with rainfall, although not significantly, whereas insects were significantly negatively affected by rainfall. However, the response among insect groups was more complex; bees were strongly negatively affected by rainfall, whereas dipterans showed similar trends to birds. Bird, bee and dipteran variation along the climate gradient can be largely explained by their physiological capabilities to respond to rainfall and temperature, but the effect of climate on other insect pollinator groups was more obscure. This study contributes to the understanding of how climate may affect neotropical plant-pollinator communities.

Nectar sugar composition and concentration in relation to pollination syndromes in Bromeliaceae

A first comprehensive dataset of nectar sugar composition and concentration in Bromeliaceae is presented, covering 111 species belonging to all three subfamilies. Based on this dataset, we examined the relationship between nectar traits and pollination syndromes in the family. Sugars in samples were assayed by high pressure liquid chromatography. All sampled species were grouped into three broad categories (trochilophilous, chiropterophilous, or lepidopterophilous) according to their main pollination mode. Significant differences between the different pollination syndromes were found in nectar sugar composition as well as concentration. For a total of four genera (Guzmania, Pitcairnia, Tillandsia and Vriesea), a comparison of nectar composition showed significant differences between trochilophilous and chiropterophilous species. Data presented here indicate that the characteristics of nectar in Bromeliaceae are predominantly determined by putative adaptations of nectar sugars to preferences of the pollinators rather than by phylogenetic relations.

Phylogenetic systematics and biogeography of hummingbirds: Bayesian and maximum likelihood analyses of partitioned data and selection of an appropriate partitioning strategy

Hummingbirds are an important model system in avian biology, but to date the group has been the subject of remarkably few phylogenetic investigations. Here we present partitioned Bayesian and maximum likelihood phylogenetic analyses for 151 of approximately 330 species of hummingbirds and 12 outgroup taxa based on two protein-coding mitochondrial genes (ND2 and ND4), flanking tRNAs, and two nuclear introns (AK1 and BFib). We analyzed these data under several partitioning strategies ranging between unpartitioned and a maximum of nine partitions. In order to select a statistically justified partitioning strategy following partitioned Bayesian analysis, we considered four alternative criteria including Bayes factors, modified versions of the Akaike information criterion for small sample sizes (AIC(c)), Bayesian information criterion (BIC), and a decision-theoretic methodology (DT). Following partitioned maximum likelihood analyses, we selected a best-fitting strategy using hierarchical likelihood ratio tests (hLRTS), the conventional AICc, BIC, and DT, concluding that the most stringent criterion, the performance-based DT, was the most appropriate methodology for selecting amongst partitioning strategies. In the context of our well-resolved and well-supported phylogenetic estimate, we consider the historical biogeography of hummingbirds using ancestral state reconstructions of (1) primary geographic region of occurrence (i.e., South America, Central America, North America, Greater Antilles, Lesser Antilles), (2) Andean or non-Andean geographic distribution, and (3) minimum elevational occurrence. These analyses indicate that the basal hummingbird assemblages originated in the lowlands of South America, that most of the principle clades of hummingbirds (all but Mountain Gems and possibly Bees) originated on this continent, and that there have been many (at least 30) independent invasions of other primary landmasses, especially Central America.