Floral Chamber Research Articles

Pollination‐related plant traits under environmental changes: Seasonal and daily mismatches produce temporal constraints

Abstract Pollination is a key tenet of ecosystem sustainability and food security, but it is threatened by climate change. While many studies investigated the response of plant‐pollination traits to temperature, few attempted multifactorial and integrative approaches with multiple floral traits. We determined which plant‐pollination traits were disrupted by environmental changes and the consequence for plant fitness. We focused on the thermogenic plant, Arum italicum, which relies on floral scent and heat production to attract its pollinators with a deceptive strategy. In a field mesocosm, we measured the response of floral phenology, thermogenesis traits, scent and plant fitness to experimental changes in shade level, water supply and soil temperature. In the laboratory, we exposed plants to extreme heat to determine the thermoregulation ability at high temperatures. Plant fitness decreased dramatically in response to soil warming and the level of shade. While both factors caused a lower number of inflorescences, soil warming was mostly responsible for the crash in number of fruits. The plant traits related to thermogenesis and scent were relatively resilient to the environmental changes in the mesocosm and were unlikely to produce the observed decrease in plant fitness. First, environmental changes only weakly modified the scent composition. Second, the appendix regulated its maximal temperature almost perfectly, while stamen regulated imperfectly. In the laboratory experiment, the appendix maintained a thermal gradient supposedly to improve scent emission while stamen became cooler than ambient air, possibly preventing the pollinators from overheating within the floral chamber. By contrast, the phenology of flowering was drastically modified. Flowers appeared earlier in the season in response to soil warming (by 39 days) or absence of shade (by 19 days). At the daily scale, flowering hour did not change across the season resulting in plants flowering before sunset late in the season and before the pollinator activity window (mostly nocturnal). The strong shift observed in the flowering period may induce a temporal mismatch with this pollinator both early and late in the season when the insects may not be active so early in the spring and during daytime, respectively, thereby altering plant fitness. Read the free Plain Language Summary for this article on the Journal blog.

What's that smell? The putrid scent of Rafflesia consueloae, its origin and developmental regulation

We report the floral scent composition of the endophytic holoparasite Rafflesia consueloae for the first time. Using a non-destructive in situ method that we developed, we identified 13 volatile compounds present in the scent of R. consuelaoe. Among the compounds detected were several benzenoids, organosilicons, an oligosulfide, a monoterpenoid, and a fatty acid-derived compound. Comparing the scent profiles of different reproductive stages, we found that all stages produced a similar set of volatiles, except for the flowers in bloom. The sulfur-containing dimethyl disulfide (DMDS), which is mainly responsible for the rotten smell of the flower, was only detected in the scent of full-bloom flowers indicating that its synthesis only takes place when the aperture is fully open and the flies are able to access the sex organs. Moreover, an analysis of the scent components of different floral parts from full-bloom flowers revealed that the different floral structures had varying scent profiles. The diaphragm and chamber floor produced the most volatiles. Notably, DMDS was only detected from the diaphragm and the central disk. Emission of putrid-smelling volatiles in these tissues may lure the flies into entering the floral chamber where the reproductive structures are located, thus increasing pollination success. Overall, this pioneering study of the R. consueloae floral scent composition provides valuable insights into the pollination mechanisms of the enigmatic Rafflesia genus and parasitic floral ecology in general.

Where are volatiles produced in the highly synorganised inflorescence of Arum maculatum L.?

Floral scents vary spatially within flowers and inflorescences, with effects on pollinator behaviour. Here, we restudied the spatial scent pattern of Arum maculatum, an Araceae, with a higher spatial resolution than previously. The inflorescence of this species consists of a spadix, whose distal part is a sterile osmophore called the appendix, whereas its basal part bears sterile and fertile male and female flowers. This spadix is surrounded by a spathe, which forms a floral chamber around the flowers. So far, it was known that the appendix is responsible for the emission of most of the volatiles, but some volatiles were specifically found within the floral chamber, with the organ(s) responsible for their emission being unclear. By repeatedly collecting (dynamic headspace) and analysing (gas chromatography/mass spectrometry) the scent of whole inflorescences and of inflorescences with the spathe and the various zones of the spadix sequentially removed, we determined and quantified all scent compounds of the major units of the inflorescence of A. maculatum. We confirm that the inflorescence scent is mainly composed of scents released by the appendix, and we for the first time provide evidence that the male flower zone of the spadix also contributes to the inflorescence scent. Future studies are needed to test whether, and if, how, this spatial scent pattern in A. maculatum affects the movement of pollinators within the inflorescence and their pollination effectiveness.

Chasmogamy and entomophily in Burmannia disticha (Burmanniaceae).

Burmannia shows a set of floral traits that suggest elaborate mechanisms of animal-mediated pollen transfer. These include flower coloration, septal nectaries and a long and narrow floral chamber. The stamens are synorganized with the common style restricting the entrance to the floral chamber, sometimes forming a gynostegium. Contrary to this apparent zoophilous floral syndrome, several species of Burmannia were reported to perform self-pollination via cleistogamy. Understanding of reproductive systems in Burmannia is complicated by scarcity of available results of direct observations on pollination process. Here we present data on pollination biology of B. disticha obtained during field investigations in Vietnam followed by laboratory analyses of ecologically important floral traits and the captured flower visitors. We found that the anthetic perianth is open, i.e. the flower is chasmogamous. The flowers are visited by various Diptera, Hymenoptera, Lepidoptera and Orthoptera. Of them, the bumblebees (Bombus burmensis), a bee (Coelioxys sp.) and some lepidopterans were revealed to carry pollen of B. disticha. Based on the amount of carried pollen, insect behavior during the visits and general knowledge on biology of these insect taxa, we concluded that the bumblebees act as the principal pollinators of B. disticha, whereas the lepidopterans are considered as its possible pollinators. We compared the lengths of proboscises of the captured insects to the depth of the floral chamber, and found that only the bumblebees and lepidopterans should be able to reach the nectar. Finally, we estimated the pollen-ovule ratio of B. disticha as 6.84, which is comparable to the ratio known in autogamous angiosperms. Based on its flower organization and pollination mechanism, we consider B. disticha an entomophilous and predominantly xenogamous species. Its gynostegium is likely an adaptation for pollen transfer by insects with long proboscises. At the same time, earlier investigations together with pollen-ovule ratio indicate that B. disticha possesses a labile pollination strategy, and autogamy sometimes occurs. Since Burmannia is one of the few angiosperm genera that comprise both mycoheterotrophic (achlorophyllous) and autotrophic (green) species, our study provides important evidence for reconstructions of ecological and morphological evolutionary pathways in relation to the mode of organic nutrition.

Transcriptomic analysis of deceptively pollinated Arum maculatum (Araceae) reveals association between terpene synthase expression in floral trap chamber and species-specific pollinator attraction.

Deceptive pollination often involves volatile organic compound emissions that mislead insects into performing nonrewarding pollination. Among deceptively pollinated plants, Arum maculatum is particularly well-known for its potent dung-like volatile organic compound emissions and specialized floral chamber, which traps pollinators-mainly Psychoda phalaenoides and Psychoda grisescens-overnight. However, little is known about the genes underlying the production of many Arum maculatum volatile organic compounds, and their influence on variation in pollinator attraction rates. Therefore, we performed de novo transcriptome sequencing of Arum maculatum appendix and male floret tissue collected during anthesis and postanthesis, from 10 natural populations across Europe. These RNA-seq data were paired with gas chromatography-mass spectrometry analyses of floral scent composition and pollinator data collected from the same inflorescences. Differential expression analyses revealed candidate transcripts in appendix tissue linked to malodourous volatile organic compounds including indole, p-cresol, and 2-heptanone. In addition, we found that terpene synthase expression in male floret tissue during anthesis significantly covaried with sex- and species-specific attraction of Psychoda phalaenoides and Psychoda grisescens. Taken together, our results provide the first insights into molecular mechanisms underlying pollinator attraction patterns in Arum maculatum and highlight floral chamber sesquiterpene (e.g. bicyclogermacrene) synthases as interesting candidate genes for further study.

The Genome-Wide Identification of Long Non-Coding RNAs Involved in Floral Thermogenesis in Nelumbo nucifera Gaertn.

The sacred lotus (Nelumbo nucifera Gaertn.) can maintain a stable floral chamber temperature when blooming, despite ambient temperature fluctuations; however, the long non-coding RNAs (lncRNAs) involved in floral thermogenesis remain unclear. In the present study, we obtain comprehensive lncRNAs expression profiles from receptacles at five developmental stages by strand-specific RNA sequencing to reveal the lncRNAs regulatory mechanism of the floral thermogenesis of N. nucifera. A total of 22,693 transcripts were identified as lncRNAs, of which approximately 44.78% had stage-specific expression patterns. Subsequently, we identified 2579 differential expressed lncRNAs (DELs) regulating 2367 protein-coding genes mainly involved in receptacle development and reproductive process. Then, lncRNAs with floral thermogenesis identified by weighted gene co-expression network analysis (WGCNA) were mainly related to sulfur metabolism and mitochondrial electron transport chains. Meanwhile, 70 lncRNAs were predicted to act as endogenous target mimics (eTMs) for 29 miRNAs and participate in the regulation of 16 floral thermogenesis-related genes. Our dual luciferase reporter assays indicated that lncRNA LTCONS_00068702 acted as eTMs for miR164a_4 to regulate the expression of TrxL2 gene. These results deepen our understanding of the regulation mechanism of floral thermogenesis by lncRNAs and accumulate data for further research.

Life history patterns of coleopteran pollinators of Annona crassiflora Mart. in the Brazilian Cerrado

ABSTRACT The large floral chambers of the Neotropical Annonaceae are pollinated by large beetles of the tribe Cyclocephalini Laporte (Melolonthidae). Previous research indicates that, depending on the geographic area, the assemblage of Cyclocephalini pollinators may differ. In this study, pollinators of Annona crassiflora Mart. were surveyed in the Cerrado of Chapada dos Guimarães, Mato Grosso, Brazil, for the first time. The analysis of 74 flowers from 24 A. crassiflora individuals revealed that the principal pollinator was Cyclocephala octopunctata Burmeister. The secondary pollinator, Cyclocephala celata Dechambre, and C. octopunctata exhibited behaviour that may promote cross pollination, visiting both female- and male-phase flowers, touching stigmas and anthers and becoming coated in pollen during anthesis. This is the first record of C. celata, a species commonly found pollinating Araceae in the Atlantic Forest, as a pollinator of an Annonaceae species in the Cerrado. Additionally, an interim phase between the female and male phases of A. crassiflora is documented here for the first time.

Diversity of Insect Flower Visitors of Xylopia aromatica (Magnoliales, Annonaceae) in a Brazilian Savanna

Small beetles are important pollinators of Annonaceae whose flower chambers are small and have diurnal and/or nocturnal anthesis. The pollinators of these flowers belong to the families Nitidulidae, Staphylinidae, Chrysomelidae, and Curculionidae. In this study, the first conducted in the Cerrado of Chapada dos Guimarães, Mato Grosso, Brazil, the behavior of the insect flower visitors of Xylopia aromatica was observed, in both the field and the laboratory. The chambers of 253 flowers were collected from 11 plants, and the biological aspects of their visitors were analyzed quantitatively and qualitatively. The most abundant visitors were thrips and beetles. Coleoptera was represented by four morphospecies occurring frequently in the floral chambers (>70% of individuals). Among beetles, one species belonged to Nitidulidae (Cillaeinae, Conotelus sp. 1) and two belonged to Staphylinidae (Aleocharinae sp. 1 and Aleocharinae sp. 2). These three morphospecies of small elongate beetles have setae where pollen may adhere. In addition, they were present on both male and female phases of the flowers, indicating potential cross-pollination. In the study area, X. aromatica possesses mixed pollination promoted by Thysanoptera and small Nitidulidae and Staphylinidae beetles. This study brings the first record of Lamprosomatinae (Chrysomelidae) and, especially, of Conotelus (Nitidulidae) in the flower chambers of X. aromatica, with new information on behavior of floral visitors coupled with their morphological traits that may promote cross-pollination in this plant species.

Coleopteran Pollinators of Annonaceae in the Brazilian Cerrado—A Review

The evolutionary trajectories of insects and angiosperms appear to be intimately interconnected. Increases in the diversity of phytophagous beetles and angiosperms co-occur in the Mesozoic fossil record, and there is fossil evidence of pollinivory and pollination by insects, both in flowering plants and in gymnosperms. The oldest records of angiosperm pollination indicate flies as pollen vectors. A basal group of angiosperms, the order Magnoliales, has retained plesiomorphic characters such as dozens of pistils and stamens spiraling around the receptacle. In a family of this order, Annonaceae, over 90% of species are pollinated by beetles. In many Annonaceae species, flowers display wide spaces, referred to as floral chambers, where beetles can find shelter from weather conditions and predators, food in the form of pollen and tissues, and a mating site. Two basic types of floral chambers can be distinguished: small chambers visited by small beetles (Nitidulidae, Staphylinidae, Chrysomelidae, and Curculionidae) with diurnal and/or nocturnal activity and large and thermogenic floral chambers visited by beetles of the tribe Cyclocephalini (Scarabaeoidea, Melolonthidae). In the latter case, the heat that the flowers produce may serve as a resource for the beetles that visit them, resulting in smaller endothermy costs for the scarabs. This study reviewed the literature including PhD and MSc theses on cantharophilous Annonaceae in the Cerrado. In this biome, both types of associations are found, although cantharophilous Annonaceae represent a small portion of the plant species (<5%). Cantharophilous Annonaceae in the Cerrado share attributes according to the beetles that pollinate them: species pollinated by small beetles, for instance, may flower throughout the year, whereas Annonaceae pollinated by Cyclocephalini normally flower in the beginning of the rainy season (October/November), in synchrony with the phenological patterns of their pollinators. Cantharophilous Annonaceae flowers, regardless of their size, tend to have light colors and sweet and fruity odors. In addition to the lack of studies on the attraction of beetles by these floral characters, the taxonomic composition of the beetles that pollinate Annonaceae in the Cerrado is poorly known. This review attempts to discuss, in light of what has already been published, potential fields of investigation concerning pollinating beetles’ behavior and evolution.

DIA-Based Quantitative Proteomics Reveals the Protein Regulatory Networks of Floral Thermogenesis in Nelumbo nucifera.

The sacred lotus (Nelumbo nucifera) can maintain a stable floral chamber temperature between 30 and 35 °C when blooming despite fluctuations in ambient temperatures between about 8 and 45 °C, but the regulatory mechanism of floral thermogenesis remains unclear. Here, we obtained comprehensive protein profiles from receptacle tissue at five developmental stages using data-independent acquisition (DIA)-based quantitative proteomics technology to reveal the molecular basis of floral thermogenesis of N. nucifera. A total of 6913 proteins were identified and quantified, of which 3513 differentially abundant proteins (DAPs) were screened. Among them, 640 highly abundant proteins during the thermogenic stages were mainly involved in carbon metabolism processes such as the tricarboxylic acid (TCA) cycle. Citrate synthase was identified as the most connected protein in the protein-protein interaction (PPI) network. Next, the content of alternative oxidase (AOX) and plant uncoupling protein (pUCP) in different tissues indicated that AOX was specifically abundant in the receptacles. Subsequently, a protein module highly related to the thermogenic phenotype was identified by the weighted gene co-expression network analysis (WGCNA). In summary, the regulation mechanism of floral thermogenesis in N. nucifera involves complex regulatory networks, including TCA cycle metabolism, starch and sucrose metabolism, fatty acid degradation, and ubiquinone synthesis, etc.

Pollination ecology of Symplocarpus foetidus (Araceae) in a seasonally flooded bog in Québec, Canada

ABSTRACT The pollination ecology of Symplocarpus foetidus (L.) W. Salisbury was studied in a seasonally forested flooded bog in Québec (Canada) in 2008 and 2009. The protogynous anthesis duration ranged from 15 to 20 days with, chronologically, a female phase of about 5 days, a bisexual phase of 2 days, and a male phase of 9 days. The spadix temperature differences with ambient air were higher during the female phase (mean: 13.6°C) than during the bisexual and male phases (mean: 4.5°C). The air inside the floral chamber was warmed by the heating spadix, particularly during the female phase (~6°C warmer than ambient air). High temperatures were maintained through nighttime during the female phase, whereas they occurred only during the daytime during the bisexual and male phases. The average natural fruit and seed sets were relatively low (18.2% and 14%), and the fruit set varied between years (13% in 2008 vs. 31% in 2009). Since spontaneous self-pollination is a rare reproductive event, sexual reproduction in Symplocarpus foetidus relies mainly on insect cross-pollination. Pollination is probably generalist considering the large variety of Coleoptera and Diptera families attracted to the plant, such as Chironomidae, Sphaeroceridae, Mycetophilidae, Phoridae, Drosophilidae, Chloropidae, and Anthomyiidae. Since many different insect types visit the inflorescences, it is unclear whether this pollination system is a deceptive interaction (its unpleasant floral scent is typical of other deceptive Araceae), a breeding site mutualism (developing larvae have been observed on the inflorescences), or a combination of the two.

Imitation of fermenting fruits in beetle-pollinated Calycanthus occidentalis (Calycanthaceae)

Calycanthus (Calycanthaceae), a genus for which three species are described, belongs to an early diverging lineage of angiosperms. As far as known, all species have highly specialized sap beetle (Nitidulidae) pollination systems. While the floral scent is likely to play a key role in attracting the beetles to the flowers, its chemistry is not known for any of the species of this genus. Herein, we analyzed the floral scent of the species Calycanthus occidentalis by dynamic headspace and gas chromatography / mass spectrometry (GC/MS), and determined its floral visitors in plants cultivated in the Botanical Garden of the University of Ulm. The protogynous flowers had one-to-two days lasting anthesis, similar to what was previously reported for native stands in California. More than ten pollinating beetle species, mainly Nitidulidae and Staphylinidae, were collected from the floral chambers of pistillate-stage flowers and identified to species level by DNA barcoding. The high number of beetle species inside the flowers was surprising, especially considering that only the nitidulid species Colopterus truncatus was known so far as pollinator in native habitats. In addition, we observed some drosophilid flies on, but not inside the flowers, which suggests that they are not pollinators. The scent of flowers had a strong alcoholic note, especially in the pistillate phase. The GC/MS data revealed that the most prominent scent compounds were ethanol, ethyl acetate, acetoin, 2,3-butanediol isomers, acetoin acetate, 2,3-butandiol monoacetate, and 2,3-butandiol diacetate. Interestingly, besides scent compounds that were previously found in plants pollinated by nitidulid and staphylinid beetles, some other compounds, including acetoin acetate and 2,3-butandiol monoacetate, were observed for the first time as floral scent of plants attracting such beetles. However, further studies will be required to investigate whether the stereoisomeric pattern of these compounds differs among plant species and whether the stereoisomers attract different pollinator species. Overall, the scent of C. occidentalis is similar to that of other plant species that release scents reminiscent of fermenting fruits and are pollinated by beetles and/or drosophilid flies, such as Asimina triloba, Ceropegia crassifolia and Arum palaestinum.

It sounds like food: Phonotaxis of a diurnal lizard

Foraging diurnal lizards are well known for their use of visual and chemical cues to detect prey. We already showed that the Balearic lizard is able to detect prey using visual and chemical cues, even from airborne odors. In this study we carried out a field experiment to test if lizards can detect prey using acoustic cues. Our results show that Podarcis lilfordi is able to detect flies trapped inside opaque cups, only using acoustic cues. To our knowledge, this is the first known case of phonotaxis of a diurnal lizard. Thus, P. lilfordi can detect, from far away, current pollinators trapped inside floral chambers of the dead horse arum, Helicodiceros muscivorus. This is another behavioral trait displayed by the Balearic lizard during its complex interaction with the dead horse arum.

The evolution of key functional floral traits in the early divergent angiosperm family Annonaceae

AbstractPotential key functional floral traits are assessed in the species‐rich early divergent angiosperm family Annonaceae. Pollinators (generally beetles) are attracted by various cues (particularly visual, olfactory, and thermogenic), with pollinators rewarded by nectar (generally as stigmatic exudate), heat, and protection within the partially enclosed floral chamber. Petals sometimes function as pollinator brood sites, although this could be deceptive. Annonaceae species are self‐compatible, with outcrossing promoted by a combination of protogyny, herkogamy, floral synchrony, and dicliny. Pollination efficiency is enhanced by pollen aggregation, changes in anthesis duration, and pollinator trapping involving a close alignment between petal movements and the circadian rhythms of pollinators. Most Annonaceae flowers are apocarpous, with syncarpy restricted to very few lineages; fertilization is therefore optimized by intercarpellary growth of pollen tubes, either by stigmatic exudate (suprastylar extragynoecial compitum) or possibly the floral receptacle (infrastylar extragynoecial compitum). Although Annonaceae lack a distinct style, the stigmas in several lineages are elongated to form “pseudostyles” that are hypothesized to function as sites for pollen competition. Flowers can be regarded as immature fruits in which the ovules are yet to be fertilized, with floral traits that may have little selective advantage during anthesis theoretically promoting fruit and seed dispersal. The plesiomorphic apocarpous trait may have been perpetuated in Annonaceae flowers as it promotes the independent dispersal of fruit monocarps (derived from separate carpels), thereby maximizing the spatial/temporal distance between seedlings. This might compensate for the lack of genetic diversity among seeds within fruits arising from the limited diversity of pollen donors.

Small RNA and Transcriptome Sequencing Reveals miRNA Regulation of Floral Thermogenesis in Nelumbo nucifera.

The sacred lotus (Nelumbo nucifera Gaertn.) can produce heat autonomously and maintain a relatively stable floral chamber temperature for several days when blooming. Floral thermogenesis is critical for flower organ development and reproductive success. However, the regulatory role of microRNA (miRNA) underlying floral thermogenesis in N. nucifera remains unclear. To comprehensively understand the miRNA regulatory mechanism of thermogenesis, we performed small RNA sequencing and transcriptome sequencing on receptacles from five different developmental stages. In the present study, a total of 172 known miRNAs belonging to 39 miRNA families and 126 novel miRNAs were identified. Twenty-nine thermogenesis-related miRNAs and 3024 thermogenesis-related mRNAs were screened based on their expression patterns. Of those, seventeen differentially expressed miRNAs (DEMs) and 1765 differentially expressed genes (DEGs) had higher expression during thermogenic stages. The upregulated genes in the thermogenic stages were mainly associated with mitochondrial function, oxidoreductase activity, and the energy metabolism process. Further analysis showed that miR156_2, miR395a_5, miR481d, and miR319p may play an important role in heat-producing activity by regulating cellular respiration-related genes. This study provides comprehensive miRNA and mRNA expression profile of receptacle during thermogenesis in N. nucifera, which advances our understanding on the regulation of floral thermogenesis mediated by miRNA.

Contrasting floral biology of Artabotrys species (Annonaceae): Implications for the evolution of pollinator trapping

AbstractArtabotrys comprises a species‐poor early divergent grade (EDG) and a main species‐rich clade (“main Artabotrys clade,” MAC). All members of the MAC exhibit a remarkably well‐conserved floral Bauplan characterized by a tightly enclosed floral chamber with an elaborate rim between the inner petal blade and claw. Conversely, EDG resembles the sister genus Xylopia in lacking the inner petal rim, with one species (Artabotrys brachypetalus) bearing petals that lack the distinction between blade and claw altogether. The floral phenology and pollination ecology of two exemplar species—Artabotrys brachypetalus from the EDG and Artabotrys blumei from the MAC—are compared, including assessment of effective pollinators and their activity patterns, scent chemistry and thermogenesis. Our study revealed that Artabotrys blumei exhibits abbreviated anthesis (c. 27 hr), with a floral phenology and morphology that are clearly consistent with pollinator trapping, and may be pollinated by small beetles. Artabotrys brachypetalus has a typical anthetic duration (c. 45 hr), lacks a pollinator trapping mechanism, and is pollinated by honey bees and curculionid beetles. The “xylopioid” traits of the EDG are likely to be plesiomorphic, whereas the tightly enclosed floral chamber is likely to be apomorphic for the MAC and functionally significant in trapping pollinators.

Biologia floral, fenologia reprodutiva e polinização de Xylopia aromatica (Lam.) Mart. (Annonaceae) em uma área de Cerrado no oeste da Bahia

A família Annonaceae é comum no Cerrado do Oeste da Bahia, mas os estudos sobre a sua biologia floral, reprodutiva e fenológica na região, bem como dados sobre seus polinizadores, são raros. Uma das espécies comuns na área é a Xylopia aromatica (Lam.) Mart. cujos aspectos reprodutivos, motivo do presente trabalho, são pouco conhecidos. O presente artigo realiza também o estudo da biologia floral e reprodutiva, a fenologia e os polinizadores dessa espécie. O estudo foi desenvolvido em uma área de Cerrado no município de Barreiras-BA de outubro de 2015 a setembro de 2017 durante o qual foram feitas as análises da fenologia reprodutiva e dos cruzamentos do sistema reprodutivo, assim como observações da biologia floral e de visitantes florais. As flores de X. aromatica são dicogâmicas do tipo protogínicas. A floração é sincrônica e contínua, possibilitando o fluxo gênico entre os indivíduos da espécie. Dentre os visitantes florais, destacou-se um Curculionidae, único encontrado dentro da câmara floral. A protoginia de X. aromatica impede a autopolinização, evidenciando a dependência de polinizadores para seu sucesso reprodutivo. A maior formação de frutos por polinização cruzada, aliada à baixa taxa por geitonogamia, sugere um sistema reprodutivo autoincompatível para essa espécie.

A new Costa Rican species of Drosophila visiting inflorescences of the hemi-epiphytic climber Monstera lentii (Araceae)

Drosophila monsterae sp. nov. is described from 11 males and 13 females collected from the inside of closed inflorescences of Monstera lentii (Araceae) at 1810m altitude in the Forest Reserve of Cerro de La Carpintera, Canton La Unión, Province of Cartago, Costa Rica. Although flies have been seen wandering and copulating inside the floral chambers of closed inflorescences during the floral female phase, eggs or larvae have not yet been found either in the spathe or in the fleshy spadix. The new species is related to Drosophila tristani Sturtevant, 1921, from San José, Costa Rica, from which it differs mainly by having smaller slightly circular compound eyes, distinctly broader genae (cheek index ca. 2.4 vs 5 in D. tristani), and the inner capsule of spermathecae with an unusual folded duct at basal half of its very wide introvert. This is the eighth species to be included in the New World, essentially Neotropical, subgenus Phloridosa. Photomicrographs of male and female terminalia are also provided.

Organ Homologies and Perianth Evolution in the Dasymaschalon Alliance (Annonaceae): Inner Petal Loss and Its Functional Consequences.

The Dasymaschalon alliance within the early divergent angiosperm family Annonaceae comprises c. 180 species in four genera (Dasymaschalon, Desmos, Friesodielsia, and Monanthotaxis). The alliance offers an excellent opportunity for investigating perianth evolution and functional adaptations because of the presence of different numbers of petal whorls and contrasting floral chamber morphologies. The absence of the inner petal whorl in Dasymaschalon renders it distinctive in the family: previous studies have suggested that its three outermost stamens might be homologous with the inner petals of the sister genus, Friesodielsia, reflecting a homeotic shift of floral organ identify from inner petals to stamens. To investigate this hypothesis and general perianth evolution in the alliance, we (i) compared the floral vascularization of selected Dasymaschalon and Friesodielsia species using paraffin serial sectioning, and (ii) mapped selected perianth characters of inferred functional significance onto a molecular phylogenetic framework of the Dasymaschalon alliance (46 accessions; five cpDNA, and two nrDNA markers). The results indicate that the vasculature of the outermost stamen whorl of Dasymaschalon does not fuse with the perianth cortical vascular system, but instead splits from the basal traces of the free stamen bundles, contradicting previous inferences of homology with the inner corolla whorl of other Annonaceae. The loss of the inner petal whorl in Dasymaschalon is less likely to be due to a homeotic mutation, and instead possibly involved either the loss of genes that are responsible for determining inner petals or else the expression failure of these genes. Optimizations of perianth characters indicate that the absence of the inner petal whorl and the connivence of outer petals during anthesis are synapomorphic for Dasymaschalon. Circadian trapping of pollinators is inferred either to be derived in the stem lineage of the Dasymaschalon–Friesodielsia clade, or else to have evolved in parallel in the Dasymaschalon and Friesodielsia lineages. Subsequent changes in the remaining petals of Dasymaschalon flowers (which do not fully separate during anthesis) are likely to have enabled perpetuation of the circadian trapping mechanism, lessening the adverse impacts of inner petal loss.

Pollination by nitidulid beetles in the hemi-epiphytic aroid Monstera lentii (Araceae: Monsteroideae)

Among aroids (Araceae family) with bisexual flowers, the reproductive biology of the neotropical genus Monstera (Subfamily Monsteroideae) is misunderstood. Nothing is known about the reproductive phenology and the sparse evidence on its pollination system is equivocal, suggesting both bees and beetles as pollinators. In order to elucidate the pollination system and reproductive behavior of Monstera, we documented the floral cycle, spathe movement, floral visitors, and heat production of the inflorescence, and the flowering and fruiting phenology of M. lentii in a montane forest in Costa Rica. We found that M. lentii was mainly visited and likely pollinated by nitidulid beetles (Cychrocephalus corvinus, Nitidulidae) from the Mystropini tribe, which were mainly known as palm pollinators so far. In this mutualism, the beetles use the floral chamber as shelter, mating place, and probably as brood site. Drosophilid flies also visited the inflorescences and might participate in a mixed-pollination system, while stingless bees are considered as pollen robbers. Flowering and fruiting peaks occurred during the rainy season. Floral development was protogynous, a mechanism likely to prevent self-pollination. We concluded that pollination in M. lentii represents a highly dependent system on biotic pollinators for successful fruit set which likely contributes to an out-crossed mating system. Our findings indicate that pollination systems of bisexual aroids are more diverse than previously suggested.