Floral Traits Research Articles

Evaluation of different China aster (Callistephus chinensis L. Nees) genotypes in the Terai region of West Bengal

The experiment was laid out in Randomized Completely Block Design with three replications. Sixteen genotypes namely, Arka Poornima, Arka Archana, Arka Aadya, Arka Kamini, Arka Shashank, Phule Ganesh White, Phule Ganesh Pink, Phule Ganesh Purple, Phule Ganesh Light pink, Pink Cushion, Arabhavi Aster Collection-1 (AAC-1), Namadhari Pink, Selected line (L-76), Selected line (L-179), Selected line (L-179/1) and Selected line (L-56) have been collected from IIHR, Hessaraghata Lake, Bengaluru, Karnataka for the trial.The different morphological, phenological as well as floral traits have been collected during the crop period which showed significant variation among the evaluated China aster genotypes. The maximum number of flowers per plant was recorded in ‘Arka Aadya’ (71.40) and ‘Arka Shashank’ (66.27) statistically at par with ‘Arka Aadya’ and the highest vase life as cut flower was noticed in Arka Shashank (11.67 days). Flower diameter was maximum in Phule Ganesh White (8.29 cm) which was at par with Arka Poornima (6.92 cm) and Phule Ganesh Purple (6.53 cm). Among the all genotypes, the maximum weight of ten fresh flowers were observed in Arka Poornima (54.17 g) which was statistically at par with Phule Ganesh White (53.61 g). These characters are considered to be very important with respect to commercial value of the variety for fulfil the consumers demand. The genotypes Arka Poornima, Phule Ganesh White, Arka Shashank, Arka Kamini and Arka Aadya may be recommended for commercial cultivation as loose flowers as well as cut flowers in the Terai region of West Bengal.

Strawberry varieties differ in pollinator-relevant floral traits.

A rising global population will need more food, increasing demand for insect pollination services. However, general insect declines conflict with this demand. One way to mitigate this conflict is to grow crop flowers that are easier for insects to find and more rewarding to those that visit them. This study quantifies variation in the pollinator-relevant traits of nectar and pollen production, flower size and flower shape in commercial strawberry, finding significant variation between varieties in all traits. Bumblebees could learn to distinguish between the extremes of variation in flower shape, but this learning is very slow, indicating that this variation is at the limit of that which can be detected by bumblebees. Bee preferences for nectar of differing sugar concentrations at field-realistic volumes were consistent with previous observations at larger volumes, suggesting that it is valid to translate lab findings to the field. This study builds on our knowledge of the range of pollinator reward present in a single cultivated species and of the impact of field-realistic levels of variation in floral traits on bumblebee preferences.

Dillenia (Dilleniaceae) pollen heteromorphy and presentation, and implications for pollination by bats.

Bat pollination of Dillenia in Fiji, a genus that was presumed to be pollinated by bees, posits that other Dillenia species may be bat-pollinated, with implications for conservation and the understanding of angiosperm evolution. Botanical descriptions of some corolla behaviours ('falling as a whole') suggest bat removal of permanently closed corollas, as in D. biflora. Considering the remoteness of species of interest, we reviewed some Dillenia floral traits to hypothesise what they may mean for bat pollination of the genus. We investigated D. biflora pollen grains apertures and reviewed Dillenia literature concerning corolla behaviour and colour, and pollen apertures and presentation, including pores and staminodes. Our samples had dramatically different ratios of tricolpate to tetracolpate pollen grains, a trait that does not exclude pollination by bees. Petal colour polymorphism occurs, with mixed colours proportionately less common in flowers with corollas that open. The proportion of species with staminodes did not differ between those presumed to be pollinated by bats and others, but anthers of the former were significantly more likely to have apical pores, and stamens all had similar length or were slightly longer in the middle, whereas stamens in two distinct groups occurred in 55% of bee-pollinated species. Pollen heteromorphy may facilitate pollination by different taxa in tropical environments. However, anther apical pores and stamen uniformity are more likely to be associated with bat-pollinated species than are other morphologies. Dillenia could be a useful model to examine evolutionary aspects of colour, heteranthery, staminodes and pollen heteromorphy. Only field work will verify bat pollination and the implications of bat dependence for Dillenia species.

Green Revolution dwarfing Rht genes negatively affected wheat floral traits related to cross-pollination efficiency.

Hybrid breeding is a promising strategy to quickly improve wheat yield and stability. Due to the usefulness of the Rht 'Green Revolution' dwarfing alleles, it is important to gain a better understanding of their impact on traits related to hybrid development. Traits associated with cross-pollination efficiency were studied using Near Isogenic Lines carrying the different sets of alleles in Rht genes: Rht1 (semi-dwarf), Rht2 (semi-dwarf), Rht1 + 2 (dwarf), Rht3 (extreme dwarf), Rht2 + 3 (extreme dwarf), and rht (tall) during four growing seasons. Results showed that the extreme dwarfing alleles Rht2 + 3, Rht3, and Rht1 + 2 presented the greatest effects in all the traits analyzed. Plant height showed reductions up to 64% (Rht2 + 3) compared to rht. Decreases up to 20.2% in anther length and 33% in filament length (Rht2 + 3) were observed. Anthers extrusion decreased from 40% (rht) to 20% (Rht1 and Rht2), 11% (Rht3), 8.3% (Rht1 + 2), and 6.5% (Rht2 + 3). Positive correlations were detected between plant height and anther extrusion, anther, and anther filament lengths, suggesting the negative effect of dwarfing alleles. Moreover, the magnitude of these negative impacts depends on the combination of the alleles: Rht2 + 3 > Rht3/Rht1 + 2 > Rht2/Rht1 > rht (tall). Reductions were consistent across genotypes and environments with interactions due to magnitude effects. Our results indicate that Rht alleles are involved in multiple traits of interest for hybrid wheat production and the need to select alternative sources for reduced height/lodging resistance for hybrid breeding programs.

REPRODUCTIVE ECOLOGY OF AN EVERGREEN DRY SEASON-BLOOMING TREE SPECIES, WALSURA TRIFOLIATA (A. JUSS.) HARMS (MELIACEAE)

Walsura trifoliata is an evergreen dry season-blooming hermaphroditic tree species. The flowers are nectariferous and characterized by urceolate androecium, strong protandry and secondary pollination mechanism, protruded bifid stigma displaying receptivity, self-compatibility and facultative xenogamy without the function of spontaneous autogamy. The floral traits indicate generalist pollination syndrome and adaptation for entomophily, with bees effecting mostly geitonogamy and wasps and butterflies effecting mostly xenogamy. Fruit-set is highest in xenogamy. Fruit is a globular drupe with 1-2 seeds embedded in fleshy aril. Seed dispersal modes include zoochory, barochory and hydrochory. The study shows that the function of generalist pollination syndrome, entomophily, facultative xenogamy and polychory enable this tree species to achieve highest fruit-set, maintain genetic variation through cross-pollination, and disperse its seeds to different distances in the forest ecosystem.

Commercial suitability and characterization of newly developed Erucastrum canariense (Can) sterile cytoplasm based cytoplasmic male sterile (CMS) lines in Indian cauliflower

The study presents the first to characterize novel Erucastrum canarianse Webb and Berthel (or Can) sterile cytoplasm-based CMS lines in Indian cauliflower (Brassica oleracea var. botrytis L.) and investigating their commercial suitability. Eleven Can-based CMS lines were examined for 12 agro-morphological and yield traits,18 floral traits, four seed yield traits together with three each of the Ogura (source: wild Japanese Radish) and Tour (Source: Brassica tournefortii) cytoplasms. All of the recorded floral and seed traits showed significant (P > 0.05) differences between the CMS lines of each group. Agro-morphological and yield traits in CMS lines and their maintainers, however, were non-significantly different. All the Can- and Ogura-based CMS lines showed flowering and appropriate seed formation by natural cross-pollination. Only two Tour cytoplasm-based CMS lines, Tour (DC-41-5) and Tour (DC-67), produced the smallest malformed flowers and stigma. The highest seed yield per plant in CMS lines was in Ogu (DC-98-4) and the lowest in Tour (DC-67). P14 and P15, two polymorphic mtDNA markers, were discovered for the Can CMS system for early detection. Five primers (ITS5a-ITS4, atpF-atpH, P16, rbeL and trnL), along with their maintainers, were sequenced and aligned to detect nucleotide changes including as additions and or deletions at different positions. The newly introduced E. canariense sterile cytoplasm-based CMS system in cauliflower is the subject of the first comprehensive report, which emphasises their potential as a further stable and reliable genetic mechanism for hybrid breeding.

Secretory Tissues and Volatile Components of Disc Florets in Several Wild Helianthus L. Species

Although flower pollinator interactions are known to be mediated by floral traits, not enough attention has been paid to the research of secretory tissues and volatile components of sunflower disc florets as potentially important parameters in breeding programs. (1) To our knowledge, this is the first integrated study aimed at better understanding the attractiveness of sunflower capitula to insects. In the study, we have made a very detailed comparative analysis of secretory tissues and the characterization of the volatile components (VOCs) of disc florets in 10 wild perennial Helianthus species. (2) For anatomical analyses, cross-sections were obtained from the nectary zone of disc florets using a cryotechnique procedure. Micromorphological observation and morphological and anatomical analysis of disc florets were performed using light and scanning electron microscopy. For VOCs, we applied headspace, GC-FID, and GC/MS analyses. (3) The obtained results indicate that there is a difference between the analyzed traits among studied species. H. eggertii, H. hirsutus, H. mollis, H. resinosus, and H. tuberosus had high disc diameter values, a high cross-section area and disc floret corolla length, as well as the largest cross-section area and thickness of the disc florets nectary. In the analyzed VOCs, 30 different compounds were detected. The highest yield and quantity of α-Pinene was observed in H. mollis. (4) Inflorescence features, such as receptacle diameter, corolla and secretory tissue properties, and floret VOCs production and characterization, provided valuable information that can be used as guidelines in sunflower breeding programs to maximize pollinator attractiveness and increase seed yield.

Phylogeny of Prosthechea (Laeliinae, Orchidaceae) based on nrITS and plastid DNA sequences: Reassessing the lumper‐splitter debate and shedding light on the evolution of this Neotropical genus

AbstractAfter a confused taxonomic history, Prosthechea (Laeliinae, Orchidaceae) has been circumscribed in a broad sense to include species previously placed in Encyclia subg. Osmophytum. However, recent alternative classifications resurrecting old names such as Anacheilium and Hormidium, and proposing new genera such as Euchile, Panarica, Pollardia, and Pseudencyclia were presented, splitting Prosthechea into narrower genera. In this study, we provide a molecular phylogeny of Prosthechea to reassess alternative generic classifications and shed light on evolutionary aspects of this highly diverse Neotropical lineage. Eighty species of Prosthechea s.l. and 12 species of related genera were sampled. Bayesian and maximum parsimony analyses of sequences from three plastid regions (rpl32‐trnL, trnD‐trnT, ycf1) and nrITS were included. Possible conflicts between nuclear and plastid data were assessed with partitioned Bremer support. Ancestral state reconstructions of morphological characters relevant to the genus taxonomy are provided. Our results reinforce the monophyly of the lineage corresponding to a broad circumscription of Prosthechea. The small lineages corresponding to Euchile, Panarica, and Hormidium are monophyletic, whereas the larger Anacheilium, Pollardia, and Pseudencyclia are not monophyletic. Splitting Prosthechea into smaller genera is not supported by our phylogeny, and nonmonophyly also hinders the proposal of a comprehensive infrageneric classification. The phylogenetic relationships recovered reflect better the biogeographic patterns than the previously proposed morphological affinities, pointing to the existence of homoplastic floral traits within the genus. Conflicts between nuclear and plastid partitions were detected, suggesting a possible scenario of reticulate evolution.

Parallel evolution of morphological and genomic selfing syndromes accompany the breakdown of heterostyly.

Evolutionary transitions from outcrossing to selfing in flowering plants have convergent morphological and genomic signatures and can involve parallel evolution within related lineages. Adaptive evolution of morphological traits is often assumed to evolve faster than nonadaptive features of the genomic selfing syndrome. We investigated phenotypic and genomic changes associated with transitions from distyly to homostyly in the Primula oreodoxa complex. We determined whether the transition to selfing occurred more than once and investigated stages in the evolution of morphological and genomic selfing syndromes using 22 floral traits and both nuclear and plastid genomic data from 25 populations. Two independent transitions were detected representing an earlier and a more recently derived selfing lineage. The older lineage exhibited classic features of the morphological and genomic selfing syndrome. Although features of both selfing syndromes were less developed in the younger selfing lineage, they exhibited parallel development with the older selfing lineage. This finding contrasts with the prediction that some genomic changes should lag behind adaptive changes to morphological traits. Our findings highlight the value of comparative studies on the timing and extent of transitions from outcrossing to selfing between related lineages for investigating the tempo of morphological and molecular evolution.

Dominance of non-wetland-dependent pollinators in a plant community in a small natural wetland in Shimane, Japan.

Many wetland plants rely on insects for pollination. However, studies examining pollinator communities in wetlands remain limited. Some studies conducted in large wetlands (> 10ha) have suggested that wetland-dependent flies, which spend their larval stage in aquatic and semi-aquatic habitats, dominate as pollinators. However, smaller wetlands surrounded by secondary forests are more prevalent in Japan, in which pollinators from the surrounding environment might be important. Additionally, information regarding floral traits that attract specific pollinator groups in wetland communities is scarce. Therefore, this study aimed to understand the characteristics of insect pollinators in a small natural wetland (2.5ha) in Japan. We examined the major pollinator groups visiting 34 plant species and explored the relationship between the flower visitation frequency of each pollinator group and floral traits. Overall, flies were the most dominant pollinators (42%), followed by bees and wasps (33%). Cluster analysis indicated that fly-dominated plants were the most abundant among 14 of the 34 target plant species. However, 85% of the hoverflies, the most abundant flies, and 82% of the bees were non-wetland-dependent species, suggesting that these terrestrial species likely originated from the surrounding environment. Therefore, pollinators from the surrounding environment would be important in small natural wetlands. Flies tend to visit open and white/yellow flowers, whereas bees tended to visit tube-shaped flowers, as in forest and grassland ecosystems. The dominance of flies in small wetlands would be due to the dominance of flowers preferred by flies (e.g., yellow/white flowers) rather than because of their larval habitats.

Intermediary floral traits between natural hybrid and its parents in the Xiquexique (Cactaceae)

Intermediary floral traits between natural hybrid and its parents in the Xiquexique (Cactaceae)

The interplay between climatic niche evolution, polyploidy and reproductive traits explains plant speciation in the Mediterranean Basin: a case study in Centaurium (Gentianaceae).

Speciation and diversification patterns in angiosperms are frequently shaped by niche evolution. Centaurium Hill is a Mediterranean genus with ca. 25 species, of which 60% are polyploids (tetra- and hexaploids), distributed mainly in the Mediterranean Basin and in areas with temperate and arid climates of Asia, Europe, North-Central Africa and North America. The evolutionary history of this genus has been studied using morphological, biogeographical and molecular approaches, but its climatic niche characterization and its relation with genome evolution (chromosome number and ploidy level) has not been addressed yet. Thus, this study aims to identify the role of the evolution of climatic niche, ploidy level, life cycle and floral traits in the diversification of Centaurium. Climatic niche characterization involved estimating present climate preferences using quantitative data and reconstructing ancestral niches to evaluate climatic niche shifts. The evolution of climatic niche towards selective optima determined by ploidy level (three ploidy levels) and different binary traits (polyploidy, floral size, floral display, herkogamy and life cycle) was addressed under the Ornstein-Uhlenbeck model. Chromosome number evolution was inferred using the ChromoSSE model, testing if changes are clado- or anagenetic. Chromosome number evolution and its link with cladogenesis, life cycle and floral traits was modeled on the phylogeny. The reconstruction of the ancestral niches shows that Centaurium originated in a mild climate and diversified to both humid and cold as well as to dry and warmer climates. Niche conservatism was estimated in the climatic niche of the ancestors, while the climatic niche of the current taxa experienced transitions from their ancestors' niche. Besides, the evolution of climatic niche towards multiple selective optima determined by the studied traits was supported, life cycle optima receiving the highest support. The reconstruction of chromosome number transitions shows that the rate of speciation process resulting from chromosomal changes (chromosomal cladogenesis) is similar to that of non-chromosomal cladogenesis. Additionally, dependent evolution of floral size, floral display and herkogamy with chromosome number variation was supported. In conclusion, polyploidization is a crucial process in the Mediterranean region that assisted speciation and diversification into new areas with different climates, entailing niche shifts and evolution of reproductive strategies.

Floral biology, pollinators and breeding system of Passiflora chrysophylla (Passifloraceae), a South American passion vine

Context Knowledge of the reproductive biology of plants is fundamental for conservation, especially of the ones with a limited distribution. Aims The sexual reproduction of the small-ranged Passiflora chrysophylla Chod. was studied. Methods Controlled pollinations were performed to assess the breeding system, whereas floral traits and visitors (identity, frequency, activity on the flowers, dimensions and pollen load) were analysed to assess the pollination mechanism. Key results Self-compatibility was partial. Anthesis was matinal. The odour emitted by the corona was sweet, whereas the odour emitted by the persistent sepals and bracts was similar to that of the leaves. Contrasting concentric circular reward guides were present in the visible and UV spectra. Nectar concentration was high, the volume increased throughout anthesis and, if removed, nectar was replenished only once during the flower lifespan. Style movements towards the anthers determined male and hermaphroditic phases in most of the flowers; in a few flowers (smaller, scented and nectarless), styles remained apart from the anthers, thus constituting a functionally andromonecious and deceptive automimicry system. The bees Ptiloglossa sp., Thygater analis and Xylocopa augusti acted as pollinators, whereas ants, butterflies and beetles were nectar or pollen thieves and florivores. Conclusions P. chrysophylla is melittophilous and pollinators increase reproductive success. Implications Pollination biology of P. chrysophylla, reported for the first time, would contribute to conservation management of this species with restricted distribution.

Nectar cardenolides and floral volatiles mediate a specialized wasp pollination system.

Specialization in plant pollination systems can arise from traits that function as filters of flower visitors. This may involve chemical traits such as floral volatiles that selectively attract favoured visitors and non-volatile nectar constituents that selectively deter disfavoured visitors through taste or longer-term toxic effects or both. We explored the functions of floral chemical traits in the African milkweed Gomphocarpus physocarpus, which is pollinated almost exclusively by vespid wasps, despite having nectar that is highly accessible to other insects such as honeybees. We demonstrated that the nectar of wasp-pollinated G. physocarpus contains cardenolides that had greater toxic effects on Apis mellifera honeybees than on Vespula germanica wasps, and also reduced feeding rates by honeybees. Behavioural experiments using natural compositions of nectar compounds showed that these interactions are mediated by non-volatile nectar chemistry. We also identified volatile compounds with acetic acid as a main component in the floral scent of G. physocarpus that elicited electrophysiological responses in wasp antennae. Mixtures of these compounds were behaviourally effective for attraction of V. germanica wasps. The results show the importance of both volatile and non-volatile chemical traits as filters that lead to specialization in plant pollination systems.

Pollination of Chamaepentas nobilis (Rubiaceae) by long‐proboscid hawkmoths in south‐central Africa: Trait mismatching and floral scent chemistry

AbstractThe evolution of extremely long (>10 cm) floral tubes in angiosperms is closely linked with adaptation for pollination by long‐proboscid hawkmoths. In most cases, pollen is placed on the head or body of these moths, selecting for floral tubes that match or slightly exceed their proboscis length as this ensures contact with reproductive parts of the flower. However, in the case of Chamaepentas nobilis (Rubiaceae), anthers are inserted inside the c. 12‐cm floral tubes and coat the proboscis of visiting hawkmoths with sticky pollen, meaning that insects with proboscides longer than the floral tube can be effective pollinators, despite trait mismatching. Direct observations and camera trapping on granite outcrops in central Zambia showed that C. nobilis was visited both by Agrius convolvuli (proboscis length c. 13 cm) and Xanthopan morganii (proboscis length c. 17 cm), which are the only moth species in Africa that can access the small amounts of dilute nectar at the base of the floral tube. Pollen on the proboscides of captured hawkmoths was confirmed to originate from C. nobilis. Key floral advertising traits of C. nobilis include early evening anthesis, the highly reflective white limbus, and the evening production of scent dominated by oxygenated aromatic and terpenoid compounds known to elicit antennal responses of A. convolvuli. This study shows that that A. convolvuli and X. morganii share floral resources and jointly pollinate C. nobilis, despite their proboscides differing in length and being mismatched with the corolla tube length.

Flowering phenology differs among wet and dry sub-alpine meadows in southwestern China.

The effect of floral traits, floral rewards and plant water availability on plant-pollinator interactions are well-documented; however, empirical evidence of their impact on flowering phenology in high-elevation meadows remains scarce. In this study, we assessed three levels of flowering phenology, i.e. population-, individual- and flower-level (floral longevity), in two nearby but contrasting (wet versus dry) sub-alpine meadows on Yulong Snow Mountain, southwestern China. We also measured a series of floral traits (pollen number, ovule number, and the ratio of pollen to ovule number per flower, i.e. pollen:ovule ratio [P/O]) and floral rewards (nectar availability and pollen presentation) as plausible additional sources of variation for each phenological level. Floral longevity in the wet meadow was significantly longer than that for the dry meadow, whereas population- and individual-flowering duration were significantly shorter. Our results showed a significant positive relationship between flowering phenology with pollen number and P/O per flower; there was no relationship with ovule number per flower. Further, we found a significant effect of flowering phenology on nectar availability and pollen presentation. Our findings suggest that shorter floral longevity in dry habitats compared to wet might be due to water-dependent maintenance costs of flowers, where the population- and individual-level flowering phenology may be less affected by habitats. Our study shows how different levels of flowering phenology underscore the plausible effects of contrasting habitats on reproductive success.

Bird‐flower colour on islands supports the bee‐avoidance hypothesis

Abstract Many insular plant species inhabiting different archipelagos worldwide present typical ornithophilous floral traits (e.g. copious nectar, red‐orange colours), but most of them are visited by insectivorous/granivorous birds and lizards, which act as generalist pollinators. Oceanic islands promote these ecological interactions mainly due to the scarcity of arthropods. Our goal is to understand how these generalist interactions contribute to the shift of floral traits from entomophily (mainland) to ornithophily or saurophily (island), where specialist nectar‐feeding birds have not inhabited. We used the well‐known pollination interactions occurring in the Canary Islands to evaluate two proposed ecological hypotheses, bee‐avoidance or bird‐attraction, explaining evolutionary transitions of floral traits. Specifically, we studied the flower colour conspicuousness of bird‐pollinated Canarian species visited by birds and lizards with their closest relatives from the mainland mainly visited by bees. We analysed the chromatic contrast of flower colours using visual models of bees, birds and lizards and the achromatic contrast in visual models of bees. We also compared reflectance spectra marker points of flowers with available spectral discrimination sensitivities of bees and birds. Using a phylogenetically corrected framework of independent plant lineages, our results revealed that bird‐pollinated Canarian species showed lower chromatic contrast according to bees and lizard visual models than their mainland relatives, but similar chromatic contrast for bird vision. In addition, reflectance spectra marker points of the Canarian species were displaced to the longest wavelengths, far from the wavelengths of maximum discrimination of bees, but close to birds. We conclude that the avoidance of bees would be a primary ecological strategy explaining the evolutionary transitions of flower colours from melittophily to ornithophily. The lower conspicuousness of bird‐pollinated Canarian flowers in lizards is perhaps a side effect of the bee‐avoidance strategy rather than an independent evolutionary strategy. Together, these findings provide insights into how vertebrate generalist pollinators can also lead to divergence of floral traits in insular habitats, but also in other arthropod‐poor habitats. Read the free Plain Language Summary for this article on the Journal blog.

Effects of experimental warming on floral scent, display, and rewards in two subalpine herbs.

Floral volatiles, visual traits, and rewards mediate attraction and defense in plant-pollinator and plant-herbivore interactions, but these floral traits may be altered by global warming through direct effects of temperature or longer term impacts on plant resources. We examined the effect of warming on floral and leaf volatile emissions, floral morphology, plant height, nectar production, and oviposition by seed predators. We used open-top chambers that warmed plants in the field +2-3 °C on average (+6-11 °C increase in daily maxima) for 2-4 weeks across 1-3 years at 3 sites in Colorado, USA. Volatiles were sampled from two closely related species of subalpine Ipomopsis with different pollinators: I. aggregata ssp. aggregata, visited mainly by hummingbirds, and I. tenuituba ssp. tenuituba, often visited by hawkmoths. While warming had no detected effects on leaf volatiles, the daytime floral volatiles of both I. aggregata and I. tenuituba responded in subtle ways to warming, with impacts that depended on the species, site, and year. In addition to the long-term effect of warming, temperature at the time of sampling independently affected the floral volatile emissions of I. aggregata during the day and I. tenuituba at night. Warming had little effect on floral morphology for either species, and no effect on nectar concentration, maximum inflorescence height, or flower redness in I. aggregata. However, warming increased nectar production in I. aggregata by 41%, a response that would attract more hummingbird visits, and reduced oviposition by fly seed predators by at least 72%. Our results suggest that floral traits can show different levels of plasticity to temperature changes in subalpine environments, with potential effects on animal behaviors that help or hinder plant reproduction. They also illustrate the need for more long-term field warming studies, as shown by responses of floral volatiles in different ways to weeks of warming versus temperature at the time of sampling.

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.

Drivers of sunbird‐plant interactions on Mount Cameroon: Between neutrality and niche‐based processes

AbstractThe drivers behind plant‐pollinator interactions still need to be fully understood. Previous research has suggested that observed interactions result from either neutral interaction between species based on their abundance or from niche‐based processes, which are reflected in the adaptations of both plants and pollinators. Furthermore, the importance of both scenarios can differ depending on seasonal dynamics translated into differences in resource availability. Extensive research has been conducted on New‐World hummingbirds (Trochilidae), whereas much less is known about Old World nectar‐feeding sunbirds (Nectariniidae). Our study aimed to explore whether sunbird‐plant interactions are explained by neutral and/or niche‐based processes. Thus, we tested the effects of abundance, morphology, and nectar sugar content on the observed interactions and the link between sunbirds and plant traits. Moreover, we explored the effects of robbing on these mechanisms. Finally, we investigated the partitioning of bird pollination niches, based on floral traits. We used a dataset of sunbird‐plant interactions collected at Mount Cameroon during two seasons (dry and wet seasons). Our study shows that sunbird‐plant interactions are influenced by both neutral and niche‐based processes. Neutral processes and nectar reward were the main mechanisms underlaying the observed interactions in the dry season. However, as more ornithophilous plants bloom during the rainy season, morphological trait‐matching becomes more important. We found a correlation between bill length and floral tube dimensions and observed niche overlap among the sunbird species. Considering this and other research, we suggest that plant‐pollinator interactions are influenced by a combination of both neutral and niche‐based processes.