Preference For Flowers Research Articles

Comparison of mechanisms of reproductive interference in Taraxacum.

Background and AimsReproductive interference may reduce fitness of either of the involved species, with potentially important ecological and evolutionary consequences. Except for the effect of shared pollinators on reproductive success, however, mechanisms underlying reproductive interference have been little studied, even though the severity of its impact may depend on the specific mechanism. The aim of this study was therefore to explore the mechanisms of reproductive interference between Taraxacum japonicum (native to Japan) and Taraxacum officinale (alien).MethodsIn a field survey, the association between alien species density and seed set in T. japonicum, and whether pollinator behaviour indicated a preference for the alien, were examined. Effects of heterospecific pollen deposition were measured in a series of hand pollination experiments, including mixed pollination experiments in which the order of application of conspecific and heterospecific pollen was varied. Finally, to investigate hybridization frequency, the parentage of seedlings produced following natural, mixed or heterospecific pollination was compared.Key ResultsAlien species density did not negatively affect native seed set, nor did pollinators appear to have a preference for alien flowers. The hand pollination experiments showed that heterospecific pollen deposition adversely affected native seed set, especially when alien pollen was applied before conspecific pollen. No viable hybrids were found following natural pollination, which suggests that hybridization might be a rare event.ConclusionAmong the examined mechanisms, heterospecific pollen deposition might have the largest deleterious effect on the native species. This effect is frequency dependent; thus, a positive feedback loop may cause the effect on the population dynamics to increase over time, with the result that the alien might eventually displace the native in a population. Effects of the examined mechanisms on population dynamics should be investigated further to improve understanding of the impact of reproductive interference on the structure of plant communities.

Preferencias de tisanópteros (Thysanoptera) por las estructuras aéreas de las plantas de algodón (Gossypium hirsutum) en Colombia

El objetivo del presente estudio fue determinar los niveles de preferencia de especies de trips por estructuras aéreas de las plantas de algodón. Para ello, en el valle cálido del alto Magdalena en la región Andina de Colombia, se coleccionaron e identificaron especies de trips asociadas al sistema productivo de algodón. Se muestrearon 60 fincas productoras en fase de llenado de cápsulas, donde la planta de algodón presentó los microhábitats: hoja joven, botón floral, flor y cápsula. Se realizaron análisis de agrupamiento de Bray-Curtis y pruebas no paramétricas de Kruskall-Wallis. Las especies registradas fueron Thrips palmi, Scirtothrips dorsalis y Frankliniella cephalica. Thrips palmi (n=3595; µ = 14,97 ± 32,35) fue la más frecuente, seguida por S. dorsalis (n = 856; µ = 3,56 ± 6,35) y Fr. cephalica (n = 405; µ = 1,68 ± 9,13). Thrips palmi se encontró en todos los microhábitats; S. dorsalis prefirió cápsula, seguido de hoja joven y botón floral. Frankliniella cephalica mostró preferencia por las flores. El presente estudio reveló la acción fitófaga de T. palmi y S. dorsalis como insectos con preferencia intra-hospedante del tipo generalista, hacia hojas (filofagía), botones florales (antofagía) y cápsulas (carpofagía). Frankliniella cephalica se comportó como especialista en flores (antofagía) de algodón.

A key floral scent component (β‐trans‐bergamotene) drives pollinator preferences independently of pollen rewards in seep monkeyflower

AbstractFloral odours play an important role in attracting insect pollinators. Because pollinators visit flowers to obtain pollen and nectar rewards, they should prefer floral odour profiles associated with the highest‐rewarding flowers (honest signals). In previous work, bumblebees exhibited a preference for flowers from outbred over inbredMimulus guttatusplants. Pollen is the only floral reward inM. guttatus, and pollen viability (a reliable indicator of protein content) is reduced in inbred plants. Yet, differences in pollen viability did not explain the observed preferences.In this study, we examined the floral volatile profiles of inbred and outbredM. guttatusto identify inbreeding effects and associations between volatile compounds and the number of viable pollen grains per flower, designated “PRQ” (pollen reward quality). We also conducted pairwise choice tests withBombus impatiensto evaluate the ability of bees to discriminate between odours of rewarding and non‐rewarding flowers and to determine whether bumblebee preferences are explained by differences in the floral odours of inbred and outbred plants.Inbred plants exhibited reduced emission of β‐trans‐bergamotene, the second‐most abundant compound in the volatile blend of outbred plants. Furthermore, pollen and fertile anthers emitted nonadecane. Six other compounds in the floral blend were positively correlated withPRQ. There was no overlap between compounds affected by inbreeding and compounds associated withPRQ.Even when given prior experience foraging onM. guttatus, bumblebees did not distinguish between the floral odours of rewarding and non‐rewarding outbred plants. However, they preferred floral odours from non‐rewarding outbred plants over rewarding inbred plants. Bumblebees without prior experience of flowers preferred volatile blends with higher versus lower amounts of β‐trans‐bergamotene.Taken together, these results suggest that the volatile emissions ofM. guttatusprovide reliable indicators of pollen rewards (potential honest signals), but that the preference of bumblebees for outbred plants is not driven by these cues but rather by a sensory bias for β‐trans‐bergamotene. This may represent a subtle form of deceit‐pollination that allows plants to attract pollinators while minimizing investment in costly rewards.Aplain language summaryis available for this article.

Flower movement balances pollinator needs and pollen protection.

Flower signaling and orientation are key characteristics that determine a flower's pollinator guild. However, many flowers actively move during their daily cycle, changing both their detectability and accessibility to pollinators. The flowers of the wild tobacco Nicotiana attenuata orientate their corolla upward at sunset and downward after sunrise. Here, we investigated the effect of different flower orientations on a major pollinator of N. attenuata, the hawkmoth Manduca sexta. We found that although flower orientation influenced the flight altitude of the moth in respect to the flower, it did not alter the moth's final flower choice. These behavioral observations were consistent with the finding that orientation did not systematically change the spatial distribution of floral volatiles, which are major attractants for the moths. Moreover, hawkmoths invested the same amount of time into probing flowers at different orientations, even though they were only able to feed and gather pollen from horizontally and upward‐oriented flowers, but not from downward‐facing flowers. The orientation of the flower was hence crucial for a successful interaction between N. attenuata and its hawkmoth pollinator. Additionally, we also investigated potential adverse effects of exposing flowers at different orientations to natural daylight levels, finding that anther temperature of upward‐oriented flowers was more than 7°C higher than for downward‐oriented flowers. This increase in temperature likely caused the significantly reduced germination success that was observed for pollen grains from upward‐oriented flowers in comparison to those of downward and horizontally oriented flowers. These results highlight the importance of flower reorientation to balance pollen protection and a successful interaction of the plant with its insect pollinators by maintaining the association between flower volatiles and flower accessibility to the pollinator.

Flower visitation by hoverflies (Diptera: Syrphidae) in a temperate plant-pollinator network.

Hoverflies (Diptera: Syrphidae) are among the most important pollinators, although they attract less attention than bees. They are usually thought to be rather opportunistic flower visitors, although previous studied demonstrated that they show colour preferences and their nectar feeding is affected by morphological constraints related to flower morphology. Despite the growing appreciation of hoverflies and other non-bee insects as pollinators, there is a lack of community-wide studies of flower visitation by syrphids. The aim of this paper is to provide a detailed analysis of flower visitation patterns in a species rich community of syrphids in a Central European grassland and to evaluate how species traits shape the structure of the plant-hoverfly flower visitation network. We found that different species varied in the level of specialisation, and while some species visited a similar spectre of flowers, others partitioned resources more strongly. There was a consistent difference in both specialisation and flower preferences between three syrphid subfamilies. Eristalinae and Pipizinae were more specialised than Syrphinae. Trait-based analyses showed that relative flower visitation (i) increased with plant height, but most strongly in Eristalinae; (ii) increased with inflorescence size in small species from all three subfamilies, but was independent of inflorescence size in large species of Eristalinae and Syrphinae; and (iii) depended on flower colour, but in a subfamily-specific way. Eristalinae showed the strongest flower colour preferences for white flowers, Pipizinae visited mostly white and yellow flowers, while Syrphinae were less affected by flower colour. Exploration of the structure of the plant-hoverfly flower visitation network showed that the network was both modular and nested. We also found that there were almost no differences in specialisation and relative visitation frequency between males and females. Overall, we showed that flower visitation in syrphids was affected by phylogenetic relatedness, body size of syrphids and several plant traits.

Discriminating unifloral honey from a dioecious mass flowering tree of Brazilian seasonally dry tropical forest through pollen spectra: consequences of honeybee preference for staminate flowers

Myracrodruon urundeuva (“aroeira”) is a dioecious tree of the seasonally dry tropical forest (SDTF) of Brazil and source of a unique unifloral honey. To discriminate this honey by its pollen spectra, we compared melissopalynological analysis of reference honey samples with those of other samples collected in the SDTF belt. Reference honeys had on average 99% of aroeira pollen, while the other honey samples averaged 84% of this pollen. We used the receiver operating characteristic (ROC) curve, applied here for the first time in honey analysis, for determining the cut-off value of at least 93% of Myracrodruon pollen in a sample for classifying unifloral aroeira honey. The over-representation of aroeira pollen in this honey reflects that honeybees visited ten times as many staminate flowers as pistillate flowers. We conclude that unifloral aroeira honey has uniform pollen spectra, as a byproduct of the preference of honeybees for staminate flowers.

Flower preferences and pollen transport networks for cavity-nesting solitary bees: Implications for the design of agri-environment schemes.

Floral foraging resources are valuable for pollinator conservation on farmland, and their provision is encouraged by agri‐environment schemes in many countries. Across Europe, wildflower seed mixtures are widely sown on farmland to encourage pollinators, but the extent to which key pollinator groups such as solitary bees exploit and benefit from these resources is unclear. We used high‐throughput sequencing of 164 pollen samples extracted from the brood cells of six common cavity‐nesting solitary bee species (Osmia bicornis, Osmia caerulescens, Megachile versicolor, Megachile ligniseca, Megachile centuncularis and Hylaeus confusus) which are widely distributed across the UK and Europe. We documented their pollen use across 19 farms in southern England, UK, revealing their forage plants and examining the structure of their pollen transport networks. Of the 32 plant species included currently in sown wildflower mixes, 15 were recorded as present within close foraging range of the bees on the study farms, but only Ranunculus acris L. was identified within the pollen samples. Rosa canina L. was the most commonly found of the 23 plant species identified in the pollen samples, suggesting that, in addition to providing a nesting resource for Megachile leafcutter bees, it may be an important forage plant for these species. Higher levels of connectance and nestedness were characteristic of pollen transport networks on farms with abundant floral resources, which may increase resilience to species loss. Our data suggest that plant species promoted currently by agri‐environment schemes are not optimal for solitary bee foraging. If a diverse community of pollinators is to be supported on UK and European farmland, additional species such as R. canina should be encouraged to meet the foraging requirements of solitary bees.

Understanding preferences of German flower consumers: the desire for sustained beauty

PurposeThe purpose of this paper is to provide insights for flower retailers, horticultural practitioners and marketing managers into the prioritisation of cut flower attributes by German residents.Design/methodology/approachApplying a best–worst scaling approach, this analysis identified the relative ranking of importance amongst product attributes relevant to German consumers when buying fresh cut flowers. A latent class analysis determined four flower consumer segments for further study. The study builds on a sample of 978 consumers and is consistent with the most recent German census in terms of age, gender, income and federal state.FindingsThe best-worst analysis showed that intrinsic flower attributes, in particular appearance, freshness and scent were found to be more important to German consumers than the extrinsic attributes studied, namely, price, country of origin and a certification indicating fair trade. The latent class analysis determined four consumer segments that desire either budget, luxury or ethical flowers or more information about flowers. For all identified consumer segments, appearance was the attribute of greatest importance. The segments that desired luxury or ethical flowers, as well as the segment that desires more information were interested in appearance, but also had relatively large shares of preferences dedicated to flower freshness guarantees. The preference for freshness guarantees in addition to appearance may be interpreted jointly as a desire for not only beautiful and aesthetically pleasing flowers, but for sustained beauty.Originality/valueInternationally, the study fills a research gap by exploring consumer’s relative preference for cut flower attributes. In contrast to existing studies on consumer preferences for flowers in Germany, the present study builds on a sample that was targeted in terms of age, gender, net household income and federal state to the most recent German census.

Taxonomic revision proves Trachusa pubescens (Morawitz, 1872) sensu lato to be a complex of allopatric and sympatric species in South-Eastern Europe and Western Asia (Hymenoptera, Apoidea, Anthidiini).

Trachusa pubescens (Morawitz, 1872) s. l. has a distribution extending from south-eastern Europe over Anatolia and the Caucasus to Iran and Turkmenistan, and was formerly regarded as a species with high intraspecific variation. By means of an examination of 208 specimens from all parts of the distribution area, covering structural features of the head (mandibles, clypeus), the apical terga and the genitalia, the colouration pattern as well as a morphometric analysis of 26 body measurements with multivariate statistical methods (Principal Component Analysis, Discriminant Analysis), it was possible to assign the material to five species of which two are new to science (Trachusa balcanica sp. n. and T. hakkariensis sp. n.). Two taxa which had previously been described as “variations” or subspecies are elevated to species rank: T. verhoeffi (Mavromoustakis, 1955), stat. n. and T. maxima (Friese, 1931), stat. n. Additionally, some populations can be distinguished by their colouration pattern or by subtle differences in size or body shape, but these features are apparently of no taxonomic significance at the species level. Trachusa balcanica sp. n. and T. verhoeffi have distribution areas which do not overlap with any of the other members of the species group and can thus be characterised as allospecies. By contrast, the distribution areas of the other three species, T. pubescens, T. maxima and T. hakkariensis sp. n., overlap to a certain extent and they co-exist at least to some degree in sympatry. While they have been found in the same region, they have so far never been found together at exactly the same location and it is suggested that species divergence occurred in parallel with ecological differentiation. Niche partitioning such as flower preferences is a mechanism which may be invoked to explain this. Some specimens with intermediate characters were found, particularly in contact zones, and it is thought that some hybridisation may occur. A partly melanistic individual of T. balcanica sp. n. was found, which is probably the first described melanistic individual in the tribe Anthidiini.

Effect of flower orientation on the male and female traits of Myrtillocactus geometrizans (Cactaceae).

Intra-individual variation in the production and size of reproductive traits has been documented in columnar cacti, being higher in equator-facing flowers. Such variation is attributed to the high amount of PAR intercepted by stems oriented towards the equator. Most studies focused on this phenomenon have documented the existence of intra-individual variation on traits associated with the female function; however, its impact on traits associated with the male function has been neglected. We tested the hypothesis that equator-facing flowers of Myrtillocactus geometrizans exhibit higher values on traits associated with both male and female functions than flowers facing against it. Number and size of anthers and ovaries, pollen:ovule ratio and number and quality of pollen grains (diameter, germinability, viability and pollen tube length) were estimated from reproductive structures facing north and south, and compared with t-tests between orientations. Number of anthers per flower, number of pollen grains per anther and per floral bud; pollen size, viability and germinability; pollen tube length; ovary length and pollen:ovule ratio were significantly higher in reproductive structures oriented towards the south (i.e. equator). These findings suggest that intra-individual variation in floral traits of M.geometrizans might be associated with different availability of resources in branches with contrasting orientation. Our results provide new evidence of the existence of a response to an orientation-dependent extrinsic gradient. To our knowledge, this is the first study documenting the existence of intra-individual variation on pollen quality and P:O ratio in Cactaceae species.

Circadian clocks of both plants and pollinators influence flower seeking behavior of the pollinator hawkmoth Manduca sexta

Most plant-pollinator interactions occur during specific periods during the day. To facilitate these interactions, many flowers are known to display their attractive qualities, such as scent emission and petal opening, in a daily rhythmic fashion. However, less is known about how the internal timing mechanisms (the circadian clocks) of plants and animals influence their daily interactions. We examine the role of the circadian clock in modulating the interaction between Petunia and one of its pollinators, the hawkmoth Manduca sexta. We find that desynchronization of the Petunia circadian clock affects moth visitation preference for Petunia flowers. Similarly, moths with circadian time aligned to plants show stronger flower-foraging activities than moths that lack this alignment. Moth locomotor activity is circadian clock-regulated, although it is also strongly repressed by light. Moths show a time-dependent burst increase in flight activity during subjective night. In addition, moth antennal responsiveness to the floral scent compounds exhibits a 24-hour rhythm in both continuous light and dark conditions. This study highlights the importance of the circadian clocks in both plants and animals as a crucial factor in initiating specialized plant-pollinator relationships.

The yellow specialist: dronefly Eristalis tenax prefers different yellow colours for landing and proboscis extension.

Droneflies, imagoes of the hoverfly Eristalis tenax, are known to possess a preference for yellow flowers, i.e. they prefer to visit yellow flowers and prefer to extend the proboscis to yellow colours. In this study we disentangle these colour preferences by investigating the landing reaction and proboscis reflex with particular reference to intensity, spectral purity and dominant wavelength of colour stimuli and their UV reflection properties. In multiple-choice tests, naïve and non-trained flies prefer to land on yellow colours independent of their UV reflection characteristics, but also accept blue, white and pink colours if they absorb UV and are of sufficient brightness. Flies trained to land on colours other than yellow still prefer yellow colours to some extent. Moreover, the flies prefer bright over dark yellow colours even if trained to dark yellow ones. The flies refuse to land on dark colours of all hues. Naïve flies exhibit the proboscis reflex only to pure yellow pollen. These experiments show for the first time that landing in droneflies is triggered by a yellow colour independent of its UV reflection properties, but proboscis extension is triggered by yellow colours strongly absorbing blue and UV. The ability to discriminate colours is better than predicted by the categorical colour vision model. The colour preferences in E. tenax represent a fine-tuned ability to visit yellow flowers displaying a UV bull's-eye pattern.

Small but attractive: female-biased nectar production and floral visitors in a dimorphic shrub.

In sexually dimorphic species, hermaphrodite flowers in gynodioecious species or male flowers in dioecious species are often larger and produce more nectar than their conspecific female flowers. As a consequence, hermaphrodite or male flowers frequently receive more pollinator visits. Sex ratio, flower size, floral display, nectar production and floral visits were evaluated in two natural populations of Fuchsia thymifolia, a morphologically gynodioecious but functionally subdioecious insect-pollinated shrub. Sex ratio did not differ from the expected 1:1 in the two studied populations. As expected, hermaphrodite flowers were larger than female flowers, but in contrast to the general pattern, hermaphrodite flowers did not produce nectar or produced much less than female flowers. Flower visitors were flies (68%) and bumblebees (24%), both of which showed a preference for female flowers. No sex difference was detected in either flower longevity or floral display across the flowering season. Higher nectar production by females may attract more pollinators, and may be a strategy to enhance female reproductive success in this species. Finally, floral dimorphism and insect preferences did not seem to hamper the maintenance of sub-dioecy or prevent the evolution of dioecy in F.thymifolia.

Bumblebees require visual pollen stimuli to initiate and multimodal stimuli to complete a full behavioral sequence in close-range flower orientation.

Flower visits are complex encounters, in which animals are attracted by floral signals, guided toward the site of the first physical contact with a flower, land, and finally take up floral rewards. At close range, signals of stamens and pollen play an important role to facilitate flower handling in bees, yet the pollen stimuli eliciting behavioral responses are poorly known. In this study, we test the response of flower‐naive bumblebees (Bombus terrestris) toward single and multimodal pollen stimuli as compared to natural dandelion pollen. As artificial pollen stimuli, we used the yellow flavonoid pigment quercetin, the scent compound eugenol, the amino acid proline, the monosaccharide glucose, and the texture of pollen‐grain‐sized glass pellets as a tactile stimulus. Three test stimuli, dandelion pollen, one out of various uni‐ and multimodal stimulus combinations, and a solvent control were presented simultaneously to individual bumblebees, whose response was recorded. The results indicate that bumblebees respond in an irreversible sequence of behavioral reactions. Bumblebees approached the visual stimulus quercetin as often as natural dandelion pollen. An additional olfactory stimulus resulted in slightly more frequent landings. The multimodal stimulus combinations including visual, olfactory, gustatory, and tactile stimuli elicited approaches, antennal contacts, and landings as often as natural pollen. Subsequent reactions like proboscis extension, mandible biting, and buzzing were more often but not regularly observed at dandelion pollen. Our study shows that visual signals of pollen are sufficient to trigger initial responses of bumblebees, whereas multimodal pollen stimuli elicit full behavioral response as compared to natural pollen. Our results suggest a major role of pollen cues for the attraction of bees toward flowers and also explain, why many floral guides mimic the visual signals of pollen and anthers, that is, the yellow and UV‐absorbing color, to direct bumblebees toward the site where they access the floral rewards.

The phylogeny of Heliconia (Heliconiaceae) and the evolution of floral presentation

Heliconia (Heliconiaceae, order Zingiberales) is among the showiest plants of the Neotropical rainforest and represent a spectacular co-evolutionary radiation with hummingbirds. Despite the attractiveness and ecological importance of many Heliconia, the genus has been the subject of limited molecular phylogenetic studies. We sample seven markers from the plastid and nuclear genomes for 202 samples of Heliconia. This represents ca. 75% of accepted species and includes coverage of all taxonomic subgenera and sections. We date this phylogeny using fossils associated with other families in the Zingiberales; in particular we review and evaluate the Eocene fossil Ensete oregonense. We use this dated phylogenetic framework to evaluate the evolution of two components of flower orientation that are hypothesized to be important for modulating pollinator discrimination and pollen placement: resupination and erect versus pendant inflorescence habit. Our phylogenetic results suggest that the monophyletic Melanesian subgenus Heliconiopsis and a small clade of Ecuadorian species are together the sister group to the rest of Heliconia. Extant diversity of Heliconia originated in the Late Eocene (39Ma) with rapid diversification through the Early Miocene, making it the oldest known clade of hummingbird-pollinated plants. Most described subgenera and sections are not monophyletic, though closely related groups of species, often defined by shared geography, mirror earlier morphological cladistic analyses. Evaluation of changes in resupination and inflorescence habit suggests that these characters are more homoplasious than expected, and this largely explains the non-monophyly of previously circumscribed subgenera, which were based on these characters. We also find strong evidence for the correlated evolution of resupination and inflorescence habit. The correlated model suggests that the most recent common ancestor of all extant Heliconia had resupinate flowers and erect inflorescences. Finally, we note our nearly complete species sampling and dated phylogeny allow for an assessment of taxonomic history in terms of phylogenetic diversity. We find approximately half of the currently recognized species, corresponding to half of the phylogenetic diversity, have been described since 1975, highlighting the continued importance of basic taxonomic research and conservation initiatives to preserve both described and undiscovered species of Heliconia.

Inheritance of leaf and flower morphologies in Kalanchoe spp.

Members of the genus Kalanchoe are morphologically diverse; this increases their commercial value. Understanding the genetic mechanism of development of morphological characters could contribute to parent screening and offspring selection in future breeding programs. In this study, we investigated the inheritance of leaf color, leaf shape, anther color, and flower orientation of Kalanchoe species or varieties. Kalanchoe garambiensis, K. garambiensis G., K. gracilis, K. spathulata, and K. manginii ‘Wendy’ were used as experimental parents to establish self and interspecific crosses. The separation ratios of the leaf and flower traits were analyzed using Chi square tests. The results showed that all progenies produced by selfing of K. garambiensis (purple leaf phenotype) had purple leaves, whereas those from selfing of K. garambiensis G. (green leaf phenotype) exhibited green and purple leaves at a ratio of approximately 3:1. The S1 and S2 populations of K. garambiensis G. exhibited an expected 3:1 ratio of leaf color, whereas the S3 populations produced all green leaf inbred lines. Reciprocal hybridization of the progenies of K. gracilis (deeply lobed leaf) with K. garambiensis G. (shallowly lobed leaf) resulted in a 1:1 ratio of shallowly lobed leaves to deeply lobed leaves. The progenies of the two cross combinations (K. garambiensis G. × K. manginii ‘Wendy’ and K. garambiensis × K. manginii ‘Wendy’) produced upright-type flowers and anthers having purplish red color. These findings suggested that leaf color, leaf shape, anther color, and flower orientation of Kalanchoe are controlled by a single pair of alleles. Green leaf, deeply loped leaves, purplish red anthers, and upright-type flowers were found to be dominant traits.

Plant Biology: Flower Orientation, Temperature Regulation and Pollinator Attraction

The reproductive performance of plants depends on the temperature of the flower. A recent study reports the mechanistic basis of flower head orientation in sunflowers and provides intriguing hints as to its functional significance.

Aspidistra globosa (Asparagaceae, Nolinoideae), a new species with erect stem from southern Vietnam

Aspidistra globosa is described and illustrated as a new species from southern Vietnam (Gia Lai province, Kon Ka Kinh National Park). The new species has long erect stem, which is a rare feature in the genus Aspidistra. Aspidistra globosa resembles A. khangii and A. locii in globoid perigone and erect stem, but differs in smaller flowers, color of perigone, position of anthers and orientation of flower.

Ectopic KNOX Expression Affects Plant Development by Altering Tissue Cell Polarity and Identity.

Plant development involves two polarity types: tissue cell (asymmetries within cells are coordinated across tissues) and regional (identities vary spatially across tissues) polarity. Both appear altered in the barley (Hordeum vulgare) Hooded mutant, in which ectopic expression of the KNOTTED1-like Homeobox (KNOX) gene, BKn3, causes inverted polarity of differentiated hairs and ectopic flowers, in addition to wing-shaped outgrowths. These lemma-specific effects allow the spatiotemporal analysis of events following ectopic BKn3 expression, determining the relationship between KNOXs, polarity, and shape. We show that tissue cell polarity, based on localization of the auxin transporter SISTER OF PINFORMED1 (SoPIN1), dynamically reorients as ectopic BKn3 expression increases. Concurrently, ectopic expression of the auxin importer LIKE AUX1 and boundary gene NO APICAL MERISTEM is activated. The polarity of hairs reflects SoPIN1 patterns, suggesting that tissue cell polarity underpins oriented cell differentiation. Wing cell files reveal an anisotropic growth pattern, and computational modeling shows how polarity guiding growth can account for this pattern and wing emergence. The inverted ectopic flower orientation does not correlate with SoPIN1, suggesting that this form of regional polarity is not controlled by tissue cell polarity. Overall, the results suggest that KNOXs trigger different morphogenetic effects through interplay between tissue cell polarity, identity, and growth.

Butterfly Learning and the Diversification of Plant Leaf Shape

Visual cues are important for insects to find flowers and host plants. It has been proposed that the diversity of leaf shape in Passiflora vines could be a result of negative frequency dependent selection driven by visual searching behavior among their butterfly herbivores. Here we tested the hypothesis that Heliconius butterflies use leaf shape as a cue to initiate approach towards a host plant. We first tested for the ability to recognize shapes using a food reward conditioning experiment. Butterflies showed an innate preference for flowers with three and five petals. However, they could be trained to increase the frequency of visits to a non-preferred flower with two petals, indicating an ability to learn to associate shape with a reward. Next we investigated shape learning specifically in the context of oviposition by conditioning females to lay eggs on two shoots associated with different artificial leaf shapes: their own host plant, Passiflora biflora, and a lanceolate non-biflora leaf shape. The conditioning treatment had a significant effect on the approach of butterflies to the two leaf shapes, consistent with a role for shape learning in oviposition behavior. This study is the first to show that Heliconius butterflies use shape as a cue for feeding and oviposition, and can learn shape preference for both flowers and leaves. This demonstrates the potential for Heliconius to drive negative frequency dependent selection on the leaf shape of their Passiflora host plants.