Floral colour change in <Emphasis Type="Italic">Byrsonima variabilis</Emphasis> (Malpighiaceae) as a visual cue for pollen but not oil foraging by oil-collecting bees

Pollinators search for multiple flora resources throughout their life cycle. Most studies, however, only assess how bees discriminate floral cues in the context of nectar foraging. In the present study, we sought to elucidate whether oil-collecting bees discriminate flowers of Byrsonima variabilis (Malpighiaceae) with petals of different colours when foraging for pollen or oil. As the colour of the standard petal changes during anthesis, we characterised the spectral reflectance patterns of flowers throughout anthesis and modelled chromatic perceptual space to determine how these colour patterns are perceived by bees. Through the quantification of flower pollen in the different phases, we found that the colour of the standard petal is an honest cue of the presence of pollen. Centridine bees preferentially visited flowers with a yellow (bee’s green) colour when searching for pollen, but indiscriminately visited flowers with different petal colours when searching for floral oil. We suggest that standard petals, in the species studied and others of the genus, like nectar guides, act as pollen guides, which oil-collecting females use to detect pollen-rich flowers. Moreover, they use different floral clues during foraging for different resources in the same host plant.     

Floral CO<Subscript>2</Subscript> emission may indicate food abundance to nectar-feeding moths

As part of a study of the roles of the sensory subsystem devoted to CO₂ in the nectar-feeding moth Manduca sexta, we investigated CO₂ release and nectar secretion by flowers of Datura wrightii, a preferred hostplant of Manduca. Datura flowers open at dusk and wilt by the following noon. During the first hours after dusk, when Manduca feeds, the flowers produce considerable amounts of nectar and emit levels of CO₂ that should be detectable by moths nearby. By midnight, however, both nectar secretion and CO₂ release decrease significantly. Because nectar production requires high metabolic activity, high floral CO₂ emission may indicate food abundance to the moths. We suggest that hovering moths could use the florally emitted CO₂ to help them assess the nectar content before attempting to feed in order to improve their foraging efficiency.Electronic Supplementary Material  Supplementary material is available in the online version of this article at     

Bird pollination of Canary Island endemic plants

The Canary Islands are home to a guild of endemic, threatened bird-pollinated plants. Previous work has suggested that these plants evolved floral traits as adaptations to pollination by flower specialist sunbirds, but subsequently, they appear to have co-opted generalist passerine birds as sub-optimal pollinators. To test this idea, we carried out a quantitative study of the pollination biology of three of the bird-pollinated plants, Canarina canariensis (Campanulaceae), Isoplexis canariensis (Veronicaceae) and Lotus berthelotii (Fabaceae), on the island of Tenerife. Using colour vision models, we predicted the detectability of flowers to bird and bee pollinators. We measured pollinator visitation rates, nectar standing crops as well as seed-set and pollen removal and deposition. These data showed that the plants are effectively pollinated by non-flower specialist passerine birds that only occasionally visit flowers. The large nectar standing crops and extended flower longevities (>10 days) of Canarina and Isoplexis suggests that they have evolved a bird pollination system that effectively exploits these low frequency non-specialist pollen vectors and is in no way sub-optimal. Seed set in two of the three species was high and was significantly reduced or zero in flowers where pollinator access was restricted. In L. berthelotii, however, no fruit set was observed, probably because the plants were self-incompatible horticultural clones of a single genet. We also show that, while all three species are easily detectable for birds, the orange Canarina and the red Lotus (but less so the yellow-orange Isoplexis) should be difficult to detect for insect pollinators without specialised red receptors, such as bumblebees. Contrary to expectations if we accept that the flowers are primarily adapted to sunbird pollination, the chiffchaff (Phylloscopus canariensis) was an effective pollinator of these species.     

The complexity of nectar: secretion and resorption dynamically regulate nectar features

In this paper, we review the phenomenon of nectar resorption, focusing on its physiological and ecological meaning. Nectar resorption is a phenomenon that has long been known but was rarely reported until the1990s. It has more recently been demonstrated in several species by various direct and indirect methodologies. It has generally been demonstrated in senescent flowers as a phenomenon separate in time from, and independent of, nectar secretion. The significance of this type of resorption is generally recognized as a resource-recovery strategy, recycling at least some materials invested in nectar production. Nevertheless, nectar resorption can occur concomitantly with nectar secretion. Nectar production is therefore best considered as a unified process comprising nectar secretion and resorption. The modulation of these two opposite phases allows nectar concentration to be maintained in a range suitable for pollinators (nectar homeostasis). The mechanism of nectar resorption at the cell level has received little attention, and its molecular basis can only be hypothesized on the basis of recent studies concerning sugar sensing.     

The use of heterospecific scent marks by the sweat bee <Emphasis Type="Italic">Halictus aerarius</Emphasis>

To forage effectively amongst flowers, some bee species utilize olfactory cues left by previous visitors in addition to direct assessment of visual cues to identify rewarding flowers. This ability can be more advantageous if the bees can recognize and use scent marks left by heterospecifics, not just marks left by members of their own species. We conducted field experiments to investigate whether the sweat bee Halictus aerarius avoids visiting flowers of trailing water willow Justicia procumbens emptied by other bee species. We found that H. aerarius rejected the flowers visited by both heterospecifics and conspecifics. They also rejected visited flowers artificially replenished with nectar. Our results demonstrate that social bees outside the Apidae can detect marks left on flowers by heterospecifics but that (on this plant species) they are unable to discriminate against flowers by directly detecting nectar volume. H. aerarius exhibited different rejection rates according to the identity of the previous bee species. We suggest that the frequency of rejection responses may depend on the amount of chemical substances left by the previous bee. In general, the use of scent marks left by previous visitors is almost certainly advantageous, enabling foragers to avoid flowers with depleted nectar levels and thereby improving their foraging efficiency.     

Conspecific flowers of <Emphasis Type="Italic">Sinapis arvensis</Emphasis> are stronger competitors for pollinators than those of the invasive weed <Emphasis Type="Italic">Bunias orientalis</Emphasis>

Biological invasions can affect the structure and function of ecosystems and threaten native plant species. Since most weeds rely on mutualistic relationships in their new environment, they may act as new competitors for pollinators. Pollinator competition is likely to be density dependent, but it is often difficult to disentangle competition caused by flower quality from effects caused by flower quantity. In order to test the effects of the presence and number of flowers of the invasive weed Bunias orientalis on the insect visitation rates in a native species (Sinapis arvensis), we performed two replacement experiments using plants with standardised flower numbers. The visitation rates in S. arvensis were significantly higher than in B. orientalis and the number of insect visits dropped significantly with increasing density of S. arvensis flowers. These results suggest that intraspecific competition among flowers of S. arvensis is stronger than the competitive effect of alien flowers. As flowers of B. orientalis do not seem to distract visitors from S. arvensis, it is unlikely that pollinator competition between these two plant species plays a crucial role. However, it cannot be excluded that mass blossom stands of B. orientalis may distract flower visitors from native species.     

Regional,seasonal and interspecific variation in <Superscript>15</Superscript>N and <Superscript>13</Superscript>C in sympatric mouse lemurs

Madagascar provides some of the rare examples where two or more primate species of the same genus and with seemingly identical niche requirements occur in sympatry. If congeneric primate species co-occur in other parts of the world, they differ in size in a way that is consistent with Hutchinson’s rule for coexisting species, or they occupy different ecological niches. In some areas of Madagascar, mouse lemurs do not follow these “rules” and thus seem to violate one of the principles of community ecology. In order to understand the mechanisms that allow coexistence of sympatric congeneric species without obvious niche differentiation, we studied food composition of two identical sized omnivorous mouse lemur species, Microcebus griseorufus and M. murinus with the help of stable isotope analyses (δ ¹⁵N and δ ¹³C). The two species are closely related sister species. During the rich season, when food seems abundant, the two species do not differ in their nitrogen isotope composition, indicating that the two species occupy the same trophic level. But they differ in their δ ¹³C values, indicating that M. griseorufus feeds more on C₄ and CAM (Crassulacean-acid-metabolism) plants than M. murinus. During the lean season, M. murinus has lower δ ¹⁵N values, indicating that the two species feed at different trophic levels during times of food shortage. Hybrids between the two species showed intermediate food composition. The results reflect subtle differences in foraging or metabolic adaptations that are difficult to quantify by traditional observations but that represent possibilities to allow coexistence of species.     

The larval parasitoid <Emphasis Type="Italic">Microplitis croceipes</Emphasis> oviposits in conspecific adults

Microplitis croceipes (Hymenoptera: Braconidae) is a larval parasitoid of Helicoverpa/Heliothis spp. In the course of mass rearing of M. croceipes, we found that females oviposited in the conspecific adults in rearing cages. When 20 pairs of inexperienced females and males or of experienced females and males were reared in a cage, the males lived for 14–15 days and the females for 18–20 days on average. At their death, 37–42% of the males and 50–57% of the females contained conspecific eggs or first instar larvae in their abdominal cavity. When two of inexperienced females met on a host-infested leaf of soybean, they attempted to sting each other. Of the attacked females, 30% contained a conspecific egg laid in their abdomen. In abdominal cavity of the adults parasitized by a conspecific female, the majority of the parasitoid eggs laid disappeared within 1 day after oviposition. Only 10–30% of the parasitoid eggs laid in conspecific adults hatched 3–4 days after oviposition, but those larvae never molted to second instar. When the adults were stung by one or two conspecific females, their subsequent longevity was significantly shorter than that for the control adults. Oviposition in conspecific adults may be prevalent in other parasitic wasps that quickly oviposit without intensive host examination, and have cuticle and size of abdomen to be stung by conspeicifcs.     

Specific dynamic action affects the hydrostatic pressure tolerance of the shallow-water spider crab <Emphasis Type="Italic">Maja brachydactyla</Emphasis>

The bathymetric distribution of marine benthic invertebrates is likely governed by a combination of ecological and physiological factors. The present study investigates oxygen consumption and heartbeat rate in response to attempted feeding at 1, 100 and 150 atm in the shallow-water spider crab, Maja brachydactyla, from temperate European waters. No significant difference was evident between the resting heartbeat rate of specimens at 1 or 100 atm, which were 56 and 65 bpm, respectively (Mann–Whitney, U = 5382.0; n = 95, 98; p = 0.079). However, at 150 atm the resting heartbeat rate was significantly higher than that observed for 100 atm at 108 bpm (Mann–Whitney, U = 149.0; n = 45, 98; p < 0.001). At 150 atm, feeding was never observed and coupled with the elevated resting heartbeat rate; it is suggested by 150 atm continued survival is unfeasible. At 1 and 100 atm, feeding instigated a distinct increase in heartbeat rate, which remained elevated for over 30 h. This increase peaked within 1 h at 1 atm. At 100 atm, this required 4 h and postprandial oxygen consumption was significantly higher than at 1 atm (Kruskal–Wallis, H = 85.036; df = 2; p < 0.001). Elevated hydrostatic pressure is hypothesized to extend the duration and the total metabolic energy devoted to specific dynamic action. The metabolic requirements of feeding under hyperbaric conditions may even reach such a critical demand that feeding is entirely inhibited.     

Flower Constancy, Insect Psychology, and Plant Evolution

 Individuals of some species of pollinating insects tend to restrict their visits to only a few of the available plant species, in the process bypassing valuable food sources. The question of why this flower constancy exists is a rich and important one with implications for the organization of natural communities of plants, floral evolution, and our understanding of the learning processes involved in finding food. Some scientists have assumed that flower constancy is adaptive per se. Others argued that constancy occurs because memory capacity for floral features in insects is limited, but attempts to identify the limitations often remained rather simplistic. We elucidate now different sensory and motor memories from natural foraging tasks are stored and retrieved, using concepts from modern learning science and visual search, and conclude that flower constancy is likely to have multiple causes. Possible constraints favoring constancy are interference sensitivity of short-term memory, and temporal limitations on retrieving information from long-term memory as rapidly as from short-term memory, but further empirical evidence is needed to substantiate these possibilities. In addition, retrieving memories may be slower and more prone to errors when there are several options than when an insect copes with only a single task. In addition to memory limitations, we also point out alternative explanations for flower constancy. We then consider the way in which floral parameters, such as interplant distances, nectar rewards, flower morphology, and floral color (as seen through bees' eyes) affect constancy. Finally, we discuss the implications of pollinator constancy for plant evolution. To date there is no evidence that flowers have diverged to favor constancy, although the appropriate tests may not have yet been conducted. However, there is good evidence against the notion that pollinator constancy is involved in speciation or maintenance of plant species integrity.     

Testing the influence of gravity on flower symmetry in five <Emphasis Type="Italic">Saxifraga</Emphasis> species

Flower symmetry is considered a species-specific trait and is categorized in asymmetry, actinomorphic symmetry, bisymmetry and zygomorphic symmetry. Here we report on the intra-individual variation of flower symmetry in the genus Saxifraga and the influence of light, gravity and intrinsic factors on the development of flower symmetry. We tested five species—Saxifraga cuneifolia, Saxifraga imparilis, Saxifraga rotundifolia, Saxifraga stolonifera and Saxifraga umbrosa—concerning six flower parameters—angles between petals, petal length, petal pigmentation, angular position of carpels, movement of stamens and (only for S. imparilis and S. stolonifera) the length of the two lower elongated petals in regard to their position towards the stem. Specimens of all species were tested on a vertical clinostat as a gravity compensator, on a horizontal clinostat as a light incidence compensator and on a stationary control. The results show that the angle of incident light has no apparent impact on flower symmetry, whereas gravity affects the angular position of petals in S. cuneifolia and S. umbrosa and the petal colouration in S. rotundifolia. In S. cuneifolia and S. umbrosa, the absence of directional gravity resulted in the development of actinomorphic flowers, whereas the corresponding control flowers were zygomorphic. The development of flowers in S. rotundifolia was not altered by this treatment. The length of the two elongated petals in S. stolonifera and S. imparilis was not affected by gravity, but rather was determined by position of the flower within the inflorescence and resulted in asymmetrical flowers.     

Background complexity affects colour preference in bumblebees

Flowers adapted for hummingbird pollination are typically red. This correlation is usually explained by the assertion that nectar- or pollen-stealing bees are “blind” to red flowers. However, laboratory studies have shown that bees are capable of locating artificial red flowers and often show no innate preference for blue over red. We hypothesised that these findings might be artefacts of the simplified laboratory environment. Using bumblebees (Bombus impatiens) that had been trained to visit red and blue artificial flowers, we tested whether colour preference was influenced by complexity of the background on which they were foraging. Many bees were indifferent to flower colour when tested using a uniform green background like those commonly used in laboratory studies, but all bees showed strong colour preferences (usually for blue) when flowers were presented against a photograph of real foliage. Overall, preference for blue flowers was significantly greater on the more realistic, complex background. These results support the notion that the red of “hummingbird syndrome” flowers can function to reduce bee visits despite the ability of bees to detect red and highlight the need to consider context when drawing inferences about pollinator preferences from laboratory data. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Pollen foraging: learning a complex motor skill by bumblebees (<Emphasis Type="Italic">Bombus terrestris</Emphasis>)

To investigate how bumblebees (Bombus terrestris) learn the complex motor skills involved in pollen foraging, we observed naïve workers foraging on arrays of nectarless poppy flowers (Papaver rhoeas) in a greenhouse. Foraging skills were quantified by measuring the pollen load collected during each foraging bout and relating this to the number of flowers visited and bout duration on two consecutive days. The pollen standing crop (PSC) in each flower decreased drastically from 0530 to 0900 hours. Therefore, we related foraging performance to the changing levels of pollen available (per flower) and found that collection rate increased over the course of four consecutive foraging bouts (comprising between 277 and 354 individual flower visits), suggesting that learning to forage for pollen represents a substantial time investment for individual foragers. The pollen collection rate and size of pollen loads collected at the start of day 2 were markedly lower than at the end of day 1, suggesting that components of pollen foraging behaviour could be subject to imperfect overnight retention. Our results suggest that learning the necessary motor skills to collect pollen effectively from morphologically simple flowers takes three times as many visits as learning how to handle the most morphologically complex flowers to extract nectar, potentially explaining why bees are more specialised in their choice of pollen flowers.     

The innate responses of bumble bees to flower patterns: separating the nectar guide from the nectary changes bee movements and search time

Nectar guides can enhance pollinator efficiency and plant fitness by allowing pollinators to more rapidly find and remember the location of floral nectar. We tested if a radiating nectar guide around a nectary would enhance the ability of naïve bumble bee foragers to find nectar. Most experiments that test nectar guide efficacy, specifically radiating linear guides, have used guides positioned around the center of a radially symmetric flower, where nectaries are often found. However, the flower center may be intrinsically attractive. We therefore used an off-center guide and nectary and compared “conjunct” feeders with a nectar guide surrounding the nectary to “disjunct” feeders with a nectar guide separated from the nectary. We focused on the innate response of novice bee foragers that had never previously visited such feeders. We hypothesized that a disjunct nectar guide would conflict with the visual information provided by the nectary and negatively affect foraging. Approximately, equal numbers of bumble bees (Bombus impatiens) found nectar on both feeder types. On disjunct feeders, however, unsuccessful foragers spent significantly more time (on average 1.6-fold longer) searching for nectar than any other forager group. Successful foragers on disjunct feeders approached these feeders from random directions unlike successful foragers on conjunct feeders, which preferentially approached the combined nectary and nectar guide. Thus, the nectary and a surrounding nectar guide can be considered a combination of two signals that attract naïve foragers even when not in the floral center.     

Visual targeting of components of floral colour patterns in flower-naïve bumblebees (Bombus terrestris; Apidae)

Floral colour patterns are contrasting colour patches on flowers, a part of the signalling apparatus that was considered to display shape and colour signals used by flower-visitors to detect flowers and locate the site of floral reward. Here, we show that flower-naïve bumblebees (Bombus terrestris) spontaneously direct their approach towards the outside margin of artificial flowers, which provides contrast between these dummy flowers and the background. If no floral guides are present, the bumblebees continue to approach the margin and finally touch the marginal area of the dummy flower with the tips of their antennae. Whilst approaching dummy flowers that also have a central floral guide, the bumblebees change their direction of flight: Initially, they approach the margin, later they switch to approaching the colour guide, and finally they precisely touch the floral guide with their antennae. Variation of the shape of equally sized dummy flowers did not alter the bumblebees’ preferential orientation towards the guide. Using reciprocal combinations of guide colour and surrounding colour, we showed that the approach from a distance towards the corolla and the antennal contact with the guide are elicited by the same colour parameter: spectral purity. As a consequence, the dummy flowers eliciting the greatest frequency of antennal reactions at the guide are those that combine a floral guide of high spectral purity with a corolla of less spectral purity. Our results support the hypothesis that floral guides direct bumblebees’ approaches to the site of first contact with the flower, which is achieved by the tips of the antennae.Electronic Supplementary Material  Supplementary material is available for this article at     

The earliest modern mongoose (Carnivora, Herpestidae) from Africa (late Miocene of Chad)

We report on the earliest modern mongooses of Africa, from the late Miocene (ca. 7 Ma) of the hominid locality TM 266, Toros-Menalla, Chad. The material is based on fragmentary dentitions of three individuals. The main diagnostic feature of the Chadian species is the great development of the shear in the carnassials, which distinguishes the Chadian specimens from all extant herpestids except Herpestes and Galerella. In comparison with most extinct and extant Herpestes, the species from Toros-Menalla differs by a markedly smaller size and, depending on the species, relatively more elongated carnassials, more transversely elongated M1 and more reduced p4. On the basis of a great morphological similarity and the absence of significant differences, we assign our material to Galerella sanguinea; the Chadian finding therefore represents the earliest appearance of an extant species of Herpestidae. This record ties the first appearance of the genus to a minimum age of ca. 7 Ma, which is consistent with the estimated divergence date of 11.4 Ma known from the literature for the species of Galerella.     

Anatomical localization and stereoisomeric composition of <Emphasis Type="Italic">Tribolium castaneum</Emphasis> aggregation pheromones

We report that the abdominal epidermis and associated tissues are the predominant sources of male-produced pheromones in the red flour beetle, Tribolium castaneum and, for the first time, describe the stereoisomeric composition of the natural blend of isomers of the aggregation pheromone 4,8-dimethyldecanal (DMD) in this important pest species. Quantitative analyses via gas chromatography–mass spectrometry showed that the average amount of DMD released daily by single feeding males of T. castaneum was 878 ± 72 ng (SE). Analysis of different body parts identified the abdominal epidermis as the major source of aggregation pheromone; the thorax was a minor source, while no DMD was detectable in the head. No internal organs or obvious male-specific glands were associated with pheromone deposition. Complete separation of all four stereoisomers of DMD was achieved following oxidation to the corresponding acid, derivatization with (1R, 2R)- and (1S, 2S)-2-(anthracene-2,3-dicarboximido)cyclohexanol to diastereomeric esters, and their separation on reversed-phase high-performance liquid chromatography at −54°C. Analysis of the hexane eluate from Porapak-Q-collected volatiles from feeding males revealed the presence of all four isomers (4R,8R)/(4R,8S)/(4S,8R)/(4S,8S) at a ratio of approximately 4:4:1:1. A walking orientation bioassay in a wind tunnel with various blends of the four synthetic isomers further indicated that the attractive potency of the reconstituted natural blend of 4:4:1:1 was equivalent to that of the natural pheromone and greater than that of the 1:1 blend of (4R,8R)/(4R,8S) used in commercial lures.     

To use or not to use torpor? Activity and body temperature as predictors

When food is limited and/or environmental conditions are unfavourable, many mammals reduce activity and use torpor to save energy. Nevertheless, reliable predictors for torpor occurrence, especially in the wild, are currently not available. Interrelations between torpor use and other energy conserving strategies are also poorly understood. We tested the hypothesis that reductions in normothermic body temperature (T _b) and the period of activity before torpor events could be used as predictors for torpor occurrence in sugar gliders, Petaurus breviceps (body mass, ∼125 g), known to display daily torpor in the wild. Occurrence of torpor was preceded by significant (∼10–25%) reductions of the duration of the activity phase. Moreover, the normothermic resting T _b fell by an average of 1.2°C over 3 days before a torpor event, relative to individuals that did not display torpor. Our new findings suggest that before entering torpor, sugar gliders, which appear to use torpor as an emergency measure rather than a routine energy saving strategy, systematically reduce activity times and normothermic resting T _bs to lower energy expenditure and perhaps to avoid employing torpor. Thus, reduced activity and normothermic T _b may provide a predictive tool for the occurrence of daily torpor in the wild.     

High-field 1H T1 and T2 NMR relaxation time measurements of H2O in homeopathic preparations of quartz, sulfur, and copper sulfate

Quantitative meta-analyses of randomized clinical trials investigating the specific therapeutic efficacy of homeopathic remedies yielded statistically significant differences compared to placebo. Since the remedies used contained mostly only very low concentrations of pharmacologically active compounds, these effects cannot be accounted for within the framework of current pharmacology. Theories to explain clinical effects of homeopathic remedies are partially based upon changes in diluent structure. To investigate the latter, we measured for the first time high-field (600/500 MHz) ¹H T₁ and T₂ nuclear magnetic resonance relaxation times of H₂O in homeopathic preparations with concurrent contamination control by inductively coupled plasma mass spectrometry (ICP-MS). Homeopathic preparations of quartz (10c–30c, n = 21, corresponding to iterative dilutions of 100⁻¹⁰–100⁻³⁰), sulfur (13x–30x, n = 18, 10⁻¹³–10⁻³⁰), and copper sulfate (11c–30c, n = 20, 100⁻¹¹–100⁻³⁰) were compared to n = 10 independent controls each (analogously agitated dilution medium) in randomized and blinded experiments. In none of the samples, the concentration of any element analyzed by ICP-MS exceeded 10 ppb. In the first measurement series (600 MHz), there was a significant increase in T₁ for all samples as a function of time, and there were no significant differences between homeopathic potencies and controls. In the second measurement series (500 MHz) 1 year after preparation, we observed statistically significant increased T₁ relaxation times for homeopathic sulfur preparations compared to controls. Fifteen out of 18 correlations between sample triplicates were higher for controls than for homeopathic preparations. No conclusive explanation for these phenomena can be given at present. Possible hypotheses involve differential leaching from the measurement vessel walls or a change in water molecule dynamics, i.e., in rotational correlation time and/or diffusion. Homeopathic preparations thus may exhibit specific physicochemical properties that need to be determined in detail in future investigations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.