Robber-like pollinators: overwintered queen bumblebees foraging on Corydalis ambigua

ABSTRACT.

• 1 The behaviour of nectar-collecting Bombus hypocrita sapporensis Cockerell queens was observed on a population of a spring ephemeral plant Corydalis ambigua Cham, et Schlecht.
• 2 Daily patterns of activity and behaviour changed with the progress of flowering. Activity peaked shortly before sunset early in the flowering season but approximately at noon towards the end of flowering. In the peak flowering period the queens tended to visit nearby plants and to change direction often, whereas early or late in the flowering period they flew further between visits and were less likely to change direction.
• 3 Each plant was visited 0 to 24 times (mean 9.4 ±SD 5.2) by the queens during the whole flowering season.
• 4 The queens collected nectar, rarely through the front of the flowers but mostly through the spurs perforated by themselves or predecessors. At the beginning of the flowering season the illegitimate foragers often visited the front of the flowers before moving to the spurs; later, most queens quickly learned to land directly on the spurs.
• 5 Even the 59.7% of plants that were visited only by illegitimate foragers set seeds. Close observation confirmed that the illegitimate foragers opened the inner petals enclosing anthers and stigma frequently when visiting the front of the flowers before robbing, or occasionally when walking about on the flowers or collecting nectar through the perforated spurs.

     

Clonal growth of sagebrush (Artemisia tridentata) (Asteraceae) and its relationship to volatile communication

To increase systemic resistance to herbivory, some clonal plants transmit internal cues among clonal ramets to prevent widespread damage to genets. Sagebrush (Artemisia tridentata) (Asteraceae) is known to use volatile cues to induce resistance within and between plants (so‐called volatile communication). In the present study, we observed the extent and frequency of clonal growth in a natural sagebrush population in western North America to understand the influence of clonal growth on volatile communication. We used genetic analysis involving microsatellite markers and excavation of the root systems. In addition, we characterized the volatile profiles from the headspace of sagebrush ramets. Excavation of the root system of sagebrush plants revealed that sagebrush propagates clonally below ground and that daughter ramets grow near the mother stem. Volatiles were variable among genetically different ramets, although clonal ramets (genetically identical ramets) released similar volatiles, suggesting a genetic basis for volatile similarity. Sagebrush has been shown to be most responsive to volatiles released from artificially produced clones and suffers less herbivore damage as a result. Therefore, these results, taken into consideration together, imply that volatile communication may occur among genetically identical ramets under natural conditions, and that volatile similarity between the releaser and receiver may be recognized by the receiver and increase resistance against herbivory.     

Karyomorphology of Incarvillea (Bignoniaceae) and its implications in distribution and taxonomy

The karyomorphology of 11 species of the genus Incarvillea Juss. is reported. The chromosome numbers of all species studied are 2 n  = 22. The interphase nuclei and prophase chromosomes were found to be of the simple chromocentre type and the interstitial type, respectively. The asymmetry of the karyotype of I. arguta (two populations) in subgenus Amphicome is type 2A. The karyotypes of Incarvillea s inensis var. sinensis , I.  s inensis var. przewalskii, and I. olgae in subgenus Incarvillea are of asymmetry type 3A. The remaining nine species and one variety in subgenus Pteroscleris are also of asymmetry 3A. Data on three species and one variety studied are first reports. This study indicates that karyotype variation at the diploid level appears to be the predominant feature of chromosome evolution in the genus Incarvillea . According to this study of karyomorphology, morphological characteristics and geographical distribution, it seems that the three subgenera should be regarded as three independent genera. The geography of the genus is discussed.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 113–121.     

Temporal Hyperacuity in the Gymnotiform Electric Fish, Eigenmannia

SYNOPSIS. The gymnotiform electric fish, Eigenmannia, exhibitsextraordinary sensitivity to small timing differences betweensensory signals. The jamming avoidance response, gradual frequencyshifts of the electric organ discharges, requires the detectionof temporal disparities between sensory signals impinging upondifferent electroreceptors. This behavior occurs reliably evenwith temporal disparities being smaller than one microsecond.Since individual sensory receptors are not capable of encodingsuch minute timing with certainty, the high behavioral sensitivitymust, therefore, emerge from signal processing within the centralnervous system. Individual neurons, at the top of a well definedneuronal hierarchy have been found to be sensitive to temporaldisparities in the range of 1 microsecond. The response propertiesof these neurons as well as behavioral results suggest thatspatial convergence of sensory information plays a major rolein the emergence of this temporal hyperacuity.     

IONIC COMPOSITION OF THE CYTOPLASM OF NITELLA FLEXILIS

The K, Na and Cl concentrations of the chloroplast layer andthe flowing cytoplasm of Nitella flexilis have been determinedby applying an internal perfusion technique, which enabled usto avoid contamination of ions from the cell sap. K, Na andCl concentrations of the chloroplast layer are 110, 26 and 136mM and those of the flowing cytoplasm are 125, 5 and 36 mM respectively.The cell sap contains 80 mM K, 28 mM Na and 136 mM Cl. Althoughthere are some variations in these values among samples, theflowing cytoplasm is rich in K and poor in Cl and especiallyin Na. The exchange of K and Na across the tonoplasl occursfairly easily (half-time, a few hours), while that of Cl occursextremely slowly (half-time, a few days). ¹This work was supported by Research Grants from the Ministryof Education of Japan     

Demography and reproductive strategies of a polycarpic perennial, Trillium apetalon (Trilliaceae)

To investigate the connection between demographic strategies and reproductive strategies of a polycarpic perennial herb, Trillium apetalon Makino, we conducted three studies. First, we monitored the fate of individuals and the flowering behavior of T. apetalon for 12 years and used a transition matrix model to analyze the demography of the population. The analysis revealed that it takes a long time for individuals to go through one-leaf stage in juveniles. Elasticity analysis showed that the survival of flowering individuals was a decisive factor in the dynamics of the population. Furthermore, we found that the average remaining lifetime of flowering individuals was high relative to the other three stages. Second, to elucidate the demographic consequences of organ preformation, we investigated the development of flower buds for future years. We observed three to six flower buds per rhizome, suggesting that flower buds for the next 3–6 years were ready in advance in this plant. Third, the results of breeding experiments clarified that although this species appears to have a substantial capacity for both inbreeding and outbreeding, inbreeding plays an important role in seed production, and that crossing experiments (direct cross-pollination and self pollination) yielded similar seed-ovule ratios to those obtained from open-pollinated individuals. Our three studies suggest that the adult survival and continuous flowering strategies of T. apetalon obtained from demographic analysis are closely interlinked with breeding systems and preformation of flower buds.