C. Eugene Jones

MALE MATING STRATEGIES IN THE BEE CENTRIS PALLIDA FOX (ANTHOPHORIDAE: HYMENOPTERA)

Males of the solitary bee Centris pallida practice one of two alternative mate-location strategies, either searching emergence areas for sites at which to dig up virgin females, or hovering by shrubs and trees, waiting for the arrival of airborne virgin females. The size of the male is related to which of these strategies he adopts, with the larger males more commonly patrolling and digging and the smaller males more commonly hovering. Large males are superior in competitive disputes over digging sites and appear to enjoy much greater reproductive success than males at the lower end of the spectrum of size. Despite this, large males are relatively rare in the population as a whole. Selection acts on females with respect to how they divide their total investment in male offspring. We examine the possibility that females which provision a number of small cells (thus producing several small males) may be as fit as or fitter than females that divide their investment into relatively few packets and produce a few large males.

Ultraviolet floral patterns as functional orientation cues in hymenopterous pollination systems

Abstract Field modifications of U.V. floral patterns of Caesalpinia eriostachys Benth. and Parkinsonia aculeata L. showed that bees used U.V. designs as orientation cues. Bees exhibited an in-flight orientation ability which was apparently correlated with size, with smaller bees frequently orienting to the manipulated position of the U.V. absorbent banner petal prior to landing on the flower. The U.V. absorptive banner petal and staminal portions of the flowers of both species seemed to be the most important visual orientation guides, and except for Trigona fuscipennis and T. pectoralis , the banner petal was the more important of the two. Emasculation of the flowers may have removed the orientation cue used by these species of Trigona , which may be orienting to the flowers solely on the basis of pollen odour. Morphological and physiological changes in the floral colour patterns of both species following pollination appear to inhibit visitation by bees. The significance of U.V. floral patterns was also considered.

Pollination and Reproduction in Natural and Mitigation Populations of the Many-Stemmed Dudleya, Dudleya multicaulis (Crassulaceae)

Abstract We investigated the reproductive biology of the rare and endangered plant, Dudleya multicaulis at five separate sites, three natural and two mitigation sites. We employed dawn to dusk observations to determine the spectrum of pollinators visiting D. multicaulis, took pollen samples from visitors to determine floral constancy, sampled nectar to determine volume produced per flower, examined the number of flowers per inflorescence, the number of those flowers that produced seed, and total seed set to determine reproductive output, completed seed germination tests to determine viability, and transplanted germinated seedlings from Petri dishes to soil to determine how well seedlings survive transplanting. Dudleya multicaulis was visited by flower beetles, native and European honey bees, flies, and a variety of other insects. Nectar production per flower averaged 0.12 µl. Bees averaged 99% floral constancy to D. multicaulis. Reproductive output measured by flower production and fruit/seed set were not significantly different among sites. Among all populations, the average fruit set ranged from 86.9 to 94.4%. The large fruit set coupled with the diversity of floral visitors suggests that D. multicaaulis is not pollinator limited. Data suggest that D. multicaulis is capable of self-pollination in absence of vectors. Seed germination and transplanted seedling survival did not differ significantly among sites. Results suggest that sowing seed may be better for plant establishment rather than transplanting when mitigation is necessitated.

Do Native Ants Play a Significant Role in the Reproductive Success of the Rare San Fernando Valley Spineflower, Chorizanthe parryi var. fernandina (Polygonaceae)?

Abstract Previous field studies of the reproductive biology of the San Fernando Valley spineflower, Chorizanthe parryi var. fernandina (S. Watson) Jeps. suggested that pollination by ants might be an important feature of this endangered polygonous taxon. This conclusion was based on observations that native ants were abundant floral visitors and constant to this species. We conducted the current study to explore more closely the possibility that native ants were facilitating pollination and resulting in viable seed set. Based on our data, ants can indeed be effective pollinators of spineflower. Fruit set was 57% higher in flowers exposed to ant visitation, compared to 27% in control flowers where ants were excluded. Further, a 25.7% germination rate was observed for achenes produced in the absence of ants, in contrast to a 61% rate in those produced in the presence of ants. We suggest that ant pollination may be more prevalent in drier climates, ant production of inhibitory substances may not be a severe limitation to their function as pollinators, invasive Argentine ants may pose a threat to plants pollinated by ants, and self-pollination may not be a negative attribute for ant pollinated plants.

FLOODPLAIN VEGETATION AND SOILS ALONG THE UPPER SANTA ANA RIVER, SAN BERNARDINO COUNTY, CALIFORNIA

ABSTRACT The patterns of vegetation and soils were documented in an approximately 20 km2 area of fluvial terraces adjacent to the Santa Ana River in southwestern San Bernardino County, California. Within this area there are three terraces of differing elevations that were last disturbed during major flood events. The oldest terrace surfaces probably were last disturbed during the Agua Mansa flood of 1862, which disturbed or created many current geomorphic features of the Santa Ana River basin. The most recent disturbance of two other terraces was identified based on photographs of flooding events in 1938 and 1969. Principal component analysis identified three assemblages of species whose distribution corresponded to the three terraces that differed in elevation, soil texture, and age since last disturbance by flooding. Canonical correspondence analysis showed that the assemblages identified by PCA were highly correlated with changes in soil texture and organic matter. The most reliable indicator species were Heterotheca sessiliflora and Lepidospartum squamatum for the first assemblage (associated with the lowest terrace, and corresponding to early successional assemblages identified by other researchers); Salvia apiana and Senecio flaccidus for the second assemblage (associated with the intermediate terrace); and Artemisia californica, Opuntia parryi, and Stephanomeria pauciflora for the third assemblage (associated with the highest terrace). Eriastrum densifolium subsp. sanctorum, the rare Santa Ana River Woolly Star, was associated with the earlier phases of succession. The most important soil factor distinguishing these assemblages was the silt/clay content of the soil.

Honeybee Constancy to Ultraviolet Floral Reflectance

SummaryHoneybees (Apis mellifera) were trained to artificial floral arrays to investigate their discrimination of, and constancy to, UV as a floral colour. The floral arrays enabled colour to be varied while other floral characteristics (odour, height, etc.) remained constant. Bees were trained to an array that had only one colour morph, and then were tested on arrays to which had been added increasing frequencies of an opposing floral colour-morph. Colours tested were yellow, UV and ‘bee purple’ (yellow plus UV). Bees trained to UV or bee purple remained constant to those colours when opposing colour morphs were inserted; bees trained to yellow were variable in their constancy. It was concluded that honeybees can not only discriminate between and remain constant to flowers when the sole floral cue difference is the presence or absence of UV reflectance, but also show a greater constancy to flowers having at least some UV reflectance.

Reproductive Biology of the San Fernando Valley Spineflower, Chorizanthe parryi var. fernandina (Polygonaceae)

Abstract In response to conservation concerns, the reproductive biology of the San Fernando Valley Spineflower was investigated, focusing on pollination interactions and seed germination. Pollination by a variety of aerial visitors, as well as autogamy (a facultative selfer, showing about 25% selfing), appear to contribute significantly to fruit/seed set. There was a significant correlation between the numerous different floral visitors (many went uncollected) and the invertebrate fauna in the immediately surrounding coastal sage scrub community indicating that this taxon is visited by a substantial variety of potential pollinators and is probably not pollinator-limited. Although there were many potential pollinators, only six species, including three species of ants, made up the vast majority of visits to the flowers at the two study sites. Many of the invertebrate visitors to the flowers of the San Fernando Valley Spineflower exhibited a high rate of constancy. An overall generalist strategy is suggested. Seed set was high and a germination rate of over 70% occurred without pre-treatment.

Significance of Bulb Polarity in Survival of Transplanted Mitigation Bulbs

Abstract Our experimental design was formulated to determine whether or not bulb polarity (orientation) at the time of replanting of bulbs to salvage plants of Calochortus weedii A. W. Wood (Liliaceae) or Weed’s Mariposa Lily affected the success of the mitigation transplant effort. Polarity of bulbs at planting clearly did influence subsequent growth, most notably in the tip-down (D) treatment. Among these bulbs, 75% failed to emerge from dormancy and only four (20%) actually set mature fruit. This was in sharp contrast to the other three treatments where 100% of the bulbs successfully emerged in this season and between 80% (S) and 95% (UG and UN) set mature fruit. The data from this study do indicate that: 1) bulb planting orientation does influence survival and growth, and 2) proper bulb planting polarity (orientation) should be an important consideration in any transplantation of this or any sensitive bulb producing plant species for mitigation purposes.