Pollination ecology has been a fast growing field since the 1960s. A previous review by Baker & Hurd (18) together with books (77, 84, 220, 221 , 244, 264) and various symposia (e.g. 5, 12, 17, 24, 149, 167, 239) have promoted anthecology so that it remains at the heart of evolutionary and ecological research. This review concentrates on the entomologically relevant litera­ ture published since 1967. Botanical works must be included, as both insects and flowers mutually aSsure reproductive success. We have attempted to cover concepts, related disciplines, and insect taxa by reference to publica­ tions through which the reader may delve deeper. We apologize to our colleagues for not citing their works more fully. We dedicate this review to the memory of Paul D. Hurd Jr. His en­ thusiasm for bees and their relations with flowers, and for insects in general, have been an inspiration to us. His contributions would form the hub of a separate review in itself and we have not attempted to cover his works.

Insects as Flower Visitors and Pollinators

Visitation rates and mean numbers of visits per flower per day are determined at three altitudinal levels (2 200–3 600 m) in the high Andes of central Chile from quantified observations of flowers visitors to a total of 134 species of plants, studied over three flowering seasons. Significant altitudinal decreases in the mean no. visits/flower/minute and per day were recorded, with Level III flowers, on the average, being pollinated only about 1/2 as frequently and to as low as 1/4 as frequently in certain months, as Level I flowers. Visitation rates are generally highest in early and mid-summer at all altitudes. — The lower visitation rates at the higher elevations are due to lower insect abundance relative to plant resources and lower levels of activity for the insects present, stemming from the generally lower ambient temperatures. Seasonal differences in visitation rates may also be related to differences in insect abundance levels. The total probability of ovule pollination cannot be estimated directly from the pollination rates, because stigmas are probably receptive for longer periods at the higher elevations. When differences in the duration of stigma receptivity are estimated from differences in flower lifelength, the probability of pollination in Level III is not very different from that expected in Level I. However, for some months, the deficit in Level III may still be substantial. — These results underline the inherent dangers of predicting pollination possibilities directly from pollination rates. They also suggest that the impoverished pollination conditions assumed in hypotheses predicting higher amounts of self-compatibility at high altitudes might not be justified for all high temperate mountains.

Community studies in pollination ecology in the high temperate Andes of Central Chile. II: Effect of temperature on visitation rates and pollination possibilities

The foraging activity of pollinator insects in relation to weather factors (ambient temperature, solar radiation, relative humidity, and wind speed) was studied in an apple orchard with special reference to two managed bee species, Osmia cornuta (Latreille) and Apis mellifera L. Over the range of observed weather values, A. mellifera activity was significantly dependent on temperature, solar radiation, and wind speed; O. cornuta activity was dependent on solar radiation and wind speed. These results were confirmed through video recordings at one O. cornuta nesting shelter and one A. mellifera hive. For both species, daily activity started at lower temperatures than it ceased, whereas solar radiation did not differ between these two events. In general, O. cornuta was active from 10 to 12°C and 200 w/m2, and A. mellifera from 12 to 14°C and 300 w/m2. O. cornuta was the only bee species seen visiting apple flowers under strong wind or light rain. Because of its greater tolerance to inclement weather, O. cornuta pollinated apple flowers for longer periods (both daily and seasonally) than other flower visitors.

Weather-Dependent Pollinator Activity in an Apple Orchard, with Special Reference to Osmia cornuta and Apis mellifera (Hymenoptera: Megachilidae and Apidae)

Reproductive biology of woody plants in a cerrado community of central Brazil.

Abiotic factors may constrain the functioning of species interactions such as plant-pollinator mutualisms. I investigated how thermal environment affects the interaction between the early-blooming daffodil, Narcissus longispathus (Amaryllidaceae) and its major bee pollinator (Andrena bicolor ; Andrenidae), focusing simultaneously on plant and pollinator sides of the interaction. I studied fruit and seed set, flower duration, and the intrafloral thermal environment of N. longispathus, and the thermal biology, foraging behavior, and thermoregulatory ability of A. bicolor, over a 6-yr period in southeastern Spain. N. longispathus flowers from February to April, when unsuitable weather often limits pollinator activity, yet most flowers are successfully pollinated in all years and sites. Fruit set was weakly pollen limited, but among flowers setting fruit the proportion of ovules developing into seeds was not. Individual flowers lasted for 17 d on average, remaining functional during this period. On sunny days, the air inside N. longispathus flowers was significantly warmer than outside. Mean temperature excess inside flowers was as high as 8°C, and was positively related to solar irradiance. Within flowers, air temperature was highest around the anthers ; this intrafloral gradient was consistent with variation among perianth parts in radiation transmittance. Andrena bicolor foraged in N. longispathus flowering patches only on sunny days with air temperature >12°-13°C, and foraging behavior and flower visitation rate were temperature dependent. Bees were able to fly at relatively low thoracic temperatures (T th ; range 22-31°C) and this was essential for successfully foraging at N. longispathus. Under the range of irradiance and air temperature found at foraging sites, A. bicolor individuals inside flowers were able to reach T th suitable for flight by passive means alone. Under laboratory conditions, A. bicolor was unable to raise or otherwise regulate T th by physiological means, but free-flying individuals thermoregulated behaviorally. Basking was used to raise T th , and intrafloral microclimate, by influencing the proportion of foraging time devoted to basking, played an important role in thermoregulation. Flower visitation rate was positively related to the average temperature inside visited flowers, and the probability of basking immediately after one floral visit declined with increasing flower temperature. I conclude that the favorable microclimate within N. longispathus flowers, their long duration, and the thermal biology of A. bicolor, were critical elements in this early-season pollination system.

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Floral Biology, Microclimate, and Pollination by Ectothermic Bees in an Early‐Blooming Herb

Pancratium maritimum L. grows wild in the light soil belt of the coastal plain of Israel, from the sea-shore to the sandy plains further inland. The habitat of P. maritimum in the immediate vicinity of the sea is characterized by direct exposure to sea breezes and to continuous sprays or salt water droplets carried by the wind, by strong radiation and by high air humidity. These characteristics become less pronounced as the distance increases from the sea. In close vicinity to the sea, Pancratium participates in the plant association of Sporobolus arenarius (Gou.) Duv.-Jouv.-Lotus creticus L. which occupies the sandy beach and the high sandy-loam shores (Eig 1939). Here, this species often produces dense stands. Our present purpose was to study pollination in Pancratium, under the unique climatic conditions of the sea shore habitat, especially the effects of wind on pollination and seed setting.

D. Eisikowitch

Papers

Effect of wind on the pollination of pancratium maritimum l. (amaryllidaceae) by hawkmoths (lepidoptera: sphingidae)