Patterns and Processes in Nocturnal and Crepuscular Pollination Services

Abstract

Night, dawn, and dusk have abiotic features that differ from the day. Illumination, wind speeds, turbulence, and temperatures are lower while humidity may be higher at night. Nocturnal pollination occurred in 30% of angiosperm families across 68% of orders, 97% of families with C3, two-thirds of families with crassulacean acid metabolism (CAM), and 71% dicot families with C4 photosynthesis. Despite its widespread occurence, nocturnal pollination occurs in more families with xerophytic adaptations than helophytes or mesophytes, suggesting that nocturnal flowering is primarily an adaptation to water stress since flowering is a water-intensive process. We propose the arid or water stress hypothesis for nocturnal flowering suggesting that plants facing water stress in a habitat (e.g., deserts) or a habitat stratum (e.g., upper canopy for epiphytes) gain a selective advantage by nocturnal flowering by reducing water loss through evapotranspiration, leading to larger flowers that provide more nectar or other resources, to support pollinators with higher rewards. Contrary to the wide taxonomic occurrence of nocturnal flowering, few animal taxa serve as nocturnal pollinators. We discuss the sensory and physiological abilities that enable pollinator movement, navigation, and detection of flowers within the nocturnal temporal niche and present a unified framework for investigation of nocturnal flowering and pollination.

Fuelling on the wing: sensory ecology of hawkmoth foraging

“…Most hawkmoths, however, visit flowers and feed on nectar—in fact, they are among the most prevalent moth pollinators (Hahn and Brühl 2016 ). Hawkmoth-pollinated flowers often share characteristics such as white (though not ultraviolet-reflective) or yellow colour, a long nectar tube or spur, the lack of a landing zone, abundant nectar and nocturnal anthesis (van der Pijl 1961 ; Borges et al 2016 ). They commonly share heavy-sweet odours, dominated by specific compounds.…”

Innate colour preferences of a hawkmoth depend on visual context

“…Blue and purple for Hymenoptera and some Lepidoptera [7,10,11] and, to a lesser degree yellow and red for some Lepidoptera and Coleoptera [7], are the innately preferred colour hues among diurnal pollinators. Visual detection is physiologically more challenging for nocturnal pollinators [12], which tend to exploit large, UV-absorbing white or creamy flowers that are characteristically very fragrant [7,8,13,14]. While strong scents facilitate long-distance detection, light coloration might favour visual recognition via achromatic (intensityrelated) signals under low-light conditions [9].…”

Rush hours in flower visitors over a day–night cycle

“…To the best of our knowledge, there is no information available on a community level for nocturnal pollinators. A recent review on nocturnal pollination, reports that nocturnal pollinators are often adapted to fly at low temperatures and in dark conditions (Borges et al, 2016). On the other hand, one of the few studies that related flower visitation of a nocturnal bee species to moon light intensity and temperature, found no relationship (Somanathan & Borges, 2001).…”