Effect of diurnal vs. nocturnal pollinators and flower position on the reproductive success of Echium simplex

Abstract

Nocturnal pollination plays an important role in sexual plant reproduction but has been overlooked, partially because of intrinsic difficulties in field experimentation. Even less attention has received the effect of within-inflorescence spatial position (distal or proximal) on nocturnal pollinators of columnar plants, despite there have been numerous studies examining the relationship between such position and reproductive success. Woody endemic Echium simplex possesses large erect inflorescences bearing thousands of flowers which are visited by a wide array of diurnal and nocturnal animals.In this study, we identified nocturnal visitors and compared their pollination effectiveness with that of diurnal pollinators in different inflorescence sections by means of selective exclosures in NE Tenerife (Canary Islands). Nocturnal visitors included at least ten morphospecies of moths (such as Paradrina rebeli and Eupithecia sp.), two coleopteran species (mainly Alloxantha sp.), neuropterans (Chrysoperla carnea), dictyopterans (Phyllodromica brullei), dermapterans (Guanchia sp.) and julidans (Ommatoiulus moreletii). In general, plants excluded from pollinators set less fruits than open-pollination (control) plants which set fruits homogeneously across sections. Diurnally-pollinated plants set more fruit in their upper parts whereas nocturnally-pollinated plants set fruit in both upper and bottom sections. We conclude that although the frequency and diversity of diurnal pollinators is far higher than that of nocturnal pollinators, both exhibit different foraging behaviour that generates complementary effects on the reproductive success of E. simplex.

Foraging Behavior and Pollen Transport by Flower Visitors of the Madeira Island Endemic Echium candicans

“…The hoverflies and the butterfly Colias croceus , which are known to carry pollen from a wide variety of plant species, seem to play a minor role in the pollination of E. candicans since they visited the plants less often than bees and presented the lowest percentages of E. candicans pollen on their bodies (nearly 50%, on average). However, several studies have stressed the importance of the complementary role of flower visitor species/groups in contributing to pollination efficiency by simultaneously considering flower visitor attributes, plant breeding systems, and reproductive traits, jointly with the assessment of plant reproductive output [ 14 , 70 ]. For instance, Barrios et al [ 11 ] showed that visitation frequency was not a good predictor of pollination efficiency since the long-tongued bees were in fact more effective in pollen transfer between the tubular flowers of Angadenia berteroi than the most common insect visitors.…”

“…For instance, Barrios et al [ 11 ] showed that visitation frequency was not a good predictor of pollination efficiency since the long-tongued bees were in fact more effective in pollen transfer between the tubular flowers of Angadenia berteroi than the most common insect visitors. More recently, Jaca et al [ 14 ] also found that differences in pollination behavior of diurnal and nocturnal flower visitors of the Canarian endemic Echium simplex led to the complementary reproductive success of the different inflorescence sections of this plant.…”

“…For example, a recent experimental study on the mechanics of pollen removal and deposition showed that proboscis width was the critical factor determining pollination effectiveness [ 11 ]. Pollinator behavior, in particular flower visitation rates and the movement patterns within and between conspecific plants, may strongly drive the differences in pollination efficiency by the different flower visitors [ 12 , 13 , 14 ].…”

“…Several studies have stressed that the conservation management of these threatened island endemic species should not strictly follow a traditional species-based approach but also value the importance of ecological interactions [ 23 , 24 ] as their survival may be influenced by the presence of other groups of organisms with which they interact [ 25 ]. In fact, pollination and seed production often represent the most vulnerable stages of many threatened plants, therefore it is critical to have good knowledge on the diversity of flower visitors, their effectiveness as pollinators, and the dynamics of pollen transfer for their effective conservation [ 14 , 26 , 27 ].…”

“…Previous investigations on the interactions between plants and their insect pollinators in Macaronesia have mostly been carried out in the Canary Islands, e.g., [ 14 , 27 , 28 ], with several other contributions from the Azores archipelago [ 28 , 29 , 30 , 31 ]. In the Madeiran archipelago, much fewer studies were carried out, usually being taxonomically biased and consisting mostly of lists of species associations resulting from unstandardized sampling [ 28 , 29 , 32 , 33 , 34 , 35 ].…”