Spatio‐temporal variation of nectar robbing in Salvia gesneriflora and its effects on nectar production and legitimate visitors

Abstract

Nectar robbing occurs when floral visitors remove floral nectar through floral damage and usually without providing pollination in return. Even though nectar robbing may have negative, neutral or even positive effects on plant fitness, few studies have investigated temporal and spatial variation in robbing rate and their consequences, particularly in the tropics. In this study, robbing levels were estimated during 3 years in four populations of Salvia gesneriflora, a hummingbird-pollinated shrub endemic to central Mexico that is mainly robbed by birds, carpenter bees and bumblebees. The effect of robbing on nectar availability, flower longevity and on visitation rate by floral visitors was also evaluated. Our results indicate great variation in robbing levels across years and populations and a positive relationship between robbing level and flower abundance per population. Moreover, our results show that nectar availability is about eight times higher in unrobbed flowers than in robbed flowers, and that nectar robbers prefer younger flowers, although lifespan of robbed and unrobbed flowers did not differ statistically. Primary and secondary nectar robbers showed a higher visitation rate compared to legitimate visitors, and neither legitimate nor illegitimate floral visitors seem to discriminate between robbed and unrobbed flowers. These results suggest that robbers may respond to food availability and that no floral visitors apparently could differentiate between robbed and unrobbed flowers. Finally, results show that nectar robbers prefer the youngest flowers, which suggests that strong competition for access to nectar between pollinators and robbers might occur, mainly at the first stages of the flowers.

Variation in composition of two bumble bee species across communities affects nectar robbing but maintains pollinator visitation rate to an alpine plant, Salvia przewalskii

“…Similar to previous studies revealing great variation in nectar robbing among individuals, species, sites, seasons, and years (Morris, 1996;Olesen, 1996;Navarro, 2000;Arizmendi, 2001;Irwin et al, 2001;Utelli & Roy, 2001;Irwin & Maloof, 2002;Cuevas & Rosas-Guerrero, 2016;Rojas-Nossa et al, 2016), we also established that nectar robbing of S. przewalskii varied spatiotemporally. In addition, our survey indicated that in all of the communities, only S. przewalskii was a target of nectar robbing.…”

“…It has been proposed that spatiotemporal variations in nectar robbing can be explained by two variables: the local availability of alternative floral resources and the abundance of floral visitors (Navarro, 2000;Irwin et al, 2001;Irwin & Maloof, 2002;Cuevas & Rosas-Guerrero, 2016;Rojas-Nossa et al, 2016); however, direct experimental evidence is still needed to support these explanations. Our results confirmed these arguments and provided evidence to explore these relationships in detail.…”

“…Our results confirmed these arguments and provided evidence to explore these relationships in detail. It has been suggested that the robbers may perceive flower abundance and associate it with food availability (Cuevas & Rosas-Guerrero, 2016). It has been suggested that the robbers may perceive flower abundance and associate it with food availability (Cuevas & Rosas-Guerrero, 2016).…”

“…For example, plant populations with suitable nesting or foraging sites for robbing bumble bees may have high nectar-robbing rates (Irwin & Maloof, 2002). A population with richer flower resources may have a higher level of nectar robbing because the robbers may perceive high flower abundance and associate it with food availability (Cuevas & Rosas-Guerrero, 2016). However, few empirical studies have attempted to investigate the underlying factors affecting the spatiotemporal variations in nectar robbing (Irwin & Maloof, 2002;Rojas-Nossa et al, 2016).…”

Lamiaceae de México

“…Se han logrado avances sustanciales en el entendimiento de sus relaciones filogenéticas (Walker et al 2004, Walker & Sytsma 2007, Drew et al 2017, Fragoso-Martínez et al 2017a. En adición, se han realizado algunos estudios cromosómicos (Epling et al 1962, Palomino et al 1986, Mercado et al 1989, anatómicos (Ceja-Romero et al 2005, Castro-Morales 2008, genéticos (Cahill 2004), quí-micos (Wasson 1962, Sánchez et al 1989, Argumedo et al 2003 (Dieringer et al 1991, Claßen-Bockhoff et al 2004, Wester & Claßen-Bockhoff 2006, Arizmendi et al 2007, Benitez-Vieyra et al 2014, Cuevas & Rosas-Guerrero 2016.…”