Temporal changes in the most effective pollinator of a bromeliad pollinated by bees and hummingbirds

Abstract

A generalist pollination system may be characterized through the interaction of a plant species with two or more functional groups of pollinators. The spatiotemporal variation of the most effective pollinator is the factor most frequently advocated to explain the emergence and maintenance of generalist pollination systems. There are few studies merging variation in floral visitor assemblages and the efficacy of pollination by different functional groups. Thus, there are gaps in our knowledge about the variation in time of pollinator efficacy and frequency of generalist species. In this study, we evaluated the pollination efficacy of the floral visitors of Edmundoa lindenii (Bromeliaceae) and their frequency of visits across four reproductive events. We analyzed the frequency of the three groups of floral visitors (large bees, small bees, and hummingbirds) through focal observations in the reproductive events of 2015, 2016, 2017, and 2018. We evaluated the pollination efficacy (fecundity after one visit) through selective exposure treatments and the breeding system by manual pollinations. We tested if the reproductive success after natural pollination varied between the reproductive events and also calculated the pollen limitation index. E. lindenii is a self-incompatible and parthenocarpic species, requiring the action of pollinators for sexual reproduction. Hummingbirds had higher efficacy than large bees and small bees acted only as pollen larcenists. The relative frequency of the groups of floral visitors varied between the reproductive events. Pollen limitation has occurred only in the reproductive event of 2017, when visits by hummingbirds were scarce and reproductive success after natural pollination was the lowest. We conclude that hummingbirds and large bees were the main and the secondary pollinators of E. lindenii, respectively, and that temporal variations in the pollinator assemblages had effects on its reproductive success. Despite their lower pollination efficacy, large bees ensured seed set when hummingbirds failed. Thus, we provide evidence that variable pollination environments may favor generalization, even under differential effectiveness of pollinator groups if secondary pollinators provide reproductive assurance.

Divergent pollination system and morph-dependent effects of corolla length on inaccuracy of reciprocity and reproductive success of a distylous species of Rubiaceae

“…This result indicates that the high frequency recorded for butterflies in PARNASO is probably not due to temporal variation of pollinators (Gómez et al 2010;Zhao & Huang 2013;Leal et al 2020). Besides that, several species of hummingbirds are resident and act as pollinators of dozens of species in montane Atlantic forests (Wolowski et al 2016), including our study site (Leal et al 2020). In contrast to our results, a recent study observed that hummingbirds were more important than insects at higher elevations (750-950 m a.s.l.…”

“…However, different from these studies, which found hummingbirds to be the main pollinators (Castro & Araújo 2004;Almeida 2005;Ribeiro et al 2018), we found that butterflies prevailed in PARNASO over the three consecutive years of the study. This result indicates that the high frequency recorded for butterflies in PARNASO is probably not due to temporal variation of pollinators (Gómez et al 2010;Zhao & Huang 2013;Leal et al 2020). Besides that, several species of hummingbirds are resident and act as pollinators of dozens of species in montane Atlantic forests (Wolowski et al 2016), including our study site (Leal et al 2020).…”

Intraspecific variability of nectar attracts different bats: the case of Pseudalcantarea viridiflora, a bromeliad with crepuscular anthesis

“…Pollinator size and the frequency and manner in which the pollinators undertake floral visits, could promote differences in the contributions of sympatric pollinating species to the reproductive success of the visited plants. It is also worth noting that pollinator effectiveness can change according to season (Fishbein & Venable 1996;Rocca & Sazima 2013;Leal et al 2020)…”

Bimodal activity of diurnal flower visitation at high elevation

“…Interactions between plants and their pollinators determine the assemblage and function of communities at various temporal and spatial scales (Artz et al., 2010 ; Barônio & Torezan‐Silingardi, 2017 ; Price et al., 2005 ; Venjakob et al., 2016 ). Interactions between flowers and their pollinators are shaped by varying degrees of coevolution/coadaptation resulting in matches of floral and floral forager traits (Faegri & van der Pijl, 2013 ; Fenster et al., 2004 ; Leal et al., 2020 ; Proctor et al., 1996 ; Zych et al., 2019 ). For coadaptation to occur, the temporal and spatial dimensions of plant–pollinator interactions must be self‐consistent (Trøjelsgaard & Olesen, 2016 ; Valverde et al., 2016 ).…”