Does beak size predict the pollination performance of hummingbirds at long and tubular flowers? A case study of a Neotropical spiral ginger

Abstract

Long‐billed hummingbirds are assumed to be better adapted than short‐billed ones for the pollination of long tubular flowers. However, the majority of the empirical evidence is derived from surveys of pollinator feeding performance, which tend to ignore the implications for plant fitness. Here, we tested the long‐billed performance hypothesis from the perspective of the pollinated plant. We conducted a comparative survey to evaluate fecundity in relation to the length of the beak of the pollinating hummingbirds visiting the long and tubular flowers of Costus spiralis (Costaceae), in the Brazilian Atlantic forest. The flowers of C. spiralis were pollinated by three hummingbird species and their nectar was thieved by the bee Eulaema sp. There was no significant difference in the frequency of floral visits nor in the production of seeds among the three hummingbirds in fruits formed from flowers exposed to a single visit by each pollinator. Unexpectedly, our results indicate that the floral morphology of C. spiralis is equally compatible with long‐ and short‐billed pollinators, and is apparently incompatible with pollination by large insects. These findings emphasize the need to test the performance of each floral visitor with the simultaneous estimation of the intensity of the interactions, to increase the accuracy of the measurement of the pollinator's relative importance in studies of plant–pollinator interactions in ornithophilous systems.

Effects of the availability of floral resources and neighboring plants on nectar robbery in a specialized pollination system

“…In addition, the relationship between the frequency of nectar robbing and the species composition scores ( Figure 6 ) indicates that nectar robbing is more frequent in patches containing the ornithophilous plants C. spiralis and P. nuda , which are also visited primarily by hummingbirds in the Brazilian Atlantic forest ( Sazima et al 1995 ; Almeida and Alves 2000 ; Castro and Araújo 2004 ; Araújo and Oliveira 2007 ; Missagia and Alves 2018 ). In terms of floral visitor attraction, ornithophilous plant species may act as visual “magnets” in mixed-species floral patches, broadening the scope of the floral display and encouraging visitors to probe the flowers of other species ( Laverty 1992 ), depending on the relative density of each species ( Seifan et al 2014 ; Nottebrock et al 2017 ).…”

Is bigger always better? Neither body size nor aggressive behavior are good predictors to measure the degree of specialization of hummingbird interaction networks in rocky outcrops

“…Our results indicate that the potential pollinators’ effectiveness may be mediated more closely by the abundance of pollinators (hummingbirds) than the trait-matching compatibility. The potential pollinators are the pollinator’s total contribution to the plant’s fitness, measure, for example, by the number of pollen grains deposited (Schupp et al 2017, Missagia and Alves 2018). Although hummingbirds’ beak was not a good predictor to explain a higher frequency of pollen grains in our study, the result points to a tendency for long, curved-billed species to carry a higher frequency of pollen grains than short-billed species.…”

A geographical perspective on the relationship between Impatiens spur lengths and bill lengths of sunbirds in Afrotropical mountains

“…These species are highly adapted and enter specific co-evolutionary relationships (Abrahamczyk et al, 2014;Stiles, 1981). Longer flowers increase the effectiveness of the pollination process by forcing birds to put their heads deeper into the flower (Temeles et al, 2013; but see Missagia & Alves, 2018) or by excluding short-billed members of the pollinator assemblage (Cronk & Ojeda, 2008).…”