Nectar ecology of the endemic epiphytic hummingbird-pollinated bromeliad Vriesea altodaserrae: secretion dynamics and pollinator visitation pattern

Abstract

Hummingbirds are the main pollinators of most bromeliad species, whose nectar traits usually respond to the selective pressures imposed by pollinators. Considering the specialization of hummingbird-pollinated bromeliads, we expect a close relationship between nectar ecophysiology and the needs of the main pollinators. In this sense, we studied the nectar ecology of the endemic epiphytic bromeliad Vriesea altodaserrae by assessing its nectar traits to address the following questions: i) do flowers respond to successive experimental removals of nectar? ii) is hummingbird visitation frequency related to nectar secretion pattern? We found that V. altodaserrae depended completely on hummingbirds for sexual reproduction, and nectar composition was consistent with that of most hummingbirdpollinated species. Most of the nectar was secreted at bud stage and, if not removed, flowers reabsorb it at the end of their lifespan. Total nectar production did not change after successive removals, and nectar secretion rhythm did not affect the frequency of hummingbird visits. Vriesea altodaserrae was visited by two-thirds of the hummingbird species recorded at the study site, but especially by those of Trochilinae subfamily, suggesting specialization for this group of hummingbirds and highlighting the importance this endemic bromeliad as a keystone species in areas of highland Atlantic forest.

Diurnal Dynamics of Nectar Secretion in <i>Cucurbita maxima </i>Duch: Implications for Effective Pollen Transfer by Japanese Wild Pollinators

“…Although the availability of wild pollinators may depend on the local environment, the offering of floral nectar is an important strategy for plants to control pollinators (Nepi et al 2018, Stout & Goulson 2002. As pollinators rely on floral nectar for energy, they often respond to such nectar characteristics as volume, sugar concentration and composition, and temporal or spatial (including among-flower) variability (Biernaskie et al 2002, Nunes et al 2018, Rathcke 2012. Temporal and among-flower variation in nectar secretion would be quite important for Cucurbita spp., which have short periods of anthesis from dawn until early afternoon.…”

Pollination by hummingbirds of Vriesea gigantea (Bromeliaceae) populations in Southern Brazil

“…As reviewed by Zanella et al (2012), bromeliads have evolved floral displays with a great diversity of colors, shapes, and scents that are related to pollinator attraction, with nectar being the usual reward. Bromeliad species are also essential resource for small, hovering vertebrate pollinators in the New World (Flemming & Muchhala 2008) and are the most important food sources for hummingbirds in many Neotropical forest regions (Sazima et al 1995(Sazima et al , 1996Dziedzioch et al 2003;Wolowski et al 2013;Pansarin & de Pedro 2016;Nunes et al 2018;Lenzi & Paggi 2020). Krömer et al (2008) strongly support the hypothesis that the composition of nectar sugars in Bromeliaceae is correlated with psychophilous, trochilophilous, or chiropterophilous pollination syndromes.…”

Intra‐seasonal and daily variations in nectar availability affect bee assemblage in a monodominant afforested Brazilian Cerrado

“…Then, we used a microliter syringe (Hamilton, NV, USA) to measure nectar volume and a pocket refractometer (0-90%; Instrutherm -RT-280) to quantify nectar sugar concentration (percentage sucrose, mass/mass). We assessed nectar dynamics for 24 h (from flower opening to senescence, 18 h00 to 18 h00) in intervals of 3 h. At each time interval, we sampled the nectar of an untouched new set of flowers to characterize the different stages of the nectar secretion dynamics, that is the periods of active nectar secretion, cessation of nectar production and nectar reabsorption (see Amorim et al 2013;Nunes et al 2018).…”

“…We tested for differences in the volume, concentration of nectar, and amount of sugar throughout the flower lifespan. To evaluate whether sequential nectar removals affect the total amount of nectar produced by each set of flowers (in terms of mg of sugar), we followed Nunes et al (2018). We used a linear mixed-effect model (LMM), in which plants were treated as random effects, and the total amount of sugar produced in each set of flowers was treated as a fixed effect.…”

“…Plant-pollinator interactions are very dynamic across space and time (Baldock et al 2011;Chacoff et al 2018;Revert e et al 2019;Hachuy-Filho et al 2020). Therefore, assessing variation in nectar availability across seasons and the dynamics in nectar production throughout flower lifespan are important tools to understand better plant-pollinator relationships (see Amorim et al 2013;Morellato et al 2016;Nunes et al 2018 andRother et al 2022).…”