Abstract Detail

Reproductive Processes

Nunes, Carlos E. P. [1], Nevard, Lucy [2], Montealegre-Zapata, Fernando [3], Vallejo-MarĂ­n, Mario [2].

Are flowers tuned at the frequency of pollinators? Stamen resonance and bee buzzing frequencies in Solanum with contrasting floral morphologies.

During buzz pollination, bees use vibrations from their flight muscles to remove pollen from flowers. Vibrations at the natural frequency of pollen-carrying stamens can be amplified through resonance, resulting in higher-amplitude vibrations. Because pollen release depends on vibration amplitude, bees could increase pollen removal by vibrating at the natural frequency of stamens of buzz-pollinated plants. Interestingly, certain groups of buzz-pollinated plants are characterized by heteranthery, the presence of two sets of stamens with strikingly different morphologies (e.g. diameter and length) associated to different functions: feeding and pollinating. Yet, few studies have characterized the natural frequencies of stamens and compared them to frequencies of buzz-pollinating bees. Here we use laser Doppler vibrometry to characterise natural frequencies of stamens of six buzz-pollinated taxa that capture three independent transitions in flower size and heteranthery in Solanum section Androceras. We also compare the fundamental frequency of bumblebee buzzes produced on two Solanum species contrasting floral morphologies and different natural frequencies, Solanum citrullifolium and S. heterodoxum. Natural frequency differed among taxa and between stamen types, with pollinating stamens overall having lower natural frequencies than feeding stamens. In each pair, pollinating stamens from the large-flowered taxon had lower natural frequencies than pollinating stamens from its small-flowered relative. After accounting for species identity and stamen type, we observed a marginally significant effect of stamen length on natural frequencies. Longer stamens tended to have lower natural frequencies than shorter stamens. Bee buzzes had a lower frequency in S. heterodoxum than in S. citrullifolium, and buzz frequency decreased with bout number. Bombus terrestris vibrated flowers of S. citrullifolium at 345.25±0.87 Hz (mean±SE) during their first bout and at 344.04±0.57 Hz in the sixth. The same individuals vibrated flowers of S. heterodoxum at 349.68±0.70 and 329.47±0.95 Hz, in their first and sixth bouts, respectively. In summary, bee vibrations at flowers remained much higher than the natural frequency of the stamens being visited. Furthermore, stamen morphology and plant identity explain variation in natural frequency of stamens. Our results show that medium-sized pollinators, such as bumblebees, produce buzzes of frequencies higher than the natural frequency of most (5/6) of the Solanum species we studied. However, the observed natural frequency of Solanum stamens is at the low end of the range of frequencies produced by other buzz-pollinating bees. Thus, our findings suggest that in some buzz pollination interactions, but not others, stamen resonance may play a role in mediating pollen release.

Related Links:
Publicly available pre-print of this work

1 - University Of Stirling, Department Of Biological And Environmental Sciences, Cottrel Building, University Of Stirling, 5A Keir Avenue, Cottrel Building, University Of Stirling, Stirling, STG, FK8 1QL, United Kingdom
2 - University of Stirling, Biological & Environmental Sciences, Department of Biological and Environmental Sciences, Cottrel Building, University of Stirling, Stirling, Stirlingshire, FK9 4LA, United Kingdom
3 - University of Lincoln, School of Life Sciences, School of Life Sciences, University of Lincoln, Lincoln, Lincolnshire, LN6 7DL

Morphologic diversity

Presentation Type: Oral Paper
Session: REP4, Reproductive Processes 4
Location: Virtual/Virtual
Date: Thursday, July 30th, 2020
Time: 3:15 PM
Number: REP4002
Abstract ID:549
Candidate for Awards:None

Copyright © 2000-2020, Botanical Society of America. All rights reserved