Differential gender selection on flower size in two Neotropical savanna congeneric species A. L. Teixido . R. L. C. Dayrell . A. J. Arruda . L. O. Azevedo . P. A. Junqueira . J. V. S. Messeder . F. A. O. Silveira Received: 12 July 2017 / Accepted: 6 November 2017 / Published online: 9 November 2017 Ó Springer Science+Business Media B.V., part of Springer Nature 2017 Abstract Larger flowers greatly increase among- individual pollen exchange within populations. How- ever, water costs associated to transpirational cooling also increase with increasing flower size. Overall, the interplay between pollen and resource limitation determines the intensity of selection on flower size and this process is mostly dependent on gender and ecological context. To examine how pollinators and water use affect flower size, we determined corolla transpiration, pollen limitation, and selection through male and female fitness in two Kielmeyera species from the Brazilian cerrado flowering at different seasons. Hand-pollination experiments suggested pol- len limitation through female fitness in both species, but K. coriacea showed lower limitation levels than K. regalis. For male fitness, the percentage of pollen removal was 1.5-times higher in K. coriacea. Higher air temperature and water deficit during flowering season of K. coriacea resulted in 4-fold higher corolla transpiration rates compared to K. regalis. Selection on flower size through male function was positive and significantly higher than selection through female components in both species. We also detected stabi- lizing selection in K. coriacea and positive selection in K. regalis on flower size through seed number. Our results suggest that selection on flower size in K. coriacea was mainly limited by water, whereas in K. regalis it was more limited by pollen. We demonstrate that differences in pollen and abiotic resource limita- tion determine gender-specific selection on flower size. Keywords Corolla transpiration  Female fitness  Kielmeyera coriacea  Kielmeyera regalis  Male fitness  Pollen limitation Introduction Flower size is a pivotal trait closely linked to pollinator attraction and subsequent plant reproduc- tion. Larger flowers favor pollen transfer and pollina- tor-mediated positive selection on flower size has been broadly documented in natural plant populations (e.g., Stanton et al. 1986; Galen 1996; Maad and Alexan- dersson 2004; Barrio and Teixido 2015). However, a unilateral view of the role of pollinators in mediating the evolution of this trait ignores the evolutionary Communicated by Philip Ladd. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11258-017-0780-4) con- tains supplementary material, which is available to authorized users. A. L. Teixido (&)  R. L. C. Dayrell  A. J. Arruda  L. O. Azevedo  P. A. Junqueira  J. V. S. Messeder  F. A. O. Silveira Departamento de Bota ˆnica, Universidade Federal de Minas Gerais, Av. Anto ˆnio Carlos 6627, E-486, Belo Horizonte, Minas Gerais 30161-970, Brazil e-mail: alberto.lopez.teixido@gmail.com 123 Plant Ecol (2018) 219:89–100 https://doi.org/10.1007/s11258-017-0780-4