Dear Colleagues We are pleased to announce the publication of the following article in Marine Mammal Science: Geographic variation in the whistles of bottlenose dolphins (*Tursiops* spp.) in the southwestern Atlantic Ocean. Marine Mammal Science, https://doi.org/10.1111/mms.12690 By Isabela M. S. Lima, Rihel Venuto, Carolina Menchaca, Lilian S. Hoffmann, Luciano Dalla Rosa, Rodrigo Genoves, Pedro F. Fruet, Andrea Milanelli, Paula Laporta, Bettina Tassino, Stephanie M. Bueno, Thales R. O. Freitas, Lis Bittencourt, José Lailson-Brito Jr, Alexandre F. Azevedo. We investigated the diferences among whistles of common bottlenose dolphins (*Tursiops truncatus truncatus*) recorded in Rio de Janeiro (Brazil) and Lahille’s bottlenose dolphins (*Tursiops truncatus gephyreus*) in areas in southern Brazil and Uruguay. Differences were found in frequency parameters and mainly between *Tursiops truncatus truncatus* and *Tursiops truncatus gephyreus*. Simultaneously, the results point to fewer differences among the whistles of the populations of Lahille's dolphins, at a finer geographic scale. The results are in agreement with genetic and morphological studies that proposed two subspecies of Tursiops in the southwestern Atlantic Ocean, but may also indicate adaptations to ecological and environmental characteristics in the different regions. The article can be found at: https://onlinelibrary.wiley.com/doi/10.1111/mms.12690 citation: Lima IMS, Venuto R, Menchaca C, et al. Geographic variation in the whistles of bottlenose dolphins (Tursiops spp.) in the southwestern Atlantic Ocean. Mar Mam Sci. 2020;1–10. https://doi.org/10.1111/mms.12690 Best wishes, Isabela Maria Seabra de Lima Bióloga - CR-BIO: 102101/02D Doutora pelo Programa de Pós-graduação em Ecologia e Evolução/UERJ