Format: ORAL

Natalia Castao-Rubiano1, 2Luna Ibez2, Eliana lvarez-Valdez2, Melisa Alegra Valencia1, Luis Alberto Nuez-Avellaneda3, Gonzalo Taborda-Ocampo2, Alejandro Zuluaga-Trochez1 Artur Campos Dalia Maia4, 5

1 Universidad del Valle, Cali, Colombia 2 Universidad de Caldas, Manizales, Colombia 3 Universidad de La Salle, Bogotá, Colombia 4 Université of Corsica, Ajaccio, France 5 Universidade Federal de Pernambuco, Recife, Brazil

Plants reliance on external agents for pollination has led to significant adaptations in floral traits, potentially contributing to the remarkable species diversity observed in this group. Reproductive isolation mechanisms between populations, particularly pre- and post-zygotic isolation in congeneric and sympatric species, play a critical role in minimizing competition for pollinators. Reproductive strategies, including flowering time, visual signals, floral fragrance chemistry, and rewards offered, facilitate coexistence and can act as prezygotic reproductive isolation barriers when gene flow persists, allowing for hybrid formation. We investigated the reproductive systems, isolation mechanisms, and pollination dynamics of coexisting species of Stenospermation (Araceae) in two localities of Colombias central and western Andes. We assessed pollen transfer and the potential for hybrid formation using pollination and hybridization tests. Additionally, we evaluated the effectiveness of phenological and ethological isolation in preventing self-pollination. Floral volatile compounds were analyzed using Dynamic Headspace and GC-MS techniques, and attractiveness assays were performed to determine pollinator preferences. Stenospermation exhibits a sexual system with androgynous flowers, and protogyny prevents self-pollination, precluding fruit production through apomixis. Our results demonstrate the possibility of hybridization through controlled experiments. Stenospermation communities exhibited low synchronicity or were asynchronous. All species display varying anthesis hours and share their floral volatile chemistry and pollinators at various degrees. We conclude that Stenospermation employs a multifactorial approach to prezygotic isolation involving ethological, phenological, and ecological factors, as no single trait thoroughly explains the observed isolation. Pollinator facilitation between syntopic species and complementary life cycles with pollinators contribute to reproductive success. Spathe tissue, the floral chamber and the thermogenesis are crucial floral rewards, particularly for large pollinators likeCyclocephala.