Format: ORAL

Ral Lois 1 Anton A. Reznicek2 Socorro Gonzlez Elizondo3 Eduardo Ruiz Snchez4 Marcial Escudero5 Ana Morales6 Carmen Acedo1 Pedro Jimnez Mejas7

1 Universidad de León 2 University of Michigan Herbarium 3 Instituto Politécnico Nacional, CIIDIR Durango 4 Universidad de Guadalajara 5 Universidad de Sevilla 6 Universidad Rey Juan Carlos 7 Universidad Pablo de Olavide

Carex, a member of the Cyperaceae family, stands as a megadiverse genus encompassing over 2000 recognized species, primarily thriving within the boreal and temperate zones of the northern hemisphere. Despite this, certain lineages of Carex have successfully ventured into the tropical zones of the southern hemisphere on multiple occasions. Notably, Carex sect. Fecundae emerges as one such lineage, displaying a distribution entirely within the Neotropics, predominantly within high-altitude forests and grasslands spanning from Central Mexico to Northern Argentina. Comprising more than 30 species, Carex sect. Fecundae stands as one of the broadest lineages withinCarex. It boasts perhaps the most intricate inflorescence patterns among its counterparts. However, akin to numerous Neotropical plant groups, the understanding of sect. Fecundae remains significantly limited. Only three treatments of this section exist to date, none of which are comprehensive. Our research addresses this gap through a comprehensive taxonomic revision of Carex sect. Fecundae, reviewing more than 1000 specimens and statistically testing more than 100 characters. We established morphometric boundaries for species within the section by selecting the most distinguishing characters, such as inflorescence conformation, utricle, glumes, and achene dimensions. Furthermore, we undertook the first complete molecular phylogeny of the section, employing HybSeq to unravel the evolutionary relationships within Carex sect. Fecundae. Our combined analysis of morphological and molecular data led to the discovery of 18 previously overlooked species within the section. Additionally, we dated the recent origin of this section to approximately 5.77 Mya, affirming the rapid adaptive radiation witnessed within Carex sect. Fecundae.Through biogeographical analysis, we inferred the most recent common ancestor of the section between the Neotropical and South American Transition Zones. This origin was followed by two independent rapid radiationsone in Mexico and the other in South Americafurther elucidatingits evolutionary history.