Shaped by Mountains, Driven by Climate: The Rise of the Neotropical Carex sect. Fecundae

Carex sect. Fecundae is a diverse group of sedges comprising 39 species, notable as a fully tropical lineage within a genus otherwise dominated by boreotemperate elements. Its distribution spans montane regions from Central Mexico to northern Chile and Argentina, where it occupies a variety of habitats. Despite its diversity and ecological importance, the section has remained understudied. This study aims to generate the first nearly complete phylogeny of sect. Fecundae to clarify evolutionary relationships, reconstruct its biogeographic history, and identify the drivers underlying its diversification.

We conducted phylogenetic analyses including 37 of the 39 known taxa of the section. Historical biogeographic reconstructions were used to infer dispersal pathways and colonization events. Climatic and ecological data were integrated to assess bioclimatic niche evolution, while morphological traits were evaluated for their potential role in diversification.

Analyses strongly support the monophyly of sect. Fecundae, with the exception of C. hebetata. The phylogeny reveals evidence of rapid diversification associated with complex geological and climatic processes, particularly the uplift of mountain ranges in Mexico, Central America, and the Andes. Biogeographic results suggest that the ancestor of the section dispersed long-distance from North America to the Central Andes, followed by a progressive northward expansion into Central America and Mexico. Diversification coincided with Miocene global cooling and mountain uplifting, promoting adaptation to montane grasslands, shrublands, and tropical moist broadleaf forests. Temperature and precipitation emerged as key variables shaping bioclimatic niches, with marked ecological differentiation between South American and Mexican lineages. Morphological features such as stigma number and nutlet invaginations appear to have influenced lineage divergence.

The evolutionary history of sect. Fecundae reflects an interplay of long-distance dispersal, niche conservatism, and local adaptation, enabling successful colonization of tropical montane environments. These findings contribute to a broader understanding of Neotropical montane biodiversity and highlight the dynamic processes shaping the evolution of tropical sedges.