Geogenomics of montane palms points to Miocene-Pliocene Andean segmentation related to strike-slip tectonics

Aim In geographically and ecologically heterogeneous landscapes, such as tropical mountains, widely distributed species may be informative proxies for studying landscape and climatic evolution. We explore historical vicariant and dispersal processes that may have determined the genetic structure and variation of a palm species complex living in cloud forests. We hypothesize that the genomic groupings reflect uplift-based isolation by vicariance, divergence via dispersal events driven by faulted montane segments or recent divergence due to climate fluctuations. Location Colombian Andes. Taxon Geonoma undata-G. orbignyana species complex (Arecaceae). Methods We sampled 195 individuals of the species complex plus the outgroup (G. interrupta) across the three cordilleras of Colombia, the Colombian Massif and the Sierra Nevada de Santa Marta. We used target capture sequencing to generate a dataset of 12,750 quality-filtered genome-wide SNPs. We conducted phylogenetic, multivariate and population genomics and structure analyses to infer demographical history. Results We found four genetically distinct groups within the species complex. The geographical distributions of the genetic groups, and their inferred phylogenetic and population divergence are consistent with a history of colonization of mountain segments that were disconnected until the late Pliocene. These breaks coincide with the distribution of Pliocene strike-slip faulting events. Main conclusions The faulting and resultant topographic disruption of the northernmost Andean cordillera prior to the onset of the Pleistocene is implied by the presence of phylogeographic breaks in areas that are topographically continuous today. These cordilleras were formed by connecting segments that were previously uplifted but historically detached in areas where dense fault systems occur. Large-scale strike-slip faulting can generate topographic gaps, features that likely caused the divergence by dispersal with gene flow of the Geonoma undata-G. orbignyana complex.

Automated summary

This study examines the genetic structure and variation of a palm species complex living in the cloud forests of the Colombian Andes. The results suggest that the genetic groups within the species complex reflect historical processes such as uplift-based isolation, dispersal events, and climate fluctuations. The presence of phylogeographic breaks coinciding with Pliocene strike-slip faulting events indicates the role of topographic disruption in the divergence of this species complex.