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The longstanding view of Andean uplift as a promoter of species diversification has become superfluous in the last decades given it would make no sense to suggest an alternative hypothesis, i.e. that the Andes have not promoted species diversification. Because we know that the Andes harbors an enormous proportion of endemics and that the Andes have evolved in the last millions of years when much of or extant biodiversity has also evolved, we know that both obligately coincide. However, we are lacking conceptual and empirical frameworks where geological and biological processes and events are causally linked through testable hypotheses. In this presentation, we show our recent work with two Andean lineages of palms, where we show that temporally and spatially constrained geological events linked to Andean uplift underlie the biogeographical processes that we infer by genomic sampling. Altogether, we sample 195 individuals of the Geonoma undata species complex and 129 individuals of genus Ceroxylon, in the tropical Andes, with a focus on the Colombian Cordilleras. We used hybrid sequence capture of nuclear regions, of where we extracted variant sites that we then used to perform multivariate statistics, coancestry analysis, phylogenetic analyses, and demographical and biogeographical model selection. We use geological cartography, petrography, and geochronology to test two main hypotheses: that the northern Andes have been disconnected in the past, to later connect by volcanic eruptions, or alternatively, that they have always been continuous and have gradually uplifted. Our biological results support a discontinuous past with repeated late Plio-Pleistocene colonization of the Colombian Cordilleras. Our geological results support 1) heavy faulting in the area of the Colombian Massif, possibly creating topographic discontinuities, and 2) a volcanic eruption of great magnitude that could have connected cordilleras by valley filling and isostatic rebound occurring in that area in the Plio-Pleistocene boundary. The observed biogeographical processes (dispersal, and divergence in the Plio-Pleistocene through the Colombian Massif) in these two lineages of palms coincide temporally and spatially with traceable geological features and events. Our studies highlight the importance of establishing causality between processes in the Earth and Life sciences under comparable geographical and temporal scales.

Keywords:

Biogeography
Ceroxylon
Geonoma
Geochronology
Topographic evolution
Phylogeny
Target sequence capture

Maria Sanin, Agustin Cardona, Margot Paris, Michael Kessler, Ingrid Olivares, Sara Carvalho

Presentation within symposium:

S-37 Biological diversification in the Andean-Amazon region

Topographic continuity and species dispersal accross the Northern Andes

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