# Reviewing the Great American Biotic Interchange: climate change as a trigger for biodiversity dispersal

## TL;DR

The Great American Biotic Interchange involved biodiversity exchange between North and South America, influenced by climate changes over millions of years.

## Contribution

This study provides new insights into the timing, direction, and climate-driven patterns of species dispersal during the GABI.

## Key findings

- The GABI began around 23 million years ago and became continuous from 15 million years ago.
- Cooling periods after the Miocene Climate Optimum favored and intensified dispersal events.
- Birds, plants, and mammals dispersed first, while amphibians dispersed last.

## Abstract

The Great American Biotic Interchange (GABI), during which an intense biodiversity interchange occurred between South and North America (SA and NA), strongly affected the biodiversity of the Americas. Despite its importance, there are still knowledge gaps regarding the factors triggering species dispersion, the taxonomic groups that first dispersed, the age at which dispersions began and intensified, and whether there was a main dispersal direction through the continent (from NA to SA or vice versa). To fill these gaps, we conducted a scientific literature review of the GABI, searching for studies with information regarding dispersal age, taxonomic groups (invertebrates, amphibians, non-avian reptiles, birds, mammals and plants), dispersion direction (towards SA or NA) and the type of data used as the source of evidence (fossil, molecular or extant species). We also investigated the effect of the climatic dynamic on the biodiversity dispersal through the relationships between oxygen-isotope levels (δ18O, as a proxy of past temperatures) and the number and geological age of dispersal records. Only 41.8% (87 publications) of the studies included information on biodiversity dispersion during GABI. We found evidence of GABI starting at 23 million years ago (Ma) and becoming a continuous process from approximately 15 Ma. Cooling periods after the Miocene Climate Optimum favoured continuous dispersals, which have since intensified. Studies based on molecular data recovered more closely related to the intermediate ages of dispersal records. In addition, birds, plants and mammals were displaced first, whereas amphibians were displaced last.