The present does not reflect the past: geographic mismatches between fossil and modern records are widespread across the tree of life.

Abstract

The distribution of organisms across Earth provides insight into the origin and maintenance of biodiversity. Abundant fossil evidence suggests taxa have undergone substantial range changes over time. However, biogeographic theory and models often tend to assume that clades originated in the regions where we observe them today. Understanding the prevalence of geographically dynamic clades across the tree of life provides a way to evaluate these assumptions, thereby refining key evolutionary hypotheses. We provide a review of such range-shifting clades using a two-pronged approach. First, literature searches uncovered examples across most major multicellular groups (comprising 129 clades with mismatches between fossil and modern ranges). Concurrently, we used the well-sampled mammalian fossil record as a case study, finding that more than half of its terrestrial families (51%) had substantial (>1000 km) geographic mismatches. Geographically dynamic lineages are both common and widespread, but despite their ubiquity, fossil-modern mismatches have only recently been integrated into phylogenetic and biogeographic methods and no comprehensive overview of their advantages and challenges exists. We therefore review the current state of the field and discuss case studies where fossil evidence reshaped prevailing biogeographic theory. Biogeographers must take advantage of these rich fossil histories to better elucidate evolutionary theory across space and time.