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How biotic and abiotic factors act together to shape biological diversity is a major question in evolutionary biology. The recent availability of large datasets and development of new methodological approaches provide new tools to evaluate the predicted effects of ecological interactions and geography on lineage diversification and phenotypic evolution. Here, we use a near complete phylogenomic-scale phylogeny and a comprehensive morphological dataset comprising more than a thousand specimens to assess the role of biotic and abiotic processes in the diversification of monitor lizards (Varanidae). This charismatic group of lizards shows striking variation in species richness among its clades and multiple instances of endemic radiation in Indo-Australasia (i.e., the Indo-Australian Archipelago and Australia), one of Earth's most biogeographically complex regions. We found heterogeneity in diversification dynamics across the family. Idiosyncratic biotic and geographic conditions appear to have driven diversification and morphological evolution in three endemic Indo-Australasian radiations. Furthermore, incumbency effects partially explain patterns in the biotic exchange between Australia and New Guinea. Our results offer insight into the dynamic history of Indo-Australasia, the evolutionary significance of competition, and the long-term consequences of incumbency effects.


Accepted manscript of: Pavón‐Vázquez, Carlos J., Ian G. Brennan, Alexander Skeels, and J. Scott Keogh. "Competition and geography underlie speciation and morphological evolution in Indo‐Australasian monitor lizards." Evolution (2021)

Molecular data is publicly available from the Dryad Digital Repository at and, and from the National Center for Biotechnology Information (accession numbers in Supporting Information). Raw morphological data is available from the Dryad Digital Repository at Code used to run the diversification analyses is available from Zenodo at

This study was funded by an Australian Research Council grant to JSK. The graduate education of CJPV was financed by the Australian Government Research Training Program.

Available for download on Monday, December 19, 2022