Alroy specializes in diversity curves, speciation, and extinction of North American fossil mammals and Phanerozoic marine invertebrates, connecting regional and local diversity, taxonomic composition, body mass distributions, ecomorphology, and phylogenetic patterns to intrinsic diversity dynamics, evolutionary trends, mass extinctions, and the effects of global climate change.
In a 3 September 2010 online article by Hugh Collins, a contributor for AOL Online Science, Alroy was quoted in a newly released study paper from Sydney's Macquarie University that "It would be unwise to assume that any large number of species can be lost today without forever altering the basic biological character of Earth's oceans."
Appearance Event Ordination (AEO) is a superior form of dating fossil collections, according to Alroy.
Age assignments to North American land mammals are provided for comparison and may disagree with the AEO estimates because they are taken straight from published sources.
That's because AEO uses explicitly recorded and clearly defined numerical data, and because it uses algorithmic search and optimization criteria instead of verbal argumentation."