Abstract: The 26 genera of aurantioids and the 28 species of one genus, Citrus, are mapped. The distributions are explained, not by using fossil-calibrated clade ages and ancestral-area algorithms, but by focusing on the geometry of the clade distributions and the tectonic history at the break-zones (nodes). Allopatry is attributed to vicariance, overlap to normal dispersal. Subfamily Aurantioideae is allopatric with its sister groups in Eurasia and the Americas. In contrast, the seven main clades within Aurantioideae show a high level of overlap. But within each of these seven main clades, there is again a high level of allopatry. The pattern is explained by vicariance events at the first and third levels. The overlap at the second level can be accounted for if vicariance (now obscured) generated the clades and subsequent dispersal caused secondary overlap of the clades. This latter phase of mobilism can be explained by the migration of coastlines and maritime flora far inland during marine transgressions, especially in the mid-Cretaceous. Many aurantioids inhabit mangrove-associate vegetation, beach thicket, limestone substrate, and areas with high levels of disturbance. Within Citrus, the five main clades overlap in south-central China (Nanling Mountains) and are allopatric elsewhere. The overlap-zone has been interpreted as a centre of origin, but it is explained here as a break-zone, the site of vicariance in a widespread ancestor, where localised, secondary overlap has developed later. The zone coincides with a belt of mid-Cretaceous deformation manifested in voluminous magmatism, subsidence, rifting, back-arc extension, and the opening of the East China sea.

Key words: China, distribution, ecology, Nanling Mountains, tectonics, vicariance