The Andes of South America are most biologically diverse mountain chain on the planet. There are many speceis rich groups which experienced adaptive, rapid, and recent radiations in the northern and central Andes. Most of this research has argued high diversificaton rates are associated with increased mountain uplift rates. In addition, the insular nature of high peaks, low valleys, plateaus, and contrasting periods of uplift have contributed to high levels of endemism and habitat diversity. The Huancabamba deflection zone is a low-lying area separating the northern from the central Andes however the central and southern Andes do not have a geographical break. Instead, they are separated by an arid and elevational barrier located in northern Chile called the western Southern American Dry Diagonal (wSADD). Historical biogeography and diversification studies have focused on the enigmatic radiations from the northern and central Andes, while far less has been revealed about the biogeography and tempo of diversification from the central and southern Andes. Here we focused on the Southern Andean Loasa (SAL, Loasaceae), a diverse clade that includes five genera distributed across the central and southern Andes. We applied a single digest restriction site next generation sequencing method (RADSeq) to obtain thousands of nuclear markers from species across SAL to 1) reconstruct a phylogeny, 2) generate divergence time estimates, 3) investigate ancestral areas, and to 4) determine the tempo of diversification across SAL and species from the central and southern Andes. Phylogenetic results were largely congruent with past studies apart from Grausa not being monophyletic. BioGeoBears results suggested that the ancestors for SAL were in arid regions during the Oligocene throughout the early Miocene. The uplifting of the central Andes indirectly created more arid habitats (rain shadows), and thus facilitated diversification of arid adapted Loasa. Montane SAL first arose within the southern Andes during the Miocene, followed by only Caiohora into the central Andes during the late Miocene. Overall, diversification rates were slow, but highest during expansion of arid habitats, and into the Andes. Diversification largely correlates to the age of habitat; high Andean SAL were the most recent to diverge; temperate rainforest SAL were found to be on long branches with much older ages. A taxonomic revision is need for Grausa and increased sampling is needed to resolve species complexes in Loasa, Pinnasa, and Caiophora. The Andes are the most diverse mountain system on the planet and increased study in all parts is urgently needed to understand its diversity and how it evolved through time and space.