Methodological steps to evaluate the interaction between Linnean and Darwinian shortfalls under LTG driving biased estimates of diversification rates. We start with a randomly generated phylogeny and define northern and southern (richer) clades, and two geographical sets are defined. In the first geographical set, associated with tests based on mean diversification rates DR, species are assigned to northern and southern regions, and mean DR are compared using a PGLS. In the second set, 20% of the species are common to both regions (widespread species), allowing comparisons of speciation, extinction, and dispersal rates using GeoSSE. When a widespread shift, it is necessary to define the geographical distribution of the new species (the species D in the above framework). We start with a random phylogeny in which rates in northern and southern regions are equal and begin the splitting cycle in the southern species. The cycle stops when a difference between mean DR values appears in the PGLS and when a ΔAIC > 3 is obtained by comparing GeoSSE fit with a null model in which rates are equal between regions. This process is repeated 5000 times, generating a statistical distribution of the minimum number of new species added to the southern region that is sufficient to shift the diversification rates.