I'm trying to detect the signal of introgression, in particular using QuIBL approach on transcriptome data. I have encountered some problems in interpreting the results.

In the first topology ((A,B),C), which is consistent with the species tree, the BIC value for the one-distribution model is much lower than for the two-distribution model. Does this mean that the two speciation events happened almost simultaneously?

Do I need to normalise the dBIC to the BIC value for the models? For example, if I have dBIC = 100 and BIC1 = -40000, BIC2=-40100, does this dBIC have the same weight as if BIC1 = -100 and BIC2 = -200?

In the two discordant trees I have almost the same value of dBIC. Does this mean that introgression has occurred everywhere (as between A,C, as between B,C)?

Does the program estimate the single mutation rate for all the loci? I mean, could I insert the mitochondrial gene into my data set and get a reliable result?

There is an example below of the QuIBL results I'm asking about.