I'm wondering if there is a difference conceptually between disruptive selection and 2 opposing directional selection. As you can read here, it seems that disruptive selection can be thought as opposing directional selection.
Here is a little pictogram showing what I mean (the first would be disruptive selection and the second one would be 2 opposing directional selection):
It seems that Lande Arnold (1983), would be only able to detect selection if the trait is unimodal and normally distributed. So it would be only possible to detect "disruptive selection" using the 2 opposing directional selection to infer it.
Lande, R., and Arnold, S. J. 1983. The Measurement of selection on correlated characters. Evolution 37:1210–1226.
Would that mean that there is no mathematical model to find disruptive selection in the first place?