Upside down bell-curve in best-fitting modal model in QuaSSE

[jamie-thompson]

The best fitting model in QuaSSE for my data is a modal model. However, this is an upside down bell curve where speciation rates are high at all values except for a dip of the bell curve.

Is this a statistical thing? I know that some ML optimisation methods (e.g. RPANDA), resulting values should be considered as absolute values if extinction is negative. This would make sense with my data when plotting trait values against tip-rates as estimated by the DR statistic and BAMM.