Skip to main content Skip to secondary navigation

Wicked Forest

Main content start
trees with a red sky in the background from wild fires

WICKED FOREST.
Stanford Arboretum.

In probabilistic models of gene trees conditional on species trees, it is possible that both of the following hold at once: (1) given a species tree \(S_1\) with topology \(T_1\), gene tree topology \(T_2\) has a greater probability than gene tree topology \(T_1\); (2) given a species tree \(S_2\) with topology \(T_2\), gene tree topology \(T_1\) has a greater probability than gene tree topology \(T_2\). Because this counterintuitive scenario generates particularly challenging scenarios for species tree inference, the species trees \(S_1\) and \(S_2\) are said to belong to a "wicked forest." Degnan & Rhodes (2015) have shown that trees with a caterpillar shape cannot be in a wicked forest—giving rise to their article title “There are no caterpillars in a wicked forest.” The occurrence of a wicked forest in tree space is a relatively unusual phenomenon—like the wildfire-induced orange sky that gives this Stanford forest a "wicked" look.

Photo: Noah Rosenberg, September 9, 2020