Data from: Ecological speciation in European whitefish is driven by a large‐gaped predator

Lake‐dwelling fish that form species pairs/flocks characterized by body
size divergence are important model systems for speciation research.
Although several sources of divergent selection have been identified in
these systems, their importance for driving the speciation process remains
elusive. A major problem is that in retrospect, we cannot distinguish
selection pressures that initiated divergence from those acting later in
the process. To address this issue, we studied the initial stages of
speciation in European whitefish (Coregonus lavaretus) using data from 358
populations of varying age (26–10,000 years). We find that whitefish
speciation is driven by a large‐growing predator, the northern pike (Esox
lucius). Pike initiates divergence by causing a largely plastic
differentiation into benthic giants and pelagic dwarfs: ecotypes that will
subsequently develop partial reproductive isolation and heritable
differences in gill raker number. Using an eco‐evolutionary model, we
demonstrate how pike's habitat specificity and large gape size are
critical for imposing a between‐habitat trade‐off, causing prey to mature
in a safer place or at a safer size. Thereby, we propose a novel mechanism
for how predators may cause dwarf/giant speciation in lake‐dwelling fish
species.