Data from: Incipient speciation driven by hypertrophied lips in Midas cichlids fish?

Sympatric speciation has been debated in evolutionary biology for decades.
Although it has gained in acceptance recently, still only a handful of
empirical examples are seen as valid (e.g. crater lake cichlids). In this
study, we disentangle the role of hypertrophied lips in the repeated
adaptive radiations of Nicaraguan crater lake cichlid fish. We assessed
the role of disruptive selection and assortative mating during the early
stages of divergence and found a functional trade-off in feeding behavior
between thick- and thin-lipped ecotypes suggesting that this trait is a
target of disruptive selection. Thick-lipped fish perform better on
non-evasive prey at the cost of a poorer performance on evasive prey.
Using enclosures in the wild, we found that thick-lipped fish perform
significantly better in rocky than in sandy habitats. We found almost no
mixed pairs during two breeding seasons and hence significant assortative
mating. Genetic differentiation between ecotypes seems to be related to
the time since colonization, being subtle in L. Masaya (1600 generations
ago) and absent in the younger L. Apoyeque (<600 generations ago).
Genome-wide differentiation between ecotypes was higher in the old source
lakes than in the young crater lakes. Our results suggest that
hypertrophied lips might be promoting incipient sympatric speciation
through divergent selection (ecological divergence in feeding performance)
and non-random mating (assortative mating) in the young Nicaraguan crater
lakes. Nonetheless, further manipulative experiments are needed in order
to confirm the role of hypertrophied lips as the main cue for assortative
mating.