Data from: Adaptive radiation along a deeply conserved genetic line of least resistance in Anolis lizards

On microevolutionary timescales, adaptive evolution depends upon both
natural selection and the underlying genetic architecture of traits under
selection, which may constrain evolutionary outcomes. Whether such genetic
constraints shape phenotypic diversity over macroevolutionary timescales
is more controversial, however. One key prediction is that genetic
constraints should bias the early stages of species divergence along
“genetic lines of least resistance” defined by the genetic (co)variance
matrix, G. This bias is expected to erode over time as species means and G
matrices diverge, allowing phenotypes to evolve away from the major axis
of variation. We tested for evidence of this signal in West Indian Anolis
lizards, an iconic example of adaptive radiation. We found that the major
axis of morphological evolution was well aligned with a major axis of
genetic variance shared by all species despite separation times of 20-40
million years, suggesting that divergence occurred along a conserved
genetic line of least resistance. Further, this signal persisted even as G
itself evolved, apparently because the largest evolutionary changes in G
were themselves aligned with the line of genetic least resistance. Our
results demonstrate that the signature of genetic constraint may persist
over much longer timescales than previously appreciated, even in the
presence of evolving genetic architecture. This pattern may have arisen
either because pervasive constraints have biased the course of adaptive
evolution or because the G matrix itself has been shaped by selection to
conform to the adaptive landscape.