G-matrix stability of clinally diverging populations of an annual weed

How phenotypic and genetic divergence among populations is influenced by
the genetic architecture of those traits, and how microevolutionary
changes in turn affect the within-population patterns of genetic
variation, are of major interest to evolutionary biology. Work on Ipomoea
hederacea, an annual vine, has found genetic clines in the means of a
suite of ecologically important traits, including flowering time, growth
rate, seed mass, and corolla width. Here we investigate the genetic
(co)variances of these clinally varying traits in two northern range-edge
and two central populations of Ipomoea hederacea to evaluate the influence
of the genetic architecture on divergence across the range. We find 1)
limited evidence for clear differentiation between Northern and Southern
populations in the structure of G, suggesting overall stability of G
across the range despite mean trait divergence and 2) that the axes of
greatest variation (gmax) were unaligned with the axis of greatest
multivariate divergence. Together these results indicate the role of the
quantitative genetic architecture in constraining evolutionary response
and divergence among populations across the geographic range.