Data and code for: Plastic and quantitative genetic divergence mirror environmental gradients among wild, fragmented populations of Impatiens capensis

Premise of the study: Habitat fragmentation generates molecular genetic
divergence among isolated populations but few studies have assessed
phenotypic divergence and fitness in populations where the genetic
consequences of habitat fragmentation are known. Phenotypic divergence
could reflect plasticity, local adaptation, and/or genetic drift. Methods:
We examined patterns and potential drivers of phenotypic divergence among
12 populations of jewelweed (Impatiens capensis Meerb.) that show strong
molecular genetic signals of isolation and drift among fragmented
habitats. We measured morphological and reproductive traits in both
maternal plants within natural populations and their self-fertilized
progeny grown together in a common garden. We also quantified
environmental divergence between home sites and the common garden. Key
results: Populations with less molecular genetic variation expressed less
maternal phenotypic variation. Progeny in the common garden converged in
phenotypes relative to their wild mothers but retained among-population
differences in morphology, survival, and reproduction. Among-population
phenotypic variance was 3-10x greater in home sites than in the common
garden for 6 of 7 morphological traits measured. Patterns of phenotypic
divergence paralleled environmental gradients in ways suggestive of
adaptation. Progeny resembled their mothers less as the environmental
distance between their home site and the common garden increased.
Conclusions: Despite strong molecular signatures of isolation and drift,
phenotypic differences among these Impatiens populations appear to reflect
both adaptive quantitative genetic divergence and plasticity. Quantifying
the extent of local adaptation and plasticity and how these covary with
molecular and phenotypic variation help us predict when populations may
lose their adaptive capacity.