Data from: Biogeography of a plant invasion: genetic variation and plasticity in latitudinal clines for traits related to herbivory

The juxtaposition of plant-species invasions with latitudinal gradients in
herbivore pressure is an important yet mostly unexplored issue in invasion
biology. Latitudinal clines in defense and palatability to herbivores are
expected to exist in native plant species but the evolution of these
clines may lag behind for invasive plant species resulting in non-parallel
latitudinal clines that may impact invasion success. Our study focused on
a native and European invasive lineages of the common reed Phragmites
australis in North America. Using native and invasive genotypes of P.
australis collected across a 17° latitudinal range, we performed
experiments in replicate northern and southern common gardens to
investigate whether these two lineages exhibited different genetically
based latitudinal clines in defenses, nutritional condition and
palatability to their herbivores, the aphid Hyalopterus pruni and the fall
armyworm Spodoptera frugiperda. We also tested whether invasive genotypes
are more phenotypically plastic than native genotypes and whether
plasticity varies with latitude. Although invasive genotypes did not
exhibit higher defense levels (leaf toughness, phenolics, % carbon), they
were considerably less palatable to their herbivores than native
genotypes. Genetic-based latitudinal clines were evident for both native
and invasive P. australis and for all defenses, nutrients and at least one
palatability trait for each herbivore. In 36% of the cases where clines
were evident, they were non-parallel between the two lineages. These data
suggest that clines in the invasive genotypes of P. australis evolved
within the past ~100 years. Moreover, our study showed that the occurrence
and direction of latitudinal clines in plant traits were commonly
dependent on where the study was conducted (north or south), indicating
strong phenotypic plasticity in these genetic-based clines. Finally,
traits for invasive genotypes of P. australis were 2.5 times more plastic
than traits for native genotypes. Interestingly, plasticity for native but
not invasive genotypes was strongly dependent on latitude of origin. Such
spatial heterogeneity within and between the native and invasive lineages
of P. australis with respect to their interactions with herbivores can
generate substantial spatial variability in biotic resistance that can
have important implications for the establishment and spread of invasive
genotypes and species.