DOI: 10.5061/dryad.gd856
title: Data from: Adaptive geographical clines in the growth and defense of a native plant

description: Broad-scale geographical gradients in the abiotic environment and
 interspecific interactions should select for clinal adaptation. How trait
 clines evolve has recently received increased attention because of
 anticipated climate change and the importance of rapid evolution in
 invasive species. This issue is particularly relevant for clines in growth
 and defense of plants, because both sets of traits are closely tied to
 fitness and because such sessile organisms experience strong local
 selection. Yet, despite widespread recognition that growth and defense
 traits are intertwined, the general issue of their joint clinal evolution
 is not well-resolved. To address heritable clinal variation and adaptation
 of growth and defense traits of common milkweed (Asclepias syriaca), we
 planted seed from 22 populations encompassing the species'
 latitudinal range in common gardens near the range center (New York [NY])
 and towards the range edges (New Brunswick [NB] and North Carolina [NC]).
 Populations were differentiated in 13 traits, and six traits showed
 genetically-based latitudinal clines. Higher latitude populations had
 earlier phenology, lower shoot biomass, more root buds and clonal growth,
 higher root-to-shoot ratio, and greater latex production. The cline in
 shoot biomass was consistent in all three locations. Selection on
 phenology was reversed in NB and NC, with early genotypes favored in the
 north but not the south. We found no clines in foliar trichomes or toxic
 cardenolides. Annual precipitation of source populations explained
 variation in phenology, clonal growth, root-to-shoot ratio, and latex.
 Across four traits measured in NB and NC, we found garden-by-latitude (and
 garden-by-precipitation) interactions, indicating plasticity in
 genetically-based trait clines. In the two gardens with substantial
 herbivory (NY and NC), northern populations showed higher resistance to
 insects. Resistance to aphids was driven by trichomes and water content,
 while resistance to monarch caterpillars was driven by latex. However,
 surveys of natural populations indicated that leaf damage and insect
 diversity on milkweed are low at the geographical extremes (NB and NC) and
 higher towards the range center. We speculate that milkweed plants evolved
 clines in growth traits in response to climate, and that this set the
 template for tolerance to herbivory, which subsequently shaped the
 evolution of defensive traits.
description: Data-Traits-roof-all veg
 traitsRaw data from the
 destructive harvest of plants for study of genetically-based plant
 allocation along the gradients studied.interactions between nc
 nb gardensData used to examine
 differential selection in the two extreme latitudinal common
 gardenspopulation
 meansPopulation means data
 used for the bulk analyses in the paper, inlcuding path
 analysesraw data ithaca garden
 2008Raw data for the main
 common garden in Ithaca 2008, including information on browsing and aphids
 naturally attacking the plantsSeed-Masses and Seed
 Counts of PodsData for the starting
 population of seeds for all populations (collected in the field at their
 sites along the gradient)surveyanalysisData on leaf damage and insect diversity at the three location over two years.