DOI: 10.5061/dryad.8tc13
title: Data from: Long-term nitrogen addition causes the evolution of less cooperative mutualists

description: Human activities have altered the global nitrogen (N) cycle, and as a
 result, elevated N inputs are causing profound ecological changes in
 diverse ecosystems. The evolutionary consequences of this global change
 have been largely ignored even though elevated N inputs are predicted to
 cause mutualism breakdown and the evolution of decreased cooperation
 between resource mutualists. Using a long-term (22 year) N addition
 experiment, we find that elevated N inputs have altered the
 legume-rhizobium mutualism (where rhizobial bacteria trade N in exchange
 for photosynthates from legumes), causing the evolution of less
 mutualistic rhizobia. Plants inoculated with rhizobium strains isolated
 from N-fertilized treatments produced 17–30% less biomass and had reduced
 chlorophyll content compared to plants inoculated with strains from
 unfertilized control plots. Because the legume-rhizobium mutualism is the
 major contributor of naturally-fixed N to terrestrial ecosystems, the
 evolution of less cooperative rhizobia may have important environmental
 consequences.
description: Weese et al Dryad
 dataThis excel file has two
 tabs: one of the tabs has the data for the soil inoculation experiment
 (“experiment 1, see manuscript), the other tab has the data for the
 genetic effects experiment (“experiment 2, see manuscript). Below are
 descriptions of the variables in this data file. More information is in
 the manuscript. plantid: randomly assigned plant ID number. shootmass: dry
 above ground mass of individual experimental plant (units is grams).
 leafnum: number of leafs counted on an individual experimental plant
 stolonnum: number of stolons counted on an individual experimental plant
 nodulenum: number of nodules counted on an individual experimental plant
 MassofNodules: mass of 1st 100 nodules (approximately, see “Nodulesintube”
 variable) taken from an individual experimental plant. Units is grams.
 NodulesinTube: the number of nodules that were weighted in for the
 “MassofNodules” variable meannodulemass: estimated average mass of a
 nodule sampled from an individual experimental plant, calculated by
 dividing the “MassofNodules” variable by the “NodulesinTube” variable
 totalnodulemass: estimated total mass of all nodules for an individual
 experimental plant, calculated by multiplying “meannodulemass” variable by
 “nodulenum” variable Chlor: measured chlorophyll level for an individual
 experimental plant (no units) Harvester: initials of individual that
 harvested an individual experimental plant. Harvestdate: date that an
 individual exerperimental plant was harvested. Harvestday: number of days
 that had past since the 1st experimental plant was harvested. strain:
 identity of rhizobia strain that inoculated that particular experimental
 plant nitrogen: describes whether the particular rhizobia strain
 inoculating this experimental plant was originally sampled from a
 fertilized field plot (1) or a nonfertilized field plot (0) field: LTER T7
 experimental field from which the particular rhizobia strain inoculating
 this experimental plant was originally sampled from plot: label associated
 with a particular plot within a particular LTER T7 field coded thusly: 1A
 = the nonfertilized subplot of LTER field 1, 1B = the fertilized subplot
 of LTER field 1, 2A = the nonfertilized subplot of LTER field 2, 2B = the
 fertilized subplot of LTER field 2, and so on… plantspori: Trifolium
 species from which a particular rhizobia strain was isolated during the
 soil inoculation experiment plantpopori: particular population (associated
 with a Trifolium species) from which a particular rhizobia strain was
 isolated during the soil inoculation experiment plantssprear: Trifolium
 species of that particular experiment plant plantpoprear: population
 (associated with a Trifolium species) of that particular experimental
 plant.