DOI: 10.5061/dryad.nvx0k6dvq
title: Combining biogeographic approaches to advance invasion ecology and methodology

description: 1) Understanding the causes of plant invasions requires that parallel
 field studies are conducted in the native and introduced ranges to
 elucidate how biogeographic shifts alter the individual performance,
 population success, and community-level impacts of invading plants. Three
 primary methods deployed in in situ biogeographic studies are directed
 surveys, where researchers seek out populations of target species,
 randomized surveys, and field experiments. Despite the importance of these
 approaches for advancing biogeographic research, their relative merits
 have not been evaluated. 2) We concurrently deployed directed surveys,
 randomized surveys, and in situ field experiments for studying six
 grassland plant species in the native and introduced ranges. Metrics
 included plant size, fecundity, recruitment, abundance, and invader
 impact, as well as soil properties and root associations with putative
 fungal mutualists and pathogens. 3) Consistent with key invasion
 hypotheses, Bromus tectorum experienced increased size and fecundity in
 the introduced range linked to population increases and significant
 invader impacts, along with altered fungal associations. However,
 performance differences did not predict population increases and invader
 impacts across species. Rather, the differential effect of disturbance in
 facilitating greater recruitment in the introduced range appeared to play
 a crucial, though previously underexplored, role in driving invader
 success. 4) Directed surveys consistently generated information on plant
 performance and fungal associations. However, soil sampling suggested that
 directed surveys may have been biased toward disturbed conditions for half
 the species. Randomized surveys generated robust data for population
 comparisons and impact, but generally failed to produce performance
 metrics for species that were uncommon or flowered outside the peak
 sampling window. Field experiments controlled for bias and confounding
 factors and provided rare information on recruitment and disturbance
 effects, but scant recruitment in the native range and ethical constraints
 on growing invaders in the introduced range limited information on
 performance and plant-fungal interactions. 5) Synthesis. Each method had
 strengths and weaknesses. However, when combined they provided
 complementary information to paint the most complete biogeographic picture
 to date for several introduced plants. We propose a hybrid approach to
 optimize biogeographic studies.
description: These data were collected as part of three related biogeographic
 studies compared in the paper: directed surveys, randomized surveys, and a
 field experiment.  Data derived included plant performance and abundance
 metrics, fungal abundance and community composition, and soil nutrient
 levels.  Datafiles are organized by study, with the exception of fungal
 community composition data found in separate files for AMF and pathogens,
 respectively.  See 1) README tab within each datafile and 2) Methods in
 the paper for full details.
description: Datafiles are excel spreadsheets.