DOI: 10.5061/dryad.34tmpg4qk
title: Data from: The interacting influences of competition, composition, and diversity determine successional community change

description: Community change is one of the few constants in nature, and the balance of
 mechanisms influencing this change is central to understanding the
 structure and functioning of communities and ecosystems. Newly established
 communities undergo succession and can change in diversity and composition
 as local environmental change, interspecific interactions, and immigration
 play out over time. Understanding the influence of initial conditions and
 priority effects (long-term consequences of the initial community
 composition and species identity) on community change is critically
 important for both evaluating ecological theory and predicting restoration
 outcomes.  Here I evaluate how initial experimental conditions in
 2012, such as initial sown species richness, phylogenetic diversity, and
 early biomass production, along with priority effects caused by the
 identity of sown species, influence subsequent plant community composition
 and the number of colonizing species after nine years of uninterrupted
 natural colonization.   I found that sown phylogenetic diversity
 (measured as mean pairwise distance) indirectly affected the number of
 colonizing species by increasing biomass production early on and plots
 with more biomass in 2012 were colonized by fewer species. Individual
 species influenced the number of colonizing species with taller species
 reducing the number of colonists and some shorter species increasing the
 number of colonists.  Synthesis: Taken together, these results
 indicate that initial composition influences the number of colonizing
 species via community-wide competition. These findings suggest that
 restoration outcomes can be greatly influenced by decisions about sown
 species composition and early management practices.
description: This experiment was conducted in an old field at the University
 of Toronto’s Koffler Scientific Reserve, located about 50 km away from
 Toronto, Ontario, Canada (44o02’ N, 79o31’ W), as is detailed in Cadotte
 (2013), but I supply important details here. In fall 2009 and early spring
 2010, a 30 x 30 m field was plowed and disked, and then 100 2 x 2 m plots
 were set up and separated by pathways 1 m in width.  In
 May 2010, the plots were seeded with 1, 2, and 4 plant species from a pool
 of 15 species, including: <em>Andropogon gerardii
 </em>(Vitman, Poaceae); <em>Schizachyrium scoparium</em>
 ([Michx.] Nash, Poaceae); <em>Elymus canadensis </em>(L.,
 Poaceae); <em>E. trachycaulus</em> ([Link) Gould ex Shinners,
 Poaceae); <em>Asclepias tuberosa</em> (L., Asclepiadaceae);
 <em>Rudbeckia hirta</em> (L. Asteraceae); <em>Solidago
 altissima </em>(L., Asteraceae); <em>Solidago nemoralis
 </em>(Aiton, Asteraceae); <em>Desmodium canadense</em>
 (L., Fabaceae); <em>Lespedeza capitata </em>(Michx.,
 Fabaceae); <em>Monarda fistulosa</em> (L., Lamiaceae);
 <em>Pycnanthemum tenuifolium</em> (Schrad., Lamiaceae);
 <em>P. virginianum </em>([L.] T. Dur & B. D. Jacks. Ex
 B. L. Rob & Fernald, Lamiaceae); <em>Penstemon
 digitalis</em> (Nutt. Ex Sims, Scrophulariaceae); and <em>P.
 hirsutus</em> (L. Willd., Scrophulariaceae). Note that subsequent
 analyses refer to 14 species as the two <em>Elymus</em>
 species were combined because many unreproductive individuals resulted in
 uncertain identification. Each plot was sown with 3,000-4,000 seeds,
 approximating natural seed fall rates, divided amongst the number of
 species in a plot. For further details on seed sources and germination,
 see Cadotte (2013). Due to a lack of germination of some species, only 89
 plots are included in subsequent analyses, and some 4-species plots became
 3-species plots. In total, there are 44 monoculture, 25 two-species, 5
 three-species, and 15 four-species plots analyzed. See Cadotte (2013) for
 full details. All species monocultures were replicated
 three times. The 2- and 4-species treatments were fully crossed with three
 phylogenetic diversity treatments: 1) small phylogenetic distances, where
 plots were comprised of closely related species; 2) large phylogenetic
 distances, with plots members being distantly related; and finally, 3)
 medium phylogenetic distances, where plots contain moderately distantly
 related species, or a mix of close and distant relatives. Since there were
 fewer possible combinations for the small and large phylogenetic distance
 treatments, these were replicated 7 times each, for both the 2 and 4
 species plots. The medium treatments were replicated 9 times for both 2
 and 4 species. The phylogeny was estimated using five commonly sequenced
 genes: <em>matK, rbcl, ITS1, ITS2</em> and
 <em>5.8s</em>. For details on the phylogenetic inference and
 the phylogeny used to estimate phylogenetic distances, see Cadotte
 (2013). In late July 2012, a single 0.1 x 1 m quadrat
 was placed in each plot, 0.25 m away from any plot edge. All aboveground
 biomass was removed, with stems clipped just above the soil surface.
 Biomass was sorted into constituent species as well as litter (i.e., dead
 or dying material not connected to a living stem). All samples were dried
 in a VWR drying oven at 50o C for two days, and then weighed.
 Following the 2012 sampling, the plots were no longer weeded or
 maintained in any way other than leaving the deer fencing in place. To
 assess colonization of species, the entire 2 x 2 m plots were assessed for
 species composition and percent cover in late July 2021. In addition to
 the original experimental plots, I also sampled 10 ‘control’ plots. These
 plots surrounded the experiment and were plowed as part of the set-up for
 the experiment. Thus, these plots represent natural colonization and
 succession without any effect of sown species.