DOI: 10.5061/dryad.r9d1m
title: Data from: Competitor relatedness, indirect soil effects and plant co-existence

description: How species co-exist is a central question in ecology. Niche
 differentiation can prevent two species from excluding each other by
 competition. However, this interaction can vary in space because of
 internal factors such as intraspecific genetic variation, or external ones
 such as the presence of a third species. While these effects have been
 repeatedly observed, their joint effect on the outcome of competition has
 rarely been considered. We experimentally investigated how a dominant
 ecosystem engineer (the shrub Thymus vulgaris) affects interactions
 between two co-occurring and closely related annuals (Medicago minima and
 M. rigidula). We ask first if the outcome of their interaction depends on
 the genetic identity of the competitors, and in particular if
 intraspecific interaction differs between genetically related versus
 unrelated conspecifics. Second, we ask if co-existence of the two species
 is modified by the presence of thyme plants altering local soil
 conditions. We grew genotypes collected in nature of both annual species
 in inter- and intraspecific competition experiments using soil collected
 directly underneath thyme plant (thyme soil), and soil collected away from
 thyme plants (no-thyme soil). We found that thyme soil affected
 interactions in a way that shifted the species’ rank. Crucial for this
 result was the division of intraspecific competition between genetically
 related and unrelated individuals. Intraspecific competition was
 significantly less detrimental to kin than to unrelated conspecifics. In
 highly structured plant populations, such effects could favor local
 dominance of a patch by one species. However this kin effect occurred for
 each species only in its preferred soil (thyme versus no-thyme), promoting
 a stabilizing co-existence mechanism at the landscape level. Synthesis:
 This study shows that the importance of intraspecific competition relative
 to interspecific competition can be highly dependent on the genotype
 identity of intraspecific competitors and of the local environment in
 which the interaction occurs. The local environment can itself be modified
 by the presence of a third species in the community. These results
 emphasize how, in order to understand the overall problem of species
 co-existence, it can be insightful to divide this into smaller local scale
 problems of co-existence.
description: DataJEcolDryadData Focalgt: The genotype identity of focal species. Focalsp: the speceis identity of focal species, mm: medicago minima, mr: Medicago rigidula. Compgt: the genotype identity of competiting individual. Compsp: the speceis identity of competiing individual. Soil: the soil that plants were grown in, t: thyme soil (soil colelcted under thyme plants), nt: no thyme soil (soil collected away from thyme plants). Comptype: competition type, intra-,or interspecific competition. Own: refers to the competition type between identical genotypes. surv: identifies whether the focal plant survived (1) or died (0). biomass: the biomass of focal plant. potnr: The identity of the pot in which plants were grown.