Data from: Plant competition alters the temporal dynamics of plant-soil feedbacks

1. Most studies on plant-soil feedback (PSF) and plant competition measure the feedback response at one moment only. However, PSFs and competition may both change over time, and how PSF and competition interact over time is unclear. 2. We tested the temporal dynamics of PSF and interspecific competition for the forb Jacobaea vulgaris and the grass Holcus lanatus. We grew both species individually and in interspecific competition in soil that was first conditioned in the greenhouse by J. vulgaris, by H. lanatus or without plant growth. For a period of 11 weeks, we harvested plants twice a week and analyzed the fungal and chemical composition of the different soils at the end of the first and second growth phase. 3. During the second growth phase, when grown in isolation, both species produced more biomass in heterospecific conditioned soil than in conspecific conditioned soil. Young J. vulgaris exhibited a strong negative conspecific feedback, but this effect diminished over time and became neutral in older plants. In contrast, when grown in competition, the negative conspecific feedback of J. vulgaris exacerbated over time. Older H. lanatus plants benefited more from heterospecific conditioning when competing with J. vulgaris, then when grown isolated. 4. Fungal community composition and soil chemistry differed significantly between soils but this was mainly driven by differences between plant-conditioned and unconditioned soils. Remarkably, at the end of the second growth phase, fungal community composition was not explained by the legacy of the species that had been grown in the soil most recently, but still reflected the legacy of the first growth phase. We reexamined plant growth during a third growth phase. Biomass of J. vulgaris was still influenced by the treatments imposed during the first phase, while H. lanatus responded only to the plant growth treatments imposed during the second phase. 5. Synthesis: Our study shows that the direction and magnitude of PSF depends on plant age and competition but also on soil legacy effects of earlier plant growth. These results highlight the need to incorporate dynamic PSFs in research on plant populations and communities

Formation of unreduced megaspores (diplospory) in apomictic dandelions (Taraxacum officinale, s.l.) is controlled by a sex-specific dominant locus.

In apomictic dandelions, Taraxacum officinale, unreduced megaspores are formed via a modified meiotic division (diplospory). The genetic basis of diplospory was investigated in a triploid (3x = 24) mapping population of 61 individuals that segregated approximately 1:1 for diplospory and meiotic reduction. This population was created by crossing a sexual diploid (2x = 16) with a tetraploid diplosporous pollen donor (4x = 32) that was derived from a triploid apomict. Six different inheritance models for diplospory were tested. The segregation ratio and the tight association with specific alleles at the microsatellite loci MSTA53 and MSTA78 strongly suggest that diplospory is controlled by a dominant allele D on a locus, which we have named DIPLOSPOROUS (DIP). Diplosporous plants have a simplex genotype, Ddd or Dddd. MSTA53 and MSTA78 were weakly linked to the 18S-25S rDNA locus. The D-linked allele of MSTA78 was absent in a hypotriploid (2n = 3x - 1) that also lacked one of the satellite chromosomes. Together these results suggest that DIP is located on the satellite chromosome. DIP is female specific, as unreduced gametes are not formed during male meiosis. Furthermore, DIP does not affect parthenogenesis, implying that several independently segregating genes control apomixis in dandelions

Appendix F. Results of t tests to analyze if feedback responses of early-successional plant species in monocultures and in mixed communities in competition with later-successional species differed from zero.

Results of t tests to analyze if feedback responses of early-successional plant species in monocultures and in mixed communities in competition with later-successional species differed from zero

Appendix G. Results of General Linear Model testing the difference in feedback effects of early-successional plant species in monocultures and in mixed communities in competition with later-successional species.

Results of General Linear Model testing the difference in feedback effects of early-successional plant species in monocultures and in mixed communities in competition with later-successional species

Appendix H. Factor loadings of principal components analysis for mid-successional plant species grown in soil with histories of early-successional plant species.

Factor loadings of principal components analysis for mid-successional plant species grown in soil with histories of early-successional plant species

Appendix B. Available nutrients in the sterilized soil and in the microbial inocula originating from soil in which monocultures of early-successional plant species were grown in experiment 1.

Available nutrients in the sterilized soil and in the microbial inocula originating from soil in which monocultures of early-successional plant species were grown in experiment 1

Appendix K. Ordination diagram of principal components analysis on bacterial and fungal denaturing gradient gel electrophoresis profiles of Poa annua rhizosphere samples.

Ordination diagram of principal components analysis on bacterial and fungal denaturing gradient gel electrophoresis profiles of Poa annua rhizosphere samples

Appendix A. Abiotic soil characteristics at the start of the feedback experiment.

Abiotic soil characteristics at the start of the feedback experiment

Appendix J. Results from PROC MIXED (SAS) analysis of effects of inoculum origin on plant biomass production of mid-successional plant species relative to the sterilized control treatment.

Results from PROC MIXED (SAS) analysis of effects of inoculum origin on plant biomass production of mid-successional plant species relative to the sterilized control treatment