Research ArticleECOLOGY

Climate warming promotes species diversity, but with greater taxonomic redundancy, in complex environments

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Science Advances  14 Jul 2017:
Vol. 3, no. 7, e1700866
DOI: 10.1126/sciadv.1700866
  • Fig. 1 Effects of experimental warming on nematode communities across the gradient of plant species richness.

    (A) Nematode taxa richness. (B) Effective number of species. (C) Pielou’s evenness. (D) Rarefied taxa richness. Amb, ambient. Please see Table 1 for the details of the results.

  • Fig. 2 Effects of experimental warming and plant species richness on nematode taxonomic redundancy and community composition.

    (A) Standardized effect sizes for the MTD of nematode communities in response to experimental warming across the gradient of plant species richness. (B) NMDS ordinations illustrating differences in nematode community composition among ambient and the highest warmed (~+3°C) plant monocultures (Mono) and ambient and the highest warmed (~+3°C) 16-plant species mixtures (Mix).

  • Fig. 3 Relationships between predator density and nematode diversity measures in plant monocultures (A and B) and 16-plant species mixtures (C and D).

    Statistical details of these relationships are provided in Table 2. Only significant (P < 0.05) relationships are shown by the dashed lines. These observed relationships do not imply causality (that is, predator density was not experimentally manipulated) but highlight the need to study the roles of trophic interactions in determining biodiversity in future global change experiments.

  • Table 1 Results for nematode communities’ responses to experimental warming and plant species richness based on linear mixed-effects models.

    Statistical significance is based on Wald type II χ² tests. Significant effects (P < 0.05) are given in bold. All regression coefficients are based on rescaled response variables. Please find the details of nematode responses in table S4 (mean responses with SD and number of samples). PSR, plant species richness; ENS, effective number of species; MTD, mean taxonomic distance.

    Nematode responsesPSRWarmingPSR × warming
    βtPβtPβtP
    Richness−0.012−0.9170.153−0.158−1.7490.9650.0242.4770.013
    ENS−0.010−0.8310.020−0.233−2.7520.4860.0303.2440.001
    Pielou’s evenness0.0010.0760.247−0.200−2.1670.0360.0090.9620.335
    Rarefied richness−0.003−0.2380.120−0.282−3.1410.0040.0151.5910.111
    MTD0.0010.0970.630−0.137−1.4410.011−0.005−0.5260.598
    Mean (rank abundance distribution)−0.004−0.3150.4860.0570.6070.534−0.002−0.2320.816
    SD (rank abundance distribution)−0.005−0.4160.3170.1531.6120.052−0.003−0.3190.750
  • Table 2 Regression results for the associations of bottom-up and top-down effects with the two nematode diversity measurements (ENS and MTD) using mixed-effects models in plant monocultures and mixed plant communities.

    Statistical significance is based on Wald type II χ² tests. Significant associations (P < 0.05) are given in bold. All regression coefficients are based on rescaled response variables. S, shoot biomass; R, root biomass 2012; PD, predator density.

    Plant monoculturesMixed plant communities (16 species)
    ENSMTDENSMTD
    βtPβtPβtPβtP
    Indicators of bottom-up effects
    S−0.252−1.5420.123−0.083−0.4930.6210.3061.4980.1340.0890.4130.679
    R−0.091−0.5410.588−0.172−0.9250.354−0.485−2.5700.010−0.017−0.0810.935
    Indicator of top-down effects
    PD0.4182.7220.0060.1570.9430.345−0.05−0.2500.8020.5392.9390.003
    Interactive effects
    S*PD0.5050.8940.371−1.331−2.2210.026−0.934−1.6530.0980.5431.0660.286
    R*PD0.1260.4270.669−0.029−0.090.9280.3270.3270.5280.6531.3450.178

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/7/e1700866/DC1

    fig. S1. Rank abundance distribution of nematode communities.

    fig. S2. Interactive effects of plant species richness and experiment warming on prey richness within nematode communities.

    fig. S3. Greater soil water content in high–plant species richness treatment as revealed by mixed-effects models (β = 0.03, t = 2.73, P = 0.01).

    table S1. Linnaean taxonomic classification of nematode species in this study.

    table S2. Effects of plant diversity [effective number of species (ENS) and phylogenetic diversity] on the effective number of nematode species and their MTD across warming treatments.

    table S3. Trophic group responses (abundance) and prey and predator richness within nematode communities as affected by plant species richness and experimental warming.

    table S4. Mean, SDs, and number of samples for the responses of selected measures of nematode and plant communities.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Rank abundance distribution of nematode communities.
    • fig. S2. Interactive effects of plant species richness and experiment warming on prey richness within nematode communities.
    • fig. S3. Greater soil water content in high–plant species richness treatment as revealed by mixed-effects models (β = 0.03, t = 2.73, P = 0.01).
    • table S2. Effects of plant diversity [effective number of species (ENS) and phylogenetic diversity] on the effective number of nematode species and their MTD across warming treatments.
    • table S3. Trophic group responses (abundance) and prey and predator richness within nematode communities as affected by plant species richness and experimental warming.
    • table S4. Mean, SDs, and number of samples for the responses of selected measures of nematode and plant communities.

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    Other Supplementary Material for this manuscript includes the following:

    • table S1 (Microsoft Excel format). Linnaean taxonomic classification of nematode species in this study.

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