Research ArticleENVIRONMENTAL SCIENCE

Individualistic sensitivities and exposure to climate change explain variation in species’ distribution and abundance changes

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Science Advances  30 Oct 2015:
Vol. 1, no. 9, e1400220
DOI: 10.1126/sciadv.1400220
  • Fig. 1 Flowchart of methodological approach.

    Species-specific climate models were built by relating year-to-year changes in relative abundance to seasonal climate variables. Species-specific sensitivity and exposure metrics were derived from the outputs of the species-specific climate models and were used as predictor variables in models explaining interspecific variation in changes in species’ abundance, distribution size, and northern range margins.

  • Fig. 2 Responses of species to climate change.

    (A to C) Frequency distributions of changes in (A) abundance, (B) distribution size, and (C) northern range margin of butterflies (dashed bars, n = 24 species) and moths (open bars, n = 131 species). Changes in distribution size and northern range margin were calculated using well-recorded hectads. In each plot, values for each taxonomic group were standardized so that mean = 0 and variance = 1.

  • Fig. 3 Variation in species’ sensitivity and exposure to climate change, and the aspects of the climate they are most sensitive to.

    (A to D) Frequency distributions of butterfly (dashed bars, n = 24 species) and moth (open bars, n = 131 species) sensitivities (A) and exposures (B) to climate, the relationship between exposure and sensitivity (C), and climate variables in species’ climate models (D). Sensitivity is the proportion of year-to-year change in a species’ population trend that can be attributed to variation in the climate. Exposure represents the mean annual change in these population trends (+, predicted increase; −, predicted decrease) expected for each species on the basis of 1970–2010 climatic conditions and the climate variables to which each species is sensitive. (C) There was no significant relationship between species’ climate sensitivity and exposure (Spearman’s r = 0.02, P = 0.82). (D) Variables represent either the sum of rainfall (white boxes) or mean temperatures (gray boxes) for a given season [spring (March–May), summer (June–August), autumn (September–November), or winter (December–February)] in the current year (“year t”), the previous year (“year t−1”), or 2 (“year t−2”) or 3 years previously (“year t−3”). Variables were standardized before analysis. The numbers of species in each column are provided in bold italic font above the x axis—each species’ best climate model contained up to three climate variables, and therefore, each species is represented in up to three columns. Medians are represented by the horizontal black lines; the top and bottom of each box are the 75th and 25th percentiles, respectively; outliers are represented by black dots; and whiskers represent data within 1.5 × interquartile range (IQR) of the upper and lower quartiles.

  • Fig. 4 Species’ distribution and abundance changes related to their sensitivity and exposure.

    (A to F) Relationships between changes in the abundance (A and B), distribution size (C and D), and northern range margin (E and F) of butterflies (n = 24) and moths (n = 131) in relation to either their exposure to climate change (B, D, E, and F) or the interaction between exposure and sensitivity to climate change (A and C). The proportions of variation explained by each model (A to F) were 0.64, 0.59, 0.53, 0.22, 0.14, and 0.03, respectively. For (B), (D), (E), and (F), modeled relationships (solid lines) ± SE (dashed lines) are depicted; for (A) and (C), modeled relationships between response variables and climate exposure are shown, with sensitivity values kept constant [at the observed minimum (−2.29; short-dashed line), mean (0.00; solid line), and maximum (1.98; long-dashed line) sensitivity values]. All variables were standardized so that mean = 0 and variance = 1.

  • Fig. 5 Population changes of two exemplar butterfly species.

    (A to H) Distributions, abundance trends, exposure, and sensitivities of two exemplar butterfly species: the comma Polygonia c-album (A, C, E, and G) and the grizzled skipper Pyrgus malvae (B, D, F, and H). (A and B) Distribution changes between 1970–1985 and 1995–2010. Black squares are well-recorded hectads occupied in both time periods, gray squares are those colonized by the second period, and red squares show locations of apparent extinctions. Northern range margins in the first and second time periods are represented by the dashed and horizontal lines, respectively. (C and D) Observed log collated indices of abundance (solid lines) and the modeled linear change in the index (dashed lines); the slope of this relationship is defined as species’ long-term change in abundance. (E and F) Observed (black lines) and predicted (red lines) change in log collated index; sensitivity represents the proportion of year-to-year change in a species index of abundance that can be attributed to variation in the climate (that is, R2), and exposure is calculated as the predicted mean annual change in index between 1970 and 2010. Predicted changes in index were calculated using climate models with coefficients depicted in (G) and (H).

  • Table 1 Candidate models (within 2 AIC units of the best model) for multivariate regressions relating response variables to the sensitivity (“Sens”) and exposure (“Exp”) of butterflies (n = 24) and moths (n = 131) to climate.

    SEs are provided within brackets; bold values indicate individually significant effects. Response variables were standardized values of changes in abundance, distribution size, and northern range margin; the latter two variables were calculated using well-recorded 10 × 10–km grid squares (hectads) and standardized before analysis to enable comparisons between the size and direction of coefficients.

    ResponseTaxaInterceptExposureSensitivityExp:SensΔAICR2
    Δ AbundanceButterfly−0.050.68 (0.12)0.16 (0.14)0.35 (0.14)0.000.64
    Moth0.290.80 (0.07)0.000.59
    Δ Distribution sizeButterfly0.560.63 (0.28)0.20 (0.24)0.26 (0.33)0.000.53
    Butterfly1.310.66 (0.12)0.130.45
    Moth0.000.45 (0.07)0.000.22
    Δ Northern range marginButterfly−0.370.25 (0.13)0.000.14
    Butterfly−0.401.580.00
    Moth−0.100.22 (0.06)0.000.03
    Moth−0.150.08 (0.06)−0.03 (0.06)−0.15 (0.06)1.890.05

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/1/9/e1400220/DC1

    Fig. S1. Variation in the strength and direction of climate coefficients in moth (n = 131; A) and butterfly (n = 24; B) species’ best climate models.

    Fig. S2. Maps showing the spatial variation in recorder effort across GB, for butterfly (A) and moth (B) recording schemes.

    Fig. S3. Significant, positive correlation between independent and fitted R2 from each species’ climate model relating annual change in abundance trends to climate variables (Pearson’s r = 0.86, t153 = 21.11, P < 0.0001).

    Fig. S4. Map showing the spatial arrangement of neighborhoods around two example focal hectads (black stars).

    Fig. S5. Correlations between distribution changes calculated using two different levels of recorder effort. Correlations between normalized (A) range size change (Spearman’s correlation: r = 0.87, P < 0.001) and (B) distribution margin change (r = 0.81, P < 0.001) for 155 species (moths, n = 131; butterflies, n = 24) using recorded and well-recorded hectads.

    Table S1. Moths and butterflies (“But.”) included in the analyses.

    Table S2. Pearson’s correlations between climate variables.

    Table S3. Shapiro tests for normality of residuals and error distributions of candidate models in Table 1.

    Table S4. Candidate models (within 2 AIC units of the best model) for multivariate regressions relating response variables to the sensitivity (“Sens”) and exposure (“Exp”) of moths (n = 131) and butterflies (n = 24) to climate.

    Table S5. Candidate models (within 2 AIC units of the best model) for multivariate regressions relating response variables to the sensitivity (“Sens”) and exposure (“Exp”) of moths (n = 131) and butterflies (n = 24) to climate, including species’ prevalence as an additional predictor.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Variation in the strength and direction of climate coefficients in moth (n = 131; A) and butterfly (n = 24; B) species’ best climate models.
    • Fig. S2. Maps showing the spatial variation in recorder effort across GB, for butterfly (A) and moth (B) recording schemes.
    • Fig. S3. Significant, positive correlation between independent and fitted R2 from each species’ climate model relating annual change in abundance trends to climate variables (Pearson’s r = 0.86, t153 = 21.11, P < 0.0001).
    • Fig. S4. Map showing the spatial arrangement of neighborhoods around two example focal hectads (black stars).
    • Fig. S5. Correlations between distribution changes calculated using two different levels of recorder effort.
    • Table S1. Moths and butterflies (“But.”) included in the analyses.
    • Table S2. Pearson’s correlations between climate variables.
    • Table S3. Shapiro tests for normality of residuals and error distributions of candidate models in Table 1.
    • Table S4. Candidate models (within 2 AIC units of the best model) for multivariate regressions relating response variables to the sensitivity (“Sens”) and exposure (“Exp”) of moths (n = 131) and butterflies (n = 24) to climate.
    • Table S5. Candidate models (within 2 AIC units of the best model) for multivariate regressions relating response variables to the sensitivity (“Sens”) and exposure (“Exp”) of moths (n = 131) and butterflies (n = 24) to climate, including species’ prevalence as an additional predictor.

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