Habitat size influences food web structure in drying streams

Peter McHugh, Ross THOMPSON, Hamish Grieg, Helen Warburton, Angus MacIntosh

    Research output: Contribution to journalArticle

    27 Citations (Scopus)

    Abstract

    Biodiversity in running waters is threatened by an increased severity and incidence of low-flow extremes resulting from global climate change and a growing human demand for freshwater resources. Although it is unknown how and to what extent riverine communities will change in the face of these threats, considerable insight will be gained from efforts aimed at quantifying habitat size-related controls on the trophic relationships among taxa in streams experiencing extreme flow loss. Here we report on a detailed space-for-time survey of replicate stream food webs sampled along the perennial- to-drying continuum in each of fourteen different intermittent South Island, New Zealand streams. We quantified several structural attributes of food webs at fifty-eight sites, including two taxonomically-based metrics (web size, predator:prey ratio) and three stable isotope-based metrics (food chain length [FCL], trophic area, d13C range); we also quantified habitat size-, disturbance-, and resource-related covariates at each site. Food web structure varied widely across sample sites within and across study streams and much of this variation was explained by habitat size. Consistent with our predictions, we found that food webs became smaller (ca 30 to ca 15 taxa, ca 20-fold reduction in stable isotope-based trophic area) and shorter (maximum trophic position [FCL] from 4.1 to 2.0, 25% reduction in predator:prey ratio) as we moved from the largest to smaller habitats. These results, and a comparison of our findings with those from a similar assessment conducted in perennial streams, suggest that there are perturbation thresholds which may trigger food web collapse when exceeded, and further imply that food webs may ultimately be 'sized' to minimum flows rather than average flow conditions. Our work provides a basis for making general predictions about how habitat contraction, and flow loss in particular, may affect communities and additionally provides insight on mechanisms warranting further attention.
    Original languageEnglish
    Pages (from-to)700-712
    Number of pages13
    JournalEcography
    Volume38
    Issue number7
    DOIs
    Publication statusPublished - 2015

    Fingerprint

    food webs
    food web
    drying
    habitat
    habitats
    food chain
    stable isotopes
    stable isotope
    predator
    predators
    prediction
    low flow
    trophic relationships
    contraction
    global climate
    perturbation
    climate change
    biodiversity
    fold
    disturbance

    Cite this

    McHugh, P., THOMPSON, R., Grieg, H., Warburton, H., & MacIntosh, A. (2015). Habitat size influences food web structure in drying streams. Ecography, 38(7), 700-712. https://doi.org/10.1111/ecog.01193
    McHugh, Peter ; THOMPSON, Ross ; Grieg, Hamish ; Warburton, Helen ; MacIntosh, Angus. / Habitat size influences food web structure in drying streams. In: Ecography. 2015 ; Vol. 38, No. 7. pp. 700-712.
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    abstract = "Biodiversity in running waters is threatened by an increased severity and incidence of low-flow extremes resulting from global climate change and a growing human demand for freshwater resources. Although it is unknown how and to what extent riverine communities will change in the face of these threats, considerable insight will be gained from efforts aimed at quantifying habitat size-related controls on the trophic relationships among taxa in streams experiencing extreme flow loss. Here we report on a detailed space-for-time survey of replicate stream food webs sampled along the perennial- to-drying continuum in each of fourteen different intermittent South Island, New Zealand streams. We quantified several structural attributes of food webs at fifty-eight sites, including two taxonomically-based metrics (web size, predator:prey ratio) and three stable isotope-based metrics (food chain length [FCL], trophic area, d13C range); we also quantified habitat size-, disturbance-, and resource-related covariates at each site. Food web structure varied widely across sample sites within and across study streams and much of this variation was explained by habitat size. Consistent with our predictions, we found that food webs became smaller (ca 30 to ca 15 taxa, ca 20-fold reduction in stable isotope-based trophic area) and shorter (maximum trophic position [FCL] from 4.1 to 2.0, 25{\%} reduction in predator:prey ratio) as we moved from the largest to smaller habitats. These results, and a comparison of our findings with those from a similar assessment conducted in perennial streams, suggest that there are perturbation thresholds which may trigger food web collapse when exceeded, and further imply that food webs may ultimately be 'sized' to minimum flows rather than average flow conditions. Our work provides a basis for making general predictions about how habitat contraction, and flow loss in particular, may affect communities and additionally provides insight on mechanisms warranting further attention.",
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    McHugh, P, THOMPSON, R, Grieg, H, Warburton, H & MacIntosh, A 2015, 'Habitat size influences food web structure in drying streams', Ecography, vol. 38, no. 7, pp. 700-712. https://doi.org/10.1111/ecog.01193

    Habitat size influences food web structure in drying streams. / McHugh, Peter; THOMPSON, Ross; Grieg, Hamish; Warburton, Helen; MacIntosh, Angus.

    In: Ecography, Vol. 38, No. 7, 2015, p. 700-712.

    Research output: Contribution to journalArticle

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    T1 - Habitat size influences food web structure in drying streams

    AU - McHugh, Peter

    AU - THOMPSON, Ross

    AU - Grieg, Hamish

    AU - Warburton, Helen

    AU - MacIntosh, Angus

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    N2 - Biodiversity in running waters is threatened by an increased severity and incidence of low-flow extremes resulting from global climate change and a growing human demand for freshwater resources. Although it is unknown how and to what extent riverine communities will change in the face of these threats, considerable insight will be gained from efforts aimed at quantifying habitat size-related controls on the trophic relationships among taxa in streams experiencing extreme flow loss. Here we report on a detailed space-for-time survey of replicate stream food webs sampled along the perennial- to-drying continuum in each of fourteen different intermittent South Island, New Zealand streams. We quantified several structural attributes of food webs at fifty-eight sites, including two taxonomically-based metrics (web size, predator:prey ratio) and three stable isotope-based metrics (food chain length [FCL], trophic area, d13C range); we also quantified habitat size-, disturbance-, and resource-related covariates at each site. Food web structure varied widely across sample sites within and across study streams and much of this variation was explained by habitat size. Consistent with our predictions, we found that food webs became smaller (ca 30 to ca 15 taxa, ca 20-fold reduction in stable isotope-based trophic area) and shorter (maximum trophic position [FCL] from 4.1 to 2.0, 25% reduction in predator:prey ratio) as we moved from the largest to smaller habitats. These results, and a comparison of our findings with those from a similar assessment conducted in perennial streams, suggest that there are perturbation thresholds which may trigger food web collapse when exceeded, and further imply that food webs may ultimately be 'sized' to minimum flows rather than average flow conditions. Our work provides a basis for making general predictions about how habitat contraction, and flow loss in particular, may affect communities and additionally provides insight on mechanisms warranting further attention.

    AB - Biodiversity in running waters is threatened by an increased severity and incidence of low-flow extremes resulting from global climate change and a growing human demand for freshwater resources. Although it is unknown how and to what extent riverine communities will change in the face of these threats, considerable insight will be gained from efforts aimed at quantifying habitat size-related controls on the trophic relationships among taxa in streams experiencing extreme flow loss. Here we report on a detailed space-for-time survey of replicate stream food webs sampled along the perennial- to-drying continuum in each of fourteen different intermittent South Island, New Zealand streams. We quantified several structural attributes of food webs at fifty-eight sites, including two taxonomically-based metrics (web size, predator:prey ratio) and three stable isotope-based metrics (food chain length [FCL], trophic area, d13C range); we also quantified habitat size-, disturbance-, and resource-related covariates at each site. Food web structure varied widely across sample sites within and across study streams and much of this variation was explained by habitat size. Consistent with our predictions, we found that food webs became smaller (ca 30 to ca 15 taxa, ca 20-fold reduction in stable isotope-based trophic area) and shorter (maximum trophic position [FCL] from 4.1 to 2.0, 25% reduction in predator:prey ratio) as we moved from the largest to smaller habitats. These results, and a comparison of our findings with those from a similar assessment conducted in perennial streams, suggest that there are perturbation thresholds which may trigger food web collapse when exceeded, and further imply that food webs may ultimately be 'sized' to minimum flows rather than average flow conditions. Our work provides a basis for making general predictions about how habitat contraction, and flow loss in particular, may affect communities and additionally provides insight on mechanisms warranting further attention.

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    DO - 10.1111/ecog.01193

    M3 - Article

    VL - 38

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    JF - Ecography

    SN - 0906-7590

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