Allochthony in stream food webs decreases with temperature across a subcontinental scale

Abstract

Riverine and riparian food webs are connected via 'allochthonous' resource flows from neighboring ecosystems. These resources, such as terrestrial leaf litter, contribute to benthic macroinvertebrate diets, supporting higher trophic levels. While allochthony occurs in streams globally, its sensitivity to broad environmental gradients remains poorly understood. We explored the drivers of allochthony across six river basins within the contiguous United States, including climate, stream size, and flow permanence. We used Bayesian mixing models to estimate macroinvertebrate dietary proportions in four functional feeding groups. Air temperature best predicted allochthony, with consumers relying less on allochthonous resources with increasing temperature. Our models indicate that macroinvertebrate diets become primarily autochthonous at approximately 15{degrees}C mean annual air temperature, with leaf litter-consuming shredders showing a slightly higher threshold for this shift. We also found increased allochthony in smaller, non-perennial streams. These findings highlight the complexity of stream allochthony and responses to multi-scale environmental factors.

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BibTeX

@misc{higgins2026allochthony,
  title = {{Allochthony in stream food webs decreases with temperature across a subcontinental scale}},
  author = {K. T. Higgins and M. T. Bogan and A. Ruhi and M. C. Mims and C. L. Atkinson and M. H. Busch and B. A. Gill and C. R. Smith and T. M. Neeson and Y. Hong and T. M. Apgar and A. J. Shogren and M. C. Malish and S. C. Silknetter and R. M. Mohammadi and A. M. Belskis and D. C. Allen},
  howpublished = {bioRxiv},
  year = {2026},
  month = sep,
  doi = {10.64898/2026.09.27.752912},
  url = {https://www.biorxiv.org/content/10.64898/2026.09.27.752912v1},
  note = {CC BY},
}

RIS

TY  - UNPB
TI  - Allochthony in stream food webs decreases with temperature across a subcontinental scale
AU  - K. T. Higgins
AU  - M. T. Bogan
AU  - A. Ruhi
AU  - M. C. Mims
AU  - C. L. Atkinson
AU  - M. H. Busch
AU  - B. A. Gill
AU  - C. R. Smith
AU  - T. M. Neeson
AU  - Y. Hong
AU  - T. M. Apgar
AU  - A. J. Shogren
AU  - M. C. Malish
AU  - S. C. Silknetter
AU  - R. M. Mohammadi
AU  - A. M. Belskis
AU  - D. C. Allen
PY  - 2026
DA  - 2026/09/27
PB  - bioRxiv
DO  - 10.64898/2026.09.27.752912
UR  - https://www.biorxiv.org/content/10.64898/2026.09.27.752912v1
AB  - Riverine and riparian food webs are connected via 'allochthonous' resource flows from neighboring ecosystems. These resources, such as terrestrial leaf litter, contribute to benthic macroinvertebrate diets, supporting higher trophic levels. While allochthony occurs in streams globally, its sensitivity to broad environmental gradients remains poorly understood. We explored the drivers of allochthony across six river basins within the contiguous United States, including climate, stream size, and flow permanence. We used Bayesian mixing models to estimate macroinvertebrate dietary proportions in four functional feeding groups. Air temperature best predicted allochthony, with consumers relying less on allochthonous resources with increasing temperature. Our models indicate that macroinvertebrate diets become primarily autochthonous at approximately 15{degrees}C mean annual air temperature, with leaf litter-consuming shredders showing a slightly higher threshold for this shift. We also found increased allochthony in smaller, non-perennial streams. These findings highlight the complexity of stream allochthony and responses to multi-scale environmental factors.
ER  -

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