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Abstract Food webs show the architecture of trophic relationships, revealing the biodiversity and species interactions in an ecosystem. Understanding which factors modulate the structure of food webs offers us the ability to predict how they will change when influential factors are altered. To date, most of the research about food webs has focused on species interactions whereas the influences of surrounding environments have been overlooked. Here, using network analysis, we identified how the structure of aquatic food webs varied across a range of geophysical conditions within a whole stream system. Within a headwater basin in the Cascade Mountain Range, Oregon, USA, macroinvertebrate and vertebrate composition was investigated at 18 sites. Predator–prey interactions were compiled based on existing literature and dietary analysis. Several structural network metrics were calculated for each food web. We show that the structure of food webs was predictable based on geophysical features at both local (i.e., slope) and broader (i.e., basin size) spatial extents. Increased omnivory, greater connectance, shorter path lengths, and ultimately greater complexity and resilience existed downstream compared to upstream in the stream network. Surprisingly, the variation in food web structure was not associated with geographic proximity. Structural metric values and abundance of omnivory suggest high levels of stability for these food webs. There is a predictable variation in the structure of food webs across the network that is influenced by both longitudinal position within streams and patchy discontinuities in habitat. Hence, findings illustrate that the slightly differing perspectives from the River Continuum Concept, Discontinuity Patch Dynamics, and Process Domains can be integrated and unified using food web networks. Our analyses extend ecologists’ understanding of the stability of food webs and are a vital step toward predicting how webs and communities may respond to both natural disturbances and current global environmental change.
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Differences in web structure of Tetragnatha tenuissima (Araneae: Tetragnathidae) due to environmental conditions
Spiders can modify their web construction behaviour according to environmental conditions. Here, we examined how the web structure of Tetragnatha tenuissima differentiates depending on habitat type (swamp or river edge) at La Selva Biological Station, Costa Rica. We characterized the web architecture based on length, number of radii, and the spiral spacing relative to web length. There were no significant differences on the length or number of radii between the webs present in the swamp and river habitats. In terms of the spiral spacing relative to web length, there was a significant difference between habitats, with less distance in river-side webs than in the ones on swamps. This could be explained by the potential differential resource avail- ability on each environment. Therefore, habitat type appears as an explanatory variable for differences on the web structure of T. tenuissima. Due to the small number of identifiable individuals of other Tetragnatha species, the effect of congeneric species co-occurrence on web structure remains as a factor to be tested in future research.
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- Award ID(s):
- 1712757
- PAR ID:
- 10354034
- Date Published:
- Journal Name:
- Arachnology
- Volume:
- 18
- Issue:
- 8
- ISSN:
- 2050-9936
- Page Range / eLocation ID:
- 953–957
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.13156/arac.2021.18.8.953
