Influence of intermittent stream dynamics on predator-prey interactions

Authors

• Milena Gonçalves-Silva (1)
• Elvira D’Bastiani (2)
• Thibault Datry (3)
• Carla Ferreira Rezende (1)

Institutions

• (1) Programa de Pós-Graduação em Ecologia e Recursos Naturais, Universidade Federal do Ceará, Brasil.
• (2) Department of Ecology and Evolutionary Biology, University of California, Los Angeles, USA.
• (3) INRAE, UR RiverLy, Centre de Lyon-Villeurbanne, Villeurbanne, France.

**Corresponding author*: Milena Gonçalves-Silva, e-mail: milenagoncalves.bio@gmail.com

ORCIDs: - Milena Gonçalves-Silva: https://orcid.org/0000-0003-1626-1216 - Elvira D’Bastiani: https://orcid.org/0000-0002-8615-2763 - Thibault Datry: https://orcid.org/0000-0003-1390-6736 - Carla Ferreira Rezende: https://orcid.org/0000-0002-2319-6558

Running headline: Effect of hydrological phases on interactions

Abstract

Intermittent rivers and ephemeral streams are dynamic ecosystems with periodic interruptions in flow, leading to temporary or complete absence of water. Such dynamics (flowing to dry phases) create a mosaic of isolated pools, which can decrease habitat volume and connectivity. In addition to reduced resource availability and increased predation levels, the drying dynamics impacts both food webs and their connectivity. In this study we asked: (i) Do species composition and environmental variables change during the hydrological phases in intermittent streams? (ii) Do hydrological phases in intermittent streams affect predator-prey network structures? (iii) Do stochastic factors during the dry phase affect predator-prey network structures? We infer predator-prey interactions using fish food items along of 1km of the intermittent river Tabocas during flowing (23 sections) and dry phases (22 isolated pools). We identified 18 predator species and 11 ecological categories of food items. We found that species composition and environmental variables change during the flowing and dry phases (semi-arid conditions) in intermittent streams. Despite similar species richness between phases, significant differences in species composition highlight the importance of considering temporal fluctuations in understanding community dynamics. Moreover, our findings demonstrate that hydrological fluctuations affect predator-prey network structures. Specifically, during the flowing phase, we noted a nested pattern in interaction networks, while during the dry phase, the networks within isolated pools displayed different patterns, including nested and/or modular pattern, high specialisation, and random structures. Our findings also highlight that stochastic factors can operate during the dry phase, leading to the formation of isolated pools and the creating predator-prey network with random structures. The key factor contributing to the emergence of random networks is the reduction in the number of predator-prey links and the increased specialisation within the pools. Given the limited number of these links of most sampled pools, fish species become more vulnerable. This highlights the importance of identifying priority aquatic refuges to sustain freshwater biodiversity in intermittent streams. Our study highlights the importance of considering hydrological variability and considering stochastic factors in devising strategies to conserve biodiversity and minimize the impact of climate change on the biota of tropical semi-arid ecosystems.

Keywords

climate changes, drying rivers networks, temporary streams, semi-arid climate.

NAMING

Data and codes (Branch)

File 1. README.txt

Folder: (i) Do species composition and environmental variables change during the hydrological phases in intermittent streams? Folder: Betadiversity File 1. script.r File 2. databetas.csv File 3. fishabundancedry.csv

    Folder: Mantel test
         File 1. script.r
         File 2. abund.csv
         File 3. amb.csv
         File 4. dist.csv
         File 5. ext.csv

    Folder: NMDS
         File 1. script.r 
         File 2. fishabundance.csv

    Folder: PCA
         File 1. script.r
         File 3. data.csv

    Folder: Pearson correlation
         File 1. script.r
         File 2. met.csv
         File 3. amb.csv

    Folder: FO
         File 1. script.r
         File 2. H2_ord.csv
         File 3. NM FO.csv
         File 4. dry.csv
         File 5. flowing.csv
         File 6. module FO.csv
         File 7. nested FO.csv
         File 8. random FO.csv

    Folder: GLM
         File 1. script.r
         File 2. interactions_pools.csv

Folder: (ii) Do hydrological phases in intermittent streams affect predator-prey network structures? (iii) Do stochastic factors during the dry phase affect predator-prey network structures? File 1. script.r File 2. fooditems_flowing.csv

         File 3. P1.csv
         File 4. P2.csv
         File 5. P3.csv
         File 6. P4.csv
         File 7. P5.csv
         File 8. P6.csv
         File 9. P7.csv
         File 10. P8.csv
         File 11. P9.csv
         File 12. P10.csv
         File 13. P11.csv
         File 14. P12.csv
         File 15. P13.csv
         File 16. P14.csv
         File 17. P15.csv
         File 18. P16.csv
         File 19. P17.csv
         File 20. P18.csv
         File 21. P19.csv
         File 22. P20.csv
         File 23. P21.csv
         File 24. P22.csv

File formats: i. Databases: .csv, ii. Scripts: .r

Units of measurement: i. m = meters

Software:

      i. R version 4.3.1 (R Core Team, 2013)

Citation: Gonçalves-Silva, M., D’Bastiani, E., Datry, T., & Rezende, C. F. (Year). Influence of intermittent stream dynamics on predator-prey interactions. Journal of [Journal Name], [Year], [Volume(Issue)], [Page Range]. DOI: [DOI Number].