Tracking seasonal food web dynamics and isotopic niche shifts in wild chubbyhead barb Enteromius anoplus within a southern temperate headwater stream

Trophic niche patterns of endangered Sandelia bainsii and Amatolacypris trevelyani in the Eastern Cape, South Africa: Insights from stable isotope analysis

“…By revealing inconsistent isotopic niche sizes for S. bainsii and A. trevelyani lineages across their sampled ranges, the current study provided evidence of the importance of spatial heterogeneity in food web dynamics and suggests that the likely influence of resource availability and interspecific interactions was largely unpredictable. It is, thus, likely that in addition to the preponderance of temporal food web dynamics that was previously reported (e.g., Kambikambi et al, 2019a), the trophic niche patterns of these lineages also reflected adaptability to the potential stochasticity in resource availability within the headwater stream habitats. This appeared to be consistent with research elsewhere, which has shown that headwater stream food webs tend to exhibit landscape-level unpredictability due to factors such as discontinuity in patch dynamics and local-scale habitat complexities (Polis et al, 1997;Zatkos et al, 2021).…”

“…Similarly, temporal gradients in headwater stream food webs, which are often attributed to seasonal differences in aspects such as photosynthesis‐driven metabolism and temperature‐driven phenological requirements of higher heterotrophic groups (Brett et al, 2017), culminate in temporal variability in community structure and functional interrelationships (Baker et al, 2023). Recent studies within the AWHE have largely demonstrated the importance of temporal heterogeneity in both functional composition and food web dynamics of the headwater streams (Kambikambi et al, 2019a; Matomela et al, 2021). By revealing inconsistent isotopic niche sizes for S. bainsii and A. trevelyani lineages across their sampled ranges, the current study provided evidence of the importance of spatial heterogeneity in food web dynamics and suggests that the likely influence of resource availability and interspecific interactions was largely unpredictable.…”

“…To evaluate the isotopic food webs and depict potential assimilation dynamics at the different sites, we plotted the means (±standard deviation) of carbon (δ 13 C) and nitrogen (δ 15 N) values of potential basal sources, macroinvertebrates and fishes. For convenience, macroinvertebrates were categorized into functional feeding groups following Palmer and O'Keeffe (1992), Palmer et al (1996), Palmer, O'Keefe, Palmer, Dunne, and Radloff (1993), Palmer, O'Keefe, and Palmer (1993) and (Kambikambi et al (2019a)) (see Appendix S1). These groups were as follows: (1) brushers, which use setae to remove loosely deposited and lightly attached organic matter; (2) gatherers/collectors, which remove loosely deposited and lightly accreted organic material from surfaces; (3) filterers, which are suspension feeders of FPOM and detrital matter; (4) scrapers, which graze on tightly accreted organic matter from surfaces; and (5) predators, which feed on animal matter.…”

“…dynamics at the different sites, we plotted the means (±standard deviation) of carbon (δ 13 C) and nitrogen (δ 15 N) values of potential basal sources, macroinvertebrates and fishes. For convenience, macroinvertebrates were categorized into functional feeding groups followingPalmer and O'Keeffe (1992),Palmer et al (1996), Palmer, O'Keefe,Palmer, Dunne, and Radloff (1993), and(Kambikambi et al (2019a)) (see Appendix S1).…”

Exploring source differences on diet-tissue discrimination factors in the analysis of stable isotope mixing models

“…The use of appropriate DTDFs in isotope mixing models has, nonetheless, become a subject of increasing attention in recent studies. For example, some studies that have explored both the biological processes and the fate of assimilated isotope tracers, and have applied experimentally derived factors in order to provide reasonable dietary estimates 38 , 75 . Despite the relevance of experimental studies in providing the appropriate DTDFs that can be used in isotope mixing models, and their recent application in studies involving both fishes 38 , 49 , 63 and other animal taxa 27 , 76 , gathering this information still remains elusive for many taxa, in part due to experimental costs and interspecific differences that potentially confound generalisations.…”