Longitudinal patterns of abundance, diversity and functional feeding guilds of benthic communities in East African tropical high‐altitude streams

Abstract

In temperate and tropical rivers, macroinvertebrates are commonly utilised for biological monitoring. Therefore, it is important to understand their functional feeding guilds and assemblage structure. However, there have been few studies in high‐altitude rivers in East Africa aimed at assessing macroinvertebrate functional guilds. In this study, we examined the macroinvertebrate assemblage characteristics using abundance/diversity metrics and the functional feeding groups (FFGs). We collected physicochemical data and macroinvertebrate samples at seven sites along the Gura River and three sites on the Sagana River. Dissolved oxygen concentration, water temperature, electrical conductivity, pH, turbidity, ammonia, and soluble reactive phosphorus showed significant differences among the sites (p < 0.05). A total of 32 families belonging to 11 orders of macroinvertebrates were collected during the study period. Overall, scrapers were the most abundant FFG, dominated by Heptageniidae (Afronurus). Collector filters and collector gatherers were the second most abundant, while shredders and predators exhibited the least relative abundance. Across all the dominant orders, macroinvertebrate abundance decreased from upstream to downstream sites, with upstream sites exhibiting high diversity and abundance of Ephemeroptera, Diptera, Coleoptera, and Trichoptera taxa. Furthermore, the FFGs in this study differed widely from the River Continuum Concept predictions. Our findings provide crucial understanding of macroinvertebrate assemblage characteristics in high‐altitude rivers. Thus, this study provides additional evidence on the high abundance and diversity of Ephemeroptera and Trichoptera taxa in tropical rivers.

Low redundancy among caddisflies sharing a mid‐mountain stream

“…The isotopic values measured in the Gilgil invertebrate assemblage broadly confirmed trophic niche attribution according to highly cited reference guidelines such as Merritt and Cummins (1996), Merritt et al (2002Merritt et al ( , 2008 and Dobson et al (2002) utilised by researchers working in the Afrotropics (Benjamin et al, 2023, El Yaagoubi et al, 2023, Edegbene et al, 2021, Masese et al, 2014a, despite acknowledged discrepancies between temperate and tropical keys (see Masese et al, 2014a and references therein). At the same time, however, the relative positioning of the Gilgil invertebrates across the isotope biplot provided new insight into the potential role of these taxa within Afrotropical stream food webs.…”