Secondary production of caddisflies reflects environmental heterogeneity among tropical Andean streams

Abstract

Macroinvertebrate life history and secondary production have rarely been measured in tropical highland streams even though these streams are highly heterogeneous and display unique ecological settings compared to both those in the tropical lowlands or in the temperate zone. We evaluated secondary production and life history attributes of the periphyton grazer caddisfly (Helicopsyche spp.) using the size-frequency method in three Ecuadorian highland stream reaches (2990–3727 meters above sea level) with contrasting riparian vegetative characteristics and differing flow and temperature regimes and periphyton biomass (as chlorophyll-a). Helicopsychedisplayed strong differences among streams in life history attributes and secondary production. We estimated the least productive reach (89 mg m-2 - year-1) to be an order of magnitude less than that of the two more productive reaches (1556–2164 mg m-2 - year-1). Secondary production positively correlated with annual mean periphyton biomass and negatively correlated with annual mean water temperature. Compared to previous studies, mean secondary production of Helicopsyche was relatively high. We conclude that Helicopsyche secondary production in tropical highland streams is highly heterogeneous among stream types. This strong variation among streams might ultimately depend on environmental factors influencing food availability (biomass of periphyton) and larval development rates (temperature regime).